handover preparation 3bk 11202 0297 dszza e05

Handover PreparationED 05 RELEASED

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SiteVELIZY MOBILE COMMUNICATION DIVISION

Originator(s)

E. BRIGANTHANDOVER PREPARATION

RELEASE B7.2

Domain : Alcatel BSSDivision : PRODUCT DEFINITIONRubric : SYS-TLAType : SYSTEM FUNCTIONAL BLOCKSDistribution Codes Internal : External :

ABSTRACT

This document specifies the algorithms to be implemented in this release of the Alcatel BSS for :

- Handover preparation,- Directed retry preparation.

Approvals

Name

App.

R. MAUGERSYT DPM

J. ACHARDSYT CCM

K. LIBERLOOBDC DPM

Name

App.

R. SABELLEKBTS DPM


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REVIEW

HISTORY

Release 2 : S/P2/3.4.1.4.3

Version Date Author Reasons for update

2.0.0.0 18/05/92 B. Maier First working version for phase 2 based on the document:- TLA/148 V 1.2.0.0 written by P. GUILLIER and D.VERHULST- CRQ/757- TLA/SN/3 v.2.1.0.0 and TLA/SN/30 v.2.2.0.0.

2.0.0.1 19/06/92 B. Maier Second working version.

2.0.0.2 10/03/93 B. Maier Third working version.The document is reviewed according to the new templatefor phase 2 documents.

2.0.1.0 14/05/93 L. Cruchant First TLA approved version for phase 2.This version takes into account remarks made duringTLA review (see RSG/160).DCS-1800 features are introduced in the document.

2.1.0.0 27/08/93 L. Cruchant First RSG approved version for phase 2.This version takes into account remarks made duringRSG/TLA review (see TLA/153).

Release 3 : 3BK 11202 0014 DSZZA

3.0.0.0 15/12/93 L. Cruchant First working version for release 3 based on thedocuments :- Power Control and Handover Algorithms v.2.1.0.0,- TLA/152 improvements, v 2.0.0.5 : PCHO 002,

PCHO 005, EXH 003.- FD/3/10.6 : Support of microcellular environment

v 3.0.0.1,- FD/3/10.7.1 : Concentric cells v 3.0.0.1,- FD/3/10.8 : Directed Retry v 3.0.0.0,

3.0.0.1 04/03/94 L. Cruchant Second working version for release 3. This documenthas been updated after the meeting TLAr3#1 (seeTLA/171).Additional information has been added based ondocuments SYS/006 : definition of parameters for cellenvironments (H. Brinkmann, G. Kreft).SYS/014 : Handover in a microcellular environment (C.Cherpantier).


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3.0.1.0 11/04/94 L. Cruchant First Level 1 approved version for release 3, updatedafter the meeting TLAr3#4 (see SYS/030).

3.1.0.0 11/05/94 L. Cruchant Level 2 approved version, updated after the meetingTLAr3#7 (see SYS/051).


4.0.0.0 04/11/94 L Julia First working version for release 4 based on thedocuments- Power Control and Handover Algorithms v 3.1.0.0- MFD 11.5 : Power control and handover algorithmimprovements- ITCC/TELACT/TEL/PP/006 : remarks made by ITC onspecifications for rel 3

4.0.0.1 26/01/94 L Julia Updated after the TLAr4#4 review ,based on thedocuments- SYS/111Minutes of the TLA review TLAr4#4- CRQ/729 Expand of POWER_INC_STEP range forDCS 1800

4.0.0.2 23/02/95 L Julia Updated after the TLAr4#8 review, based on the writtencomments form S. De FOORT and A. KADELKA andthe minutes SYS/142 of the TLAr4#8 meeting

4.0.1.0 03/04/95 L Julia Level 1 approved version, Updated after the TLAr4#9review, written comments by N. De BODE, minutesSYS/149 of the TLA review.

4.1.0.0 05/05/95 L Julia Level 2 approved version, Updated after writtencomments by N. De BODE and C. CHERPANTIER.approved Release 3 CRQ taken into account : CRQ 924,CRQ 1153, CRQ 1173, CRQ 1258, CRQ 1279, CRQ1281, CRQ 1282, CRQ 1283, CRQ 1294, CRQ 1312


Ed. 01 Proposal 01 08/03/96 F Colin First working version for release 5 based on the documents:- Power Control and Handover Algorithms v 4.1.0.0

(This document has been split in two : the presentdocument resumes the part 'Handover algorithms')

- TFD 11.22 a : Handover algorithms improvementsMultiband Handover

- Approved Release 4 CRQs : CRQ 1428, CRQ 1705, CRQ1806, CRQ 2027, CRQ 2093, CRQ 2109, CRQ 2144, CRQ2234Moreover, the original document has been partly modified :- Mode A has been removed- Section 3 has been reorganised, section 2.2 removed- Appendix B and F have been removed, Appendic C is newMinor changes are listed in Appendix D


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Ed. 01 Proposal P1 30/04/96 F Colin Document updated after the internel review TLAr5#9according to the minutes in ref. TD/SAS/LCR/747.96

Ed. 01 Proposal R1 14/06/96 F Colin Document updated after the prereview TLAr5#12 accordingto the minutes in ref. TD/SAS/LCR/1062.96, based on thecomments of N. de Bode and G. Van DijckIntroduction of DCS1900 supportIntroduction of approved Release 4 CRQs : CRQ 1971,CRQ 2408 and CRQ 2472.

Ed. 01 Released 23/07/96 F Colin Document updated after the external review TLAr5#15according to the minutes in ref. TD/SAS/LCR/1377.96,based on the comments of N. de Bode.Creation of Section 5 'Release changes'Introduction of approved Release 4 CRQs : CRQ 2504,CRQ 2505

Release 6.1 : 3BK 11202 0170 DSZZA

Ed. 01 Proposal 01 29/08/97 PJPIETRI

First working version for release 6 based on the documents:- Handover preparation release 5 Ed. 01- TFD 11.31: general handover algorithms improvements- TFD 10.8b: external directed retry- TFD 11.22.e controlled handover in multilayer/multivendorenvironment- TFD 11.30: traffic management in handover algorithms- TFD 3.19: HSCSD- TFD 11.32: improvements in radio channel selection- Approved Release 5 CRQs 18579, 3028, 2736, 10645,19733The section 2 is reorganised. Some descriptions have beenput in a new step 1 document (refer to [20]).The section Active channel preprocessing is in the newdocument Radio measurements data processing [19].A new handover alarm management is specified in section3.2.4.


Document updated after the review TLAr6#15 according tothe minutes in ref. TD/SAS/LCR/1218.97Modification of the directed retry management.

Ed. 01 Released 15/10/97 PJPIETRI

Approved version, updated following TLA review TLAr6#17,as detailed in TD/SAS/EDE/1317.97


Second working version for release 6 based on the followingmodifications :- Suppresion of the handover cause 24- HSCSD calls are allowed in the inner zone of a concentriccell.-Inhibition of the filtering process for the handovers cause20.


Approved version, updated following TLA review TLAr6#20,as detailed in TD/SAS/EDE/0104.98


Updated after inclusion of approved Crqs: Crq 29140, Crq29147 and Crq 30481


Updated after inclusion of approved Crqs: Crq 30932, Crq32529, Crq 33156 and Crq 40894.


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First working version for release 6 based on the documents:- Handover preparation release 6.1 Ed. 04- TFD GPRS


Approved version, updated as detailed inTD/SYT/PJP/1159.98


Ed. 01 Proposal 01 30/11/99 E. Brigant First working version for release 7.1 based on thedocuments: - Handover preparation release 6.2 Ed. 01- SFD 3.6.6: Indoor layer support- SFD 3.6.1: Instantaneous peaks management- SFD 3.1.1: Adaptive multi-rate speech codec- SFD 3.3.1: Anti ping-pong improvements- SFD 3.5.1: Multiband cell improvements- SFD 3.x.x: Telecom improvement- SFD 3.2.1: Tandem free operation

Ed 01 Proposal 02 13/01/00 E. Brigant - Updated after review TLAB7#24. See review reportMCD/TD/SYT/EBR/90732.99- B6.2 CRQs included: 3BKA20CBR064608 v1

Ed 01 Proposal 03 25/01/00 E. Brigant - Updated after review. See review reportMCD/TD/SYT/EBR/0064.2000

Ed 01 Proposal 04 11/02/00 E. Brigant - Updated after the review reportMCD/TD/SYT/EBR/0126.2000- SFD 3.x.x: E-GSM support included

Ed 01 Released 09/03/00 E. Brigant Updated after the review reportMCD/TD/SYT/EBR/0234.2000

Ed 02 Released 08/01/01 E. Brigant Updated after inclusion of approved CR3BKA20CBR080300 “HR reshuffling removal”

Ed 03 Released 09/08/01 E. Brigant Updated after inclusion of approved CR3BKA20CBR088497 “Removal of an non-existing OMCrule for enabling Cause 29”

Ed 04 Proposal 01 10/10/01 E. Brigant Updated after inclusion of approved CR3BKA20CBR097487 “GSM 850 : impacts on HOP”

Ed 04 Released 26/10/01 E. Brigant Updated and released according to review reportMND/TD/SYT/EBR/0500.2001

Ed 05 Released 22/04/02 E. Brigant Updated after inclusion of approved CR3BKA20CBR109079 “DCS1800-G1 multiband cells”Removal of any reference to Release B7.1

INTERNAL REFERENCED DOCUMENTS

[i2] 3BK 10204 0327 DTZZA - General handover improvements[i3] 3BK 10204 0326 DTZZA - Traffic management in handover algorithms[i4] 3BK 10204 0363 DTZZA - Improvements in radio channel selection[i5] 3BK 10204 0364 DTZZA - Controlled handover in multilayer/multivendor environment[I6] 3BK 10204 0165 DRZZA - External directed retry[i7] 3BK 10204 0481 DRZZA - Indoor layer support[i8] 3BK 10204 0475 DRZZA - Instantaneous peaks management[i9] 3BK 10204 0479 DTZZA - Adaptive multirate speech codec

[i10] 3BK 10204 0477 DTZZA - Anti ping-pong improvements[i11] 3BK 10204 0484 DTZZA - Multiband cell improvements[i12] 3BK 10204 0469 DTZZA - Telecom improvement[i13] 3BK 10204 0478 DTZZA - Tandem free operation


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[i14] 3BK 10204 0519 DTZZA - E-GSM support[i15] 3BK 10204 0547 DTZZA - Support of the GSM 850 MHz band

FOR INTERNAL USE ONLY

By derogation to the QS recommendation (see document 8BL 14106 0000 BGZZA - TDdocumentation layout) more than 3 levels used in the table of contents with agreement of the PQE.

END OF DOCUMENT


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SYSTEM FUNCTIONAL BLOCKS

TABLE OF CONTENTS

HISTORY.......................................................................................................................................... 2

REFERENCED DOCUMENTS.......................................................................................................... 2

RELATED DOCUMENTS ............................................................................................................... .. 2

PREFACE......................................................................................................................................... 2

1. SCOPE ...................................................................................................................................... 7

2. FUNCTIONAL DESCRIPTION ................................................................................................... 72.1 Overview ........................................................................................................................... 72.2 Cell configuration........................................................................................................... .. 7

2.2.1Cell Environments ...................................................................................................... 72.2.1.1 ........................................................................... Conventional cell environment 82.2.1.2 ............................................................................. Hierarchical cell environment 112.2.1.3 ................................................................................ Multiband cell environment 12

2.2.2Cell profiles .............................................................................................................. 132.3 Handover preparation .................................................................................................... 18

2.3.1Functional entities of handover preparation .............................................................. 182.3.2Specific cases of application..................................................................................... 192.3.3Handover detection .................................................................................................. 19

2.3.3.1 .......................................................................... Emergency intercell handovers 212.3.3.1.1 ....................................Quality and Level causes (Causes 2, 3, 4, and 5) 212.3.3.1.2 ............................................. Too long MS-BS distance cause (Cause 6) 212.3.3.1.3 .......................................... Too short MS-BS distance cause (Cause 22) 222.3.3.1.4 ........................Handovers specific to micro cells (Causes 7, 17, and 18) 22

2.3.3.2 ..................................................................Better conditions intercell handovers 222.3.3.2.1 ..............................................................Power budget cause (Cause 12) 222.3.3.2.2Inter-layer handovers based on MS speed discrimination (Causes 12 and 14) 232.3.3.2.3 ............................................................Preferred band cause (Cause 21) 242.3.3.2.4 ....................................................................Traffic handover (Cause 23) 252.3.3.2.5 .....................................................General capture handover (Cause 24) 252.3.3.2.6 ............................................................. Fast traffic handover (Cause 28) 25

2.3.3.3 .......................................................................... Emergency intracell handovers 252.3.3.3.1 Interference or low level intracell handovers (Causes 10, 11, 15, and 16) 26

2.3.3.4 ..................................................................Better conditions intracell handovers 262.3.3.4.1 ...................................Better conditions interzone handovers (Cause 13) 26

2.3.3.5 ...........................................................................Channel adaptation handovers 262.3.3.5.1 ................................................HR-to-FR channel adaptation (Cause 26) 272.3.3.5.2 ................................................FR-to-HR channel adaptation (Cause 27) 27

2.3.3.6 .....................................................................Resource management handovers 272.3.4Handover candidate cell evaluation.......................................................................... 28

2.3.4.1 .......................................Cell ordering according to target layer and target band 282.3.4.2 .................................................................................................Filtering process 282.3.4.3 ........................................................................................Candidate cell ranking 28

2.3.5Inhibition of handover ............................................................................................... 292.3.6Functional diagram of Handover preparation ............................................................ 31

2.4 Directed retry preparation .............................................................................................. 362.4.1System aspects ........................................................................................................ 362.4.2Functional description............................................................................................... 362.4.3Directed retry on handover alarms............................................................................ 362.4.4Forced directed retry ................................................................................................ 372.4.5Inhibition of directed retry ......................................................................................... 37


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3. DYNAMIC BEHAVIOUR .......................................................................................................... 393.1 Functions linked to handover prep aration ................................................................... 39

3.1.1Biband mobile stations ............................................................................................. 393.1.2Concentric cell and multiband cell ............................................................................ 39

3.1.2.1 .................................Allocation in the inner zone in case of Normal Assignment 393.1.2.2 ..................................Allocation in the inner zone in case of incoming handover 403.1.2.3 .........................................................Handover in a concentric or multiband cell 41

3.1.3MS speed discrimination........................................................................................... 413.1.3.1 ....................................................................................................Basic principle 413.1.3.2 ....................................................................Required parameters and variables 423.1.3.3 ............................................................ Parameter initialisation and modification 43

3.1.4Load management in hierarchical environment ........................................................ 453.2 Handover preparation .................................................................................................... 47

3.2.1General .................................................................................................................... 473.2.1.1 ............................................................................. HO preparation configuration 473.2.1.2 ...............................................................HO preparation enabling and disabling 473.2.1.3 ..................................................................................... HO preparation function 47

3.2.2Handover detection .................................................................................................. 503.2.2.1 ............................................................................................... Handover causes 50

3.2.2.1.1 ........................................................................Intercell handover causes 513.2.2.1.1.1 .................................................. Emergency intercell handover causes 523.2.2.1.1.2 ...........................................Forced intercell handover cause on quality 543.2.2.1.1.3 ..........................................Better conditions intercell handover causes 553.2.2.1.2 ........................................................................Intracell handover causes 613.2.2.1.2.1 .................................................. Emergency intracell handover causes 613.2.2.1.2.2 ........................................... Better conditions intracell handover cause 623.2.2.1.2.3 ...................................................Channel adaptation handover causes 633.2.2.1.2.4 .............................................. Resource management handover cause 65

3.2.2.2 ....................................................................................Handover causes priority 683.2.2.3 .......................................................Indication of raw cell list and preferred layer 68

3.2.3HO Candidate Cell Evaluation.................................................................................. 713.2.3.1 ................................................................................................Ordering process 713.2.3.2 .................................................................................................Filtering process 753.2.3.3 ......................................................................... ORDER cell evaluation process 753.2.3.4 ......................................................................... GRADE cell evaluation process 76

3.2.4Handover alarm management .................................................................................. 783.2.4.1 .............................................Alarm filtering process based on the timer T_Filter 78

3.2.4.1.1 ...........................................................................................General case 783.2.4.1.2 ............... Specific case of resource management handovers (Cause 29) 793.2.4.1.3 ...................................Specific case of fast traffic handovers (Cause 28) 79

3.2.4.2 ............................... Alarm filtering process based on the timer T_INHIBIT_CPT 813.3 Directed retry preparation .............................................................................................. 82

3.3.1General .................................................................................................................... 823.3.1.1 ............................................... Directed retry preparation enabling and disabling 823.3.1.2 ..................................................................... Directed retry preparation function 82

3.3.2Alarm Detection........................................................................................................ 823.3.3Candidate cell evaluation ......................................................................................... 83

4. INTERFACES DESCRIPTION ................................................................................................. 853GPP interfaces/Physical interfaces ..................................................................................... 854.2 Internal interfaces .......................................................................................................... 854.3 Timers list ....................................................................................................................... 864.4 Parameters and variables list ........................................................................................ 87

4.4.1Handover ................................................................................................................. 874.4.2Directed retry............................................................................................................ 994.4.3Relationships between parameters ..........................................................................100

5. RELEASE CHANGES.............................................................................................................10 4

6. FEATURES.............................................................................................................................106


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7. GLOSSARY..................................................................................................................... .......1077.1 Abbreviat ions ................................................................................................................1077.2 Definitions ................................................................................................................. ....109


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APPENDIXES

A: Power budget equation

B: Recapitulation of the cell types a llowed for the serving and the ca ndidate cell for eachhandover cause

C: Compliancy with the 3GPP requi rements

05 22/04/02 MND/TD MND/TD/SYT04 26/10/01 MND/TD MND/TD/SYT03 09/08/01 MND/TD MND/TD/SYTED DATE CHANGE NOTE APPRAISAL AUTHORITY ORIGINATOR


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HISTORY

Release B7.2 : 3BK 11202 0297 DSZZA

Ed. 01 09/03/00 First editionEd. 02 08/01/01 Second editionEd. 03 09/08/01 Third editionEd. 04 26/10/01 Fourth editionEd. 05 22/04/02 Fifth edition

REFERENCED DOCUMENTS

3GPP references

[1] 04.08 MS-BS Layer 3 Specifications.[2] 05.08 Radio Subsystem Link Control.[3] 08.58 BSC-BTS Layer 3 specification.

Version numbers of the 3GPP Technical Specifications are given in ref [14].

Doctree references

[4] 3BK 11202 0194 DSZZA - Application document 05.xx.[5] 3BK 11202 0309 DSZZA - Radio & link establishment.[6] 3BK 11202 0286 DSZZA - Normal Assignment[7] 3BK 11202 0293 DSZZA - Radio measurements and codec adaptation.[8] 3BK 11202 0289 DSZZA - Internal channel change.[9] 3BK 11202 0290 DSZZA - External channel change.

[10] 3BK 11202 0291 DSZZA - Call release.[11] 3BK 11202 0305 DSZZA - BSS initialisation of the telecom part.[12] 3BK 11203 0062 DSZZA - BSS Telecom parameters.[13] 3BK 11202 0288 DSZZA - Handover management[14] 3BK 11203 0012 DSZZA - Alcatel BSS Application document to 3GPP - General Overview.[15] 3BK 11202 0292 DSZZA - Resource allocation and management.[16] 3BK 11202 0185 DSZZA - Extended Cell[17] 3BK 11202 0295 DSZZA - Power Control & Radio link supervision[18] 3BK 11202 0298 DSZZA - System Information management[19] 3BK 11202 0294 DSZZA - Radio Measurements Data Processing[20] 3BK 11203 0042 DSZZA - Radio link and radio resource management

[20bis] 3BK 11202 0310 DSZZA - Classmark Handling

RELATED DOCUMENTS

[21] CCITT Z100. Structured Definition Language.[22] GEODE user manual. VERILOG.[23] ART/DST/PFK/20 - ALCATEL_BSS phase 1 description of radio link control algorithms and

guidelines for setting parameters values. ART/DST/PFK/20

Note : most of the SDL diagrams have been produced with the software tool GEODE which is atrademark of VERILOG [22]. The SDL standard is defined in [21].

PREFACE

Handover

Preparation

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All rights reserved. Passing on and copying of thisdocument, use and communication of its contents

not permitted without written authorization from Alcatel

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RENVRENVRENVRENVRENVRENV

1. SCOPE

This document specifies the algorithms to be implemented in this release of the ALCATEL BSS for :- handover preparation,- directed retry preparation,

Handover preparation consists of two functions which are considered separately in this document :- detection of the need to handover a radio connection,- candidate cell list evaluation.

Directed retry preparation is specified along with handover preparation.

2. FUNCTIONAL DESCRIPTION

2.1 Overview

The main objective of the handover preparation, in connection with power control (see [17]), is toallow a maximum number of MS to operate in the network while maintaining a minimum interferencelevel. The algorithms shall ensure that any mobile is connected with the cell in which the outputpowers from the MS and the BS are as low as possible (to reduce MS power consumption andinterference in the network) while keeping a satisfactory link quality.

When on a sufficient duration the propagation conditions keep worsening, then action must be taken.The first action is to increase the output power levels at the MS or the BS (for further details, see[17]). When the maximum allowed value has been reached, a handover may become necessary.

To reflect this philosophy in macrocells (not in microcellular environment), the algorithm allows forhandover on quality and strength reasons only when the last step of power control has been reached.

Great care must be taken in choosing the relative values of the thresholds for power control andhandover as well as the averaging window sizes (smaller window size and higher threshold for powercontrol than for handover). It must be remembered that, although it is desired that the MS transmitswith the lowest possible power, it is more important not to lose a call. Thus early triggering for thepower control is possible, by choosing small values for the averaging window sizes and highercomparison thresholds.

For further description about handover preparation refer to [20].

2.2 Cell configuration

2.2.1 Cell Environments

Three types of cell environments are supported : conventional cell environment, hierarchical cellenvironment and multiband cell environment.In the conventional cell environment, the cell planning is made so as to obtain a continuousgeographical coverage .The hierarchical cell environment corresponds to a layout of three cell layers with different cell sizes.The larger outdoor cells layer is called "upper layer", the smaller outdoor cells layer "lower layer", andthe indoor cell layer “indoor layer”. This environment is meant to be used in advanced networks.

The interest of the indoor cell layer is to:

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- ensure a better radio coverage inside large buildings such as hotels, shopping malls, andcorporate centers,

- unload the outdoor cells which are accessible from these buildings.

The interest of the lower cell layer is twofold:- densify the traffic by providing a smaller frequency reuse distance in the lower layer- compensate traffic density unbalance by using small cells located at traffic "hot spots"

The interest of the upper cell layer is to :- provide continuous geographical coverage- handle fast moving mobiles in order to avoid high handover rate- provide overflow and rescue channels for the lower and indoor cell layers

Reflecting this representation, the upper layer cells are often called "umbrella cells".

In a multiband network environment, the above three layers available for one frequency band can beduplicated for the other frequency band so as to form a multiband network composed of six layers:

− DCS upper layer and GSM upper layer,− DCS lower layer and GSM lower layer,− DCS indoor layer and GSM indoor layer,

where GSM stands for GSM900 or GSM850 bands and DCS stands for DCS1800 or DCS1900bands.The interest of the multiband network is to increase the capacity or the coverage of thenetwork.

2.2.1.1 Conventional cell environment

Four different layouts are provided for conventional cell environment , in order to adapt to the trafficdensity :

- single cellFigure 1 represents the possible geographical layouts with single cells.

- concentric cell : a macrocell with two frequency groups covering two concentric zones. Thisallows to use a smaller reuse distance for the inner zone frequencies and hence to densify anexisting network by introducing a small number of frequencies at the needed places.Figure 2 shows the smaller reuse factor (here 3) for the inner zone frequencies in a traditional 9cell cluster.

- multiband cell : a concentric cell in which:the outer zone, that includes the BCCH, the SDCCH and several TCH channels, will usefrequencies from the classical band.The inner zone, that includes only TCH, will all use frequencies from the preferred band. Amonoband MS has only access to the outer zone, whereas a biband MS (or a biband and E-GSMMS in the case of a EGSM-DCS1800 muliband cell where there is only G1 TRXs in the innerzone), which supports both the frequency band of the outer zone and of the inner zone, has accessto both the inner and the outer zones.

- extended cell where two cells with collocated antennas provide coverage up to 70 km. Theapplication fields are both the low density areas and the off-shore coverage for coastal radiocommunications.Figure 3 and Figure 4 illustrate the layout of two associated cells making an extended cell. Forreference information on that feature, see [16].

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sectorized cell for site reductionomnidirectional macrocell

Figure 1: Normal cell environment with one cell layer.

f1

f1

f3

f2

f2

f3

f3 f1

f2

Inner zone

Outer zone

One concentric cell

Figure 2: Concentric cell frequency planning.


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Figure 3: Extended cell with directionalantennas.

inner cell

outer cell

50 km radius

outer limit

inner limitouter limit

Figure 4: Extended cell with omnidirectionalantennas.

outer cell

innercell

Highway

70km

35 km


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2.2.1.2 Hierarchical cell environment

In much denser traffic areas, depending on the required traffic capacity, the operator may wish tohave a hierarchical network, where continuous coverage is provided by a standard macrocell, andtraffic hot spots are covered with dedicated cells of limited range.The solution for medium density areas is to have small macrocells (called mini cells) , to handlepedestrian traffic, overlapped with one big umbrella macrocell , to handle fast moving mobiles.The solution for higher traffic densities will be to install microcells in all the streets where verydense traffic occurs, and to deploy indoor cells inside high traffic buildings. Umbrella macrocellswill be providing the continuous coverage and the traffic channels for saturated microcells and"emergency" handovers.

- mini cells with umbrella macrocells

This configuration will be of main interest for dense urban areas where some hot-spots arecovered by very small macrocells (less than 500 m radius) and continuous coverage is providedby a big macrocell (5 to 10 km radius).Figure 5 presents a possible application of the two-layer hierarchical network with macrocells forboth layers, in a middle size town.

Super umbrella cellR~10 km

mini cells0.5<R<1 km

pedestrian area

Figure 5: Cell layout with mini cells below one umbrella cell

- microcells with umbrella cells

One layout is provided for microcellular applications, that should apply to very highly dense trafficareas or when the available spectrum is very reduced. Figure 6 presents the cell layout formicrocells covered by an umbrella cell to provide continuous coverage and decreased blockingrate.The densification strategy for microcellular enables to use the already existing macrocell layer forthe umbrella cells.Therefore, it may be possible for the operator to use already installed single (or concentric ormultiband) cells as umbrella cells for a microcellular network.

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existing cells1<R<2 km

microcellsR < 300 m

Figure 6: Typical microcellular layout

- indoor cells with lower l ayer cells and umbrella cells

In high traffic buildings, it is of main interest to install indoor cells. The addition of the indoor cellsallows to unload the existing micro and umbrella outdoor cells and to ensure a better radiocoverage inside buildings. Figure 7 shows an example of a cellular network including the indoorlayer cells.

Umbrella cell 1800

Umbrella cell 900

Micro cell 1800Micro cell 900



Lower layer

Indoor cell 1800

indoor cell 900

Inside buildin gs

Upper l ayer

Indoor laye r

Figure 7: Typical cellular network using three cell layers and two frequency bands.

2.2.1.3 Multiband cell environment

An operator with licenses in the different frequency bands (GSM900 and DCS1800) can mix in itsnetwork cells which use GSM frequency band with cells using DCS frequency band. This case isreferred to as multiband cell environment. In the Alcatel BSS, the multiband cells using the GSM850band or the DCS 1900 band are not supported.

Multiband cell environment is supposed to be made out of a main part with cells of same frequencyband. This band is the oldest one acquired by the operator and it is the most used in its network : it iscalled the classical band.

With the other new frequency band, the operator will add new cells to its network. These cells will bedeployed either to extend the coverage of the existing network or to increase the traffic capacity ofthe network rather than to improve the coverage.

When the operator cell deployment strategy is to increase the capacity of its network, the bibandmobiles (mobiles with capability in both frequency bands) are preferentially directed towards the new

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cells which use the frequency band different from the classical one. That is why this band is calledthe preferred band.

Multiband cell environment can be applied to conventional cell environment as well as hierarchicalcell environment. In this last case, the multilayer structure will interact with the multiband concept.

2.2.2 Cell profiles

The optimisation of the use of the frequency resources is a main concern for network operators.The Alcatel BSS provides a span of cell environments that allows to cover the whole range of trafficdensity requirements : from very dense urban centres with microcells up to very low traffic areas(desert or off shore) with extended cell sites.These different types of cell environment must be controlled and administered in a flexible way by theoperator.For this purpose, the Alcatel BSS provides a set of cell profiles, which enable the operator to make astarting point configuration by just applying the default values of the profile. Each profile provides allthe configuration data associated to one given cell as default settable values. This includes handoverparameters, but also power control settings, timers .

Nine main monoband profiles are defined : single cell, micro cell, mini cell, umbrella cell, extendedinner cell, extended outer cell, concentric cell, concentric umbrella cell, and indoor micro cell. Theseprofiles are duplicated by the internal parameter cell_band_type which can have two different valuesfor each profile. In order to give the operator the possibility to have its personal usage of theALCATEL parameters, the profiles are user-editable. This means that all default values associated toone given profile can be modified to reflect the standard usage of the operator.

These cell profiles correspond to one unique combination of the five parameters :- Cell dimension type : this parameter identifies the cell size in a finite set of cell dimensions(macro or

micro).- Cell layer type : this parameter defines the layer type of a cell in connection with other cells and with

itself. In single layer cell environment, all cells have the same layer type (single). In a hierarchicalcell environment, three cell layer types distinguish the upper layer cells, the lower layer cells, andthe indoor layer cells.

- Cell_partition type : this parameter defines the type of frequency partitioning that is used in the cell.- Cell range : this parameter identifies the cell as a normal cell or a part of an extended cell- Cell_band_type : this parameter defines the type of frequency band used in the cell

The first three parameters are settable on a per cell basis and changeable on-line by O&M.The cell_range parameter is set at BTS initialisation time and only changeable off-line.Cell_band_type is an internal parameter derived from the BCCH frequency of the serving cell(BCCH_FREQUENCY) or from the BCCH frequency of the neighbour cells n(BCCH_FREQUENCY(n)), reported by the mobile.

Cell dimension typeTwo values are possible : ### Macrocell.

### Microcell.

Cell layer typeFour values are possible (See Figure 8):

### Single : this applies to all cells in normal environment (1 cell layer)### Upper : this indicates the upper layer cells in a hierarchical cell

environment with two or three layers. These cells are also called "umbrellacells" and they will have at least one associated lower or indoor layer cell,otherwise they are single cells.

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### Lower : this indicates the lower layer cells in a hierarchical cellenvironment with two or three layers. Each lower layer cell will have oneassociated umbrella cell, otherwise it is deemed "single".

### Indoor : this indicates the indoor layer cells in a hierarchical cellenvironment with two or three layers. Each indoor layer cell will have oneassociated umbrella cell, otherwise it is deemed "single".

A single cell has no cells included within its coverage area.

Cell partition typeTwo values are possible : ### Normal partition.

### Concentric partition.

The concentric partition corresponds to the concentric or multiband cell case. In this case, thefrequency carriers are assigned to one or the other of the two concentric zones : inner and outer.

Cell rangeThree values are possible : ### Normal

### Extended inner### Extended outer

Cell band typeTwo values are possible : ### GSM

### DCS

Cell_band_type is an internal parameter whose value depends on the BCCH frequency of the servingcell (BCCH_FREQUENCY) or on the BCCH frequency given by the mobile for every reportedneighbour cell (BCCH_FREQUENCY(n), refer to [19]).

For the serving cell :

Cell_band_type = GSM if BCCH_FREQUENCY is in the P-GSM or GSM850 frequency band.Cell_band_type = DCS if BCCH_FREQUENCY is in the DCS1800 or DCS1900 frequency band.

For neighbour cell n :

Cell_band_type(n) = GSM if BCCH_FREQUENCY(n) is in the P-GSM or GSM850 frequencyband.Cell_band_type(n) = DCS if BCCH_FREQUENCY(n) is in the DCS1800 or DCS1900 frequencyband.

Note : the correspondence between the neighbour cell index and the frequency band of theneighbour cell n is performed through the neighbour cell list (for further details see [18]).


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Single layer cell

Lower layer

Upper layerUpper layer cell Upper layer cell Upper layer cell

Lower layer cell

Indoor layer cell

Lower layer cell

Indoor layer cell Indoor layer

One layer configuration Two layers configuration Three layers configuration

Figure 8: Allowed one, two and three layers configurations.

Cell configurationIn the following "Cell configuration" will refer to the combination of the five parameters :- Cell dimension type,- Cell layer type,- Cell partition type,- Cell range,- Cell band type.

The frequency range supported by the cell is indicated by the parameter FREQUENCY_RANGE. Theallowed ranges are PGSM, EGSM, DCS1800, DCS1900, and GSM850 for monoband cells, andPGSM-DCS1800 or EGSM-DCS1800 for multiband cells. The term “E-GSM” is used for the wholeGSM-900 frequency band, i.e. the primary band (890-915 MHz / 935-960 MHz) plus the extensionband G1 (880-890 MHz / 925-935 Mhz). The term “G1” is used for the extension band, whereas theterm “P-GSM” is used for the primary band. In the following, a cell supporting only the E-GSM band,i.e. the P-GSM and G1 bands, is never referred to as a multiband cell.

In this release of the ALCATEL BSS, all the possible monoband cell configurations are given in Table1. In the first column “Cell Profile” of Table 1, the term GSM stands for the GSM900 or GSM850 bandand the term DCS for the DCS1800 or DCS1900 band depending on thePLMN_FREQUENCY_BANDS parameter. All the other monoband cell configurations are forbiddenas they are not relevant for operation.The O&M functions shall ensure that the cell configurations managed by the handover preparationare authorised. The selection of one given cell profile for applying default values will force the valueof the cell configuration.

In monoband cells, the frequency range parameter FREQUENCY_RANGE can be set to PGSM,EGSM, DCS1800, DCS1900, or GSM850. If the parameter FREQUENCY_RANGE equals to PGSMEGSM, or GSM850 the cell band type is GSM. If the parameter FREQUENCY_RANGE equals toDCS1800 or DCS1900, the cell band type is DCS.

Cell Profile Celldimension

type

Celllayertype

Cellpartition

type

Cell range Cellbandtype

Frequencyrange

GSM single cell Macro Single Normal Normal GSM PGSM,EGSM, orGSM850

DCS single cell Macro Single Normal Normal DCS DCS1800 orDCS1900

GSM micro cell Micro Lower Normal Normal GSM PGSM,EGSM, orGSM850

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DCS micro cell Micro Lower Normal Normal DCS DCS1800 orDCS1900

GSM mini cell Macro Lower Normal Normal GSM PGSM,EGSM, orGSM850

DCS mini cell Macro Lower Normal Normal DCS DCS1800 orDCS1900

GSM umbrella cell Macro Upper Normal Normal GSM PGSM,EGSM, orGSM850

DCS umbrella cell Macro Upper Normal Normal DCS DCS1800 orDCS1900

GSM extended inner cell Macro Single Normal Extended-inner GSM PGSM,EGSM, orGSM850

DCS extended inner cell Macro Single Normal Extended-inner DCS DCS1800 orDCS1900

GSM extended outer cell Macro Single Normal Extended-outer GSM PGSM,EGSM, orGSM850

DCS extended outer cell Macro Single Normal Extended-outer DCS DCS1800 orDCS1900

GSM concentric cell Macro Single Concentric Normal GSM PGSM,EGSM, orGSM850

DCS concentric cell Macro Single Concentric Normal DCS DCS1800 orDCS1900

GSM concentric umbrella Macro Upper Concentric Normal GSM PGSM,EGSM, orGSM850

DCS concentric umbrella Macro Upper Concentric Normal DCS DCS1800 orDCS1900

GSM indoor micro cell Micro Indoor Normal Normal GSM PGSM,EGSM, orGSM850

DCS indoor micro cell Micro Indoor Normal Normal DCS DCS1800 orDCS1900

Table 1: Allowed monoband cell configurations.

Cell Profile Celldimension

type

Celllayertype

Cellpartition

type

Cellrange

Cellbandtype

Frequencyrange

GSM900 multiband single cell Macro Single Concentric Normal GSM PGSM-DCS1800 orEGSM-DCS1800

DCS1800 multiband single cell Macro Single Concentric Normal DCS PGSM-DCS1800 orEGSM-DCS1800

GSM900 multiband micro cell Micro Lower Concentric Normal GSM PGSM-DCS1800 orEGSM-DCS1800

DCS1800 multiband micro cell Micro Lower Concentric Normal DCS PGSM-DCS1800 orEGSM-DCS1800

GSM900 multiband mini cell Macro Lower Concentric Normal GSM PGSM-DCS1800 orEGSM-DCS1800

DCS1800 multiband mini cell Macro Lower Concentric Normal DCS PGSM-DCS1800 orEGSM-DCS1800

GSM900 multiband umbrella cell Macro Upper Concentric Normal GSM PGSM-DCS1800 orEGSM-DCS1800


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DCS1800 multiband umbrellacell

Macro Upper Concentric Normal DCS PGSM-DCS1800 orEGSM-DCS1800

GSM900 multiband indoor microcell

Micro Indoor Concentric Normal GSM PGSM-DCS1800 orEGSM-DCS1800

DCS1800 multiband indoormicro cell

Micro Indoor Concentric Normal DCS PGSM-DCS1800 orEGSM-DCS1800

Table 2: Allowed multiband cell configurations.

A multiband cell is declared by setting the FREQUENCY_RANGE to either PGSM-DCS1800 orEGSM-DCS1800. The CELL_PARTITION_TYPE of the cell is then forced to CONCENTRIC. Theallowed cell profiles for multiband cells are given together within Table 2.

Note : - The duplication of the main profiles according to the values of the cell band type isperformed for every main profile. It gives a few cell profiles not really relevant (such as DCSextended outer cell profile) but it prevents from dealing with exceptions.

Figure 9 depicts the outdoor monoband configurations of Table 1 for cell_range = normal and withdifferent values of cell band type. In Figure 9, GSM stands for GSM900/GSM850 and DCS forDCS1800/DCS1900.

Cell_dimension type : macroCell_layer_type : upperCell_partition_type : concentricCell_band_type : GSM

Cell_dimension type : macroCell_layer_type : upperCell_partition_type : normalCell_band_type : GSM

Cell_dimension type : macroCell_layer_type : singleCell_partition_type : concentricCell_band_type : DCS

Cell_dimension type : macroCell_layer_type : lowerCell_partition_type : normalCell_band_type : GSM

Cell_dimension_type : macroCell_layer_type : singleCell_partition_type : normalCell_band_type : DCS

Cell_dimension type : microCell_layer_type : lowerCell_partition_type : normalCell_band_type : DCS

Figure 9: Allowed outdoor monoband cell configurations for cell_range = normal and different valuesof cell band type. The indoor micro cells are not represented here.

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2.3 Handover preparation

This function can also be named "handover algorithms" as the algorithms described in section 3 arethe "heart" of this function. In the following the word "handover preparation" will be preferred to"handover algorithms".

The ALCATEL handover preparation is derived from the basic algorithm found in Annex A of the3GPP Technical Specification 05.08 [2]. The main differences between both algorithms are describedin [4].

2.3.1 Functional entities of handover prep aration

The handover preparation is in charge of detecting a need for handover and proposing a list of targetcells. Therefore it can be divided into two processes : handover detection and handover candidatecell evaluation .

The handover detection process analyses the radio measurements reported by the BTS and thepossible alarms sent by RAM. Then, the candidate cell evaluation process is started each time ahandover cause (emergency or better conditions type) is fulfilled.

The handover candidate cell evaluation works out a list of possible candidate cells for the handover.

This list is sorted according to the evaluation of each cell as well as the layer they belong to (in ahierarchical network) and the frequency band they use (in a multiband network).Once the handover preparation is completed, the handover decision and execution (handovermanagement entity refer to [13]) is performed under the MSC or BSC control. The directed retrypreparation (see definition in section 2.4) is performed by the handover preparation function.

Once the directed retry preparation is completed, the directed retry is performed either under the BSCcontrol (internal directed retry) or under the MSC control (external directed retry). These proceduresuse signalling protocols described respectively in [8] and [9].

An example of implementation of these functions except for directed retry is given in the 3GPPTechnical Specification 05.08 [2].

The handover preparation requires indirectly (see below) input parameters provided by the function incharge of the radio link measurements. This function is described in [7].

Most of the input data required by the handover functions are provided by a function called : Activechannel pre-processing . This function is described in [19]. It processes raw data given by the radiolink measurements (quality, level and distance) through the A-bis interface in compression mode ornon compression mode. The compression mode uses two functions: Radio measurements datacompression in the BTS and Radio measurements data decompression in the BSC. They aredescribed in [19].

The functions handover detection and handover candidate cell evaluation are specified in thisdocument.

Figure 10 depicts in a general way :- the interconnections between these functions,- the implementation of these functions in the ALCATEL BSS. The functions which are specified inthis document are represented in bold type.

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BTS BSC

MSC

RadiolinkMeasurements

ActiveChannelPreprocessing

HOdetection

HOcandidatecellevaluation

HOmanage-ment

BTS

RadioMeasurementsData Compression

RadioMeasurementsData Decompression

EN_MEAS_COMPRESSION

YES

NO

Figure 10: Assignment of HO functions in the ALCATEL BSS.

2.3.2 Specific cases of a pplication

The handover preparation applies both for TCH and SDCCH , i.e. it uses the same messages andparameters. Whenever a different handling is necessary, it is indicated in the text. These few casesare :- counting of free channels and load of cells (See [15]),- number of frames in reporting period (102 for SDCCH, 104 for TCH),- weighting in case of DTX on TCH/FS. DTX is not allowed on SDCCH (refer to [19]).- inhibition of SDCCH handover when SDCCH_COUNTER is running (see section 3.2.1.2).- inhibition of better conditions intercell handovers from SDCCH to SDCCH except for the causepower budget (see section 3.2.2.1.1.3). In case of directed retry from SDCCH to TCH on handoveralarms the better conditions intercell handover causes are not inhibited (except Cause 28).

2.3.3 Handover detection

The handover detection process is achieved in the BSC. Its role is to detect the need for handovers.Four families of handovers are defined in order to ease the presentation of the handover detectionprocess:− Emergency handover family: The emergency handovers are triggered in a situation of

emergency. The triggering is based on the radio measurements made by the MS and the BTS.− Better conditions handover family: When better radio conditions are detected, a better conditions

handover is triggered. The triggering is based on the radio measurements made by the MS andthe BTS.

− Channel adaptation handover family: The channel adaptation handovers are triggered to adaptthe channel rate to the voice quality of the communication. The triggering is based on the radiomeasurements made by the MS and the BTS.

− Resource management family: The resource management handovers are triggered when ahandover request is sent by RAM to HOP [15].

For the handovers based on the radio measurements, each time a set of preprocessed (averaged)measurements is available, the HO detection process checks whether a handover is needed or not. Ifthe need for a handover is detected, the target cell evaluation process is triggered. The need forhandovers often comes to compare a predefined threshold with a radio measurement. That is whythis process is sometimes called ‘HO threshold comparison’.

In case of an intercell handover alarm, the handover detection process gives to the cell evaluationprocess :

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- the preferred target cell layer : indoor, lower, upper or none- the raw candidate cell list, which can be either all neighbours, or the subset which verify thehandover causes (plus other specific cells in particular cases). With each cell is given one of thehandover causes which have been verified.

Depending of the context of application, the emergency and better conditions HOs can be eitherintercell or intracell HO. Six HO categories are then defined as shown in Table 3.


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Context of application →

↓ Handover family

Intracell HO Intercell HO

Emergency HO Emergency intracell HO Emergency intercell HO

Better conditions HO Better conditions int racell HO Better c onditions int ercell HO

Channel adaptation HO Channel adaptation HO N/A

Resource management HO Resource management HO N/A

Table 3: Main categories of handover

The detection of a need for handover is performed through handover causes which are going to bedetailed. In what follows, each cause is thus identified with a number. The following sections detailthe different categories of handover according to the context of application (intercell or intracell) andthe handover cause.

2.3.3.1 Emergency intercell ha ndovers

These handovers are triggered when the call conditions deteriorate significantly in order to rescue thecall. The handover causes concerned are listed in Table 4.

Handover Cause Cause NumberToo low quality on the uplink Cause 2Too low level on the uplink Cause 3Too low quality on the downlink Cause 4Too low level on the downlink Cause 5Too long MS-BS distance Cause 6Too short MS-BS distance Cause 22Consecutive bad SACCH frames received in a microcell Cause 7Too low level on the uplink in a microcell compared to a high threshold Cause 17Too low level on the downlink in a microcell compared to a high threshold Cause 18

Table 4: Emergency intercell handover causes.

2.3.3.1.1 Quality and Level causes (Causes 2, 3, 4, and 5)

The aim of these causes is to keep the call going when the radio link is degrading otherwise the radiolink failure might be detected and the call released. These causes wait generally for the power controlprocess to increase the BS and MS power to their maximum values.

Handover on "too low level" is used to avoid situations where the interference level is low, while theattenuation is quite high. These conditions may appear for example in big city streets which enable aline of sight propagation from the BTS antenna. There is in this case a risk of abrupt qualitydegradation, if the MS moves away from the line of sight street.

In case of simultaneous low-level low-quality signals, an intercell handover is requested.

2.3.3.1.2 Too long MS-BS distance cause (Cause 6)

This cause is used when a dominant cell provides a lot of scattered coverages inside other cells, dueto propagation conditions of operational network. These spurious coverages have the consequenceof producing a high level of co-channel interference probability ([23]).

This cause is different from the others as it is more preventive. It does not make use of thepropagation conditions of a call. It just does not allow a MS to talk to a BS if it is too far away.

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为什么不把这4个Cause合为一个？我的理解是上行和下行要分开，因为涉及到BS或MS进行PC的问题。那为什么把电平和质量分开，是因为如果只有质量差，还要分小区内的和小区间的。只有电平和质量都差的情况下才触发小区间的。


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It may happen for example that some peculiar propagation conditions exist at one point in time thatprovide exceptional quality and level although the serving BS is far and another is closer and shouldbe the one the mobile should be connected with if the conditions were normal.

It may then happen that these exceptional conditions suddenly drop and the link is lost which wouldnot have happened if the mobile had been connected to the closest cell. For these reasons also, thiscause does not wait for the power control to react.

2.3.3.1.3 Too short MS-BS distance cause (Cause 22)

The too short MS-BS distance handovers are introduced to detect when a MS that is located in anextended outer cell reaches the inner/outer extended cell limit and requires to be handed overtowards the extended inner cell. Therefore, it is only valid when the MS is in an extended outer cell.The case the MS is in the extended inner cell and requires to be handed over the extended outer cellcan be performed by using the handover Cause 6.

2.3.3.1.4 Handovers specific to micro cells (Causes 7, 17, and 18)

In a microcellular network, the radio propagation conditions vary so fast that the handover requires tobe triggered without waiting for the action of the power control process. An example of thisphenomena is the street corner effect.

The handovers Cause 7 come to check if the last consecutive SACCH frames have been correctlyreceived. The handovers Causes 17 and 18 are triggered when the level of the received signal isbelow a certain threshold. These latter causes are sometimes called “level dropping under highthreshold”.

2.3.3.2 Better conditions int ercell ha ndovers

Better conditions intercell handovers are triggered to improve the overall system traffic capacity. Thisspans : interference reduction, signalling load reduction, traffic unbalance smoothing. The basicassumption for these handovers is that they should respect the cell planning decided by the operator.The better conditions intercell handover causes are listed in Table 5.

Handover Cause Cause NumberPower budget Cause 12High level in neighbour lower or indoor cell for slow mobile Cause 14High level in neighbour cell in the preferred band Cause 21Traffic handover Cause 23General capture handover Cause 24Fast traffic handover Cause 28

Table 5: Better conditions intercell handover causes.

The main drawback of this handover category is the risk of "ping-pong " effect , which is an oscillatingback and forth handover between two (or three) cells. As the "better conditions intercell" handover aremeant to find the "best cell", the variation of the radio conditions will trigger a big amount of betterconditions intercell handovers, if the algorithms have a too sensitive reaction. Hence, somemechanisms are forecast, in order to prevent these oscillations from occurring repeatedly at givenplaces.

2.3.3.2.1 Power budget cause (Cause 12)

In this case, there is another cell with a better power budget i.e. the link quality can be improved ormaintained with a reduced transmission power of both the MS and the BTS. The radio link is notdegraded but there is the opportunity to decrease the overall interference level by changing theserving cell of the given MS.In conjunction with power control it presents the advantage to keep the interference as low aspossible, since it minimises the path loss between the BTS and MS.

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This cause is especially designed to cope with the requirement that the mobile should be connectedwith the cell with which the lowest possible output powers are used. To assess which of the cells isthis "best cell", the algorithm performs every measurement reporting period the comparison of thepath loss in the current and in the neighbour cell. This is a feature special to 3GPP standard which ismade possible because the mobile measures the adjacent cell signal levels and reports the six bestones.

The power budget calculation is described in details in appendix A.This power budget gives the difference in path loss between the current cell and the adjacent cellsreported by the mobile.When PBGT(n) is greater than 0, then the path loss from cell n is less than the path loss from theserving cell and thus the radiated power in the downlink direction, and therefore in the uplinkdirection as well, will be lower in cell n than in the current cell.

However it would not be advisable to hand over the MS to another cell as soon as PBGT is greaterthan 0, because the MS would probably oscillate between the two adjacent cells as the propagationconditions vary. A hysteresis mechanism is implemented to avoid this undesirable effect.

The MS may be handed over from the serving cell indexed 0 to a neighbour cell indexed n only if thepower budget exceeds the handover Margin(0,n). The handover Margin(0,n) can be modifiedaccording to the traffic situation in the serving cell and the neighbour cell n. In this way, power budgethandover can be delayed towards a loaded cell and traffic load handover can be triggered from aloaded cell (see section 2.3.3.2.4.). Once the MS is handed over, the same algorithm is applied in thenew cell, and a new PBGT is computed (which will be close to the opposite value of PBGT in the oldcell) and compared to a new HOMargin. (Thus, the global hysteresis (from cell 0 to cell n and back tocell 0) is the sum of the two HOMargins).

However, It is still possible that a ping-pong mechanism is created by different handover causes, forinstance a handover may be triggered towards a neighbour cell for bad quality, but in the neighbourcell, a handover back may be triggered for power budget reasons. In order to avoid this, an additionalanti-ping-pong mechanism is implemented in the power budget calculation. It enables to penalise fora certain time the cell on which the call has precedently been (see Appendix A).

In case of handover from SDCCH to SDCCH, this cause does not take the traffic situation intoaccount.

In multiband cell environment, the mobile can operate in a different band than the frequency band ofthe BCCHs. This can lead to circular ping-pong handovers from the inner zone if the new band isDCS 1800 or to the impossibility to trigger PBGT handovers from the inner zone if the preferred bandis GSM 900.To avoid this problem, when the MS is in the inner zone of a multiband cell, it may be handed overfrom the serving cell indexed 0 to a neighbour multiband cell indexed n only if the power budgetexceeds the handover Margin(0,n) plus the offset handover margin which allows to handicap orfavour the PBGT (In the inner zone, the cause “power budget” is only checked between multibandcells, in a way to maintain the MS in the preferred band).The offset handover margin can possibly be used in concentric cells.

In some specific network, the operator may have two different frequency band areas in its network,the first one using the classical frequency band cell (e.g. GSM900 or GSM850), and the second oneusing the new frequency band (e.g. DCS1800 or DCS1900). At the border of these two areas,handovers based on a power budget comparison are required so as to approach the behaviour ofpower budget handovers between cells having the same frequency band. These handovers areallowed by setting the specific flag EN_MULTIBAND_PBGT_HO defined on a per cell basis at theOMC. Only biband MS can perform these multiband power budget handovers.

2.3.3.2.2 Inter-layer ha ndovers based on MS speed discrimination (Causes 12 and 14)

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In a hierarchical cell environment, the following types of inter-layer handovers based on the MSspeed discrimination can be triggered (See Figure 11):

− Handovers from an indoor layer cell to an upper layer cell,− Handovers from a lower layer cell to an upper layer cell,− Handovers from an upper layer cell to an lower layer cell,− Handovers from an upper layer cell to an indoor layer cell,− Handovers from a lower layer cell to an indoor layer cell.

Upper layer cell

Lower layer cell

Indoor layer cell

HO Cause 14and MS_SPEED = slow

HO Cause 14and MS_SPEED = slow or indefinite

HO Cause 12and MS_SPEED = fast

Figure 11: Interlayer handovers based on the MS speed discrimination.

The MS speed is estimated from the measure of the residence time of the MS in the indoor and lowerlayer cells. If this residence time is shorter than a certain threshold, the MS is deemed to move fast.On the other hand, if the residence time is higher that another threshold, the MS is deemed to moveslowly.

A MS which moves fast in a lower or indoor layer cell is preferentially handed over to an upper layercell, i.e. an umbrella cell, so as to limit the repetition of intra-layer handovers that would haveoccurred if the MS were stayed in the same layer cells. This has also the advantage of reducing thesignalling generated by the repetitive intra-layer handovers. In such a situation, the power budgetcause (Cause 12) associated with the MS speed measure is employed to trigger a handover from alower or indoor layer to an upper layer.

The frequencies on the upper layer can not be reused within a small range and will therefore be acritical resource in hierarchical cell structures. Therefore, the load of the umbrella cell may be acritical problem and a mechanism is required to stop handovers into the upper layer when it becomesoverloaded. That is why the estimation of the MS speed and the calculation of the power budgetPBGT(n) depend on the load of the upper layer cells.

Another advantage of the hierarchical cell structure is that the umbrella cell can offer a number ofoverflow channels, for calls which are queued in the lower or indoor layers (see directed retry Section2.4). This allows a much better usage of the traffic capacity of the lower or indoor layers cells,especially when they have only 1 or 2 TRX. This is a second reason why the upper layer cells shouldnot be overloaded.

In order to unload the umbrella cells, the MS that moves slowly in an upper layer cell must be handedover the lower or indoor layers cells. Without such an handover, the GSM Phase 1 slow moving MScan connect to the upper layer cell, and can stay in this layer even if the MS do not move at all. Thehandovers (Cause 14) from an upper layer cell to an indoor or lower layer cell allow to capture theslow mobile.

When a MS moves slowly in a lower layer cell and receives a good signal from a neighbour indoorlayer cell, the MS will be captured by the indoor layer cell with Cause 14. This type of capture allowsto unload the lower layer cell.

Cause 14 is inhibited for handover from SDCCH to SDCCH.

2.3.3.2.3 Preferred band cause (Cause 21)


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If two frequency bands (either GSM900 and DCS1800 bands, or GSM850 and DCS1800 bands, orGSM850 and DCS1900 bands) coexist in the same network, an operator can define a preferred band(PREFERRED_BAND parameter adjustable on a per BSS basis) where the biband mobiles (mobileswith the both frequency bands capability) should be transferred in case of too much traffic load in theclassical band (the opposite of the preferred band) and no high load in the preferred band.

This is achieved by monitoring the traffic load of the cells which use the classical band and thepreferred band. If a biband mobile is connected to a cell in the classical band where a specificcondition on the traffic load is verified, and if this mobile receives good signal level from oneneighbour cell which uses the preferred band and where the traffic load is considered as not high, thepreferred band cause will be verified for this mobile.

Then, an intercell multiband handover will be performed towards the neighbour cell. The onlyrequirement for this handover is that the serving cell uses the classical band and the target cell, thepreferred band.This cause is inhibited for handover from SDCCH to SDCCH.

2.3.3.2.4 Traffic handover (Cause 23)

The principle of this handover is to reduce the size of the serving cell when it is high loaded relativelyto a low loaded cell.When the mobile moves away from the BTS, the power budget will increase and a better cellhandover will be triggered earlier.It is recommended to inhibit Traffic handover towards 1 TRX cells. These cells do not have enoughresources to receive incoming handovers due to congestion of neighbour cells. Moreover because ofthe great variation of traffic in the 1 TRX cells, traffic load is never considered as low.This cause is inhibited for handover from SDCCH to SDCCH.

2.3.3.2.5 General capture ha ndover (Cause 24)

In hierarchical network where cells use different frequency bands, a general capture handover isrequired to manage, on a per cell adjacency basis, the possibility for the mobiles to be captured. Thisis needed in order to synchronise the capture from a macrocell to a microcell (as described in2.3.3.2.2) or from the same macrocell to another cell of preferred band (as described in 2.3.3.2.3).This general capture handover takes into account the load in the serving and in the target cell.This cause is inhibited for handover from SDCCH to SDCCH.

2.3.3.2.6 Fast traffic handover (Cause 28)

A fast traffic handover is initiated by the RAM request “Fast traffic handover request” when theserving cell is congested. Like directed retry, a fast traffic handover is triggered when a call request isqueued in RAM. However, instead of pushing the queued request into a neighbour cell, the fast traffichandover pushes an established call out in a neighbour cell in order for the queued request to beserved in the serving cell. With the fast traffic handover alarms, HOP detects the MS that couldperform such an handover.

Cause 28 only applies to handovers from TCH to TCH.

2.3.3.3 Emergency intracell ha ndovers

The causes specific to emergency intracell handovers are listed in Table 6.

Handover Cause Cause NumberToo low level on the uplink, inner zone Cause 10Too low level on the downlink, inner zone Cause 11Too high interference level on the uplink Cause 15Too high interference level on the downlink Cause 16


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Table 6: Emergency intracell handover causes.

2.3.3.3.1 Interference or low level intracell ha ndovers (Causes 10, 11, 15, and 16)

Emergency handovers Causes 15 and 16 are triggered for intracell application when the radio link isdeemed to suffer a high level of interference. In this case, the channel assigned to the call ischanged for another channel in the same cell, on which the measured interference level is thesmallest possible. Since AMR calls can be performed over worse carrier-to-interference ratios thannon AMR calls, the parameter setting for Causes 15 and 16 is different for non AMR and AMR calls.

In the case of concentric cell or multiband cell environment, emergency intracell handovers Causes10 and 11 concern handovers from the inner to the outer zone of the same cell (they are calledinterzone handovers) as well as handovers performed within one zone (they are called intrazonehandovers). The possible interzone handovers in a concentric or multiband cell are shown in Figure12.

Inner zone

Outer zone

Cause 13

Causes 10 or 11

Figure 12: Possible interzone handovers in a concentric or multiband cell.

2.3.3.4 Better conditions int racell ha ndovers

The only better conditions intracell handovers is shown in Table 7.

Handover Cause Cause NumberToo high level on the uplink and downlink, outer zone Cause 13

Table 7: Better conditions intracell handover causes.

2.3.3.4.1 Better conditions interzone hando vers (Cause 13)

For concentric cells, the "outer zone uplink and downlink level too high" cause forces an intracellhandover from an outer zone TCH to an inner zone TCH. This handover is considered as interzonehandover (See Figure 12).Then the MS can operate on frequency channels with lower BS and MS maximum powers. If theinner zone is congested, the MS will stay on the outer zone. The flag EN_LOAD_BALANCE can beenabled at the OMC to balance the load between the inner and outer zones. In case the load balanceis allowed, the handovers Cause 13 are inhibited as long as the inner zone is more loaded than theouter zone.

For multiband cells, this same cause forces an intracell handover from an outer zone TCH in theclassical band to an inner zone TCH in the preferred band.

The handover detection is made on signal levels coming from the serving cell and possibly from theneighbour cells.

2.3.3.5 Channel adaptation handovers

The causes specific to the channel adaptation handovers are listed in Table 8.


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Handover Cause Cause NumberHR-to-FR channel adaptation due to bad radio quality Cause 26FR-to-HR channel adaptation due to good radio quality Cause 27

Table 8: Channel adaptation handover causes.

2.3.3.5.1 HR-to-FR channel adaptation (Cause 26)

The HR-to-FR channel adaptation handovers aim to increase the channel rate of the ongoing callwhen a bad radio quality is detected. The channel adaptation consists in changing the current halfrate TCH to a full rate TCH. The handover only applies to adaptive multirate (AMR) calls. When aCause 26 is triggered, a HR-to-FR channel adaptation together with an intracell handover due to badquality is performed. The related handover cause is called “HR-to-FR channel adaptation due to badradio quality”.

There are two ways to trigger Cause 26. The first way consists of triggering Cause 26 only if aprevious intracell handover Cause 15 or 16 have been previously detected in the serving cell for thecurrent MS. This way is intended to non-hopping channels for which an intracell handover Cause 15or 16 is sometimes not sufficient to improve the quality of the call. If the quality is not sufficient due toa too high interference level, instead of continuing triggering intracell handover Cause 15 or 16, a HR-to-FR channel adaptation is triggered thanks to Cause 26. The second way applies when the intracellhandover Causes 15 and 16 are both disable for AMR calls. If a too high level of interference isdetected in the serving cell for the current MS, Cause 26 is then triggered. This second way intends toimprove the quality of hopping channels which quality is generally not much improved after anintracell handover Cause 15 or 16.

2.3.3.5.2 FR-to-HR channel adaptation (Cause 27)

The FR-to-HR channel adaptation handovers aim to reduce the number of busy TCH when the radioquality is very good and the serving cell becomes high loaded. The channel adaptation consists tochange the current full rate TCH to a half rate TCH. The handover only applies to adaptive multiratecalls. The related cause is called “FR-to-HR channel adaptation due to good radio quality”.

2.3.3.6 Resource management ha ndovers

The resource management handover is listed in Table 9. In the opposite of the others handovercauses which are based on the radio measurements given by the active channel processing function(See Section 2.3.1), the need for Causes 29 is detected in RAM. When detected, the relatedhandover alarms are sent to HOP in the message “Start HO”, which contains the HO cause number,and the reference of the call concerned by the handover.

Handover Cause Cause NumberTFO handover Cause 29

Table 9: Resource management handover cause.

In case of codec mismatch between two MS in communication, an handover Cause 29 is performedin order to match their speech codec. For further details on Cause 29, refer to [15]. In HOP, Cause 29consists in checking whether the current call is the one concerned by the call reference. Then, whenCause 29 is triggered, HOP sends the alarm to HOM with the serving cell as only candidate cell. Thenew codec type is also forwarded to HOM.


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2.3.4 Handover candidate cell evaluation

The handover candidate cell evaluation process is performed in the BSC and only applies to intercellhandovers, i.e. emergency and better conditions HO. Once a need for handover is detected, thisprocess looks for possible target cells (except if it is an intracell handover) and provides HOM entitywith the list of candidate cells, the HO Cause (per cell in the list), and the MS zone indication (perconcentric cell in the list) .

2.3.4.1 Cell ordering accor ding to target l ayer and target band

In hierarchical or multiband environment, cells are characterised by the layer they belong to or/andthe frequency band they use. The candidate cell evaluation process takes into account thesecharacteristics in the candidate cell ordering.

In hierarchical environment, the HO detection process can indicate a preferred layer where thehandover must be directed to. If this indication is used, the candidate cell evaluation puts in the firstplaces of the list, the candidate cells belonging to the preferred layer. They are followed by the cellsof the other layer, providing they are also correct candidates.

After this possible distinction, in each part of the list, the candidate cell evaluation sorts the candidatecells according to the parameter PRIORITY(0,n) (parameter on line changeable from the OMC-R).The cells having the highest priority are put in the first place of the list. They are followed by the cellshaving lowest priorities. The PRIORITY(0,n) is only used when the flag EN_PRIORTY_ORDERING isset to enable.

In case of emergency handover, for each category (preferred layer and other layer) and between cellshaving the same priority, the candidate cell evaluation sorts the candidate cells according to thefrequency band they use : the cells which use the same frequency band as the serving cell are putfirst and they are followed by the cells which use the other frequency band.

The cell evaluation function (see section 3.2.3.) is then applied to the different candidate cell listsdefined from the preferred layer indication, the PRIORITY(0,n) parameter and the frequency band ofthe serving cell (only in case of emergency handover).

2.3.4.2 Filtering pro cess

The filtering process allows to filter out cells from the target list before sending them to the ORDER orGRADE evaluation process.It can be enabled/disabled on-line on a per cell basis from the OMC-R with the flagEN_PBGT_FILTERING.The candidate cells are filtered on their power budget in relation to a handover margin thresholdbased on the handover cause.

2.3.4.3 Candidate cell ranking

Two types of cell evaluation algorithms can be used : ORDER and GRADE.ORDER and GRADE are two different methods of cell ranking. They both consist in giving a mark or'figure of merit' to each candidate cell.

The basic differences between ORDER and GRADE are that :

with ORDER

- The candidate cell evaluation process interacts with the handover detection by use of causedependent handover margins.

- The candidate cell evaluation process takes into account the number of free TCH in the candidatecells.


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with GRADE, :- The candidate cell evaluation process does not interact with the handover detection.- The candidate cell evaluation process takes into account the relative load of traffic channels in the

candidate cells.

The type of cell evaluation is chosen by the operator on a (serving) cell basis and is provided to theBSC with the parameter CELL_EV.

Each algorithm uses the following parameters to compare candidate cells:

ORDER GRADEPower budget X XNumber of free TCH/FS X(1)Cell load (%) X(1)

Handover type X

Table 10: Comparison of candidate cell evaluation algorithms

(1) The number of free TCH in the calculation of ORDER and the cell load in the calculation ofGRADE will only be used in case of an internal candidate cell and when the flag EN_LOAD_ORDERis set to ENABLE. Otherwise, there is no offset due to load information in the candidate cellevaluation.

2.3.5 Inhibition of handover

The operator has the possibility to inhibit selectively the different handover causes via O&Mcommands on a cell basis.

Inhibition and control of handover management

The following flags are set per cell and are on-line changeable.These flags are used by the handover management entity (see [13]). They are not used by thehandover preparation function , except for HO_INTERCELL_ALLOWED andEN_INTRACELL_REPEATED. They are mentioned only for information with respect to the flagsdescribed in the next paragraph.

The following flags can be used to inhibit and control the execution of a handover in the BSC :- HO_INTERCELL_ALLOWED : enable/disable intercell handover,- HO_INTRACELL_ALLOWED : inhibition of all intracell (BSC internal) handovers (TCH and

SDCCH). This flag does not control the inhibition of interzone handover (see below).- EN_IC_HO : inhibition of all incoming handovers- EN_INTRACELL_REPEATED : inhibition of repetition of intracell handover , by triggering an

intercell handover with cause "Quality too low".

Inhibition of the handover preparation

The following flags can be used to inhibit the detection of a handover cause.- HO_INTERCELL_ALLOWED : enable/disable intercell handover causes,- EN_INTRACELL_REPEATED : enable/disable repetition of intracell handover causes,- EN_RXQUAL_UL : enable/disable too low quality uplink cause,- EN_RXQUAL_DL : enable/disable too low quality downlink cause,- EN_RXLEV_UL : enable/disable too low level uplink cause,- EN_RXLEV_DL : enable/disable too low level downlink cause,- EN_PBGT_HO : enable/disable power budget cause,- EN_MULTIBAND_PBGT_HO : enable/disable power budget handovers Cause 12 between different

frequency band cells- EN_DIST_HO : enable/disable too long MS-BS distance cause,- EN_INTRA_UL : enable/disable too high interference uplink cause for non AMR calls,- EN_INTRA_UL_AMR : enable/disable too high interference uplink cause for AMR calls,


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- EN_INTRA_DL : enable/disable too high interference downlink cause for non AMR calls,- EN_INTRA_DL_AMR : enable/disable too high interference downlink cause for AMR calls,- EN_MCHO_H_UL : enable/disable level uplink, high threshold, microcell cause,- EN_MCHO_H_DL : enable/disable level downlink, high threshold, microcell cause,- EN_MCHO_RESCUE : enable/disable microcell to macrocell handover on missing MS

measurement reports,- EN_MCHO_NCELL : enable/disable upper to lower layer handover cause.- EN_PREFERRED_BAND_HO : enable/disable multiband handover cause.- EN_BETTER_ZONE_HO : enable/disable too high level on the uplink and the downlink, outer zonecause.- EN_TRAFFIC_HO(0,n) : enable/disable traffic HO cause from the serving cell to the cell n.- EN_GENERAL_CAPTURE_HO : enable/disable general capture handover cause.- EN_AMR_CA : enable/disable intracell HO for AMR channel adaptation (Causes 26 and 27)When these flags are set to DISABLE, the corresponding handover alarms are not checked by thehandover detection function.

For the flags controlling handover cause :- If the flag is set to "ENABLE", the checking of the handover cause is enabled.- If the flag is set to "DISABLE" the checking is disabled.

Note 1 : For the multiband handover cause, the enabling of the flag EN_PREFERRED_BAND_HOdoes not imply automatically the execution of multiband handovers. It depends also on theflag EN_INTERBAND_NEIGH used on a per BSS basis (see [18]).

Note 2 : The flag to enable or disable Cause 29 is controlled by RAM and the transcoder (See [15]).

The flags are per cell and on-line changeable, this means that for each cell the operator can enable ordisable some handover causes without releasing active calls in the cell.Consistency checks are performed by the OMC-R, in order to maintain the overall coherence of allflags with the type of the cell.

Providing the conditions defined in Section 3.2.4 are fulfilled, the timer T_INHIBIT_CPT inhibits thecapture handover causes for a while so as to avoid the ping pong effects in a multilayer/multibandenvironment.

The parameter SDCCH_COUNTER allows to inhibit SDCCH handovers after completion of theImmediate Assignment procedure during SDCCH_COUNTER successive SACCH frames (SeeSection 3.3).

Particular cases for concentric or multiband cells

In the case of concentric or multiband cells, a handover cause due to high interference level (causes15 or 16, see 3.2.2) triggers an intrazone or an interzone handover. Those are particular cases ofintracell handovers.

A handover cause due to too low level in the inner zone (causes 10 or 11) or the better zone cause(cause 13) triggers an interzone handover (see section 3.2.2.1.2). An interzone handover is aparticular case of intracell handover.

The two HO causes (10, 11) cannot be enabled or disabled individually. These causes are enabledand disabled when the parameter CELL_PARTITION_TYPE = CONCENTRIC and = NORMALrespectively (see sections 2.2 and 3.2.2). Moreover the HO cause 13 must not be disabled in case ofallocation in the inner zone during Normal Assignment (the flag EN_BETTER_ZONE_HO should notbe looked at when deciding whether the MS should go to the inner zone or outer zone).

Therefore, HO_INTRACELL_ALLOWED flag does not control the enabling/disabling of the interzonehandover, but only of the intrazone handover (or interzone handover causes 15 or 16).


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Finally , the flag EN_INTRACELL_REPEATED does not control the repetition of the interzonehandover.

2.3.6 Functional diagram of Handover prep aration

Figure 13 is the SADT diagram of the handover functions in the BSC. This diagram is just a functionaldescription. It does not constrain the implementation.

The BSC receives raw measurement data from the BTS in the message MEASUREMENT RESULT ifEN_MEAS_COMPRESSION=DISABLE or compressed measurement data in the messagePREPROCESSED MEASUREMENT RESULT every SACCH multiframe period (see radio linkmeasurements, ref. [7] and Radio measurements data processing, ref. [19]). The BSC pre-processesthat data to detect HO threshold conditions for emergency, better conditions, and channel adaptationhandovers. The preprocessed measurement reports are therefore generated internally by the BSCwhich uses them also for candidate cell evaluation.

The Active Channel Preprocessing function is not specified in this document (refer to [19]). That iswhy it is not represented in bold type.


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Active channelpreprocessing

Handoverdetectionaveraged measurements

for handover detection

P

MS & BSparameters

HO candidatecell evaluation

“TCH usage information”

CELL_EV

candidate cell evaluation parameters

T_FILTER

“Alarm”

HO and DRenabling flags

HO detection parameters

HO cause,

raw cell list,

"Start DR algos" EN_LOAD_ORDER

MS speed discrimination parameters

PREF_LAYERNew codec type

cellconfigurationparameters

T_HCP

"Start T_HCP"EN_CAUSE_28

“MS Zone Indication Request”

"Fast traffic HO Request"

“MS Zone Indication ACK (ZONE)”

“Fast traffic HO ACK”

T_INHIBIT_CPT

"Start T_INHIBIT_CPT"

"Start HO"

Figure 13: SADT diagram of handover functions in the BSC


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Flows d escriptionThe description is done at BSC level (see Figure 13).

Input flows

- “TCH usage informat ion”* FREEfactor(n), LOADfactor(n), AV_LOAD, t(n): respectively correction factor of ORDERdepending on free level of cell n, correction factor of GRADE depending on load of cell n,averaged traffic load and absolute number of free TCH in the cell n (refer to [15]). In concentriccells, if the flag EN_LOAD_OUTER is set to enable, the load is evaluated considering the TCHresource in the outer zone instead of in the whole cell. If G1 TRXs are installed in the cell and theflag EN_LOAD_EGSM is set to enable, the load is evaluated including the G1 TCH resource of thecell (See [15] for more details in the specific case of concentric cells). These flows are BSCinternal.

* Traffic_load(n): situation of the traffic in the cell n (refer to [15]).

* LOAD_SV3(n): indicates whether or not the cell n is loaded [15].

* EN_CAUSE_13: flag that indicates in concentric or multiband cells whether or not the inner zoneis more loaded than the outer zone.

- Averaged measurements for ha ndover detection :* AV_RXQUAL_UL_HO, AV_RXQUAL_DL_HO, AV_RXLEV_UL_MCHO,* AV_RXLEV_UL_HO, AV_RXLEV_DL_HO, AV_RXLEV_DL_MCHO,* BS_TXPWR, MS_TXPWR, AV_RANGE_HO, AV_RXLEV_PBGT_DR,* AV_BS_TXPWR_HO, AV_BS_TXPWR_DR,* AV_RXLEV_PBGT_HO, AV_RXLEV_NCELL(n), AV_RXLEV_NCELL_BIS(n).* AV_RXLEV_NCELL_DR(n), n=1..BTSnum.* BFI_SACCH* AV_RXQUAL_DL_CA_HR_FR, AV_RXQUAL_UL_CA_HR_FR,* AV_RXQUAL_DL_CA_FR_HR, AV_RXQUAL_UL_CA_FR_HR

Control flows

- Cell configuration parameters : CELL_DIMENSION_TYPE, CELL_LAYER_TYPE,CELL_PARTITION_TYPE, CELL_BAND_TYPE, ZONE_TYPE, CELL_RANGE,FREQUENCY_RANGE.

- MS and BS parameters :Maximum and minimum MS/BS powers allowed in the cell :MS_TXPWR_MAX, BS_TXPWR_MAX, MS_TXPWR_MIN, BS_TXPWR_MIN,Maximum MS power in the inner zone of a concentric or multiband cell :MS_TXPWR_MAX_INNER,Maximum BS power in the inner zone of a concentric or multiband cell :BS_TXPWR_MAX_INNER.

- T_FILTER : Time after which a “no alarm” message (an alarm message with no candidate cell, seesection 3.2.4) is sent to the handover management entity, if no new alarm has been detectedwhilst running.

- T_HCP : time during which penalty PING_PONG_HCP is applied to the preceding cell (cause 12);time during which penalty is applied to the preceding inner zone (cause 13).

- T_INHIBIT_CPT : Time during which the capture handover Causes 14, 21, and 24 are inhibited.

- P : MS classmark (maximum MS power) for the concerned frequency band(s) (GSM900, GSM850,DCS1800, DCS1900). In case of biband mobiles, depending on the setting of the


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PLMN_FREQUENCY_BANDS parameter, both MS classmark for GSM900 and MS classmark forDCS1800 band are considered, OR both MS classmark for GSM850 and MS classmark forDCS1800 band are considered, OR both MS classmark for GSM850 and MS classmark forDCS1900 band are considered.

- Candidate cell evaluation parameters :* MS_TXPWR_MAX(n) : n=1..NBR_ADJ,* HO_MARGIN(0,n) : n=1..NBR_ADJ,* HO_MARGIN_LEV(0,n) : n=1..NBR_ADJ,* HO_MARGIN_QUAL(0,n) : n=1..NBR_ADJ,* HO_MARGIN_DIST(0,n) : n=1..NBR_ADJ,* PRIORITY(0,n) : n=1..NBR_ADJ,* EN_PRIORITY_ORDERING,* OFFSET_HO_MARGIN_INNER,* RXLEV_MIN(n) : n=1..NBR_ADJ,* LINKFACTOR(0,n) : n=1..NBR_ADJ,* NBR_ADJ : number of adjacent cells.* identity (BSIC + BCCH ARFN) of the preceding cell if internal to the BSC* EN_SPEED_DISC : flag enabling the sending of fast MS to the umbrellas* EN_PBGT_FILTERING : flag enabling/disabling the filtering process* L_LOAD_OBJ : maximum load on the umbrella to hand over a fast moving mobile* PING_PONG_HCP : handicap applied to the preceding cell for power budget calculation orhandicap applied to the preceding inner zone in the cause 13.See definition of these parameters in section 3.2.2.

- CELL_EV : indicator of GRADE/ORDER handover (cell evaluation indicator).

- "Start DR algos " : indication to the handover preparation to start the preparation for directed retry.This message is sent by the HOM entity.

- "Start HO" : indication to the handover preparation to start the handover for Causes 28 and 29. Thismessage is sent by the RAM entity.

- "Fast traffic HO request" : Request from the RAM entity for checking if the current call canperform a fast traffic handover.

- “MS zone Indication Request” : Request from the RAM entity (refer to [15]) for determining thezone location of the mobile in a concentric or multiband cell (see section 3.1.1) in case of allocationduring Normal assignment in the concentric or multiband cell.

- HO and DR enabling flags : HO_INTERCELL_ALLOWED, EN_INTRACELL_REPEATED,EN_FORCED_DR,EN_RXQUAL_UL, EN_RXLEV_UL,EN_RXQUAL_DL, EN_RXLEV_DL,EN_DIST_HO, EN_PBGT_HO, EN_MULTIBAND_PBGT_HOEN_INTRA_UL, EN_INTRA_UL_AMR,EN_INTRA_DL, EN_INTRA_DL_AMR,EN_MCHO_H_UL, EN_MCHO_H_DL, EN_MCHO_RESCUE,EN_MCHO_NCELL,EN_PREFERRED_BAND_HO,EN_GENERAL_CAPTURE_HO,EN_TRAFFIC_HO(0,n),EN_BETTER_ZONE_HO,EN_AMR_CA.

- EN_LOAD_ORDER : flag controlling the use of the FREEFACTOR and LOADFACTOR in thecalculation of candidate cell list (ORDER and GRADE modes).


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- HO detection parameters :* RXLEV_UL_ZONE, RXLEV_DL_ZONE, ZONE_HO_HYST_UL, ZONE_HO_HYST_DL,* L_RXQUAL_UL_H, L_RXQUAL_UL_H_AMR, L_RXLEV_UL_H, RXLEV_UL_IH,* L_RXQUAL_DL_H, L_RXQUAL_DL_H_AMR, L_RXLEV_DL_H, RXLEV_DL_IH,* U_TIME_ADVANCE, L_TIME_ADVANCE,* N_BAD_SACCH,* L_RXLEV_CPT_HO(0,n), n=1..NBR_ADJ,* U_RXLEV_UL_MCHO, U_RXLEV_DL_MCHO,* L_RXLEV_NCELL_DR(n), n = 1..NBR_ADJ,* EN_BI-BAND_MS(n),* OUTDOOR_UMB_LEV(0,n), n ### { neighbour umbrella cells}* PREFERRED_BAND : Frequency band type preferably used by biband mobiles.

* MULTIBAND_TRAFFIC_CONDITION : Condition on traffic load in the serving cell for amultiband handover.* CAPTURE_TRAFFIC_CONDITION : Condition on traffic load in the serving cell for a generalcapture handover.* NEIGHBOUR_RXLEV(0,n),* RXLEV_LIMIT_PBGT_HO,* DELTA_INC_HO_margin, DELTA_DEC_HO_margin,* THR_RXQUAL_CA_HIGH, THR_RXQUAL_CA_NORMAL,* OFFSET_CA_HIGH, OFFSET_CA_NORMAL.* EN_LOAD_BALANCE : Flag that enables or disables the load balance between the inner andouter zones in concentric cells,* EN_AMR_HR, EN_AMR_FR.

- Speed discrimination parameters and variables* MS_SPEED* PREC_LAYER_TYPE* C_DWELL* L_LOAD_OBJ, H_LOAD_OBJ* MIN_DWELL_TIME, MIN_CONNECT_TIME* L_MIN_DWELL_TIME, H_MIN_DWELL_TIME, DWELL_TIME_STEP

Internal flows

- Candidate cell evaluation input* HO cause* raw cell list of potential candidate cells with the MS zone indication in concentric cells* PREF_LAYER : preferred target cell layer* New codec type for Cause 29

- "Start T_HCP" : This timer is started in the target cell after an incoming internal handover. Thistimer is also started after an intracell handover in a concentric cell when the preceding zone is theinner zone.

- “Start T_INHIBIT_CPT” : This timer is started under the conditions specified in Section 3.2.4. Whilerunning, it inhibits the capture handover Causes 14, 21, and 24.

- EN_CAUSE_28: This flag enables or disables the triggering of Cause 28 in HOP. The enabling ofCause 28 is controlled via RAM messages.

Output flows

- “Alarm”: message that is sent to HOM when an alarm has been detected. This message containsthe Candidate cells list (with the MS Zone Indication for each concentric cell of the candidate cellslist), the HO cause, and the new codec type (for Cause 29).


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- “Fast handover alarm ACK” : message that is sent to RAM when a fast traffic handover has beendetected. This message contains the reference of the queued request, and the call reference.

- “MS Zone Indication ACK(ZONE)” : message that is sent to RAM (refer to [15]). This messagecontains the zone in the concentric or multiband cell where the mobile is situated.

2.4 Directed retry preparation

2.4.1 System aspects

The directed retry consists in an SDCCH to TCH intercell handover during the call set-up process.The directed retry is triggered when given radio conditions are met and the serving cell is congested.The handover to TCH in another cell reduces the call set-up time (queuing phase) and allows thesharing of resources from one cell with another, thus overcoming traffic load unbalance.In this release of the ALCATEL BSS, the directed retry can be internal or external to the BSS (see [8]and [9]).

The start and stop of the directed retry preparation are described in section 3.3.1.1.

The directed retry may be performed :- either on handover alarms : If a handover alarm is detected during queuing, and the candidate cell

evaluation process indicates at least an internal or external cell, then the BSS will perform adirected retry .

- or on alarm of forced directed retry : If during queuing, an internal or external neighbour cell isreported with a sufficient level and has free TCH, then the BSS will perform a directed retry .

The expression "Forced directed retry" refers to this case, because the radioconditions in the serving cell do not represent a need for handover. The cause which leads to forceddirected retry is assimilated to a "better conditions cause" in the handover preparation.

2.4.2 Functional d escription

The directed retry preparation is supported :- by the same processes as the handover preparation for directed retry on handover alarms,- by a specific condition in the alarm detection process (new cause pertaining to forced directed retry)and a specific candidate cell list evaluation process for forced directed retry.

The detection process for directed retry consists in the checking of the handover alarms and of theforced directed retry alarm.

If an alarm for forced directed retry is raised, then the target cell evaluation is performed by thecandidate cell evaluation process for forced directed retry.For all other alarms, the target cell evaluation is performed by the candidate cell evaluation processfor handover (see section 3.2.3.).

For further details about this process and the alarm priority order, refer to section 3.2.2.2.

2.4.3 Directed retry on ha ndover alarms

The preparation of directed retry on handover alarms is performed by the handover preparationfunction. All the processes of this function operate in the same way as for preparation of SDCCH orTCH handover at the exception of the candidate cell evaluation process.

The candidate cell evaluation process (see section 3.2.3.) looks for target cells so as to do an SDCCHto TCH handover.TCH load (i.e. Freelevels and Loadlevels related to TCH) in neighbour cells may be used for targetcell evaluation and ranking (the TCH load is not known in case of external cells).


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Note : in case of handover preparation, the candidate cell evaluation process looks for target cells soas to do a SDCCH handover. The SDCCH load is not taken into account (see section 3.2.3).

2.4.4 Forced directed retry

The preparation of forced directed retry is composed of two processes :- forced directed retry detection,- candidate cell evaluation.

The forced directed retry detection requires specific preprocessed measurements (refer to [19]).The detection is performed every SACCH measurement reporting period when preprocessedmeasurements are available.The averaged received levels of all neighbour cells are compared to a threshold. If one or severalcells are found with a received level higher than the threshold, an alarm of forced directed retry israised : high level in a neighbour cell for forced directed retry. This cause is included in the "betterconditions causes" of the handover preparation.

When detected, this alarm is sent , with the list of internal and external cells fulfilling the condition, tothe candidate cell evaluation process for forced directed retry if there is no handover alarm raised atthe same time. A handover alarm raised at the same time is prior and is sent to the candidate cellevaluation process (see section 3.2.3.).

Then, the candidate cell evaluation process looks for cells :a. where the MS can communicate,b. where the received level at MS is higher than a given threshold,c. and which have a minimum number of TCH channels free (in case of internal cell).The condition b. allows the control of the interference level in the network.The condition c. is a means to forbid "retry traffic" from a congested cell to a neighbour cell if theneighbour cell has less than a minimum number of channels free. This condition controls the amountof "retry traffic" and therefore the additional interference generated by this type of traffic.

2.4.5 Inhibition of di rected retry

Outgoing directed retryThe directed retry from a serving cell is inhibited by the O&M flag EN_DR. This flag is defined in [13].When EN_DR = ENABLE, the type of directed retry is determined by the combination of all inhibitionflags for handover (see section 2.3.5) and forced directed retry detection :

The forced directed retry is enabled/disabled on a per cell basis with the O&M flag EN_FORCED_DR.EN_FORCED_DR : DISABLE = forced directed retry disabled.

ENABLE = forced directed retry enabled.

The flag EN_FORCED_DR is only relevant when EN_DR = ENABLE as the detection of forceddirected retry may operate only when the directed retry function is enabled. On the opposite, thehandover alarm detection operates whatever the value of EN_DR flag as this detection is used notonly for directed retry but also for SDCCH handover.

The flag HO_INTERCELL_ALLOWED applies to the cause of forced directed retry as for the otherhandover causes (see section 2.3.5).

Incoming directed retry

### Forced directed retry : the incoming retry traffic in a cell n can be forbidden by setting theparameter FREElevel_DR(n) to its maximum value i.e. 255 (see section 3.3.3).


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### Directed retry on handover alarms : the incoming retry traffic in a cell can be forbidden by settingthe parameters FREEfactors_i and LOADfactors_i to their minimum values.


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3. DYNAMIC BEHAVIOUR

3.1 Functions linked to handover prep aration

3.1.1 Biband mobile stations

In this document, an MS is defined as biband if it supports the two frequency bands given by theparameter PLMN_FREQUENCY_BANDS. In other terms, a biband MS supports [20bis]:

− the PGSM and DCS1800 bands if PLMN_FREQUENCY_BANDS = “GSM900 and DCS1800bands”,

− the GSM850 and DCS1800 bands if PLMN_FREQUENCY_BANDS = “GSM850 andDCS1800 bands”,

− the GSM850 and DCS1900 bands if PLMN_FREQUENCY_BANDS = “GSM850 andDCS1900 bands”.

3.1.2 Concentric cell and multiband cell

A concentric cell is identified in the BSS by setting its attached flag CELL_PARTITION_TYPE toCONCENTRIC.

A multiband cell is identified in the BSS by setting its FREQUENCY_RANGE to PGSM-DCS1800 orEGSM DCS1800 (CELL_PARTITION_TYPE is forced to concentric). It can be noted that in anEGSM-DCS1800 multiband cell, the configuration where only G1 TRX are defined in the inner zone,and DCS1800 TRX are defined in the outer zone is supported.

Each frequency carrier of the cell is allocated to either the inner zone or the outer zone. Thisallocation is indicated by the flag ZONE_TYPE (OUTER ZONE or INNER ZONE) on a per frequencycarrier basis.Any SDCCH connection is always allocated to the outer zone (ZONE_TYPE = OUTER ZONE).

3.1.2.1 Allocation in the inner zone in case of Normal Ass ignment

In order to assign from the start a TCH in the zone corresponding to the MS location, the informationon the measured level gathered by the handover detection function is used.The RAM entity (refer to [15]) during Normal Assignment in a concentric cell or in a multiband cell willrequest to the handover detection function (with the indication “MS Zone Indication Request”, seesection 2.3.6) the zone where the MS is deemed to be : inner or outer zone.

The HOP entity first checks whether or not the MS supports the frequency band of the inner zone:− If the MS is in a PGSM-DCS1800 or a EGSM-DCS1800 multiband cell and the MS is not biband ,

then the indication is always OUTER.− If the MS is in a EGSM-DCS1800 multiband cell, there is only G1 TRXs in the inner zone, and the

MS is biband but does not support the E-GSM band, then the indication is always OUTER.

To this avail, the handover detection function will check all the relations in the cause "outer zone toohigh” (cause 13) except the condition EN_BETTER_ZONE_HO=ENABLE in (HO-17) using

− the AV_RXLEV_UL/DL_HO averages, if A_LEV_HO measurements have been received,− the average of the RXLEV_UL/DL measurements already received.

The checking of Cause 13 will indicate in which zone the MS is deemed to be on a radio criterion.

The load balance between the inner and outer zones is managed by the RAM entity [15]. The MS isallocated to the inner zone if the MS is deemed to be in the inner zone on a radio criterion, and theinner zone is less loaded than the outer zone.

The MS zone indication is sent to RAM in the message “MS zone indication ACK” (See Sections 2.4.2and 4.2).


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In (HO-17), the average of the RXLEV_NCELL(n) measurements is computed for each neighbour cellwith a same window whose size is determined by the number of MEASUREMENT RESULTmessages which have already been received since the first received MEASUREMENT RESULTmessage with a Layer 3 info present.As long as this number is lower than A_PBGT_HO, it is used as window to calculate these averages.When this number becomes higher than A_PBGT_HO, then A_PBGT_HO is used as window tocalculate these averages.

3.1.2.2 Allocation in the inner zone in case of incoming ha ndover

Two cases must be distinguished according that the incoming handover is based on a SDCCHchannel or on a TCH channel.

Case of an incoming ha ndover on SDCCHIn case of an incoming intercell handover on SDCCH a channel of the outer zone of the concentric ormultiband cell is always assigned to the mobile station.

Case of an incoming ha ndover on TCHIn case of an incoming intercell handover on TCH, the MS will be handed over in the zonecorresponding to its location if the flag EN_BETTER_ZONE_HO is set to enable (ifEN_BETTER_ZONE_HO is set to disable the MS is handed over in the OUTER ZONE).

For that the information on the downlink measured level of the target cell RXLEV_NCELL is used.Each time, a candidate cells list is provided to the HOM entity, it must indicate for each concentric ormultiband cell, the zone where the MS is deemed to be in the target cell: inner or outer zone. If theMS is in a PGSM-DCS1800 or a EGSM-DCS1800 multiband cell and the MS is not biband, theindication is always OUTER zone. Furthermore, if the MS is in a EGSM-DCS1800 multiband cell,there is only G1 TRXs in the inner zone, and the MS is biband but does not support the E-GSM band,then the indication is always OUTER.

So each time a concentric or multiband cell is in the candidate cells list, the handover detectionfunction checks the equation (HO-0) in a way to determine the MS zone location in this concentric ormultiband cell.

As mentioned in Section 3.1.2.1, the load balance between the inner and outer zones is managed byRAM [15].

MS zone location

If { AV_RXLEV_NCELL(n) > RXLEV_DL_ZONE + ZONE_HO_HYST_DL (HO-0)+ BS_TXPWR_MAX – BS_TXPWR_MAX_INNER,

andEN_BETTER_ZONE_HO

}Then The MS is in the inner zoneElse The MS is in the outer zone.

The equation is checked using:- the AV_RXLEV_NCELL(n) average, if A_LEV_HO measurements have been received from thistarget cell n.- the average of the RXLEV_NCELL(n) measurements already received from the neighbour celltarget cell n (if between two measurements, in which the neighbour cell is reported, a measurementcomes in, in which the neighbour cell is not reported, a 0 will be used to calculate the average).


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RXLEV_DL_ZONE, ZONE_HO_HYST_DL, BS_TXPWR and BS_TXPWR_MAX_INNER are theparameters of the target concentric or multiband cell. They are available only if the intercell handoveris performed in the same BSC.

3.1.2.3 Handover in a concentric or multiband cell

For concentric cell environment, the cause "power budget" is applied in the inner zone as well as inthe outer zone.

For multiband cell environment, the cause "power budget" is applied in the inner zone as well as inthe outer zone. In the inner zone, if the flag EN_MULTIBAND_PBGT_HO is set to disable, the cause“power budget” is only checked between multiband cells, in a way to maintain the MS in the preferredband.

In order to avoid unnecessary handover alarms on SDCCH for all mobiles geographically located inthe inner zone, the handover alarms cause 13 on SDCCH (from outer zone towards inner zone) mustbe filtered by the handover preparation function.

For initiation of an intercell handover between a concentric or multiband cell (inner and outer zone)and the defined adjacent cell, the same handover criteria and handover strategies hold true as fornon-concentric cells.

The criteria for handover between the inner and outer zones is based either on the received signallevel or on the interference level (see section 3.2.2.1.2). This kind of handover is called "interzonehandover".

A handover due to interference (cause = 15 or 16) will change, when it is possible, the frequency ofthe radio channel in case of non-hopping channels.As the inner zone contains only a few frequencies, this will give the opportunity to make an interzonehandover from the inner to the outer zone in case of interference problems in the inner zone.In case of interference problems in the outer zone, the MS will always make an intrazone handover (itwill stay connected to the outer zone).In case of hopping channels an interzone handover may occur from the inner to outer zone but neverin the reverse direction (as with non-hopping channels).

Both intrazone and interzone handovers are intracell handovers.

3.1.3 MS speed discrimination

3.1.3.1 Basic princ iple

The speed discrimination procedure can only be activated in a hierarchical cell environment, i.e.when the serving CELL_LAYER_TYPE = upper or lower or indoor . It is based on the dwell time in thelower or indoor layer cells, either as serving or neighbour cells.

The knowledge of the speed of a MS is indicated with a flag MS_SPEED that has the values "fast","slow" and "indefinite". The value of this flag is kept for the whole call duration, once it has been set to"fast". This choice relates to the assumption that a prediction is possible on the MS speed. Wheneverthe MS moves into another cell and was not recognised "fast" at this occasion, or at a precedentoccasion, the MS_SPEED is reset to "indefinite".

The time experienced in a serving lower or indoor layer cell is kept in a counter C_DWELL (inSACCH multiframes).

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When a handover cause "power budget" is triggered, and the preceding cell was already a lower layercell (Respectively an indoor layer cell), this time is compared to a threshold MIN_CONNECT_TIME.If it is found smaller than the threshold, this indicates that the MS has crossed the serving lower layercell (Respectively the serving indoor layer cell), in less than MIN_CONNECT_TIME seconds. In thiscase , the MS is considered to be moving fast and the handover is directed towards the upper layerpreferentially.If it is found bigger than the threshold, this indicates that the MS has not yet been recognised as fastand the handover is directed towards the neighbour lower layer cell (Respectively the neighbourindoor layer cell).

The handover cause power budget is used because it is assumed that in any cell environment thiscause will indicate that the MS is leaving the "better cell" zone of the serving cell, and not because ofinterference, shadowing, or street corner effect.

The MS speed discrimination can only happen when the preceding cell is already a lower layer cell(Respectively indoor layer cell) this ensures that the MS has entered the cell at its edge and not at anarbitrary position inside the cell. This would be the case after call setup, or after a handover from anumbrella cell.Because the measured dwell time in the serving lower or indoor layer cell is taken between two pointslocated at the edge of the cell, the time interval can be related to the MS speed, assuming that themain road on which fast moving mobiles are, is known beforehand.

The MIN_CONNECT_TIME shall be set to the value necessary for a fast moving car (mean speed vabout 40 km/h) necessary to travel along the cell on the main road.If there is no information available about a privileged direction of fast MS, then the

MIN_CONNECT_TIME shall be set to the value 2xCell_ Diameter

v∏ × where v represents the average

speed of fast moving mobiles.

The speed discrimination function can be enabled/disabled on a per cell basis, using a flag :EN_SPEED_DISC.If EN_SPEED_DISC is set to DISABLE, then the dwell time in a serving lower or indoor layer cell isnot used to determine if an MS is fast. Nevertheless, when the MS is on the upper layer, the dwelltime in the neighbour lower and indoor layer cells is used to decide a handover to the lower layer or tothe indoor layer cell, after a fixed period of time. The same behaviour applies if the MS is on thelower layer: the dwell time in the serving lower layer cell is used to decide a handover to the indoorlayer after a fixed period of time. Table 11 shows which cells is used for the estimation of the MSspeed as a function of the serving cell layer.

Layer of the serving cells Cells used for the estimation of MS_SPEED

Upper layer The neighbour lower cellsand

The neighbour indoor cellsLower layer The serving lower layer cellIndoor layer The serving indoor layer cell

Table 11: Cells used for the estimation of the MS speed as a function of the layer of the serving cell.

3.1.3.2 Required parameters and variables

For each call a variable PREC_LAYER_TYPE is used to store the cell layer type of the precedingcell. It has five values : single, upper, lower, indoor, or indefinite.

For each call, a variable MS_SPEED is used to store the already determined mobile speed, if any. Ithas three values : "fast", "slow" and "indefinite".

The initialisation of the parameters will occur at call set-up and after external handover.

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After internal handover, the variables MS_SPEED and PREC_LAYER_TYPE will be transferred tothe new call context, after possible modification.

For each call on the upper layer,for each neighbour cell n belonging to the lower or indoor layer

a counter C_DWELL(n) measures the number of SACCH periods of monitoring the neighbourcell n over a threshold L_RXLEV_CPT_HO(0,n) (see 3.1.2.3)

each time the cell n is monitored, C_DWELL(n) is compared to threshold 2*MIN_DWELL_TIME(n)

For each call on the lower or indoor layera counter C_DWELL measures the number of SACCH periods of connection to the serving cell(see 3.1.2.3).a threshold MIN_CONNECT_TIME is used at PBGT handover to decide on the MS speed

3.1.3.3 Parameter initialisation and modification

In what follows, the counters C_DWELL and C_DWELL(n) are expressed in SACCH periods, and thethresholds MIN_CONNECT_TIME and MIN_DWELL_TIME are expressed in second. Hence, anapproximation of the SACCH period to 0.5 s is made. This will have no impact on the behaviour ofthe speed discrimination process.

The initialisation and modification of the MS speed parameters depend on the layer of the servingcell.

### Case the serving cell is an indoor l ayer cell (CELL_LAYER_TYPE = indoor )

After call set-up or inter-cell handoverC_DWELL = 0.After an intra-cell handover, C_DWELL is kept unchanged.

After call set-up or external handover

PREC_LAYER_TYPE = indefiniteMS_SPEED = indefinite

After an internal handover :MS_SPEED is kept to the preceding value. PREC_LAYER_TYPE is set to the precedingCELL_LAYER_TYPE (upper, lower, single, or indoor). Both values are transmitted to the new callcontext.

Each time a MEASUREMENT RESULT is received for a call in an indoor layer cellC_DWELL is incremented by 1. When it reaches the maximum value of 255, it is no moreincremented.

When a handover cause "power budget" is triggered in an indoor layer celland PREC_LAYER_TYPE = indoorand the parameter EN_SPEED_DISC = enable for the serving celland C_DWELL < 2*MIN_CONNECT_TIME ,

then MS_SPEED is set to "fast".

Note 1 : By default, the flag EN_SPEED_DISC is set to disable for indoor layer cells.

### Case the serving cell is a lower l ayer cell (CELL_LAYER_TYPE = lower )

After call set-up or inter-cell handoverC_DWELL = 0.


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After an intra-cell handover, C_DWELL is kept unchanged.

After call set-up or external handover


After an internal handover :MS_SPEED is kept to the preceding value. PREC_LAYER_TYPE is set to the precedingCELL_LAYER_TYPE (upper, lower, single, or indoor). Both values are transmitted to the new callcontext.

Each time a MEASUREMENT RESULT is received for a call in a lower layer cellC_DWELL is incremented by 1. When it reaches the maximum value of 255, it is no moreincremented.

When a handover cause "power budget" is triggered in a lower layer celland PREC_LAYER_TYPE is lowerand the parameter EN_SPEED_DISC = ENABLE for the serving celland C_DWELL < 2*MIN_CONNECT_TIME ,

then MS_SPEED is set to "fast".

### Case the serving cell is an upper l ayer cell (CELL_LAYER_TYPE = upper )

After call set-up, intra-cell or inter-cell handover

for every neighbour cell n belonging to the lower or indoor layer :if EN_SPEED_DISC = ENABLE

Phase 1 MS : C_DWELL(n) = (MIN_DWELL_TIME - L_MIN_DWELL_TIME)*2Phase 2 MS : C_DWELL(n) = 0

else if EN_SPEED_DISC = DISABLEC_DWELL(n) = (MIN_DWELL_TIME - L_MIN_DWELL_TIME) * 2

After call set-up and external handover


After internal handoverMS_SPEED is turned to "indefinite" if it was not precedently "fast", otherwise it is kept to "fast".PREC_LAYER_TYPE is set to the preceding CELL_LAYER_TYPE (upper, lower, single, or indoor)and transmitted to the new call context.

Each time a MEASUREMENT RESULT is received for a call on the upper layer :

- Each time a measurement is received for the neighbour lower layer cell n or for the neighbourindoor layer cell n (in MEASUREMENT REPORT), with a value RXLEV_NCELL(n) strictlyabove the threshold L_RXLEV_CPT_HO(0,n), C_DWELL(n) is incremented by 1. When itreaches the maximum value of 255, it is no more incremented.- Each time no measurement is received or the reported level is smaller or equal to thethreshold L_RXLEV_CPT_HO(0,n), C_DWELL(n) is decremented by 1. When it reaches theminimum value of 0, it is no more decremented.

If for one neighbour lower or indoor layer cell n, C_DWELL(n) ### 2*MIN_DWELL_TIME,and the MS_SPEED was "indefinite"then MS_SPEED is set to "slow".


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Remarks :

For phase 1 MS, or when EN_SPEED_DISC = DISABLE in the umbrella cell, the initialisation ofC_DWELL(n) is done in such way that they will make a handover to the lower or indoor layer, afterL_MIN_DWELL_TIME seconds, provided they are under the coverage area of a lower or indoor layercell.This will give an efficient way to reduce the load of the umbrella cell, caused by a large proportion ofPhase 1 MS, which will camp on this cell, because it has the best received level.

For phase 2 MS and when EN_SPEED_DISC = ENABLE in the umbrella cell, the mobiles will have toreceive sufficient level from a lower or indoor layer cell during MIN_DWELL_TIME seconds beforeleaving the upper layer for the lower or indoor layer. The variable MIN_DWELL_TIME is modifiedaccording to the traffic load in the umbrella cell in order to enable the slow mobiles to leave moreeasily a loaded umbrella cell (see 3.1.3.).

The "leaky bucket" mechanism on counter C_DWELL(n) allows to do with the statistical shadowingaffecting raw level measurements : if exactly 50% of the measurements are strictly above theL_RXLEV_CPT_HO(0,n) threshold, the value of C_DWELL(n) grows, otherwise it stays at 0.The value for the threshold L_RXLEV_CPT_HO(0,n) should be equal to the measured or plannedmean signal level at the border of the lower or indoor layer cells.

The counters C_DWELL(n) only work for neighbour cells, which belong to the lower layer or to theindoor layer. The counter C_DWELL only work for the serving cell which belongs to the lower layer orto the indoor layer. In other words, C_DWELL is never used for a serving cell in the upper layer.

3.1.4 Load management in hierarchical environment

In a hierarchical environment, it is very important to control the traffic load of the umbrella cells. Thereason for this is that the umbrella cell may get saturated very easily, and hence unable to assume itstwo major functionalities : handle fast moving mobiles and provide overflow channels for the lower orindoor layers, in order to improve the total capacity at a constant grade of service.

Therefore, a control mechanism is forecast, in order to have the averaged traffic load on the umbrellacell held between two limits L_LOAD_OBJ and H_LOAD_OBJ.

This is done by two actions :- not performing handover towards the umbrella cell for power budget cause with fast mobileswhen the umbrella is loaded (see section 3.2.2.3).- reducing the MIN_DWELL_TIME variable, so as to enable slow MS to leave more quickly theumbrella cell (see section 3.1.2. and below).

Thus, the variable MIN_DWELL_TIME is modified according to the averaging of traffic load, calledAV_LOAD (refer to [15]), on the umbrella cell (See Figure 14).

Each time the averaged load on the umbrella is recalculated, AV_LOAD is compared with the valuesL_LOAD_OBJ and H_LOAD_OBJ.

If AV_LOAD > H_LOAD_OBJMIN_DWELL_TIME := max(MIN_DWELL_TIME - DWELL_TIME_STEP, L_MIN_DWELL_TIME)

If AV_LOAD < L_LOAD_OBJMIN_DWELL_TIME := min(MIN_DWELL_TIME + DWELL_TIME_STEP, H_MIN_DWELL_TIME)

The default value of MIN_DWELL_TIME will be H_MIN_DWELL_TIME.

The setting of the DWELL_TIME_STEP parameter will be made using experiences in pilot sites.It will be incorporated in the user-settable default cell profile for umbrella cells, taking advantage ofthe compromise value found between reactivity and oscillating behaviour.

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Note : The umbrella load control mechanism can be disabled by setting the L_LOAD_OBJ to 0% andH_LOAD_OBJ to 100%, in this way MIN_DWELL_TIME is blocked to its current value. For settingMIN_DWELL_TIME to H_MIN_DWELL_TIME, the operation (setting L_LOAD_OBJ to 0% andH_LOAD_OBJ to 100%) must be made off-line or with no load in the cell.

L_MIN_DWELL_TIMEH_MIN_DWELL_TIME

load in umbrella cell

100 %

H_LOAD_OBJ

L_LOAD_OBJ

start : low traffic

end : low traffic

regulation of traffic peak

DWELL_TIME_STEP

Figure 14: Traffic regulation with MIN_DWELL_TIME modified according to the traffic load

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3.2 Handover preparation

3.2.1 General

3.2.1.1 HO preparation conf iguration

At BSS initialisation, the parameters of handover preparation (see control flows of SADT diagrams insection 2.3.6) are contained in the BSC database (for further details on BSS initialisation, see [11]).

Concerning the BSS reconfiguration, all the handover preparation parameters can be modified atOMC side and then provided to the concerned BSS.

For both initialisation and reconfiguration, the algorithms are configured in the BTS by the BSC withthe message PREPROCESS CONFIGURE (see message description in [19]). This message is senton the Abis radio signalling link (see [3]) on a TRX basis.

Note : In case of TCU restart, the message is sent to the BTS (i.e. to the TRX(s) connected to thecorresponding TCU).

3.2.1.2 HO preparation ena bling and disabling

Enabling

The enabling may result from :- the establishment of a new connection,- an intracell handover,- an intercell handover,- an handover request from RAM.

So, the specifications are the following ones :- the BSC enables the algorithms upon receipt of the ESTABLISH INDICATION message from theBTS. During an SDCCH connection, the BSC filters internally the handover alarms for a givennumber of MEASUREMENT RESULT messages (defined by the parameter SDCCH_COUNTER, forfurther details refer to [5]).

For further details on the call establishment and handover protocol refer to [6], [8] and [9].

Disabling

- the BSC disables the algorithms whenever it initiates a channel release on the radio interface.

For further details on the call release procedure, refer to [10].

3.2.1.3 HO preparation function

The handover preparation function is completely handled by the BSC. The input parameters of thisfunction are provided by the Active channel preprocessing function every SACCH multiframe (refer to[19]), and by the RAM entity (See [15]).

The following sections describe the general behaviour of the handover preparation function with itstwo processes :- HO detection : see section 3.2.2,- HO candidate cells list evaluation : see section 3.2.3.

Handover detection


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An emergency, better conditions, and channel adaptation handover alarm can be detected everySACCH multiframe upon reception of the averaged measurements for handover detection. Aresource management handover is detected as soon as the message “Start HO” is received fromRAM, and concerns the current MS.

Handover candidate cells list evaluation

Once a handover alarm is detected, the HO detection process sends to the HO candidate cellevaluation process the list of the MS neighbouring cells with for each of them one of the handovercauses which have been verified. It is an internal BSC action (implementation dependent).

The handover candidate cells list evaluation builds a cells list which is, according to the case and thevalue of the timer T_FILTER, sent or not to HOM (see 3.2.4.). The specific management of Cause 28is explained in Section 3.2.4.1.3. Within the list of candidate cell, the message sent to HOM alsocontains the HO cause, the zone indication for concentric cells, and the new codec type for Cause 29.

Figure 15 is the SDL diagram of the HO preparation function.

Note : the event "HO parameters change" corresponds to a on-line reconfiguration (managed by thenetwork operator) of the handover parameters used for HO detection and HO candidate cellevaluation.


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Figure 15: SDL diagram - HO preparation/BSC.- partition 1/1. The specific alarm management for Causes 28 and 29 is not described in the figure.

Document produced by GEODE <VERILOG (C)>

Partition 1/1

1.5

DESCRIPTION: PCHO

PROCESS PCHO/Handover_preparation/Mode_B/BSC

Page: 1

03-Feb-1995

HO thresholdcomparison

HO candidatecell evaluation

idle channel

activate HOpreparation

'init T FILTER'

active channel

active channel

HOparameters

change

active channel

deactivateHO

preparation

idle channel

preproc measfor HO

HO thresholdcomparison

'conditionoccurs?'

(Yes)

HO candidatecell

evaluation

candidate cells ,HOcause TOHO execution

'triggerT FILTER'

Wait T FILTER

(No)

active channel

wait T FILTER

HOparameters

change

Wait T FILTER

T FILTERexpiry

active channel

deactivateHO

preparation

idle channel

for HO

comparison

'conditionoccurs?'

(Yes)

HO candidatecell

evaluation

candidate cells ,HOcause TOHO execution

'restartT FILTER'

Wait T FILTER

preproc meas

HO threshold

(No)

Wait T FILTER

‘Candidate celllist changes?'

(Yes)(No)

Wait T FILTER

'restartT FILTER'


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3.2.2 Handover detection

When dealing with emergency, better conditions and channel adaptation handovers, the HO detectionprocess is also called 'HO threshold comparison'. Threshold comparisons are performed for everynew set of average values AV_xxx_HO (i.e. every SACCH multiframe period) to detect possible needfor handover. The detection of a handover cause can be enabled/disabled by flags. For each possiblehandover cause a flag is foreseen except for Causes 10 and 11 (See Section 2.3.5). These two lattercauses are automatically enabled in a concentric cell.

For resource management handover Cause 29, the HO detection process consists in checking if amessage “Start HO” concerning the current call is received from RAM. The flag that allows to enableor disable Cause 29 is controlled by RAM and the transcoder.

Accordingly, HO alarms are sent to initiate the candidate cell evaluation function when a thresholdcondition occurs or an appropriate message is received from RAM. After each intercell handoveralarm, the raw list of candidate cells and the preferred target cell layer are indicated to the handovercandidate evaluation process.

3.2.2.1 Handover causes

Twenty four different causes can lead the ALCATEL handover algorithm to detect a need forhandover. These causes are identified with a number that is used for performance measurementcounters (See Table 12).


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Handover causes no

Too low quality on the uplink 2

Too low level on the uplink 3

Too low quality on the downlink 4

Too low level on the downlink 5

Too long MS-BS distance 6

Several consecutive bad SACCH frames received (rescue microcell handover) 7

Too low level on the uplink, inner zone (inner to outer zone handover, concentric or multibandcell)

10

Too low level on the downlink, inner zone (inner to outer zone handover, concentric ormultiband cell)

11

Power budget 12

Too high level on the uplink and the downlink, outer zone (out. to in. zone hand., concentric ormultiband cell)

13

High level in neighbour lower layer cell for slow mobile 14

Too high interference level on the uplink 15

Too high interference level on the downlink 16

Too low level on the uplink in a microcell compared to a high threshold 17

Too low level on the downlink in a microcell compared to a high threshold 18

Forced Directed Retry 20

High level in neighbour cell in the preferred band 21

Too short MS-BTS distance 22

Traffic HO 23

General capture HO 24

HR-to-FR channel adaptation due to bad radio quality 26

FR-to-HR channel adaptation due to good radio quality 27

Fast traffic handover 28

TFO handover 29

Table 12: Handover causes

These causes can be sorted into the four families :

- emergency HO causes : 2,3,4,5,6,7,10,11,15,16,17,18,22- better conditions HO causes : 12,13,14,20,21,23,24,28- channel adaptation HO causes : 26, 27- resource management : 29

Note : the relationships between the handover cause values used on the A interface and the handovercause values used by the ALCATEL BSS are given in reference [8].

In the following, the handover causes will be detailed according to the handover categories, asdefined in 2.3.3. The recapitulation of the cell types allowed for the serving and the candidate cell foreach handover cause can be found in appendix B.

3.2.2.1.1 Intercell ha ndover causes


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The equations (HO-1) to (HO-6) and (HO-18) to (HO-26) are checked only ifHO_INTERCELL_ALLOWED = ENABLE.

3.2.2.1.1.1 Emergency intercell ha ndover causes

The following general remarks need to be taken into account when reading this section.

The 3GPP coding of quality is contra-intuitive, since the value 0 codes for the best quality and 7 forthe worst. Thus, the comparison between two quality values must be understood in the opposite wayin terms of quality.

In order to take into account the frequency hopping in the RXQUAL evaluation the variableOFFSET_RXQUAL_FH is introduced (for more information refer to [20]).If on the corresponding channel,

Frequency hopping is applied then OFFSET_RXQUAL_FH = Offset_Hopping_HOotherwise OFFSET_RXQUAL_FH = 0

Offset_Hopping_HO is a parameter defined on a per cell basis.

In case of concentric or multiband cell, if an MS uses a TCH which belongs to the inner zone,MS_TXPWR_MAX must be replaced by MS_TXPWR_MAX_INNER in (HO-1) and (HO-2) andBS_TXPWR_MAX must be replaced by BS_TXPWR_MAX_INNER in (HO-3) and (HO-4).

The case where L_RXQUAL_XX_H_XXX + OFFSET_RXQUAL_FH > 7 corresponds in the equationsto L_RXQUAL_XX_H_XXX + OFFSET_RXQUAL_FH = 7.

Cause 2

CAUSE = 2 (too low quality on the uplink)

AV_RXQUAL_UL_HO > L_RXQUAL_UL_H + OFFSET_RXQUAL_FH (HO-1)and AV_RXLEV_UL_HO <= RXLEV_UL_IHand MS_TXPWR = min(P, MS_TXPWR_MAX)and EN_RXQUAL_UL = ENABLE

Note : This handover cause can also be triggered in case of repetitive intracell handover, see section3.2.2.1.1.2

Cause 3

CAUSE = 3 (too low level on the uplink)

AV_RXQUAL_UL_HO <= L_RXQUAL_UL_H + OFFSET_RXQUAL_FH (HO-2)and AV_RXLEV_UL_HO < L_RXLEV_UL_Hand MS_TXPWR = min(P, MS_TXPWR_MAX)and EN_RXLEV_UL = ENABLE

In (HO-1) and (HO-2), MS_TXPWR is the last MS_TXPWR_CONF value reported by the BTS in themessage MEASUREMENT RESULT or PREPROCESSED MEASUREMENT RESULT (refer to [19]).

Cause 4


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CAUSE = 4 (too low quality on the downlink)

AV_RXQUAL_DL_HO > L_RXQUAL_DL_H + OFFSET_RXQUAL_FH (HO-3)and AV_RXLEV_DL_HO <= RXLEV_DL_IHand BS_TXPWR = BS_TXPWR_MAXand EN_RXQUAL_DL = ENABLE

Note : This handover cause can also be triggered in case of repetitive intracell handover, see section3.2.2.1.1.2

Cause 5

CAUSE = 5 (too low level on the downlink)

AV_RXQUAL_DL_HO <= L_RXQUAL_DL_H + OFFSET_RXQUAL_FH (HO-4)and AV_RXLEV_DL_HO < L_RXLEV_DL_Hand BS_TXPWR = BS_TXPWR_MAXand EN_RXLEV_DL = ENABLE

Unlike the previous causes, the five following handover causes do not take into account the increaseof the MS or the BS power to its maximum.

Cause 6

CAUSE = 6 (too long MS-BS distance)

AV_RANGE_HO > U_TIME_ADVANCE (HO-5)and EN_DIST_HO = ENABLE

Cause 22

Cause 22 is only checked if the Cell range of the cell is set to extended_outer.

CAUSE = 22 (too short MS-BS distance)

AV_RANGE_HO ≤ L_TIME_ADVANCE (HO-23)

- L_TIME_ADVANCE : Minimum distance for handover from the extended outer zone

The three following equations are only used in microcells, i.e. the corresponding flags are set toENABLE if the cell profile is microcell (or CELL_DIMENSION_TYPE = micro) and to DISABLE for allother cell profiles.

Cause 7


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CAUSE = 7 (consecutive bad SACCH frames received in a microcell))

last N_BAD_SACCH consecutive SACCH frames are not correctly received (HO-20)and EN_MCHO_RESCUE = ENABLE

The cause 7 is managed with an internal BSC variable which counts the number of bad SACCHframes consecutively received :- this counter is incremented every time a MEASUREMENT RESULT or PREPROCESSEDMEASUREMENT RESULT message with BFI = 1(Bad Frame Indication) is received,- this counter is reset every time a MEASUREMENT RESULT or PREPROCESSEDMEASUREMENT RESULT message with BFI = 0 is received.The format of these two messages is given in [19].

Cause 17

CAUSE = 17 (Too low level on the uplink in a microcell compared to a high threshold)

AV_RXLEV_UL_MCHO(i) ### U_RXLEV_UL_MCHO (HO-18)and AV_RXLEV_UL_MCHO(i-1) > U_RXLEV_UL_MCHOand EN_MCHO_H_UL = ENABLE

In (HO-18) and (HO-19), 'i' is the index of the last MS measurement report.

Cause 18

CAUSE = 18 (Too low level on the downlink in a microcell compared to a high threshold)

AV_RXLEV_DL_MCHO(i) ### U_RXLEV_DL_MCHO (HO-19)and AV_RXLEV_DL_MCHO(i-1) > U_RXLEV_DL_MCHOand EN_MCHO_H_DL = ENABLE

3.2.2.1.1.2 Forced intercell ha ndover cause on quality

If on the uplink or on the downlink :i. either the intracell handovers for AMR or non AMR calls are forbidden in the serving cell (i.e.

EN_INTRA_UL/DL = DISABLE or EN_INTRA_UL/DL_AMR = disable),ii. or the repetition of intracell handover is not allowed in the serving cell,the handover detection function will indicate an intercell handover with cause "UL/DL quality too low",so far as the conditions on power level MS/BS_TXPWR_MAX, and on the flags EN_RXQUAL_UL/DLand HO_INTERCELL_ALLOWED are fulfilled.If EN_INTRA_UL/DL = disable, the condition AV_RXLEV_UL/DL=<RXLEV_UL/DL_IH is not checkedfor non AMR calls as it is done for a non-forced quality handover (see equations (HO-1) and (HO-3)).If EN_INTRA_UL/DL_AMR = disable, the condition AV_RXLEV_UL/DL=<RXLEV_UL/DL_IH is notchecked for AMR calls as it is done for a non-forced quality handover (see equations (HO-1) and(HO-3)).

The priority order of UL/DL is UL (uplink) and then DL (downlink).

The repetition may be inhibited by setting the O&M flag EN_INTRACELL_REPEATED to DISABLE.


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Concerning the case ii, the condition 'no previous intracell handover for this connection failed' is givenby the function handling the call in the BSC. This condition is used to avoid repetitive intracellhandovers. If an intracell handover for a given connection was not successful (handover failure, nofree timeslot, etc...) it is not repeated when the next handover alarm occurs.If an intracell handover is still required for this connection, the handover is turned into an intercellhandover as described above. Then for the same call in the new cell, intracell handover is allowedagain.

3.2.2.1.1.3 Better conditions int ercell ha ndover causes

Cause 12

Cause 12 is checked over all the neighbour cells belonging to the same layer . It means that it ischecked between cells whose CELL_LAYER_TYPE is single or upper, between cells whoseCELL_LAYER_TYPE is lower, and between cells whose CELL_LAYER_TYPE is indoor.

In addition to the condition on the cell layer type, the cell frequency band condition for checkingCause 12 in Eq. (HO-6) is as follows whether or not the MS is in the inner zone of a multiband cell:

Case the MS is not in the inner zone of a multiband cell− If the flag EN_MULTIBAND_PBGT_HO is set to disable, Cause 12 must not be checked

between cells which use different frequency band (i.e cells having differentCELL_BAND_TYPE).

− If the flag EN_MULTIBAND_PBGT_HO is set to enable, Cause 12 will be checked overall the neighbours cells without any cell frequency band restriction.

Case the MS is in the inner zone of a multiband cell− If the flag EN_MULTIBAND_PBGT_HO is set to disable, Cause 12 is checked over all the

neighbour multiband cells (FREQUENCY_RANGE= PGSM-DCS1800 or EGSM-DCS1800) which belong to the same BSC as the serving cell.


Cause 12 for handover from TCH to TCH and for directed retry on handover alarms from SDCCH toTCH is:

CAUSE = 12 (Power budget)

If EN_TRAFFIC_HO(0,n)=ENABLE (HO-6)then PBGT(n) > HO_MARGIN(0,n) + OFFSET_HO_MARGIN_INNER

+ max(0, DELTA_HO_MARGIN(0,n)) (n=1...BTSnum)else PBGT(n) > HO_MARGIN(0,n) + OFFSET_HO_MARGIN_INNER

and AV_RXLEV_PBGT_HO ≤ RXLEV_LIMIT_PBGT_HOand EN_PBGT_HO = ENABLE

with PBGT(n) = AV_RXLEV_NCELL(n) - AV_RXLEV_PBGT_HO (HO-7)- (BS_TXPWR_MAX - AV_BS_TXPWR_HO)- (MS_TXPWR_MAX(n) - MS_TXPWR_MAX)

- PING_PONG_MARGIN(n,call_ref)


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Note 1: Since a monoband MS can only receive measurements from the target cells having the samefrequency band as the serving cell, the case the flag EN_MULTIBAND_PBGT_HO is set toenable and the MS is monoband comes to check Cause 12 over all the target cells having thesame frequency band as the serving cell.

Note 2: In case the flag EN_MULTIBAND_PBGT_HO is set to enable and the MS is in the inner zoneof a multiband cell, the offset OFFSET_HO_MARGIN_INNER is kept unchanged whateverthe target cell frequency band is.

Note 3 : In (HO-7), OFFSET_HO_MARGIN_INNER is only used in the inner zone of a concentric ormultiband cell.

In addition to the same layer condition, the cell frequency band condition for checking Cause 12 inEq. (HO-6bis) is:

− If the flag EN_MULTIBAND_PBGT_HO is set to disable, Cause 12 must not be checkedbetween cells which use different frequency band (i.e. cells having differentCELL_BAND_TYPE).


Cause 12 for handover from SDCCH to SDCCH is:

CAUSE = 12 (Power budget)

PBGT(n) > HO_MARGIN(0,n) (n=1...BTSnum) (HO-6bis)and AV_RXLEV_PBGT_HO ≤ RXLEV_LIMIT_PBGT_HOand EN_PBGT_HO = ENABLE

The equation of PBGT is explained in details in appendix A.

- RXLEV_LIMIT_PBGT_HO : threshold above which it is not necessary to trigger a handover onpower budget.

- AV_RXLEV_NCELL(n) : average of RXLEV_NCELL(n) over A_PBGT_HO measurements(neighbour cell(n)).

- AV_RXLEV_PBGT_HO : average of the received levels RXLEV_DL_FULL or RXLEV_DL_SUBover A_PBGT_HO measurements (serving cell).

- BS_TXPWR_MAX : max power of the BTS in the serving cell (fixed value for each BTS).- AV_BS_TXPWR_HO : Average of BS_POWER over A_PBGT_HO measurements.- MS_TXPWR_MAX(n) : max. power level the MS is allowed to use in its neighbour cell(n).- MS_TXPWR_MAX : max. power the MS is allowed to use in the serving cell.- OFFSET_HO_MARGIN_INNER: offset which allows to take account of the radio differences

between outer and inner zone (especially in case of multiband cell).- PING_PONG_MARGIN(n,call_ref) is a penalty put on the cell n if :

it is the immediately precedent cell on which the call has been,this cell belongs to the same BSC as the serving cell,the call has not performed a forced directed retry towards the serving cell,less than T_HCP seconds have elapsed since the last handover.In this case PING_PONG_MARGIN(n,call_ref) = PING_PONG_HCP.If the call was not precedently on cell n, or if the preceding cell was external to theserving BSS, or if the call has just performed a forced directed retry, or if the timerT_HCP has expired, then PING_PONG_MARGIN(n,call_ref) = 0


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- DELTA_HO_MARGIN(0,n) is evaluated according to the traffic situation of the serving cell and theneighbour cell n (Traffic_load(n), refer to [15]) in the following way.If Traffic_load(0)=high and Traffic_load(n)=lowDELTA_HO_MARGIN(0,n)= -DELTA_DEC_HO_marginIf Traffic_load(0)=low and Traffic_load(n)=highDELTA_HO_MARGIN(0,n)= DELTA_INC_HO_marginelse DELTA_HO_MARGIN(0,n)=0where DELTA_DEC_HO_margin allows the cause 23 (traffic handover) detectionwhen the traffic in the serving cell is high and is low in the cell n.DELTA_INC_HO_margin allows to penalise the cause 12 detection when thetraffic in the serving cell is low and is high in the cell n.

Note 1 : In the case of concentric or multiband cells, if the channel is in the inner zone (ZONE_TYPE= INNER), BS_TXPWR_MAX and MS_TXPWR_MAX in equation (HO-7) must be replacedby BS_TXPWR_MAX_INNER and MS_TXPWR_MAX_INNER respectively.If the channel is in the outer zone (ZONE_TYPE = OUTER), the formulation of equation(HO-7) is not changed.

Note 2 : The value of PBGT(n) is calculated every SACCH period for each neighbour cell n whosemeasures are kept in the book-keeping list.

Note 3 : If no traffic load evaluation is available in an external cell n, the Traffic_Load(n) parameteris set to indefinite.

The four following equations are only checked for handover from TCH to TCH and for directed retryon handover alarms from SDCCH to TCH. For handover from SDCCH to SDCCH, they are notchecked.

Cause 14

Cause 14 is checked if and only if CELL_LAYER_TYPE = upper or lower (this rule is applied at theOMC by disabling the flag EN_MCHO_NCELL when CELL_LAYER_TYPE is different from bothupper and lower).

The two following cases have to be considered depending on the cell layer of the serving cell.

Case the serving cell is in the upper layer (CELL_LAYER_TYPE(0) = upper)

− If the MS is in the inner zone of a multiband cell, the cause 14 is checked over all theneighbour cells with CELL_LAYER_TYPE(n) = lower or indoor except the ones withEN_BI-BAND_MS(n)=DISABLE and CELL_BAND_TYPE(n)=CELL_BAND_TYPE(0).

− If the MS is not in the inner zone of a multiband cell and the MS is in a cell withCELL_BAND_TYPE(0)=PREFERRED_BAND, the cause 14 is checked over all theneighbour cells with CELL_LAYER_TYPE(n) = lower or indoor except the ones withEN_BI-BAND_MS(n)=DISABLE and CELL_BAND_TYPE(n)<>PREFERRED_BAND.

− If the MS is not in the inner zone of a multiband cell and the MS is in a cell withCELL_BAND_TYPE(0)<>PREFERRED_BAND, the cause 14 is checked over all theneighbour cells with CELL_LAYER_TYPE(n) = lower or indoor.

Case the serving cell is in the lower layer (CELL_LAYER_TYPE(0) = lower)− If the MS is in the inner zone of a multiband cell, the cause 14 is checked over all the

neighbour cells with CELL_LAYER_TYPE(n) = indoor except the ones with EN_BI-BAND_MS(n)=DISABLE and CELL_BAND_TYPE(n)=CELL_BAND_TYPE(0).


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− If the MS is not in the inner zone of a multiband cell and the MS is in a cell withCELL_BAND_TYPE(0)=PREFERRED_BAND, the cause 14 is checked over all theneighbour cells with CELL_LAYER_TYPE(n) = indoor except the ones with EN_BI-BAND_MS(n)=DISABLE and CELL_BAND_TYPE(n)<>PREFERRED_BAND.

− If the MS is not in the inner zone of a multiband cell and the MS is in a cell withCELL_BAND_TYPE(0)<>PREFERRED_BAND, the cause 14 is checked over all theneighbour cells with CELL_LAYER_TYPE(n) = indoor.

In order to limit the ping-pong effect, Cause 14 is not checked while the timer T_INHIBIT_CPT isrunning (See section 3.2.4).

CAUSE = 14 (high level in neighbour lower or indoor layer cell for slow mobile)

(HO-21)

CELL_LAYER_TYPE(0) = upperand AV_RXLEV_NCELL(n) > L_RXLEV_CPT_HO(0,n) n= (1...BTSnum)and MS_SPEED = slowand EN_MCHO_NCELL = ENABLE

Or

CELL_LAYER_TYPE(0) = lowerand AV_RXLEV_NCELL(n) > L_RXLEV_CPT_HO(0,n) n = (1...BTSnum)and MS_SPEED <> fastand EN_MCHO_NCELL = ENABLE

Note 1 : In (HO-21), the condition on the MS_SPEED variable depends on the cell layer type. Thereason for this is that the MS_SPEED variable is by default set to indefinite. Then, theMS_SPEED can changed from indefinite to slow only when the MS is in a upper layer cell.To give an ease access to the MS in the indoor layer, it is therefore necessary to allowCause 14 when MS_SPEED = indefinite in the lower layer.

Cause 21

Cause 21 is checked if and only if CELL_BAND_TYPE is different from the parameterPREFERRED_BAND (This checking is performed at the BSC). It is checked for all neighbour cells nin the preferred band (i.e. CELL_BAND_TYPE(n) = PREFERRED_BAND). If the parameterPREFERRED_BAND is set to 'none', the equation is never checked.


CAUSE = 21 (high level in neighbour cell in the preferred band) (HO -22)

Traffic_load(0) = MULTIBAND_TRAFFIC_CONDITIONand Traffic_load(n) <> highand AV_RXLEV_NCELL(n) > L_RXLEV_CPT_HO(0,n) + max(0,[MS_TXPWR_MAX(n)-P])and EN_PREFERRED_BAND_HO = ENABLE

- Traffic_load(0) : situation of the traffic in the serving cell.


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- MULTIBAND_TRAFFIC_CONDITION : Condition on traffic load in the serving cell for a multibandhandover. This parameter can have three different values:

ANY_LOAD: the condition on traffic load is always fulfilled.NOT_LOW: the condition on traffic load is fulfilled only if Traffic_load(0)<>low.HIGH: the condition on traffic load is fulfilled only if Traffic_load(0)=high.

Note : MS_TXPWR_MAX(n) and P are the powers in the preferred band.

Cause 23

Cause 23 is checked over all the neighbour cells belonging to the same layer. It means that it ischecked between cells whose CELL_LAYER_TYPE is single or upper, between cells whoseCELL_LAYER_TYPE is lower, and between cells whose CELL_LAYER_TYPE is indoor.This cause must not be checked between cells which use different frequency band (i.e cells havingdifferent CELL_BAND_TYPE)

In addition to the condition on the cell layer type, if the MS is in the inner zone of a multiband cell, thecause 23 is checked over all the neighbour multiband cells (FREQUENCY_RANGE= PGSM-DCS1800 or EGSM-DCS1800) which belong to the same BSC as the serving cell.

CAUSE = 23 (Traffic HO) (HO -24)

DELTA_HO_MARGIN(0,n) < 0dBand PBGT(n) > HO_MARGIN(0,n) + OFFSET_HO_MARGIN_INNER +DELTA_HO_MARGIN(0,n)

(n=1...BTSnum)and EN_TRAFFIC_HO(0,n) = ENABLE

DELTA_HO_MARGIN(0,n) is evaluated as for cause 12.

Cause 24

If the MS is in the inner zone of a multiband cell, Cause 24 is checked over all the neighbour cellsexcept the ones with EN_BI-BAND_MS(n)=DISABLE and CELL_BAND_TYPE(n) =CELL_BAND_TYPE(0).

If the MS is not in the inner zone of a multiband cell and the MS is in a cell withCELL_BAND_TYPE(0)=PREFERRED_BAND, the cause 24 is checked over all the neighbour cellsexcept the ones with EN_BI-BAND_MS(n)=DISABLE and CELL_BAND_TYPE(n) <>PREFERRED_BAND.

If the MS is not in the inner zone of a multiband cell and the MS is in a cell withCELL_BAND_TYPE(0)<>PREFERRED_BAND, the cause 24 is checked over all the neighbour cells.


CAUSE = 24 (General capture HO) (HO -25)

Traffic_load(0) = CAPTURE_TRAFFIC_CONDITIONand Traffic_load(n) <> highand AV_RXLEV_NCELL(n) > L_RXLEV_CPT_HO(0,n) + max(0,[MS_TXPWR_MAX(n)-P])and EN_GENERAL_CAPTURE_HO = ENABLE


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- Traffic_load(0) : situation of the traffic in the serving cell.- CAPTURE_TRAFFIC_CONDITION : Condition on traffic load in the serving cell for a generalcapture handover. This parameter can have three different values:

ANY_LOAD: the condition on traffic load is always fulfilled.NOT_LOW: the condition on traffic load is fulfilled only if Traffic_load(0)<>low.HIGH: the condition on traffic load is fulfilled only if Traffic_load(0)=high.

Cause 28

Cause 28 is only checked if the channel of the current MS can support the channel rate required bythe queued request. If the channel rate of the queued request is HR, Cause 28 is only checked if theMS is using a HR or a FR channel on a dual rate TRX. If the channel rate of the queued request isFR, Cause 28 is only checked if the MS is using a FR channel whatever the TRX type is dual rate ornot.

In case the serving cell is a monoband cell, and CELL_BAND_TYPE = GSM, andPLMN_FREQUENCY_BANDS = GSM900_and_DCS1800_bands, Cause 28 is only checked if thecurrent MS is allocated to a P-GSM TRX.

In case the serving cell is a concentric cell or a multiband cell, Cause 28 is only checked if the currentMS is located in the outer zone of the serving cell. Furthermore, if CELL_BAND_TYPE = GSM andPLMN_FREQUENCY_BANDS = GSM900_and_DCS1800_bands, Cause 28 is checked only if thecurrent MS is allocated to a P-GSM TRX.

This cause only applies to handovers from TCH to TCH.

CAUSE = 28 (Fast traffic HO)

AV_RXLEV_NCELL(n) > L_RXLEV_NCELL_DR(n) + max(0,[MS_TXPWR_MAX(n)-P])for n = 1,..., BTSnum (HO -

26)and

t(n) > FREElevel_DR(n)and

EN_CAUSE_28 = enable

where- FREElevel_DR(n) is the minimum threshold of free TCHs in the neighbour cell n for forced directedretry and fast traffic handover.- t(n) is the absolute number of free TCHs in the neighbour cell n.

Note 1: The threshold L_RXLEV_NCELL_DR(n) is the observed level from the neighbour cell n atthe border of the area where fast traffic handovers are enabled. This threshold fixes the sizeof the overlapping area where fast traffic handovers can be performed. It should be greaterthan RXLEVmin(n).

Note 2: For external cells, t(n) is fixed to the arbitrary value t(n) = 255. Therefore, settingFREElevel_DR(n) to 255 for an external cell inhibits outgoing external fast traffic handovertowards this cell. Setting FREElevel_DR(n) to any other value will allow outgoing externalfast traffic handover towards this cell.

Note 3: If the BTS has dual rate capability, t(n) = absolute number of free Dual Rate TCH

Note 4: The flag EN_CAUSE_28 is not an OMC flag but an HOP flag. Its enabling and disabling isexplained in Section 3.2.4.


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3.2.2.1.2 Intracell ha ndover causes

The following general remarks need to be taken into account when reading this section.

The 3GPP coding of quality is contra-intuitive, since the value 0 codes for the best quality and 7 forthe worst. Thus, the comparison between two quality values must be understood in the opposite wayin terms of quality.

In order to take into account the frequency hopping in the RXQUAL evaluation the variableOFFSET_RXQUAL_FH is introduced (for more information refer to [20]).If on the corresponding channel,

Frequency hopping is applied then OFFSET_RXQUAL_FH = Offset_Hopping_HOotherwise OFFSET_RXQUAL_FH = 0

Offset_Hopping_HO is a parameter defined on a per cell basis.

The case where L_RXQUAL_XX_H_XXX + OFFSET_RXQUAL_FH > 7 corresponds in the equationsto L_RXQUAL_XX_H_XXX + OFFSET_RXQUAL_FH = 7.

3.2.2.1.2.1 Emergency intracell ha ndover causes

Cause 15

Two set of parameters are defined to control Cause 15 whether the current call is AMR or not:− If the current call is not an AMR call,

EN_CAUSE_15 = EN_INTRA_UL,THR_RXQUAL_CAUSE_15 = L_RXQUAL_UL_H.

− If the current call is an AMR call,EN_CAUSE_15 = EN_INTRA_UL_AMR,THR_RXQUAL_CAUSE_15 = L_RXQUAL_UL_H_AMR.

CAUSE = 15 (too high interference level on the uplink)

AV_RXQUAL_UL_HO > THR_RXQUAL_CAUSE_15 + OFFSET_RXQUAL_FH(HO-8)

and AV_RXLEV_UL_HO > RXLEV_UL_IHand EN_CAUSE_15 = ENABLEand ( no previous intracell handover for this connection failed

or EN_INTRACELL_REPEATED = ENABLE ).

Note 1: The variables EN_CAUSE_15 and THR_RXQUAL_CAUSE_15 are specific to HOP.

Cause 16

Two set of parameters are defined to control Cause 16 whether the current call is AMR or not:− If the current call is not an AMR call,

EN_CAUSE_16 = EN_INTRA_DL,THR_RXQUAL_CAUSE_16 = L_RXQUAL_DL_H.

− If the current call is an AMR call,EN_CAUSE_16 = EN_INTRA_UL_AMR,THR_RXQUAL_CAUSE_16 = L_RXQUAL_DL_H_AMR.


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CAUSE = 16 (too high interference level on the downlink)

AV_RXQUAL_DL_HO > THR_RXQUAL_CAUSE_16 + OFFSET_RXQUAL_FH(HO-9)

and AV_RXLEV_DL_HO > RXLEV_DL_IHand EN_CAUSE_16 = ENABLEand (no previous intracell handover for this connection failed

A or EN_INTRACELL_REPEATED = ENABLE )

Note 1: The variables EN_CAUSE_16 and THR_RXQUAL_CAUSE_16 are specific to HOP.

The following handover Causes 10 and 11 are specific to concentric or multiband cell configurations.They are checked only if CELL_PARTITION_TYPE = CONCENTRIC and the active channel is aTCH.Furthermore, they are only valid for handover from the inner zone to the outer zone of the concentricor multiband cell. Thus, the following conditions are checked only if ZONE_TYPE = INNER_ZONE (itmeans that the channel is in the inner zone partition).

Cause 10

CAUSE = 10 (too low level on the uplink, inner zone)

AV_RXLEV_UL_HO < RXLEV_UL_ZONE (HO-15)and MS_TXPWR = min(P, MS_TXPWR_MAX_INNER)

Cause 11

CAUSE = 11 (too low level on the downlink, inner zone)

AV_RXLEV_DL_HO < RXLEV_DL_ZONE (HO-16)and BS_TXPWR = BS_TXPWR_MAX_INNER

3.2.2.1.2.2 Better conditions int racell ha ndover cause

Cause 13

Cause 13 is specific to concentric or multiband cell configurations. It is checked only ifCELL_PARTITION_TYPE = CONCENTRIC and the active channel is a TCH.Furthermore, it is only valid for handover from the outer zone to the inner zone of the concentric ormultiband cell. Thus, the following condition is checked only if ZONE_TYPE = outer (it means that thechannel is in the outer zone partition).

If the FREQUENCY_RANGE = PGSM-DCS1800 or EGSM-DCS1800 (the MS is in a multiband cell),the cause is checked only if the MS is biband. Furthermore, if the MS is in a EGSM-DCS1800multiband cell, there is only G1 TRXs in the inner zone, and the MS is biband but does not supportthe E-GSM band, then the cause is not checked.

The following cause must be checked for all the neighbour cells in the same layer and the samefrequency band as the serving cell.


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If the load balance between the inner and outer zones is allowed, i.e. EN_LOAD_BALANCE = enable,Cause 13 is only checked if the flag EN_CAUSE_13 is set to enable. This later flag is sent to HOP byRAM in the “TCH usage information” message. EN_CAUSE_13 is set to enable by RAM when theinner zone is less loaded than the outer zone.

CAUSE = 13 (Too high level on the uplink and the downlink, outer zone)

AV_RXLEV_UL_HO > RXLEV_UL_ZONE + ZONE_HO_HYST_UL + (HO-17)(MS_TXPWR - MS_TXPWR_MAX_INNER)+ PING_PONG_MARGIN(0, call_ref)

and AV_RXLEV_DL_HO > RXLEV_DL_ZONE + ZONE_HO_HYST_DL +BS_TXPWR - BS_TXPWR_MAX_INNER+ PING_PONG_MARGIN(0, call_ref)

and AV_RXLEV_NCELL_BIS(n) ≤ NEIGHBOUR_RXLEV(0,n)and EN_CAUSE_13 = enableand EN_BETTER_ZONE_HO = ENABLE

ZONE_TYPE = OUTER ZONE means that the channel is in the outer zone partition.RXLEV_DL_ZONE : Threshold of downlink received level for interzone handover,RXLEV_UL_ZONE : Threshold of uplink receive level for interzone handover,ZONE_HO_HYST_UL : Hysteresis uplink for interzone handover from the outer to the inner zone

which also takes account of the propagation difference between GSM and DCS in the case ofmultiband cell,

ZONE_HO_HYST_DL : Hysteresis downlink for interzone handover from the outer to the inner zonewhich also takes account of the propagation difference between GSM and DCS and of thedifference of output power in the BTS in the two bands in the case of multiband cell,

MS_TXPWR_MAX_INNER : Maximum permissible transmission power of the mobile station in theinner zone of the concentric or multiband cell,

BS_TXPWR_MAX_INNER : Maximum permissible transmission power of the base station in the innerzone of the concentric or multiband cell,

AV_RXLEV_DL_HO and AV_RXLEV_UL_HO : see previous sections,MS_TXPWR and BS_TXPWR : last BS_POWER and MS_TXPWR_CONF reported by the BTS in

the MEASUREMENT RESULT (see section 4.1).NEIGHBOUR_RXLEV(0,n) : Threshold of maximum downlink received level from the neighbour cells.PING_PONG_MARGIN(0,call_ref) is a penalty put on the cause 13 if :

the immediately precedent zone on which the call has been is the inner zone ofthe serving cell, the last handover was not an external intracell handover (casewhich can occur in the DCS inner zone of a multiband cell in case of emergencyhandover see 3.2.2.3), less than T_HCP seconds have elapsed since the lasthandover.In this case PING_PONG_MARGIN(0,call_ref) = PING_PONG_HCP.If the call was not precedently on the serving cell’s inner zone (case of intercell orintrazone handover), or if the timer T_HCP has expired, thenPING_PONG_MARGIN(0,call_ref) = 0

Note : For the computation of AV_RXLEV_NCELL_BIS(n) refer to [19].

3.2.2.1.2.3 Channel adaptation handover causes

Cause 26

The triggering of Cause 26 depends on the set of parameters and the triggering of Causes 15 and 16for AMR calls. When the intracell HO Causes 15 or 16 are allowed for an AMR call in the serving cell,


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i.e. EN_INTRA_UL_AMR = enable or EN_INTRA_DL_AMR = enable, Cause 26 shall be checked onlyif a previous intracell HO Cause 15 or 16 has already been triggered for this call in the serving cell.This condition allows to perform one intracell HO before triggering a HR-to-FR channel adaptation.

The check of Cause 26 is always allowed when the intracell HO Causes 15 and 16 are both set todisable, i.e. EN_INTRA_UL_AMR = disable and EN_INTRA_DL_AMR = disable.

Cause 26 is only checked if the current channel is half rate, and corresponds to an AMR call.Furthermore, the current channel has to be dual rate (DR) and changes allowed (CA) for checkingCause 26.

According to the load of the serving cell, the variables THR_RXQUAL_CA and OFFSET_CA are setas follows:

If LOAD_SV3(0) = falseTHR_RXQUAL_CA = THR_RXQUAL_CA_NORMALOFFSET_CA = OFFSET_CA_NORMAL

If LOAD_SV3(0) = trueTHR_RXQUAL_CA = THR_RXQUAL_CA_HIGHOFFSET_CA = OFFSET_CA_HIGH


CAUSE = 26 (HR-to-FR channel adaptation due to bad radio quality)

Current rate is Half Rate (HO-27)and The current channel is dual rate and changes allowedand EN_AMR_FR = enableand { { AV_RXQUAL_UL_CA_HR_FR > THR_RXQUAL_CA

+ OFFSET_CA + OFFSET_RXQUAL_FHand

AV_RXLEV_UL_HO > RXLEV_UL_IH}

or{ AV_RXQUAL_DL_CA_HR_FR > THR_RXQUAL_CA

+ OFFSET_CA + OFFSET_RXQUAL_FHand

AV_RXLEV_DL_HO > RXLEV_DL_IH}

}and

EN_AMR_CA = enableand { (a previous intracell HO Cause 15 or 16 has been raised for this call in the serving cell)

or(EN_INTRA_UL_AMR = disable and EN_INTRA_DL_AMR = disable)

}}

Note 1 : The variables THR_RXQUAL_CA and OFFSET_CA are specific to Causes 26 and 27 inHOP. The relevant parameters that have to be set at the OMC areTHR_RXQUAL_CA_NORMAL, THR_RXQUAL_CA_HIGH, OFFSET_CA_NORMAL, andOFFSET_CA_HIGH.

Note 2 : Only the speech channels are allowed for Cause 26.

Cause 27


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Cause 27 is only checked if the current channel is full rate and corresponds to an AMR call.Furthermore, the current channel has to be dual rate (DR) and changes allowed (CA) for checkingCause 27.

According to the load of the serving cell, the variable THR_RXQUAL_CA is set as follows:If LOAD_SV3(0) = false

THR_RXQUAL_CA = THR_RXQUAL_CA_NORMAL,If LOAD_SV3(0) = true

THR_RXQUAL_CA = THR_RXQUAL_CA_HIGH


CAUSE = 27 (FR-to-HR channel adaptation due to good radio quality)

Current rate is Full Rateand The current channel is dual rate (DR) and changes allowed (CA)and EN_AMR_HR = enableand AV_RXQUAL_UL_CA_FR_HR ≤ THR_RXQUAL_CA + OFFSET_RXQUAL_FHand AV_RXQUAL_DL_CA_FR_HR ≤ THR_RXQUAL_CA + OFFSET_RXQUAL_FH (HO-

28)and EN_AMR_CA = enable

Note 1 : The variable THR_RXQUAL_CA is specific to Causes 26 and 27 in HOP. The relevantparameters that have to be set at the OMC are THR_RXQUAL_CA_NORMAL,THR_RXQUAL_CA_HIGH.

Note 2 : Only the speech channels are allowed for Cause 27.

The way Cause 27 interacts with Cause 26 is illustrated in Figure 16.

THR_RXQUAL_CA_NORMAL

THR_RXQUAL_CA_HIGH

good quality:0

bad quality:7

THR_RXQUAL_CA_NORMAL +OFFSET_CA_NORMAL

THR_RXQUAL_CA_HIGH +OFFSET_CA_HIGH

Load = FALS E Load = TRU E

HO cause 26

HO cause 27

Full Rate

Half Rate

Quality

HO cause 26

HO cause 27

Full Rate

Half Rate

Figure 16: Thresholds for channel adaptation. The frequency hopping offset is not shown in the figure.

3.2.2.1.2.4 Resource management ha ndover cause


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Unlike the other handover causes, the resource management handover cause is triggered upon thereception of a message from RAM independently of the radio measurements available every SACCHframe.

Cause 29

Cause 29 is checked upon the reception of the message “Start HO” from RAM. If Cause 29 istriggered, the new codec type is forwarded to HOM (See Section 3.2.4). This cause shall be triggeredonly once per received message checking the cause.

CAUSE = 29 (TFO handover)

(HO-29)The HO cause parameter in the message “Start HO” equals 29

and The call reference parameter in the message “Start HO” is the reference of the current call

Note 1 : The enabling/disabling of Cause 29 is independent of the flag HO_INTRACELL_ALLOWED.

Figure 17 is the state diagram of the handover detection process (signal level - signal quality) in caseof conventional cell environment. The HO causes for microcellular handover are not shown.The threshold values are only indicative.

Figure 17: State diagram for handover detection (signal level - signal quality)

RXLEV

RXQUAL

605040302010

0

0

1

2

3

4

5

6

7

L_RXQUAL_XX_H

L_RXLEV_XX_H L_RXLEV_XX_IH

(HO-8,HO-9)

Levelintercell HO

(HO-2,HO-4)

Quality intercell HO Intracell HO

(HO-1,HO-3)

Power Control


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Figure 18 represents the triggering areas of PBGT and traffic handovers according to the traffic loadin the serving cell and in the neighbour cell.

HO_MARGIN(n1,n2)

HO_MARGIN(n1,n2)-

DELTA_DEC_HO_margin

Traffic_load

PBGT(n2)

Traffic_load(n1)=lowTraffic_load(n2)=high

Traffic_load(n1)=highTraffic_load(n2)=low

Other cases

PBGT Handover

PBGT Handover

Traffic Handover

Traffic Handover

HO_MARGIN(n2,n1)-

DELTA_DEC_HO_margin

HO_MARGIN(n2,n1)+

DELTA_INC_HO_margin

PBGT Handover PBGT Handover

PBGT(n1)

2*H

O_M

AR

GIN

2*H

O_M

AR

GIN

+DE

LTA

_IN

C_H

O_m

argi

n-D

ELT

A_D

EC

_HO

_mar

gin

2*H

O_M

AR

GIN

+DE

LTA

_IN

C_H

O_m

argi

n-D

ELT

A_D

EC

_HO

_mar

gin

HO_MARGIN(n2,n1)

HO_MARGIN(n1,n2)+

DELTA_INC_HO_margin

Handover from n1 to n2

Handover from n2 to n1

Figure 18: PBGT(n) according to the traffic load in the serving cell and the neighbour cell.


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3.2.2.2 Handover causes priority

The handover causes are checked with the priority order defined in Table 13. The order 1corresponds to the highest priority whereas the order 19 to the lowest. The resource managementhandover 29 will have no priority since it is checked with a different trigger than the other handovercauses.

Order HO family HO cause HO causereference

1 Emergency HO - Consecutive bad SACCH frames Cause = 72 Emergency HO - Level uplink microcell - high threshold Cause = 173 Emergency HO - Level downlink microcell - high threshold Cause = 184 Emergency HO - Too low quality Uplink Cause = 25 Emergency HO - Too low quality Downlink Cause = 46 Emergency HO - Too low level Uplink Cause = 37 Emergency HO - Too low level Downlink Cause = 58 Emergency HO - Too long MS-BS distance Cause = 69 Emergency HO - Too short MS-BS distance Cause = 2210 Emergency HO - Inner zone too low level Uplink Cause = 1011 Emergency HO - Inner zone too low level Downlink Cause = 1112 Channel adapt. HO - HR-to-FR channel adaptation due to bad quality Cause = 2613 Emergency HO - Too high interference intracell Uplink Cause = 1514 Emergency HO - Too high interference intracell Downlink Cause = 1615 Better conditions HO - high level in neighbour cell in the preferred band Cause = 21

Better conditions HO - high level in neighbour lower layer cell for slowMS

Cause = 14

Better conditions HO - General capture handover Cause = 24Better conditions HO - Power budget Cause = 12Better conditions HO - Traffic handover Cause = 23

16 Better conditions HO - Outer zone level Uplink & Downlink Cause = 1317 Channel adaptation - FR-to-HR channel adaptation due to good quality Cause = 2718 Better conditions HO - Forced Directed Retry Cause = 2019 Better conditions HO - Fast traffic handover Cause = 28

Table 13: Priority order of alarms for Handover.

The better condition causes 21, 14, 24, 12 and 23 have the same priority. For each cell in the list ofpossible candidate cell is associated a cause.If a cell is in the candidate cell list because of 2 different causes, only the one with the highest priorityin the ordered list (cause 21, cause 14, cause 24, cause 12 and cause 23) in which cause 21 has thehighest priority is kept.

3.2.2.3 Indication of raw cell list and pref erred layer

This section is skipped for intracell handovers.

After an inter cell handover alarm has been detected, the candidate cell evaluation receives a rawcell list with for each cell one of the handover causes which have been verified and the indication ofthe preferred layer for the target cell.

### Case the serving CELL_LAYER_TYPE is single

When the serving CELL_LAYER_TYPE is single, the following rules are applied :The raw cell list is :

− for Better conditions intercell handover (Causes 12, 14, 20, 21, 23, 24, and 28) : the neighbourcells which verify the cause,


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− for Emergency handover : all neighbour cells; and if the MS is in the DCS1800 inner zone of amultiband cell, the serving cell must be added to the raw cell list with the MS zone indicationOUTER.

However, in both cases, if the serving cell is an extended-inner cell, the extended-outer cell must befiltered from the raw cell list except in case of handover cause 6.If the serving cell is an extended-outer cell, the extended-inner cell must be filtered from the raw celllist except in case of handover cause 22.

The indication of the preferred layer is PREF_LAYER = upper+single

### Case the serving CELL_LAYER_TYPE is upper

When the serving CELL_LAYER_TYPE is upper, the following rules are applied :

The cell raw list is calculated as :

- for better conditions intercell handover causes (causes 12, 14, 20, 21, 23, 24, and 28)

the subset of neighbour cells which verify the handover causes.

- for emergency handover causes:

the whole set of neighbour cells; and if the MS is in the DCS1800 inner zone of a multibandcell, the serving cell must be added to the raw cell list with the MS zone indication OUTER.

The indication of the preferred layer is calculated on basis of two rules

- Better conditions intercell handover causes (12, 14, 20, 21, 23, 24, and 28) will indicate :

PREF_LAYER = none

- the "Emergency" handover causes will indicate :

PREF_LAYER = upper+single

### Case the serving CELL_LAYER_TYPE is lower or indoor

When the serving CELL_LAYER_TYPE is lower or indoor, the following rules are applied :

The cell raw list is calculated as :

- for better conditions intercell handover causes (causes 12, 14, 20, 21, 23 , 24, and 28)

the subset of neighbour cells which verify the handover causes.If there is a cell in the list because of Cause 12, and MS_SPEED = fast, the cell raw list mustalso contain the whole set of internal neighbour umbrella cells with information Traffic_load(n)= low and CELL_LAYER_TYPE(n) = upper (they do not need to verify the HO cause).

- for emergency handover causes

Select the whole set of neighbour cells except the umbrella cells n (CELL_LAYER_TYPE(n) =upper), which do not verify:


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AV_RXLEV_NCELL(n)>OUTDOOR_UMB_LEV(0,n)and if the MS is in the inner zone of a multiband cell, the serving cell must be added to the rawcell list with the MS zone indication OUTER.

The indication of the preferred layer is calculated on basis of two rules

-"Better conditions intercell" handover causes (12, 14, 20, 21, 23 , 24, and 28) will indicate :

If there is a cell in the list because of Cause 12 and MS_SPEED = fast then PREF_LAYER =upper, else PREF_LAYER = none.

- the "Emergency" handover causes will indicate :

if EN_RESCUE_UM = enable (used generally for microcells) then PREF_LAYER = upper +singleif EN_RESCUE_UM = disable (used for other cell types ) then PREF_LAYER = lower + indoorif EN_RESCUE_UM = indefinite then PREF_LAYER = none

Table 14 and Table 15 resume the indications given to the candidate cell evaluation process whenthe serving CELL_LAYER_TYPE = lower or indoor.

Indication MS_SPEED = fast andthere is a cell in the list

because of cause 12

MS_SPEED <> fast orHandover cause <> 12

Raw cell listfor Better cell HO

subset of cells verifyingthe HO causes plus all

neighbour umbrellacells with

Traffic_load(n)=low

subset of cells verifyingthe HO causes

PREF_LAYERfor Better cell HO

upper none

Table 14: Indications to candidate evaluation for better conditions intercell handovers when theserving CELL_LAYER_TYPE = lower or indoor.

Indication EN_RESCUE_UM =ENABLE

EN_RESCUE_UM =DISABLE

EN_RESCUE_UM =indefinite

Raw cell listfor Emergency HO

all neighbour cells (1)except the umbrella cells

which do not verifyAV_RXLEV_NCELL(n)>OUTDOOR_UMB_LEV(0

,n).

all neighbour cells (1)except the umbrella cells

which do not verifyAV_RXLEV_NCELL(n)>OUTDOOR_UMB_LEV(0

,n).

all neighbour cells (1)except the umbrellacells which do not

verifyAV_RXLEV_NCELL(n)>OUTDOOR_UMB_

LEV(0,n).PREF_LAYERfor Emergency HO

upper + single lower + indoor none

Table 15: indications to candidate evaluation for emergency handovers when the servingCELL_LAYER_TYPE = lower or indoor.

(1): if the MS is in the DCS inner zone of a multiband cell, the serving cell must be added to the rawcell list with the MS zone indication OUTER.


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3.2.3 HO Candidate Cell Evaluation

The HO candidate evaluation process is run after all intercell handover alarms as shown in Figure 19.In case of intra-cell handover alarm (HO causes 10, 11, 13, 15, 16, 26, 27 and 29), the candidate cellevaluation process is skipped since the target cell is also the serving cell. For intracell handovers in aconcentric or multiband cell, the zone which the MS is currrently allocated to (either outer or innerzone) is forwarded to RAM via HOM together with the serving cell. In this case, the MS zoneindication is not determined by the radio criterion presented in Cause 13 and Section 3.1.2.1.

Handover Causes2,3,4,5,6,7,17,

18,22,28

Handover Cause20

Ordering process foremergency HO based on theORDER/GRADE evaluation

HO Detection HO Candidate Cell Evaluation

Handover Causes10,11,13,15,16,26,

27,29

Ordering process for betterconditions HO based on theORDER/GRADE evaluation

Ordering process foremergency HO based on the

forced directed retry evaluation

Filteringprocess

Handover Causes12,14,21,23,24

Figure 19: Functional diagram of the HO candidate cell evaluation function.

3.2.3.1 Ordering process

The handover detection gives as indication the raw cell list and the preferred layer for the handover.In case of emergency handover alarms, cause 20 alarm, or Cause 28 alarm, the cell evaluation willorder the cells given in the raw list, putting in the first position the cells belonging to the preferredlayer, having the highest priority (if EN_PRIORITY_ORDERING=ENABLE) and/or having the samefrequency band type as the serving cell. In case of an intercell handover alarm, if the serving cellbelongs to the raw cell list (emergency handover from the DCS inner zone of a multiband cell), thiscell is put at the end of the candidate cell list with the MS zone indication OUTER.In case of better condition handover alarms (except causes 20 and 28), the cell evaluation will orderthe cells given in the raw list, putting in the first position the cells belonging to the preferred layer andhaving the highest priority (if EN_PRIORITY_ORDERING=ENABLE).

Input p arametersThe ordering process receives (refer to input flows described in section 2.3.6) :

- measurements of up to 32 neighbour cells (TCU internal indication) handled by the BSC cellbook-keeping function.- the raw cell list of potential candidates to be ordered with for each of them one of the handovercauses which have been verified.- the preferred layer for the target cell indicated by the variable PREF_LAYER- the cell configuration parameters which contains the variable CELL_BAND_TYPE.


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atel Ordering process for emergency HO alarm ( plus Causes 20 and 28)

In case of emergency handover alarm, cause 20 alarm, or Cause 28 alarm, the target cell list is builtfrom the cell ordering according to target layer, target band (see Section 2.3.4.1) and the priority ofeach cells (if EN_PRIORITY_ORDERING=ENABLE) and from the cell evaluation function indicatedby the flag CELL_EV associated to the serving cell (see Sections 3.2.3.3 and 3.2.3.4).

Unlike the other causes, the cell evaluation of Cause 20 is directly based on the directed retry powerbudget PBGT_DR(n) without using the ORDER and GRADE cell evaluation processes. The specificcase of Cause 20 is further detailed in Section 3.3.3.

The priority of each cells is defined by the parameter PRIORITY(0,n). The cell priority introduced hereshall not be confused with the cause priority of Section 3.2.2.2.

The ordering of the target cell list (from the higher priority to the lower one) is performed according tothe following scheme :

{Candidate cells whose CELL_LAYER_TYPE = PREF_LAYER{

Candidate cells which have the lowest PRIORITY(0,n){

Candidate cells whose CELL_BAND_TYPE = serving CELL_BAND_TYPE{

cell ordering according to cell evaluation function}Candidate cells whose CELL_BAND_TYPE <> serving CELL_BAND_TYPE{

cell ordering according to cell evaluation function}

}Candidate cells which have the next lowest PRIORITY(0,n){




}...

}Candidate cells whose CELL_LAYER_TYPE <> PREF_LAYER{




cell ordering according to cell evaluation function


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}}Candidate cells which have the next lowest PRIORITY(0,n){




}...

}Serving cell (MS zone indication = OUTER)}

Ordering process for better c onditions HO alarm ( except Causes 20 and 28)

In case of better condition handover alarm except causes 20 and 28, the target cell list is built fromthe cell ordering according to target layer and the priority of each cells (ifEN_PRIORITY_ORDERING=ENABLE) and from the cell evaluation function indicated by the flagCELL_EV associated to the serving cell (see Sections 3.2.3.3 and 3.2.3.4).

The priority of each cells is defined by the parameter PRIORITY(0,n). The cell priority introduced hereshall not be confused with the cause priority of Section 3.2.2.2.

The ordering of the target cell list (from the higher priority to the lower one) is performed according tothe following scheme :

Candidate cells whose CELL_LAYER_TYPE = PREF_LAYER{


cell ordering according to cell evaluation function}Candidate cells which have the next lowest PRIORITY(0,n){


.

.

.}Candidate cells whose CELL_LAYER_TYPE <> PREF_LAYER{


cell ordering according to cell evaluation function}Candidate cells which have the next lowest PRIORITY(0,n){


.


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.

.}

Note : - if PREF_LAYER = none, only the second part of the scheme (i.e. candidate cells whoseCELL_LAYER_TYPE <> PREF_LAYER) is considered.

- if PREF_LAYER = upper+single, the condition for the first part of the scheme will be :CELL_LAYER_TYPE = upper or CELL_LAYER_TYPE = single. The condition for thesecond part will be CELL_LAYER_TYPE <> upper and CELL_LAYER_TYPE <> single.

- if PREF_LAYER = lower+indoor, the condition for the first part of the scheme will be :CELL_LAYER_TYPE = lower or CELL_LAYER_TYPE = indoor. The condition for thesecond part will be CELL_LAYER_TYPE <> lower and CELL_LAYER_TYPE <> indoor.

- if EN_PRIORITY_ORDERING=DISABLE, the priority(0,n) is not taken into account.

The flag CELL_EV is managed by the network operator on a per cell basis. It has two values, whichcorrespond to the two cell evaluation functions ORDER and GRADE (see Sections 3.2.3.3 and3.2.3.4) .A filtering process can be applied to the target list before the ORDER or GRADE evaluation processin case of emergency handovers. The filtering process, the ORDER or GRADE evaluation processare not applied to the serving cell when it is in the target cell list. The serving cell is always at the endof the target cell list.After the cell evaluation processing, the list of candidate target cells with their cause is provided toHOM. For Cause 28, the list of candidate cells is sent to the HOM only when the message “Start HO”concerning the current call and Cause 28 has been received from RAM.

Output parametersThe ordering process (after the filtering process) should provide to the handover alarm managementdescribed in Section 3.2.4 the list of candidate cells with their cause and with the serving cell at theend of the list in case of emergency handover from the DCS inner zone of a multiband cell.

The HO causes together with the CELL_PARTITION_TYPE parameter shall be used by HOM (forfurther details, see [13] and [15]) as described in Table 16:

CELL_PARTITION_TYPE###

HO cause###

Normal Concentric

15, 16Intracell handoverSelect a channel in thesame cell

Intrazone or interzonehandoverSelect a channel in thesame cell

26, 27 Intracell handoverChange the speechchannel rate and select achannel in the same cell

Intracell handoverChange the speechchannel rate and select achannel in the same cell

29 Intracell handoverSelect a new codec type

Intracell handoverSelect a new codec type

10, 11, 13Not applicable Interzone handover

Select a channel in theother zone


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OthersIntercell handoverChannel allocation isdescribed in ref [13] and[15].

Intercell handoverChannel allocation isdescribed in ref [13] and[15].

Table 16: Channel allocation strategy

3.2.3.2 Filtering pro cess

The filtering process allows to filter out cells from the target list before the ORDER or GRADEevaluation process.This process can be enabled or disabled by the flag EN_PBGT_FILTERING.This filtering process is inhibited for better conditions intercell handovers (HO causes 12, 14, 20, 21,23, or 24) except for Cause 28. It is not applied to the serving cell when it is in the target cell list.

If EN_PBGT_FILTERING is set to enable, all the cells(n) which do not fulfil the following condition(HO-13) are rejected from the cell list sent to the ORDER or GRADE evaluation process.

PBGT(n) > HO_MARGIN_XX(0,n) + OFFSET_HO_MARGIN_INNER (HO-13)

OFFSET_HO_MARGIN_INNER is only applied when the MS is in the inner zone of a concentric ormultiband cell.

HO_MARGIN_XX(0,n) has the following values:HO_MARGIN_XX(0,n)=HO_MARGIN_QUAL(0,n) If cause =2, 4 or 7HO_MARGIN_XX(0,n)=HO_MARGIN_LEV(0,n) If cause =3, 5, 17, 18, or 28HO_MARGIN_XX(0,n)=HO_MARGIN_DIST(0,n) If cause =6 or 22

If no cell fulfils the condition and the serving cell does not belong to the target cell list, the target celllist is empty and no further action is carried out.If the target list is not empty, it is sent to the ORDER or GRADE evaluation process according toCELL_EV.

3.2.3.3 ORDER cell evaluation process

The ORDER cell evaluation process is used by the ordering process of Section 3.2.3.1. Note that theword "PATHLOSS" was in the past sometimes used instead of "ORDER".

The value of ORDER(n) for each neighbour cell(n) is computed according to the following formula :

if EN_LOAD_ORDER = ENABLE and cell n is internal to the BSC

ORDER(n) = PBGT(n) + LINKfactor(0,n) (HO-10)+ FREEfactor(n) - FREEfactor(0)- HO_MARGIN_XX(0,n)

if EN_LOAD_ORDER = DISABLE or cell n is external to the BSC

ORDER(n) = PBGT(n) + LINKfactor(0,n) - HO_MARGIN_XX(0,n) (HO-10bis)


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For emergency handover causes (plus Cause 28), HO_MARGIN_XX(0,n) has the following values:HO_MARGIN_XX(0,n)=HO_MARGIN_QUAL(0,n) If cause =2, 4 or 7HO_MARGIN_XX(0,n)=HO_MARGIN_LEV(0,n) If cause =3, 5, 17,18, or 28HO_MARGIN_XX(0,n)=HO_MARGIN_DIST(0,n) If cause =6 or 22

For better cell handover causes, HO_MARGIN_XX(0,n)=HO_MARGIN(0,n)

- The flag EN_LOAD_ORDER is settable by OMC command.- LINKfactor(0,n), HO_MARGIN_QUAL(0,n), HO_MARGIN_LEV(0,n), HO_MARGIN_DIST(0,n) and

HO_MARGIN(0,n) are parameters set by OMC command for each neighbour cell(n).- FREEfactor(n) : weighting factor that takes into account the number of free traffic channels in a cell.

It is received in the message “TCH usage information” from RAM [15].- For TCH, FREEfactor(n) is set to the value specified in [15],- for SDCCH : FREEfactor(n) = 0.

- PBGT(n) is the power budget between the serving cell(0) and cell(n). For the formula, see appendixA.All neighbour cells(n) which fulfil the following condition (HO-11) are sorted according to theirORDER(n) :

AV_RXLEV_NCELL(n) > RXLEVmin(n) + max(0,[MS_TXPWR_MAX(n)-P]) (HO-11)

For multiband handover, P considered in (HO-11) corresponds to the classmark power in thefrequency band used by the cell n.

Equation (HO-11) ensures that the MS can communicate in the cell n.

For any handover cause, the first cell in the list is taken as target cell, i.e. the cell with the highestvalue of ORDER(n). The cells do not need to fulfil any other condition.

If no cell fulfils the condition and the serving cell does not belong to the target cell list, the target celllist is empty and no further action is carried out.

3.2.3.4 GRADE cell evaluation process

The GRADE cell evaluation process is used by the ordering process of Section 3.2.3.1. The value ofGRADE(n) for each neighbour cell(n) is computed according to the following formula :

if EN_LOAD_ORDER = ENABLE and cell n is internal to the BSC

GRADE(n) = PBGT(n) + LINKfactor(0,n) (HO-12)+ LOADfactor(n)

if EN_LOAD_ORDER = DISABLE or cell n is external to the BSC

GRADE(n) = PBGT(n) + LINKfactor(0,n) (HO-12bis)

- The flag EN_LOAD_ORDER is settable by OMC command.- LINKfactor(0,n) is a parameter set by OMC command for each cell(n).

LINKfactor (n1,n2) allows the operator to handicap or to favour the cell n1 with respect to itsneighbour cell n2. In particular, it can be used to disadvantage an external cell when an internal cellis also a possible candidate.


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- LOADfactor(n) : weighting factor that takes into account the relative load of traffic channels in a cell.It is received in the message “TCH usage information” from RAM [15]For TCH: LOADfactor(n) is set to the value specified in [15],For SDCCH : LOADfactor(i) = 0.

The real time traffic load and corresponding FREEfactor and LOADfactor are only known for thecells that are controlled by the current BSC. For the cells controlled by another BSC the traffic loaddoes not influence the candidate evaluation.

- PBGT(n) is the power budget between the serving cell(0) and the cell(n) (see appendix A fordefinition).

The greater is GRADE(n), the most suitable is the neighbour cell n compared to the serving cell.

All neighbour cells(n) which fulfil the following condition are sorted according to their GRADE(n).

Equation (HO-11) ensures that the MS can communicate in the cell n.

AV_RXLEV_NCELL(n) > RXLEVmin(n) + max(0,[MS_TXPWR_MAX(n)-P]) (HO-11)

For multiband handover, P considered in (HO-11) corresponds to the classmark power in thefrequency band used by the cell n.

For any handover cause the first cell in the list is taken as target cell, i.e. the cell with the highestvalue of GRADE(n). If no cell fulfils the condition and the serving cell does not belong to the targetcell list, the target cell list is empty and no further action is carried out.


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3.2.4 Handover alarm management

The handover alarm management is a part of the handover candidate cell evaluation entity. Its mainrole is to prepare the message that should be sent to HOM when an handover alarm has beendetected.

3.2.4.1 Alarm filtering process based on the timer T_ Filter

3.2.4.1.1 General case

The purpose of the alarm filtering process is (i) to avoid to send several times the same alarm to theHOM entity, and (ii) to send a specific message when the alarm disappears. This process is based onthe timer T_FILTER.

Each time a candidate cell list is provided by the handover candidate cell evaluation function or bythe candidate cell evaluation function for forced directed retry and T_FILTER is not running, themessage “ Alarm is sent to the HOM entity, and T_FILTER is started. This message contains:

− The list of the candidate cells as given by the handover candidate cellevaluation function,

− The HO Cause (per cell in the list), which is the number of the handovercause,

− The MS zone location (per concentric cell in the list),− The new codec type for Cause 29.

Each time a candidate cell list is provided by the handover candidate cell evaluation function or bythe candidate cell evaluation function for forced directed retry and T_FILTER is running, T_FILTER isrestarted and the new list is compared to the previous candidate cell list (See Figure 20).

If the list has changed (ie one or more cells have disappeared in relation to the previous list and/orone or more cells are new in the list), a handover alarm containing the candidate list is sent to theHOM entity.If the new list has not changed (ie the cells are the same, the number of cells is the same but theorder in the list can be different), no handover alarm is sent to the handover management entity.

hp

Highlight


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1) Compute the HOdetection function enabling

Cause 282) Compute the HO

candidate cell evaluation

Is thecandidate cell listdifferent from the

previousone?

Yes

HO Cause29 Others

28bis

HO Cause 28?No

(1)

1) Start T_FILTER2) Send the "Alarm"

message to HOM with thelist of candidate cell

(1)

1) Start T_FILTER2) Send the "Alarm"

message to HOM with theserving cell

Send the "Alarm" messageto HOM with the list of

candidate cell

Start T_FILTER

No(1)

Yes

New HO alarm detected

(except Cause 28)

Figure 20: Alarm filtering process based on the timer T_FILTER.

If the timer T_FILTER expires, a handover alarm message containing no candidate cell is sent to thehandover management entity. This message means: “no more alarm”. The expiry of T_FILTERmeans that the handover alarm initially triggered is considered as no longer valid.

3.2.4.1.2 Specific case of resource management ha ndovers (Cause 29)

Each time a HO Cause 29 is triggered by the handover detection process, T_FILTER is started orrestarted, and an “Alarm” message is sent to HOM independently of the triggering of the othercauses. In this case, only the serving cell is in the list of candidate cells.

3.2.4.1.3 Specific case of fast traffic ha ndovers (Cause 28)

The specific alarm management for Cause 28 is described in this section. Two steps are required inHOP to deal with Cause 28. The first step consist in checking whether the current MS is capable ofperforming a fast traffic handover when requested by RAM. In a second step, if RAM sends the “StartHO” message and it concerns the current call and Cause 28, HOP will send the HO alarm Cause 28to HOM through the T_FILTER mechanism.

Upon the reception of the message “Fast traffic HO request” from RAM, the check of Cause 28 isenabled by setting the HOP flag EN_CAUSE_28 to enable, and the reference and the channel rate ofthe queued request is stored. When a new candidate cell list is received from the HO candidate cellevaluation function because of Cause 28, the checking of Cause 28 is disabled by settingEN_CAUSE_28 to disable, and the message “Fast traffic HO ACK” is sent to RAM. This messagecontains (See also Section 4.2):

− The reference of the queued request, which is given in the message “Fast traffic HOrequest” sent by RAM,

− The call reference, which is the reference of the current call.


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At this step, even if Cause 28 is detected, the “Alarm” message is not send to HOM. This messagehandling is described in Figure 21.

If two “Fast traffic HO request” arrive after each other, only the last one will be taken into account.This last one concerns the top request of the queue. So only for the last received queued requestreference and channel rate, Cause 28 will be checked on reception of measurements. Every newreceived “Fast traffic HO request” will overwrite the queued request reference and channel rate to betaken into account when checking Cause 28.

1) EN_CAUSE_28 = enable2) Store the reference and the channel

rate of the queued request

Reception of the message "Fast trafficHO request" from RAM with the

reference and the channel rate of thequeued request

HO alarmCause 28?

Yes

No

1) Send the message "Fast traffic HOACK" to RAM with the reference of thequeued request and the call reference

2) EN_CAUSE_28 = disable

Figure 21: Enabling and disabling of the HOP flag EN_CAUSE_28.

In the same way that the Causes 29 and 30 are managed, we introduced here the Cause 28bis.Cause 28bis is checked upon the reception of the message “Start HO” from RAM. This cause shall betriggered only once per received message checking the cause.

CAUSE = 28bis (Fast traffic handover bis)

(HO-31)The HO cause parameter in the message “Start HO” equals 28

and The call reference parameter in the message “Start HO” is the reference of the current call

When an HO alarm is detected because of Cause 28bis, the handover detection function is computedwith the available radio measurements. All the relations for Cause 28 in (HO-26) are checked exceptthe condition EN_CAUSE_28 = enable. The handover cell evaluation function is then performedincluding Cause 28 if triggered. If a candidate cell list is received from the candidate cell evaluationfunction because of Cause 28, the timer T_FILTER is started or restarted, and the message “Alarm” is


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sent to HOM containing the list of the candidate cells. The interaction of Cause 28 with the T_FILTERmechanism is described in Figure 20.

Note 1 : Since several MS can acknowledge the “Fast traffic HO request”, RAM needs to obtain thecall reference to distinguish the different MS acknowledgement.

3.2.4.2 Alarm filtering process based on the timer T_INHIBIT_CPT

The role of the timer T_INHIBIT_CPT is to inhibit the capture handover Causes 14, 21, and 24 for awhile so as to reduce the ping-pong effect. The immediately preceding cell on which the MS has beenis here denoted n-1. According to the layer of the serving cell the following conditions must bechecked for starting the timer T_INHIBIT_CPT:− Case the serving cell is in the upper layer (CELL_LAYER_TYPE(0) = upper)

Condition 1 : The immediately preceding cell n-1 is in the indoor or lower layer, i.e.CELL_LAYER_TYPE(n–1) = lower or indoor, or the frequency band of theimmediately preceding cell n-1 is different from the frequency band of theserving cell 0, i.e. CELL_BAND_TYPE(n–1) <> CELL_BAND_TYPE(0).

Condition 2 : The call has previously performed an emergency internal handover onquality (Cause 2, 4, and 7) towards the serving cell or an externalhandover with the A interface GSM cause “uplink quality or downlinkquality” and there is a bi-directional adjacency link between the precedingexternal cell and the target cell.

If Conditions 1 and 2 are fulfilled the timer T_INHIBIT_CPT is started.

− Case the serving cell is in the lower layer (CELL_LAYER_TYPE(0) = lower)

Condition 3 : The immediately preceding cell is in the indoor layer, i.e.CELL_LAYER_TYPE(n–1) = indoor, or the frequency band of theimmediately preceding cell n-1 is different from the frequency band of theserving cell 0, i.e. CELL_BAND_TYPE(n–1) <> CELL_BAND_TYPE(0).

Condition 4 : The call has previously performed an emergency internal handover onquality (Cause 2, 4, and 7) towards the serving cell or an externalhandover with the A interface GSM cause “uplink quality or down linkquality” and there is a bi-directional adjacency link between the precedentexternal cell and the target cell.

If Conditions 3 and 4 are fulfilled the timer T_INHIBIT_CPT is started.

If these conditions are not fulfilled, the timer T_INHIBIT_CPT is not started.


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3.3 Directed retry preparation

3.3.1 General

3.3.1.1 Directed retry preparation ena bling and disabling

Enabling

The directed retry preparation is enabled upon reception of an indication from the handovermanagement entity (BSC internal message, see [13]). This indication is called "Start DR algos " in theSADT diagram of section 2.3.6.The directed retry is supported by the same processes as the handover preparation except for forceddirected retry (see section 2.4), consequently :- for directed retry on handover alarms, the enabling consists in changing the behaviour of the

candidate cell evaluation process (see section 3.2.3). This process looks for target cells for TCHchannel instead of SDCCH channel.

- for forced directed retry : both the detection and candidate cell evaluation processes are enabled atthis point in time.

Note : The handover preparation function is enabled when the SDCCH connection is established(reception of the ESTABLISH INDICATION from the corresponding BTS). Therefore the handoverpreparation is always enabled before the directed retry preparation. This allows the detectionprocess for forced directed retry, after its enabling, to get immediately measurements from theneighbouring cell measurements book-keeping.

When the directed retry preparation is enabled, SDCCH_COUNTER is stopped and not restarted.

Disabling

The directed retry preparation is disabled whenever the BSC initiates a channel release on the radiointerface.

3.3.1.2 Directed retry preparation function

The directed retry preparation function is completely handled by the BSC. The input parameters ofthis function are provided by the active channel preprocessing function (refer to [19]) which handlesthe neighbour cell list book-keeping. As the handover preparation function, the directed retrypreparation function can be divided into two processes : Alarm detection and Candidate cellevaluation.

Once the directed retry preparation enabled, a directed retry on handover alarms or forced directedretry alarm can be detected every SACCH multiframe upon reception of the averaged measurementsfor directed retry detection.

Once a directed retry alarm is detected, the alarm detection process sends to the candidate cellevaluation process the list of MS neighbouring cells with for each of them one of the handover causeswhich have been verified.

The candidate cell evaluation builds a cells list which is according to the case and the value ofT_FILTER sent or not to the BSC function in charge of the handover management entity (see 3.2.4.).

3.3.2 Alarm Detection


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Directed retry on handover alarms

The detection process is the Handover detection process described in section 3.2.2. except thatintracell handover alarms and Cause 28 must be ignored.Only intercell handover alarms are taken into account i.e. all handover causes except causesmentioned above.

Forced directed retry

The following condition is checked every measurement reporting period and if at least one inputpreprocessed parameter AV_RXLEV_NCELL_DR(n) is available.

CAUSE = 20 (high level in neighbour cell for forced directed retry)

AV_RXLEV_NCELL_DR(n) > L_RXLEV_NCELL_DR(n) ( n = 1 ... BTSnum ) (DR -1)and EN_FORCED_DR = ENABLE

The threshold L_RXLEV_NCELL_DR(n) is the observed level from the neighbour cell n at the borderof the area where forced directed retry is enabled (see 2.4.1). This threshold fixes the size of theoverlapping area where forced directed retry can be performed. It should be greater thanRXLEVmin(n).

Alarms priority

As explained in section 2.4, the handover alarms have priority over the forced directed retry alarm(HO cause 20). The priority order for handover alarms is indicated in section 3.2.2.2.

3.3.3 Candidate cell evaluation

Directed retry on handover alarmsThe candidate cell evaluation process is the one described in section 3.2.3 for TCH channel.

Forced directed retryThe candidate cell evaluation is performed when an alarm for forced directed retry is raised (cause =20).

This candidate cell evaluation process is performed as specified in Section 3.2.3. except that the cellevaluation function is reduced to a specific power budget evaluation called PBGT_DR(n).

All neighbour cells n which meet the following condition (DR-3) and (DR-4) are sorted according to theordering process for emergency HO described in Section 3.2.3.1 . Instead of using the ORDER orGRADE cell evaluation processes, the cell evaluation is computed according to the PBGT_DR(n) :

PBGT_DR(n) = AV_RXLEV_NCELL_DR(n) - AV_RXLEV_PBGT_DR (DR-2)- (BS_TXPWR_MAX - AV_BS_TXPWR_DR)- (MS_TXPWR_MAX(n) - MS_TXPWR_MAX)

For further details on the PBGT formula, see section 3.2.2.1.1.3 and appendix A.

AV_RXLEV_NCELL_DR(n) > RXLEVmin(n) + max(0,[MS_TXPWR_MAX(n)-P]) (DR-3)


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t(n) > FREElevel_DR(n) (DR-4)

with :- FREElevel_DR(n) : minimum threshold of free TCHs in the neighbour cell n for forced directed retry.- t(n) : absolute number of free TCHs in the neighbour cell n.

For external cells, t(n) is fixed to the arbitrary value t(n)=255.Therefore, setting FREElevel_DR(n) to 255 for an external cell inhibits outgoing external directedretry towards this cell. Setting FREElevel_DR(n) to any other value will allow outgoing externaldirected retry towards this cell.

Note : if the BTS has dual rate capability, t(n) = absolute number of free Dual Rate TCH

L_RXLEV_NCELL_DR(n) and FREElevel_DR(n) are parameters set by O&M for each neighbour celln.

If no cell fulfils the condition, the target cell list is empty and no further action is carried out.


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4. INTERFACES DESCRIPTION

4.1 3GPP interfaces/Physical interfaces

The messages used by the handover algorithms are carried on the Abis interface only.Note that for handover decision and execution, all the relevant messages transmitted on the Air, Abis,A interfaces are described in [8] and [9].

Note : In ref [19] is given the general structure of the Abis messages required by the handoveralgorithm. In particular, the fields for which it is stated in the 3GPP Technical Specification 08.58 ([3])"the coding of this field requires further elaboration" are described. For the coding of the othersinformation elements, refer to [3].

4.2 Internal interfaces

The different BSC internal interfaces with HOP are detailed in this section (See Figure 22). Theinformation exchanged between handover functions is also described in Sections 2 and 4.4.

HOP : Handover preparationThis entity is responsible of triggering handover alarms. To detect handover alarm, HOP checks

continuously i) the radio environment of the mobile (radio level, radio quality, possible target cells,traffic load, multi-layer network, etc.) and ii) the requests for handovers sent by RAM.

HOM : Handover managementThis entity is responsible of managing the channel changes depending on handover alarms sent

by the HOP entity, the O&M configuration of the BSS, the events arriving from the protocol entities,etc. The HOM behaviour is described in [13].

ICC : Internal channel changeThis entity is responsible of running the internal channel change protocol when the HOM asks for

it. The ICC behaviour is described in [8].

ECC : External channel changeThis entity is responsible of running the external channel change protocol, either for an outgoing

external channel change when the HOM asks for it (serving BSC) or autonomously for an incomingchannel change (target BSC). The ECC behaviour is described in [9].

RAM : Resource allocation and managementThis entity is responsible for managing the radio resources of the BSS. RAM can also trigger

handover alarm messages that are sent to HOP. The RAM behaviour is described in [15].

Direction Message Parameters of informationRAM --> HOP TCH usage information − Cell reference

− Total number of free TCH− LOADfactor and FREEfactor− AV_LOAD− Traffic_load− LOAD_SV3− EN_CAUSE_13

MS zone indication requestFast traffic HO request − Reference of the queued request

− Channel rate of the queued requestStart HO − HO cause

− Call reference− New codec type (for Cause 29)


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HOP --> RAM MS zone indication ACK − Indication of the zone where the MS is located inthe serving cell: outer or inner

Fast traffic HO ACK − Call reference− Reference of the queued request

HOM --> HOP Start DR algosHOP --> HOM Alarm − HO cause (per cell in the list)

− List of the candidate cells− MS zone indication (per concentric cell in the

list)− New codec type (for Cause 29)

Table 17: Details of the BSC internal interfaces with HOP.

ICC

HOP

HOMRAM

ECC

"TCH usage information""MS zone indication request""Fast traffic HO request""Start HO"

"MS zone indication ACK""Fast tra ffic HO ACK"

"Alarm""Start DR algos"

Figure 22: BSC internal interfaces with HOP.

4.3 Timers list

NAME RANGE BIN.RANGE BITS

T_FILTER (0 to 31)x960 ms 0:31 8


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Time after which a “no alarm” message (analarm message with no candidate cell, seesection 3.3.) is sent to the handovermanagement entity, if no new alarm has beendetected whilst running.

0=0 ms

31=31x960ms

T_HCP (0 to 240 ) sec 0:240 8

Time during which a handicap of PING_PONG_HCPis applied to the preceding cell power budget

0=0 s 240 = 240s

T_INHIBIT_CPT (0 to 240 ) sec 0:240 8

Time during which the HO Causes 14, 21, and 24 areinhibited

0=0 s 240 = 240s

LOAD_EV_PERIOD 1 to 30 1:30 8

Number of load samples (received everyTCH_INFO_PERIOD) for load averaging

1=1 , 30 = 30

TCH_INFO_PERIOD 2 to 25.5 sec 20:255 8

periodicity of the sending of the message 'TCHusage information' to the TCUs.

20=2 s, 255 =25.5 s

4.4 Parameters and variables list

This section provides a list of all the variables and parameters used in the algorithms and thusencountered in the text. For each entry will be found :- its name,- its meaning,- its physical range,- its binary range,- the number of bits into which it is encoded.The variables and parameters are ranked in the alphabetical order.

4.4.1 Handover

NAME RANGE BIN. RANGE BITS

AV_BS_TXPWR_DR max -30 to min 0 dB 0:30 5

Average Transmit Power at BS for PBGT_DRevaluation

step size 1 dB (relativevalue)

0 = 0 dB30 = -30 dB

AV_BS_TXPWR_HO max -30 to min 0 dB 0:30 5

Average Transmit Power at BS for PBGT evaluation step size 1 dB (relativevalue)

0 = 0 dB30 = -30 dB

AV_LOAD(n) 0 to 100 % 0:100 8

Averaging load of the cell n step size 1%

with a period equal to LOAD_EV_PERIOD

AV_RXLEV_DL_HO -110 to -47 dBm 0:63 8


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Average Receive Downlink Level step size 1 dBm 0=-110

of serving cell (used for Handover) 63=-47

AV_RXLEV_DL_MCHO -110 to -47 dBm 0:63 8

Average Receive Downlink Level of serving step size 1 dBm 0=-110

cell (used for Microcellular Handover) 63=-47

AV_RXLEV_NCELL(n) -110 to -47 dBm 0:63 8

Average Receive Level step size 1 dBm 0=-110

neighbour cell n at MS 63=-47

AV_RXLEV_NCELL_BIS(n) -110 to -47 dBm 0:63 8

Average Receive Level step size 1 dBm 0=-110

neighbour cell n at MS used for cause 13 63=-47

AV_RXLEV_UL_HO -110 to -47 dBm 0:63 8

Average Receive Uplink Level step size 1 dBm 0=-110

of serving cell (used for Handover) 63=-47

AV_RXLEV_UL_MCHO -110 to -47 dBm 0:63 8

Average Receive Uplink Level of serving step size 1 dBm 0=-110

cell (used for Microcellular Handover) 63=-47

AV_RXLEV_PBGT_HO -110 to -47 dBm 0:63 8

Average Receive Downlink Level of step size 1 dBm 0=-110

serving cell (PBGT calculation) 63=-47

AV_RXQUAL_DL_CA_HR_FR 0 to 7 0:7 coded with a 8

Average receive downlink quality of stepsize 0.1 stepsize of 0.1

serving cell (HR-to-FR channel adaptation)

AV_RXQUAL_UL_CA_HR_FR 0 to 7 0:7 coded with a 8

Average receive uplink quality of stepsize 0.1 stepsize of 0.1

serving cell (HR-to-FR channel adaptation)

AV_RXQUAL_DL_CA_FR_HR 0 to 7 0:7 coded with a 8

Average receive downlink quality of stepsize 0.1 stepsize of 0.1

serving cell (FR-to-HR channel adaptation)

AV_RXQUAL_UL_CA_FR_HR 0 to 7 0:7 coded with a 8

Average receive uplink quality of stepsize 0.1 stepsize of 0.1

serving cell (FR-to-HR channel adaptation)

AV_RXQUAL_UL_HO 0 to 7 0:7 coded with a 8

Average Receive Uplink Quality of stepsize 0.1 step size of 0.1

serving cell (used for Handover)

AV_RXQUAL_DL_HO 0 to 7 0:7 coded with a 8

Average Receive Downlink Quality of stepsize 0.1 step size of 0.1

serving cell (used for Handover)


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AV_RANGE_HO 0 to 63 x 3.69µs 0:63 8

Average Distance between MS and BS

BCCH_FREQUENCY 0 to 1023 0:1023 16

BCCH frequency used in the serving cell.

BCCH_FREQUENCY(n) 0 to 1023 0:1023 16

BCCH frequency used in the neighbour cell n.

SACCH_BFI 0 or 1 0:1 1

Bad Frame Indicator 0 : good frame

of the SACCH frame 1 : bad frame

BS_TXPWR max -30 to min 0 dB 0:15 5

Transmit Power at BS step size 2 dB (relativevalue)

0 = 0 dB15 = -30 dB

BS_TXPWR_MAX max -30 to min 0 dB 0:15 8

Maximum Transmit Power at BS step size 2 dB 0 = 0 dB

(relative value) 15= -30 dB

BS_TXPWR_MAX_INNER max - 30 to min 0 dB 0:15 8

Maximum BS Transmit Power permissible in the step size 2 dB 0 = 0 dB

inner zone of the concentric or multiband cell. (relative value) 15= -30 dB

BS_TXPWR_MIN max - 30 to min 0 dB 0:15 8

Minimum Transmit Power at BS step size 2 dB 0 = 0 dB

(relative value) 15= -30 dB

BSIC(n) 0 to 63 0:63 8

Base Station Identity Code of cell n

BTSnum 0 to 32 0:32 8

Number of neighbouring cells for whichmeasurements made by the MS are available

CAPTURE_TRAFFIC_CONDITION ANY_LOAD, NOT_LOW,HIGH

0 : 2 8

Condition on traffic load in the serving cell for ageneral capture handover

0 : ANY_LOAD1 : NOT_LOW2 : HIGH

C_DWELLcounter for time during which the MS has been insidethe serving lower layer cell

0 : 255 SACCH framesstepsize 1

0 : 255 0

C_DWELL(n)counter for time during which the MS has beenreporting the neighbour lower layer cell when on theupper layer with a minimum receive level ofL_RXLEV_CPT_HO(0,n)

0 : 255 SACCH framesstepsize 1

0 : 255 0


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CELL_BAND_TYPE GSM or DCS 1 : GSM 2

Indication of the BCCH frequency band 2 : DCS

CELL_DIMENSION_TYPE Macro or Micro 0 : Macro 2

Indicator of BTS dimension type 1 : Micro

CELL_EV ORDER or GRADE 0 : ORDER 1

Indicator of which cell evaluation process is chosen 1 : GRADE

CELL_LAYER_TYPEIndicator of BTS layer type

Single, or Upper, Lower,indoor

0 : Single1 :Upper

2

2 : Lower3: indoor

CELL_PARTITION_TYPE Normal or Concentric 0 : Normal 2

Indicator of cell partition type (frequency use) 1 : Concentric

CELL_RANGE Normal, Extended inneror Extended outer

0 : Normal1 : Extended outer

2

Indicator of extended cell feature 2 : Extended inner

DELTA_DEC_HO_margin 0 to 24 dB 0:24 8

allows the cause 23 detection when the traffic inthe serving cell is high and is low in the cell n

stepsize 1 dB

DELTA_HO_MARGIN(0,n) 0 0 8

-DELTA_DEC_HO_marginDELTA_INC_HO_margin

-DELTA_DEC_HO_marginDELTA_INC_HO_margin

DELTA_INC_HO_margin 0 to 24 dB 0:24 8

penalises the cause 12 detection when thetraffic in the serving cell is low and is high in thecell n

stepsize 1 dB

DWELL_TIME_STEP 0 :30 s 0:0 8

increment or decrement value of MIN_DWELL_TIME stepsize 1s 30 : 30

for traffic load control in the umbrella cells

EN_AMR_CA enable or disable 0 : disable 1

Enable/disable intracell HO for AMR channeladaptation (Causes 26 and 27)

1 : enable

EN_AMR_FR enable or disable 0 : disable 1

Enable/disable AMR full rate 1 : enable

EN_AMR_HR enable or disable 0 : disable 1

Enable/disable AMR half rate 1 : enable

EN_BETTER_ZONE_HO enable or disable 0 : disable 1


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Enable/disable flag for HO cause 13 1 : enable

EN_BI-BAND_MS(n) enable or disable 0 : disable 1

Enables/disables the incoming handovers of bi-bandMSs from the preferred-band into a classical bandcell

1 : enable

EN_CAUSE_13 enable or disable 0 : disable 1

Enable/disable flag for HO cause 13. The flag is setto enable when the inner zone is less loaded than theouter zone

1 : enable


Enable/disable variable for HO cause 15 1 : enable


Enable/disable variable for HO cause 16 1 : enable


HOP enable/disable variable for HO cause 28 1 : enable

EN_DIST_HO enable or disable 0 : disable 1


EN_GENERAL_CAPTURE_HO enable or disable 0 : disable 1


EN_INTRACELL_REPEATED enable or disable 0 : disable 1

Enable/disable flag for repetition of intracell HO 1 : enable

EN_INTRA_DL enable or disable 0 : disable 1

Enable/disable flag for HO cause 16 for non AMRcalls

1 : enable

EN_INTRA_DL_AMR enable or disable 0 : disable 1

Enable/disable flag for HO cause 16 for AMR calls 1 : enable

EN_INTRA_UL enable or disable 0 : disable 1

Enable/disable flag for HO cause 15 for non AMRcalls

1 : enable

EN_INTRA_UL_AMR enable or disable 0 : disable 1

Enable/disable flag for HO cause 15 for AMR calls 1 : enable

EN_LOAD_BALANCE enable or disable 0 : disable 1

Enable/disable load balance between inner and outerzones

1 : enable

EN_LOAD_ORDER enable or disable 0 : disable 1

Enable/disable influence of traffic load in thecandidate cell ranking process

1 : enable


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EN_MCHO_NCELL enable or disable 0 : disable 1


EN_MCHO_H_DL enable or disable 0 : disable 1


EN_MCHO_H_UL enable or disable 0 : disable 1


EN_MCHO_RESCUE enable or disable 0 : disable 1


EN_PREFERRED_BAND_HO enable or disable 0 : disable 1


EN_PBGT_HO enable or disable 0 : disable 1


EN_MULTIBAND_PBGT_HO enable or disable 0 : disable 1

Enable/disable power budget handovers Cause 12between different frequency band cells

1 : enable

EN_PBGT_FILTERING enable or disable 0 : disable 1

Enable/disable flag for filtering process 1 : enable

EN_PRIORITY_ORDERING enable or disable 0 : disable 1

Enables/disables the use of the parameterPRIORITY(0,n) in the candidate cell evaluationprocess

1 : enable

EN_RESCUE_UM enable, disable orindefinite

0 : disable 2

Enable/disable to direct emergency handoverstowards umbrellas preferentially

1 : enable2 : indefinite

EN_RXLEV_DL enable or disable 0 : disable 1


EN_RXLEV_UL enable or disable 0 : disable 1


EN_RXQUAL_DL enable or disable 0 : disable 1


EN_RXQUAL_UL enable or disable 0 : disable 1


EN_SPEED_DISC enable or disable 0 : disable 1

Enable/disable flag for speed discrimination onmobiles in the lower layer cells

1 : enable


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EN_TRAFFIC_HO(0,n) enable or disable 0 : disable 1

Enable/disable flag for HO cause 23 from the servingcell and the cell n

1 : enable

FREEfactor_k -16 to 16 dB -16:16 8

5 correction factors of ORDER depending on freelevel of cell (n) expressed in number of free TCH(See [15]).

step size 1 dB

FREElevel_k 0 to 255 channels 0:255 8

4 boundaries for free TCH channel classification (See[15])

step size : 1 channel

FREQUENCY_RANGEIndicates in which frequency range the cell operates.

PGSM, DCS1800,EGSM, DCS1900,PGSM-DCS1800,EGSM-DCS1800,GSM850

0:60 : PGSM1 : DCS18002 :EGSM3 : DCS19004 : PGSM-DCS18005 : EGSM-DCS18006: GSM850

8

GRADE(n) -179 to 149 dB -179:+149 16

Grade Evaluation of cell n used for ranking

H_LOAD_OBJ 0 to 100% 0 : 10 8

Maximum desired load on umbrella cell step size 10 % 0 = 0 %

defined for each umbrella cell 10 = 100%

H_MIN_DWELL_TIME 0 to 120 s 0 : 0 s 1

maximum value for MIN_DWELL_TIME step size 1 s 120 : 120 s

HO CauseHandover Cause

2, 3, 4, 5, 6, 7, 10, 11,12, 13, 14, 15, 16, 17,18, 20, 21, 22, 23, 24,26, 27, 28, 29

0:290=0.. 29=29

8

HO_INTERCELL_ALLOWED enable or disable 0 : disable 1

Enable/disable flag for HO intercell 1 : enable

HO_MARGIN(n1,n2) -127 to +127 dB -127 :+127 8

Basic Margin for Handover between cell n1 and n2 step size 1 dB

HO_MARGIN_DIST(n1,n2) -127 to +127 dB -127 :+127 8

Basic Margin for Handover (distance causes)between cell n1 and n2

step size 1 dB

HO_MARGIN_LEV(n1,n2) -127 to +127 dB -127 :+127 8

Basic Margin for Handover (level causes) betweencell n1 and n2

step size 1 dB


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HO_MARGIN_QUAL(n1,n2) -127 to +127 dB -127 :+127 8

Basic Margin for Handover (quality causes) betweencell n1 and n2

step size 1 dB

L_LOAD_OBJ 0 to 100% 0 : 10 8

Minimum desired load on umbrella cells step size 10 % 0 = 0 %

defined for each umbrella cell 10 = 100%

L_MIN_DWELL_TIME 0 to 120 s 0 : 0 s 1

minimum value for MIN_DWELL_TIME step size 1 s 120 : 120s

L_RXLEV_DL_H -110 to -47 dBm 0:63 8

Minimum Receive Level step size 1 dBm 0=-110 dBm

for Downlink Level Handover 63=-47 dBm

L_RXLEV_CPT_HO(0,n) -110 to -47 dBm 0:63 8

Minimum Receive Level on Downlink for handover step size 1 dBm 0=-110 dBm

from umbrella to neighbour lower layer cell n orfrom classical band cell to preferred band cell n

63=-47 dBm

L_RXLEV_UL_H -110 to -47 dBm 0:63 8


for Uplink (Handover) 63=-47 dBm

L_RXQUAL_DL_H 0 to 7 0:7 coded with a 8

Minimum Receive Quality stepsize 0.1 stepsize of 0.1

on Downlink (Handover) for non AMR calls

L_RXQUAL_DL_H_AMR 0 to 7 0:7 coded with a 8


on Downlink (Handover) for AMR calls

L_RXQUAL_UL_H 0 to 7 0:7 coded with a 8


on Uplink (Handover) for non AMR calls

L_RXQUAL_UL_H_AMR 0 to 7 0:7 coded with a 8


on Uplink (Handover) for AMR calls

L_TIME_ADVANCE 0 to 63 x 3.69µs 0:63 8

Minimum Distance for Handover from the extendedouter zone of a cell

LINKfactor(n1,n2) -24 to +24 dB -24:24 8

static handicap for handover evaluation between celln1 and n2

step size 1 dB

LOAD_SV3(n) true or false 0 : false 1

Flag that indicates for AMR calls whether or not thecell n is loaded

1 : true


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LOADfactor_k -16 to 0 dB -16:0 8

5 correction factors of GRADE depending on load ofcell(n) expressed in percentage of TCH load (See [15])

LOADlevel_k 0 to 100 (% of free TCH) 0:100 8

4 boundaries for TCH cell load classification (See [15])

MIN_CONNECT_TIME 0 to 120 s 0 : 0 s 8

time in a lower layer cell to separate slow and fastMS

step size 1 s 120 : 120 s

MIN_DWELL_TIME 0 to 120 s 0 : 0 s 8

time reporting a neighbour lower layer cell in anumbrella cell to trigger a handover to the lower layer

step size 1 s 120 : 120 s

MS_SPEEDEstimation for mobile speed discrimination process indefinite, slow, fast

0 :2,0 : indefinite1 : slow2 : fast

2

MS_TXPWRTransmit Power at MS

See [17] See [17] 5

MS_TXPWR_CONF See [17] See [17] 8

Confirmation of new Transmit Power to BS

MS_TXPWR_MAXMaximum Transmit Power at MS

See [17] See [17] 8

MS_TXPWR_MAX(n)Maximum Transmit Power from MS allowed by cell n

See [17] See [17] 8

MS_TXPWR_MAX_INNERMaximum MS transmit power permissible in the innerzone of the concentric or multiband cell.

See [17] See [17] 8

MS_TXPWR_MINMinimum Transmit Power at MS

See [17] See [17] 8

MULTIBAND_TRAFFIC_CONDITION ANY_LOAD, NOT_LOW,HIGH

0 : 2 8

Condition on traffic load in the serving cell for amultiband handover

0 : ANY_LOAD1 : NOT_LOW2 : HIGH

N_BAD_SACCH 1 to 128 1:128 8

Threshold of consecutive bad SACCH frames 1=1 SACCHframes128=128 SACCHframes

NBR_ADJ 0 to 64 cells 0:64 8

Number of adjacent 0=0

cells for this BTS 64=64


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NEIGHBOUR_RXLEV(0,n) -110 to -47 dBm 0:63 8

Threshold of maximum downlink received level from step size 1 dBm 0=-110 dBm

the neighbour cells for cause 13. 63=-47 dBm

OFFSET_CA 0 to 7 stepsize 0.1 0:70 8

Offset for channel adaptation hysteresis 0=070=7

OFFSET_CA_HIGH 0 to 7 stepsize 0.1 0:70 8

Offset for channel adaptation hysteresis under highload

0=070=7

OFFSET_CA_NORMAL 0 to 7 stepsize 0.1 0:70 8

Offset for channel adaptation hysteresis undernormal load

0=070=7

OFFSET_RXQUAL_FH 0 to 7 stepsize 0.1 0:70 8

Offset added to quality thresholds 0=070=7

Offset_Hopping_HO 0 to 7 step size 0.1 0:70 8

Offset used in handover quality causes in case offrequency hopping

0=070=7

OFFSET_HO_MARGIN_INNER -127 to +127 dB -127 :+127 8

Offset which allows to take account of the radiodifferences between the inner and the outerzone (especially in multiband cells)

step size 1 dB

ORDER(n) -290 to 260 dB -290:+290 16

Order Evaluation of cell n used for ranking

OUTDOOR_UMB_LEV(0,n) 0 to 63 dBm 0:63 8

minimum receive level to trigger HO towardsumbrella cell n for all emergency causes triggered inlower layer.

step size 1 dBm 0=-110 dBm63=-47 dBm

PMaximum Transmit Power for class of MS and forthe corresponding frequency band (GSM900,GSM850, DCS1800, DCS1900)

See [17] See [17] 8

PBGT(n) -147 to +97 dB -147:+97 8

Power Budget evaluation of reception

of cell n related to current cell

PING_PONG_HCPDynamic handicap applied to the precedent cell onwhich the call has been (see appx B). Defined on acell basis.

0 to 20 dBstepsize 1 dB

0:20 8

PREC_LAYER_TYPE indefinite,upper, 0 : 4 8


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indication of the CELL_LAYER_TYPE of thepreceding cell

lower,single, indoor 0 : indefinite1 : upper2 : lower3 : single4 : indoor

PREF_LAYERindication of the preferred layer for the target cell

none, upper, lower +indoor, upper+single

0:3 ; 0 = none1 = upper2 = lower + indoor3 = upper + single

2

PREFERRED_BAND none, GSM or DCS 0 = none 2

Frequency band type where the biband 1 = GSM

mobiles will be preferably directed 2 = DCS

PRIORITY(n1,n2) 0 to 5 step size 1 0:5 3

Priority of cell n2 when serving cell=n1 0: highest priority

5: lowest priority

RXLEV_DL_IH -110 to -47 dBm 0:63 8

Maximum Receive Level step size 1 dBm 0=-110 dBm

for Downlink (intracell and quality Handover) 63=-47 dBm

RXLEV_UL_IH -110 to -47 dBm 0:63 8

Maximum Receive Level step size 1 dBm 0=-110 dBm

for Uplink (intracell and quality Handover) 63=-47 dBm

RXLEV_DL_ZONE -110 to -47 dBm 0:63 8


for Downlink (Interzone Handover) 63=-47 dBm

RXLEV_LIMIT_PBGT_HO -110 to -47 dBm 0:63 8

Minimum Level above which an handover on power step size 1 dBm 0=-110 dBm

budget is not triggered 63=-47 dBm

RXLEV_UL_ZONE -110 to -47 dBm 0:63 8


for Uplink (Interzone Handover) 63=-47 dBm

RXLEV_DL_FULL -110 to -47 dBm 0:63 6

Measurement of signal level assessed step size 1 dBm 0=-110

over the full set of TDMA frames 0=-47

within an SACCH block on the Downlink

RXLEV_DL_SUB -110 to -47 dBm 0:63 6

Measurement of signal level assessed step size 1 dBm 0=-110

over a subset of 12 TDMA frames within 0=-47

an SACCH block on the Downlink

RXLEV_NCELL(n) -110 to -47 dBm 0:63 6

Receive Level from step size 1 dBm 0=-110



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RXLEV_UL -110 to -47 dBm 0:63 6

Measurement of Level on step size 1 dBm 0=-110

the Uplink 63=-47

RXLEVmin(n) -110 to -47 dBm 0:63 8

Minimum allowable received step size 1 dBm 0=-110

Level at the MS from cell n 63=-47

THR_RXQUAL_CA 0 to 7 0:7 coded with a 8

Threshold for channel adaptation stepsize 0.1 stepsize of 0.1

THR_RXQUAL_CA_HIGH 0 to 7 0:7 coded with a 8

Threshold for channel adaptation under high load stepsize 0.1 stepsize of 0.1

THR_RXQUAL_CA_NORMAL 0 to 7 0:7 coded with a 8

Threshold for channel adaptation under normal load stepsize 0.1 stepsize of 0.1

THR_RXQUAL_CAUSE_15 0 to 7 0:7 coded with a 8


on Downlink (Handover) used for Cause 15

Traffic_load(n) indefinite, low, high 0 : 2 8

Situation of the traffic in the cell n 0 : indefinite1 : low2 : high

U_RXLEV_DL_MCHO -110 to -47 dBm 0:63 8

High threshold of minimum Receive Level step size 1 dBm 0=-110 dBm

for Downlink (Level microcellular Handover) 63=-47 dBm

U_RXLEV_UL_MCHO -110 to -47 dBm 0:63 8

High threshold of minimum Receive Level step size 1 dBm 0=-110 dBm

for Uplink (Level microcellular Handover) 63=-47 dBm

U_TIME_ADVANCE 0 to 63 x 3.69µs 0:63 8

Maximum Distance for Handover

ZONE_HO_HYST_DL -40 to +40 dB 0 : 80 8

Hysteresis downlink for Interzone Handover from theouter

step size 1 dB

zone to the inner zone of a concentric cell ormultiband cell

ZONE_HO_HYST_UL -40 to +40 dB 0 : 80 8

Hysteresis uplink for interzone Handover from theouter zone to the inner zone of a concentric cell or

step size 1 dB

multiband cell

ZONE_TYPE outer or inner 0 : Outer 1

Indicator of cell zone 1 : Inner


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4.4.2 Directed retry

The following parameters are used by the directed retry procedure only.

NAME RANGE BIN. RANGE BITS

AV_RXLEV_NCELL_DR(n) -110 to -47 dBm 0:63 8

Average receive level of neighbour step size 1 dBm 0=-110

cell n at MS for forced directed retry 63=-47

AV_RXLEV_PBGT_DR -110 to -47 dBm 0:63 8

Average receive level of serving cell step size 1 dBm 0=-110

at MS for forced directed retry (PBGT) 63=-47

EN_DR enable or disable 0 : disable 1

Enable/disable directed retry procedure 1 : enable

EN_EXT_DR enable or disable 0 : disable 1

Enable/disable external directed retry procedure 1 : enable

EN_FORCED_DR enable or disable 0 : disable 1

Enable/disable forced directed retry (cause 20) 1 : enable

FREElevel_DR(n) 0 to 255 TCH channels 0:255 16

Min. threshold of free TCH channels inneighbour cell n for forced directed retry

step size : 1 channel

L_RXLEV_NCELL_DR(n) -110 to -47 dBm 0:63 8

Min. threshold of receive level at MS for step size 1 dBm 0=-110

forced directed retry to neighbour cell n 63=-47

RXLEV_NCELL(n) -110 to -47 dBm 0:63 6

Receive Level from step size 1 dBm 0=-110


SDCCH_COUNTER 0 to 31 0:31 5

Time during which SDCCH handovers are forbiddenafter completion of the Immediate Assignmentprocedure

step size : 1 SACCHframe

0=031=31


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4.4.3 Relationships between p arameters

The document "BSS telecom parameters" ([12]) specifies also the rules to be fulfilled by the handoverparameters. The present specification is the reference document in case of discrepancy.The default values for parameters are indicated in the document [12].

Each relationship is either mandatory or recommended.The recommended relationships are not checked by an automatic procedure.

Note : - for thresholds relative to quality measurements, the 3GPP coding is assumed, as alreadystated, it is contra-intuitive.

- The relationships between the parameters relative to HO preparation and the ones relative toPower control are included. The parameters of power control are characterised by the suffix_P or _PC. For more information about them, refer to [17].

Mandatory relationships

### RXLEV_UL_IH > L_RXLEV_UL_H.

### U_RXLEV_UL_P > L_RXLEV_UL_H.

### RXLEV_DL_IH > L_RXLEV_DL_H.

### U_RXLEV_DL_P > L_RXLEV_DL_H.

### Relations between LOADlevel_i :For i=1 to 3, LOADlevel_i < LOADlevel_i+1

### Relations between LOADfactor_i :For i=1 to 4, LOADfactor_i >= LOADfactor_i+1

### Relations between FREElevel_i :For i=1 to 3, FREElevel_i < FREElevel_i+1

### Relations between FREEfactor_i :For i=1 to 4, FREEfactor_i =< FREEfactor_i+1

### L_LOAD_OBJ =< H_LOAD_OBJ

Recommended relationships

### L_RXQUAL_UL_H >= L_RXQUAL_UL_P.

### L_RXQUAL_UL_H_AMR >= L_RXQUAL_UL_P.

### L_RXQUAL_DL_H >= L_RXQUAL_DL_P.

### L_RXQUAL_DL_H_AMR >= L_RXQUAL_DL_P.

### L_RXLEV_UL_H < L_RXLEV_UL_P.

### L_RXLEV_DL_H < L_RXLEV_DL_P.

### A_LEV_HO = 2 * A_LEV_PC.


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### A_QUAL_HO = 2 * A_QUAL_PC.

### A_PBGT_HO = 2 * A_LEV_HO

• T_FILTER > 0.5 seconds

###ZONE_HO_HYST >= BS_TXPWR_MAX - BS_TXPWR_MAX_INNER

• L_RXLEV_NCELL_DR(n) >= RXLEVmin(n)

### FREElevel_DR(n) > N_TCH_HO(n).N_TCH_HO(n) is the number of TCH channel reserved in the best interference band (see [15] forfurther details).

### The parameters FREElevel_k shall be updated according to the cell loadevaluation. For instance, in a concentric cell, if EN_LOAD_OUTER = enable, only the TCHresources of the outer zone of the cell shall be considered for the determination of the parametersFREElevel_k. Regarding the G1 TCH resources of the cell, these parameters shall also beupdated according to the value of the flag EN_LOAD_EGSM [15].

### For a microcell configuration, it is recommended :

N_BAD_SACCH = RADIO_LINK_TIMEOUT_BS - N_BSTXPWR_M + 1(for more information, see [17]).Cause 7 shall be checked before the release of the channel by the autocleaning procedure.Therefore, N_BAD_SACCH x 0.5 s < T_AUTOCLEANING_MEAS_REP + 30 s (See also [15])

### It is recommended to inhibit Traffic handover towards 1 TRX cells. These cells do not haveenough resources to receive incoming handovers due to congestion of neighbour cells. Moreoverbecause of the great variation of traffic in the 1 TRX cells, their Traffic_load is always different fromlow.

### If PRIORITY(0,n) is used from cell of preferred band to cell of classical band, then it isrecommended :EN_PREFERRED_BAND_HO = DISABLE in the classical band cell.

### If PRIORITY(0,n) is applied in order to manage inter-bands handover in a multiband network,then it is recommended :

PREFERRED_BAND = none.

### If PRIORITY(0,n) is used from microcell to macrocell, then it is recommended :EN_RESCUE_UM = INDEFINITE in the microcell.

• For transferring fast mobiles from a minicell n1 to an umbrella cell n2 through a power budgethandover, it is recommended :- if CELL_EV=GRADE

HO_MARGIN(n1,n2)=-127dBLINKfactor(n1,n2)=24dB

• THR_RXQUAL_CA_HIGH >=THR_RXQUAL_CA_NORMAL

• OFFSET_CA_HIGH >= OFFSET_CA_NORMAL

• A_QUAL_CA_FR_HR >= A_QUAL_CA_HR_FR


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• When the channel adaptation handovers are enabled together with Causes 15 and 16 in the cell, itis recommanded to use the same window size for averaging the quality measurements of Cause15, 16 and 26: A_QUAL_CA_HR_FR = A_QUAL_HO and W_QUAL_CA = W_QUAL_HO.

• SDCCH_COUNTER <= T_SDCCH_PC. The parameter T_SDCCH_PC is defined in [17].

• In multiband cells, setting both flags EN_LOAD_OUTER and EN_LOAD_BALANCE to enablemust be avoided. Setting the flag EN_LOAD_OUTER to enable is useful when the population ofmonoband MS is higher than biband ones, whereas setting the flag EN_LOAD_BALANCE toenable is useful when the population of biband MS is higher than monoband ones.

### Compatibility checking between cell configurations and handover inhibitionflags.

For the definition of the different cell profiles, see section 2.4

The following relationships are mandatory , whatever CELL_BAND_TYPE.

- Single cell profile

EN_MCHO_NCELL = DISABLE.EN_MCHO_H_DL = DISABLE.EN_MCHO_H_UL = DISABLE.EN_MCHO_RESCUE = DISABLEEN_SPEED_DISC = DISABLE

- Micro cell profile

EN_MCHO_NCELL = DISABLE if there is no indoor layer

- Mini cell profile

EN_MCHO_NCELL = DISABLE if there is no indoor layerEN_MCHO_H_DL = DISABLE.EN_MCHO_H_UL = DISABLE.EN_MCHO_RESCUE = DISABLE

- Umbrella cell profile

EN_MCHO_H_DL = DISABLE.EN_MCHO_H_UL = DISABLE.EN_MCHO_RESCUE = DISABLE

- Extended inner and outer cell profile

HO_SDCCH_INHIBIT = DISABLE (SDCCH handovers are disabled)FREElevel_DR = 255 for the serving inner and outer cellEN_MCHO_NCELL = DISABLE.EN_MCHO_H_DL = DISABLE.EN_MCHO_H_UL = DISABLE.EN_MCHO_RESCUE = DISABLE


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EN_SPEED_DISC = DISABLE

- Concentric cell profile

EN_MCHO_H_DL = DISABLE.EN_MCHO_H_UL = DISABLE.EN_MCHO_RESCUE = DISABLEEN_MCHO_NCELL = DISABLEEN_SPEED_DISC = DISABLE

- Concentric Umbrella cell profile

EN_MCHO_H_DL = DISABLE.EN_MCHO_H_UL = DISABLE.EN_MCHO_RESCUE = DISABLE

- Indoor micro cell profile

EN_MCHO_NCELL = DISABLE.

### Cells in the preferred band.

If BCCH_FREQUENCY is in the P-GSM or GSM850 frequency band and if PREFERRED_BAND= GSM,

or if BCCH_FREQUENCY is in the DCS1800 or DCS1900 frequency band, and ifPREFERRED_BAND = DCS,

then it is is recommended to check that EN_PREFERRED_BAND_HO = DISABLE.

### Cells having different frequency bands

Providing the conditions:− the cells n1 and n2 are adjacent− the flag EN_MULTIBAND_PBGT_HO is set to disable in the cell n1 and in the cell n2 or

CELL_LAYER_TYPE(n1) <> CELL_LAYER_TYPE(n2)− the frequency band of the cell n1 is different from the one of cell n2. In other words,

If BCCH_FREQUENCY(n1) is in the P-GSM or GSM850 frequency band.and BCCH_FREQUENCY(n2) is in the DCS1800 or DCS1900 frequency band

or if BCCH_FREQUENCY(n1) is in the DCS1800 or DCS1900 frequency bandand BCCH_FREQUENCY(n2) is in the P-GSM or GSM850 frequency band

then it is recommended :HO_MARGIN_QUAL(n1,n2) = -127 dBHO_MARGIN_LEV(n1,n2) = -127 dBHO_MARGIN_DIST(n1,n2) = -127 dB


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5. RELEASE CHANGES

Changes from ALCATEL BSS release 2 to ALCATEL BSS release 3

The changes from Release 2 to Release 3 are based on the 3 following features descriptions :

- FD/3/10.6 : Support of microcellular environment. Concepts presented in SYS/006 and SYS/012 areintroducedSYS/006 : definition of parameters for cell environments, H. Brinkmann and G. KreftSYS/014 : handovers in a microcellular environment, C. Cherpantier.

- FD/3/10.7.1 : Concentric cells,- FD/3/10.8 : Directed Retry,- CRQ/298 : improvements for phase 2.1

Inhibition of the feature to transform an intracell HO to an intercell HO,Processing of L1 info in the case where L3 info (measurement report) is missing,The timer T_7 used by the Handover algorithms is renamed T_FILTER.

- CRQ/362 : introduction of conditions PC-9 and PC-10 : power control with good quality and lowlevel.

- CRQ/361 : relationship between MS power control and radio link supervision. When a radio linkrecovery occurs, the MS power control function is resumed immediately.

- clarification about the power control and handover algorithms defined in the ALCATEL BSS. Theseclarifications are based on document ST2/53 "rationale for the power control and handoveralgorithm" from P.Guillier.


The changes from Release 3 to Release 4 are based on the following documents :

- MFD 11.5 Power control and handover algorithm improvements ed 05 :inhibition of radiolink recovery by O&M flagdisabling of ORDER calculation based on number of free TCH by O&M flagEnabling of MS power control and uplink measurements related handover causes in case ofmissing SACCH frames.

- ITCC/TELACT/TEL/PP/006 : remarks made by ITC on specifications for rel 3- fax SDEF/94/HO.001 from Steve DEFOORT on rel3 document inconsistency for the causes HO-8and HO-9.- MFD 10.11 Mobile velocity dependent handover- AMCF/ITD/SAS/CC/1333 : "Description of Release 4 handover algorithms in hierarchical networks"memo by Corinne CHERPANTIER


The changes from Release 4 to Release 5 are based on the following documents :

- TFD 11.22a : Handover algorithm improvements, Multiband Handover- TFD 10.14 : DCS1900 support, Telecom part- Approved Release 4 CRQs : CRQ 1428, CRQ 1705, CRQ 1806, CRQ 1971, CRQ 2027, CRQ 2093,CRQ 2109, CRQ 2144, CRQ 2234, CRQ 2408, CRQ 2472, CRQ 2504, CRQ 2505

Moreover, the original document is partly modified :- Mode A is removed


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- Section 3 is reorganised, section 2.2 removed- Section 5, 'Release changes' has been created- Appendix B and F are removed, Appendix C is new

Minor changes are performed on the specifications :- The TFD 11.22a is completed with recommendations on HO_margins and LINKfactors foremergency handovers between cells of different frequency band- Handover causes on quality are rewritten (inversion of the quality comparisons)- Recommendation CELL_EV = ORDER for mini-cell profile becomes mandatory- Handover cause 6 is no longer forbidden for micro-cell profile.- The recommendation for N_BAD_SACCH is modified.


The changes from Release 5 to Release 6 are based on the following documents:

- TFD 11.31: general handover algorithms improvements- TFD 10.8b: external directed retry- TFD 11.22.e: controlled handover in multilayer/multivendor environment- TFD 11.30: traffic management in handover algorithms- TFD 3.19: HSCSD- TFD 11.32: improvements in radio channel selection- Approved Release 5 CRQs 18579, 3028, 2736, 10645, 19733

The section 2 is reorganised. Some descriptions have been put in a new step 1 document (refer to[20]).The section 3.1. Active channel preprocessing, the appendix C are in the new document Radiomeasurements data processing [19].A new handover alarm management is specified in section 3.2.4.

Changes from ALCATEL BSS release 6 to ALCATEL BSS release 6.2

The changes from Release 6 to Release 6.2 are based on the following documents:

- TFD XX.XX: GPRS

Changes from ALCATEL BSS release 6.2 to ALCATEL BSS release 7.2

The changes from Release 6.2 to Release 7.2 are based on the following documents:

- SFD 3.6.6: Indoor layer support- SFD 3.6.1: Instantaneous peaks management- SFD 3.1.1: Adaptive multi-rate speech codec- SFD 3.3.1: Anti-ping-pong improvements- SFD 3.5.1: Multiband cell improvements- SFD 3.x.x: Telecom improvement- SFD 3.2.1: Tandem free operation- SFD 3.x.x: E-GSM support- SFD: Support of the GSM 850 MHz band- Approved CRQ 64608

The HSCSD feature is removed.


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The GPRS redirection preparation is removed.The section “Calculation of LOADfactor, FREEfactor” is removed since this section is now inserted inRAM [15].

6. FEATURES

Release 6 feature list

11.31: general handover algorithms improvements (improvements 2, 3, 4, 5, 6, 7, 10)10.8b: external directed retry11.22.e: controlled handover in multilayer/multivendor environment11.30: traffic management in handover algorithms3.19: HSCSD11.32: improvements in radio channel selection

Release 6.2 feature list

XX.XX: GPRS

Release 7.2 feature list

3.6.6 Indoor layer support3.6.1 Instantaneous peak management3.1.1 Adaptive multi-rate speech codec3.3.1 Anti ping-pong improvements3.5.1 Multiband cell improvements3.x.x Telecom improvement3.2.1 Tandem free operation3.x.x E-GSM support3.x.x Support of the GSM 850 MHz band


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7. GLOSSARY

7.1 Abbreviat ions

3GPP 3rd Generation Partnership ProjectAMR Adaptive multi-rateARFCN Absolute Radio Frequency Channel NumberBA BCCH-allocationBFI Bad Frame IndicationBS Base StationBSC Base Station ControllerBSIC Base Station Identity CodeBSS Base Station SubsystemBTS Base Transceiver StationCA Channel adaptation or Changes alloweddB deciBelDC Direct CurrentDR Directed Retry or dual rateDTX Discontinuous transmissionDCS-1800 Digital Cellular system using the uplink frequency band [1710,...,1785] MHz and the

downlink frequency band [1805,...,1880] MHzDCS-1900 Digital Cellular system using the uplink frequency band [1850,...,1910] MHhz and the

downlink frequency band [1930,...,1990] MhzE-GSM Extended-GSMFH Frequency HoppingFR Full rateGSM850 Global System for Mobile communications using the uplink frequency band

[824,...,849] MHz and the downlink frequency band [869,...,894] MHzGSM-900 Global System for Mobile communications using the uplink frequency band

[880,...,915] MHz and the downlink frequency band [925,...,960] MHz (including theG1 band)

HO HandoverHOP Handover preparationHOM Handover managementHR Hall rateLOS Line Of SightMSC Mobile Switching CentreMS Mobile StationO&M Operation and MaintenanceOMC Operation and Maintenance CentreP-GSM Primary-GSMPBGT Power BudgetPC Power ControlRAM Resource allocation and managementSACCH Slow associated control channelSADT Structured Analysis and Design TechnicsSDCCH Slow dedicated control channelSDL Specification Description LanguageTFO Tandem free operationTCH Traffic channelTCH/FS Traffic channel Full SpeechTCU Terminal Control UnitTOA Time Of ArrivalTRX Transmitter ReceiverTS Technical Specification


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Note : all the parameters and variables used in the algorithms are thoroughly described in thededicated sections and in section 4.


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7.2 Definitions

- internal HO : the handover execution is controlled by the BSC (only intracell and intercell-intra-BSCHO).

- external HO : the handover execution is controlled by the MSC (necessary for all intercell-inter-BSCHO, possible for intercell-intra-BSC HO).

- intracell HO : handover between two channels of the same cell.

- intercell HO : handover between two channels of adjacent cells. The old channel belongs to theserving cell, the new channel to the target cell.

- intra-BSC HO : the serving cell and the target cell belong to the same BSC.

- Interlayer HO: An interlayer HO is an intercell HO which is performed between two differentlayers. This HO is encountered in a hierarchical environment.

- Intralayer HO: An intralayer HO is an intercell HO which is performed between two cellspertaining to the same layer.

- interzone HO : intracell handover between the inner zone and the outer zone of a concentric ormultiband cell configuration.

- intrazone HO : intracell handover within a zone (inner or outer) of a concentric or multiband cellconfiguration.

- directed retry : handover from SDCCH to TCH when the serving cell is congested at the startingtime of the assignment procedure.

In this release of the ALCATEL BSS, the directed retry is internal or external to the BSS.

- decibel unit :The "decibel" is a unit currently used in radio communications. It is the logarithmic expression of theratio of two terms :

N dB = 10 log10(P1/P2) with P1, P2 = signal power.

M dB = 20log10(V1/V2) with V1, V2 = signal voltage.

The "dB" is the usual unit for the gains of power or voltage.

The dBm is a variant of the dB unit :Power expressed in dBm = 10 log10(P) with P expressed in mW.Ex : 1W corresponds to 30 dBm. 1pW (10-9 mW) corresponds to -90dBm.

The dBW is a variant of the dB unit :Power expressed in dBW = 10 log10(P) with P expressed in W.Ex : 10W corresponds to 10 dBW.

The dBi is a variant of the dB unit which is currently used for the antenna gains. The index "i" means"isotropic" as an antenna gain is referred to the gain of an isotropic antenna (same gain in alldirections).

- log normal fa ding : The signal attenuation during propagation is the product of small independentattenuations. Expressed in dB, this attenuation becomes a random variable which has a normal (or


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gaussian) pdf, (central limit theorem). The log normal fading is defined as a centred (mean value is 0)gaussian variable that must be added to the mean signal value resulting from propagation attenuationin order to have the reported value of the signal level (by MS or BS).The log normal fading standard deviation ### normally ranges about 6-7 dB in urban macrocellularenvironment and about 5 dB for rural environment.


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Appendix A

(2 pages)

Power budget equation

The Power budget criterion PBGT is used to estimate the difference of path loss between twoneighbouring cells.

PBGT(n) = AV_RXLEV_NCELL(n) - AV_RXLEV_PBGT_HO- (BS_TXPWR_MAX - AV_BS_TXPWR_HO)- (MS_TXPWR_MAX(n) - MS_TXPWR_MAX)

- PING_PONG_MARGIN(n,call_ref)

PBGT_DR(n) = AV_RXLEV_NCELL_DR(n) - AV_RXLEV_PBGT_DR- (BS_TXPWR_MAX - AV_BS_TXPWR_DR)- (MS_TXPWR_MAX(n) - MS_TXPWR_MAX)

with :

- AV_RXLEV_NCELL(n) : average of RXLEV_NCELL(n) over A_PBGT_HO or A_PBGT_DRmeasurements (neighbour cell(n)).

- AV_RXLEV_NCELL_DR(n) : average of RXLEV_NCELL(n) over A_PBGT_DR measurements(neighbour cell(n)).

- AV_RXLEV_PBGT_HO : average of the received levels RXLEV_DL_FULL or RXLEV_DL_SUBover A_PBGT_HO measurements (serving cell).

- AV_RXLEV_PBGT_DR : average of the received levels RXLEV_DL_FULL or RXLEV_DL_SUBover A_PBGT_DR measurements (serving cell).

- BS_TXPWR_MAX : max power of the BTS in the serving cell (fixed value for each BTS).- AV_BS_TXPWR_HO : average of the BS_POWER values over A_PBGT_HO measurements.- AV_BS_TXPWR_DR : average of the BS_POWER value over A_PBGT_DR measurements.- MS_TXPWR_MAX(n) : max power level the MS is allowed to use in its neighbour cell(n).- MS_TXPWR_MAX : max. power the MS is allowed to use in the serving cell.- PING_PONG_MARGIN(n,call_ref) is a penalty put on the cell n if :

it is the immediately precedent cell on which the call has been,this cell belongs to the same BSC as the serving cell,the call has not performed a forced directed retry towards the serving cell,less than T_HCP seconds have elapsed since the last handover.In this case PING_PONG_MARGIN(n,call_ref) = PING_PONG_HCP.,If the call was not precedently on cell n, or if the preceding cell was external, or ifthe call has just performed a forced directed retry, or if the timer T_HCP hasexpired, then PING_PONG_MARGIN(n,call_ref) = 0

With abstraction of the PING_PONG_MARGIN, which is purely a handicap given to the preceding cellfor a certain time, the PBGT can be described in two steps :


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### ###BCCH = AV_RXLEV_NCELL(n) - (AV_RXLEV_PBGT_HO + C)with C = BS_TXPWR_MAX - AV_BS_TXPWR_HO.

###BCCH corresponds to the difference of received BCCH signal levels.A correction factor C is taken into account for the serving cell, because the received signal level (i.e.AV_RXLEV_PBGT_HO) may not be measured on BCCH,

Then, another correction factor must be taken into account because the maximum BS powers of theserving and neighbouring cells may be different :

### ###TXPWR = MS_TXPWR_MAX(n) - MS_TXPWR_MAX.

As the first step of calculation is based on the downlink parameters, this correction factor should bebased on the maximum BS powers used in the serving and neighbouring cells.

Two reasons (which are not completely decorrelated) for not using the BS powers can be envisaged :- for a given cell, the 3GPP standard does not specify formally the maximum BS power of the

neighbouring cells. Only BS_TXPWR_MAX is defined (it is sent on the air interface),- it is not easy for the evaluating BSC to know the maximum BS powers of the neighbouring cells.

The use of the maximum MS powers requires that the difference of MS powers is equal to thedifference of BS powers. This condition is met in most cases. If it is not the case, the difference canbe corrected by the operator with the HO_MARGIN(0,n) parameter (HO hysteresis).

PBGT >0 : the neighbour cell is more advantageous as the path loss is less than in the current cell.PBGT <0 : the serving cell is more advantageous as the current cell.

The PBGT equation (without temporary handicap) can be interpreted in another way.

PBGT = ###BCCH - ###TXPWR

The PBGT is a balance or a trade-off between two opposite indicators. As a matter of fact :### ###BCCH > 0 : the neighbouring cell n is more advantageous than the serving cell as the

reception of BCCH is better.

### ###BCCH < 0 : the neighbouring cell n is more disadvantageous than the serving cell.

### ###TXPWR > 0 : the neighbouring cell n is more disadvantageous than the serving cell as themaximum permissible power of the MS is higher.

### ###TXPWR < 0 : the neighbouring cell n is more advantageous than the serving cell.

The PBGT can be seen as a balance, at MS side, between a probability to have a better receptionand the probability of requests of transmission at higher levels in the neighbouring cells.


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Appendix B

(1 page)

Recapitulation of the cell types allowed for the serving and the candidate cell for each handovercause

Handover causes Serving cell / zone types Target cell / zone types

Too low quality uplink (cause 2) All All cells except serving cell (1)Too low level uplink (cause 3) All All cells except serving cell (1)Too low quality downlink (cause 4) All All cells except serving cell (1)Too low level downlink (cause 5) All All cells except serving cell (1)Too long distance (cause 6) All All cells except serving cell (1)Bad SACCH frames (cause 7) CELL_DIMENSION_TYPE =

microAll cells except serving cell (1)

Too low level uplink, inner zone(cause 10)

CELL_PARTITION TYPE =concentric

ZONE_TYPE = inner

Same cellZONE_TYPE = outer

Too low level downlink, inner zone(cause 11)

CELL_PARTITION TYPE =concentric

ZONE_TYPE = inner

Same cellZONE_TYPE = outer

Power budget (cause 12)

(CELL_LAYER_TYPE = singleor

CELL_LAYER_TYPE = upper)

CELL_LAYER_TYPE = singleor

CELL_LAYER_TYPE = upper

Same CELL_BAND_TYPE (ifEN_MULTIBAND_PBGT =

disable)The MS is not in the inner zoneof a multiband cell

CELL_LAYER_TYPE = lower CELL_LAYER_TYPE = loweror

upper (if MS_SPEED = fast)


disable)CELL_LAYER_TYPE = indoor CELL_LAYER_TYPE = indoor

orupper (if MS_SPEED = fast)


disable)

Power budget (cause 12)The MS is in the inner zone of amultiband cell


CELL_LAYER_TYPE = upper)


CELL_LAYER_TYPE = upper)and FREQUENCY_RANGE=PGSM-DCS1800 or EGSM-

DCS1800 (ifEN_MULTIBAND_PBGT =

disable)


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CELL_LAYER_TYPE = lower (CELL_LAYER_TYPE = loweror

upper (if MS_SPEED = fast))and FREQUENCY_RANGE =PGSM-DCS1800 or EGSM-


disable)CELL_LAYER_TYPE = indoor (CELL_LAYER_TYPE = indoor

orupper (if MS_SPEED = fast))and FREQUENCY_RANGE =PGSM-DCS1800 or EGSM-


disable)Too high level uplink or downlinkouter zone (cause 13)

CELL_PARTITION_TYPE =concentric

ZONE_TYPE = outer

Same cellZONE_TYPE = inner

High level in neighbour lower orindoor layer cell for slow mobile(cause 14)The MS is in the inner zone of amultiband cell

CELL_LAYER_TYPE = upperCELL_LAYER_TYPE = lower

or indoorand

(EN_BI-BAND_MS(n)=ENABLE orCELL_BAND_TYPE(n) <>

CELL_BAND_TYPE(0))

CELL_LAYER_TYPE = lowerCELL_LAYER_TYPE = indoor

and(EN_BI-

BAND_MS(n)=ENABLE orCELL_BAND_TYPE(n) <>

CELL_BAND_TYPE(0))High level in neighbour lower orindoor layer cell for slow mobile(cause 14)The MS is not in the inner zoneof a multiband cell

CELL_LAYER_TYPE = upperand

CELL_BAND_TYPE =PREFERRED_BAND

CELL_LAYER_TYPE = loweror indoor and

(EN_BI-BAND_MS(n)=ENABLE orCELL_BAND_TYPE(n) =

PREFERRED_BAND)

CELL_LAYER_TYPE = upperand

CELL_BAND_TYPE <>PREFERRED_BAND

CELL_LAYER_TYPE = loweror indoor

CELL_LAYER_TYPE = lowerand


CELL_LAYER_TYPE = indoorand

(EN_BI-BAND_MS(n)=ENABLE orCELL_BAND_TYPE(n) =

PREFERRED_BAND)

CELL_LAYER_TYPE = lowerand


CELL_LAYER_TYPE = indoor


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Too high interference level uplink(cause 15)

All Same cell

Too high interference leveldownlink (cause 16)

All Same cell

Too low level uplink compared toHigh Threshold (cause 17)

CELL_DIMENSION_TYPE =micro

All cells except serving cell (1)

Too low level downlink comparedto High Threshold (cause 18)

CELL_DIMENSION_TYPE =micro

All cells except serving cell (1)

Forced directed retry (cause 20) All All cells except serving cellHigh level in neighbour cell in thepreferred band (cause 21)



Too short distance (cause 22) CELL_RANGE = extendedouter

All cells except serving cell

Traffic handover (cause 23)The MS is not in the inner zoneof a multiband cell




CELL_LAYER_TYPE = upperSame CELL_BAND_TYPE

CELL_LAYER_TYPE = lower CELL_LAYER_TYPE = lowerSame CELL_BAND_TYPE

CELL_LAYER_TYPE = indoor CELL_LAYER_TYPE = indoorSame CELL_BAND_TYPE

Traffic handover (cause 23)The MS is in the inner zone of amultiband cell




CELL_LAYER_TYPE = upperand FREQUENCY_RANGE =PGSM-DCS1800 or EGSM-

DCS1800CELL_LAYER_TYPE = lower CELL_LAYER_TYPE = lower

and FREQUENCY_RANGE =PGSM-DCS1800 or EGSM-

DCS1800CELL_LAYER_TYPE = indoor CELL_LAYER_TYPE = indoor

and FREQUENCY_RANGE =PGSM-DCS1800 or EGSM-

DCS1800General capture handover (cause24)The MS is in the inner zone of amultiband cell

All EN_BI-BAND_MS(n)=ENABLEor

CELL_BAND_TYPE(n) <>CELL_BAND_TYPE(0)

General capture handover (cause24)The MS is not in the inner zoneof a multiband cell


EN_BI-BAND_MS(n)=ENABLEor

CELL_BAND_TYPE(n) =PREFERRED_BAND



Fast traffic handover (Cause 28) (CELL_PARTITION_TYPE =concentric and ZONE_TYPE =

outer)or

CELL_PARTITION_TYPE =normal


TFO handover (Cause 29) All Same cell

(1): The serving cell is a candidate cell if the MS is connected to the inner GSM 1800 zone of amultiband cell.

Handover

Preparation

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All rights reserved. Passing on and copying of thisdocument, use and communication of its contents

not permitted without written authorization from Alcatel


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Appendix C

(1 page)

Compliancy with the 3GPP requirements

Handover algorithm

As stated in [2] : "the exact handover strategies will be determined by the network operator".Document [2] provides also a "detailed example of a basic overall algorithm" which is the basis ofthe one implemented in the ALCATEL BSS.The complete ALCATEL algorithm is described in section 3.2 of this document.

For further details about the compliance of this function with the requirements of the 3GPP TechnicalSpecification 05.08 ([2]), see [4].

Directed retry algorithm

The 3GPP standard has not specified any requirement. The algorithm is implementation dependent.

END OF DOCUMENT

handover preparation 3bk 11202 0297 dszza e05

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