07_handovercontrol_2006_06

1 © 2006 Nokia

Course Content

Radio Resource Management Overview

Parameter Configuration

Common Channels & Power Control

Load Control

Admission Control

Packet Scheduling

Handover Control

Resource Manager

2 © 2006 Nokia

Course Objectives

At the end of the module you will be able to:

• Name and describe the different Handover types

• Describe and list the steps of the Handover procedure for each Handover type

• Name and describe the main RAN parameters related to Handover reporting triggering

• Describe the main difference between inter system Handover and other Handover types

• Name and describe the main RAN parameters related to inter system Handover

3 © 2006 Nokia

Handover Control

• Handover Types

• Intra-Frequency Handover

• SRNS Relocation

• Inter-Frequency & Inter-System Handover

• GSM ISHO

• Overview of HSDPA mobility

• Appendix

4 © 2006 Nokia

Handover Types• Intra-Frequency Handovers

• Softer Handover• Handover between sectors of the same Node B (handled by BTS)• No extra transmissions across Iub interface• Maximum Ratio Combining (MRC) is occurring in both the UL and DL

• Soft Handover• MS simultaneously connected to multiple cells (from different Node Bs)• Extra transmission across Iub, more channel cards are needed (compared to non-SHO)• Mobile Evaluated Handover (MEHO)• DL/UE: MRC & UL/RNC: Frame selection combining

• Hard Handover• Arises when inter-RNC SHO is not possible (Iur not supported or Iur congestion)• Decision procedure is the same as SHO (MEHO and RNC controlled)• Causes temporary disconnection of the (RT) user

• Inter-Frequency Handover• Can be intra-BS, intra-RNC, inter-RNC • Network Evaluated Handover (NEHO)• Decision algorithm located in RNC

• Inter-RAT Handover • Handovers between GSM and WCDMA (NEHO)

6 © 2006 Nokia

Handover Control

• Handover Types

• Intra-Frequency Handover• Parameter Mapping• SHO Events and Measurements• Hard Handover & RRC Connection Release

• SRNS Relocation


• GSM ISHO

• Overview – HSDPA mobility

• Appendix

7 © 2006 Nokia

Handover Control Parameters

• Handover are controlled mainly by four groups of parameters

• ADJx Adjacency definition, specific offset, HOPx set selection

• FMCx Handover related measurement report triggering and decision

• HOPx Intra-frequency hard handover, cell re-selection

• WCEL FMCx set selection, Cell re-selection hysteresis

8 © 2006 Nokia

HC Parameter Database Structure

• RNC = Radio Network Controller level parameters• WBTS = Node B level parameters• WCELL = Cell level parameters• FMCx = Frequency Measurement Control parameters (S=intra-frequency set; I=inter-

frequency; G=inter-RAT)• ADJx = Adjacent Cell parameters (S=intra-frequency set; I=inter-frequency; G=inter-

RAT)• HOPx = Handover Path parameters (S=intra- frequency set; I=inter-frequency; G=inter-

RAT)

S:Intra-FrequencyS:Intra-

Frequency

I:Inter-Frequency

I:Inter-Frequency

G:Inter-SystemG:Inter-System

WCELL

ADJG

ADJI

ADJS

WBTS

RNC

FMCS

FMCI

FMCG

100

100

100

HOPS 100

HOPI 100

HOPG 100

32

48

32

9 © 2006 Nokia

ADJS, HOPS & FMCSHO Parameter Categories

Intra-Frequency

Inter-Frequency

Inter-System

Handover Control Parameters

RNC parametersWCEL parametersHOPS parameters FMCS parametersADJS parameters HOPI parameters FMCI parametersADJI parameters HOPG parameters FMCG parameters ADJG parameters

100HOPS parameters

Cell Re-selection HCS PriorityCell Re-selection HCS ThresholdCell Re-selection Minimum QualityCell Re-selection Minimum RX LevelCell Re-selection Penalty TimeCell Re-selection Quality Offset 1Cell Re-selection Quality Offset 2Cell Re-selection Temporary Offset 1Cell Re-selection Temporary Offset 2CPICH Ec/No Averaging WindowEnable Inter-RNC Soft HandoverEnable RRC Connection ReleaseHHO Margin for Average Ec/NoHHO Margin for Peak Ec/NoRelease Margin for Average Ec/NoRelease Margin for Peak Ec/No

Define Target Cell Selection

1100

FMCS parameters

Active Set Weighting CoefficientAddition Reporting IntervalAddition TimeAddition WindowCPICH Ec/No Filter CoefficientCPICH Ec/No HHO CancellationCPICH Ec/No HHO Cancellation TimeCPICH Ec/No HHO ThresholdCPICH Ec/No HHO Time HysteresisCPICH RSCP HHO CancellationCPICH RSCP HHO Cancellation TimeCPICH RSCP HHO Filter CoefficientCPICH RSCP HHO ThresholdCPICH RSCP HHO Time HysteresisDrop TimeDrop WindowMaximum Active Set SizeReplacement Reporting IntervalReplacement TimeReplacement Window

Define Adjacent Cell Measurement Control

1

In GSM:

Define HO TriggerHoThresholdsLevDL Rx (LDR): -92 dBm Px (LDP): 3 Nx (LDN): 4

Define Target Cell SelectionRx Lev Min Cell: -95 dBm

Define Adj Cell

31ADJS parameters

Cell Identifier CPICH Ec/No Offset Disable Effect on Reporting Range Location Area Code Maximum UE TX Power on RACH Mobile Country Code Mobile Network Code Mobile Network Code LenPrimary CPICH power NRT HOPS Identifier Primary Scrambling Code RNC Identifier Routing Area Code RT HOPS Identifier Tx Diversity Indicator

Define Adj Cell

1

10 © 2006 Nokia

SHO: Neighbour Cell Definition

• Each intra-frequency neighbour (ADJS) is identified using ADJSid (ADJS)

• The ADJS parameters provide information on the identity of each neighbour cell together with its properties (i.e. Handover parameter set identifier, scrambling code etc..)

• Each neighbour cell is defined using the UTRAN cell identifier which comprises

UTRAN Cell Identifier = MCC + MNC + RNC identifier + Cell identifier

UTRAN Cell Identifier = MCC + MNC + RNC identifier + Cell identifier

• Each neighbor cell is defined using the UTRAN cell identifier which comprises;

MCC (Mobile Country Code) = AdjsMCC MNC (Mobile Network Code) = AdjsMNC RNC Identifier = AdjsRNCid Cell Identifier = AdjsCI• The LAC (AdjsLAC) & RAC (AdjsRAC) are also in ADJS parameter set

ADJS Parameters

12 © 2006 Nokia

AdjsMCC AdjsMNC AdjsRNCid AdjsCI

UTRAN Cell ID

ADJSid

MaxActiveSetSize

RNC

AdjsScrCodeAdjsTxDiv

AdjsTxPwrRACH

• RT HO Control Parameter: RtHopsIdentifier

• NRT HO Control Parameter: NrtHopsIdentifier

• NRT HO Control Parameter: HSDPAHopsIdentifier

SHO: Neighbour Cell Definition

13 © 2006 Nokia

Maximum number of neighbours

• The maximum number of neighbours that can be defined in RNC database is

• ADJS: 31• 31 neighbours + serving cell = 32 cells to measure

• ADJI: 32/carrier, total 48• ADJG: 32

• Total: max. 111 in RNC database

• Limitation due to specifications of SIB11/12 size

15 © 2006 Nokia

Handover Control

• Handover Types

• Intra-Frequency Handover• Parameters Mapping• SHO Events and Measurements• Hard Handover & RRC Connection Release

• SRNS Relocation


• GSM ISHO


• Appendix

16 © 2006 Nokia

Soft Handover

• HC supports the following measurement reporting events and features:• Event 1A: A primary CPICH enters the reporting range (Ncell addition)• Event 1B: A primary CPICH leaves the reporting range (Ncell deletion)• Event 1C: A non-active CPICH becomes better than an active primary

CPICH (Ncell replacement)• Cell individual offsets for modifying measurement reporting behaviour• Mechanism for forbidding a neighbor ing cell to affect the reporting range

• Handover decision performed by RNC based on measurements and available resources

• Admission Control can reject the branch addition in case the maximum load is achieved in DL (threshold + offset), valid both for RT and NRT bitrates.

• Hard blocking may prevent branch addition

18 © 2006 Nokia

SHO: Measurement Averaging – Filter response

Filter response

-25

-20

-15

-10

-5

0

t 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33

Measurements

Val

ue,

dB Measured

Filtered, k = 3

Filtered, k = 5

Filter response

-12

-10

-8

-6

-4

-2

0

t 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33

Measurements

Val

ue,

dB Measured

Filtered, k = 3

Filtered, k = 5

Decrease effect of noise

Delay to fast changes

19 © 2006 Nokia

SHO: Measurement Control

Node B

UTRAN

RNCUE

Measurement Control [ ]

I am in the CELL_DCH sub-state

Measurement Type: Intra-frequency measurements• Reporting events:

1A: A primary CPICH enters the reporting range 1B: A primary CPICH leaves the reporting range 1C: A non-active CPICH becomes better than an active primary CPICH

• Periodical reporting / event triggered• Measurement quantity: CPICH Ec/No• etc.

System Information [ ]

SIB 11/12• EcNoFilterCoeffici

entMeasurement accuracy depends on• speed &• Filter Coefficient

EcNoAveragingWindowApplied for averaging of

periodical meas. reports

21 © 2006 Nokia

1A: A Primary CPICH Enters the Reporting Range

Strongest CPICH in AS

time

Ec/Io

P CPICH 3

P CPICH 1

P CPICH 2

1

2

AdditionWindow

AdditionTime

AdditionReportingInterval

RNC

MeasurementReport

Add tothe AS?

no

ActiveSetWeightingCoefficient

34

24 © 2006 Nokia

Strongest CPICH in AS

time

Ec/Io

P CPICH 3

P CPICH 1

P CPICH 2

1

2

3

DropWindow

DropTime

MeasurementReport

1B: A Primary CPICH leaves the Reporting Range

Remove the

reported cell from the AS

26 © 2006 Nokia

reportCriteria intraFreqReportingCriteria : { eventCriteriaList { { event e1a : { triggeringCondition monitoredSetCellsOnly, reportingRange 4, w 0, reportDeactivationThreshold t2, reportingAmount ra-Infinity, reportingInterval ri0-5 }, hysteresis 0, timeToTrigger ttt100, reportingCellStatus allActiveplusMonitoredSet : viactCellsPlus2 } event e1b : { triggeringCondition activeSetCellsOnly, reportingRange 6, w 0 }, hysteresis 0, timeToTrigger ttt640, reportingCellStatus withinActiveSet : e3 },

Extract from SIB 11

• SIB 11 contains the relevant parameters to read when in idle mode

• These are valid in connected mode prior to receiving the measurement control that overwrites them

• In this example:• Addition window= 2 dB (factor of 2

mapping between the signalled value and the actual value, TS 25.331 defines this mapping)

• Addition time = 100 ms

• Reporting interval = 500 ms

• Drop window = 3 dB (factor of 2 mapping between the signalled value and the actual value)

• Drop time = 640 ms

Soft and Softer Handover (case1)

28 © 2006 Nokia

time

weakest CPICH3 in AS

Ec/Io

P CPICH 3

P CPICH 1

P CPICH 2

P CPICH 4

AS has 3 cells

ReplacementReportingInterval3

1

2

ReplacementWindow

ReplacementTime

MeasurementReport

RNC

ASupdate?

no

1C: A non-active CPICH becomes better than an active primary CPICH

30 © 2006 Nokia

event e1c : { replacementActivationThreshold t3, reportingAmount ra-Infinity, reportingInterval ri0-5 }, hysteresis 4, timeToTrigger ttt100, reportingCellStatus withinActiveSet : e3 }

Extract from SIB 11 cont.

Soft and Softer Handover (case 2)

• In this example:• Replacement window = 1 dB

• Replacement time = 100 ms

• Reporting interval = 500 ms

• Replacement window requires mapping to its truevalue according to:

4/(2*2) = 1 dB

• There are two mappings – first is the signalled value to actual value mapping and second is the way in which hysteresis is applied in the event triggering equation (TS25.331)

• Once in connected mode the networks sends the same set of information elements via a measurement control message

• Nokia’s implementation is that the values in the measurement control message are the same as those within SIB 11

• Events 6F and 6G are configured in a similar fashion i.e. within SIB 11 and subsequently with a measurement control message

32 © 2006 Nokia

Individual Ncell Offset

time

P CPICH 1

P CPICH 2

P CPICH 3

Reporting

Range

Reporting Event

1B

Reporting Event

1A

AdjsEcNoOffset

Enlarging Cell 3 by x dB

Ec/Io

33 © 2006 Nokia

Forbidding Neighbour Cell from Reporting Range

Time

P CPICH 1

P CPICH 2

P CPICH 3

PCPICH3 is forbidden to affect the reporting range as its quality is quite unstable.

Reporting

Range AdjsDERR

Ec/Io

34 © 2006 Nokia

Branch addition

RRC: Measurement Report (e1a)

RRC: Active Set Update

RRC: Active Set Update Complete

RRC: Measurement Report (e1b)

RRC: Active Set Update

RRC: Active Set Update Complete

UE moving

Branch deletion

Soft Handover signalling

35 © 2006 Nokia

Event 1A(Add)

Event 1B(Drop)

Event 1C(Replace)

Active set cells +2 monitored set

cells

Monitored set cells

Addition Window/4 dB

Active set cellsActive set cellsDrop Window/

6 dB

Active set cells +2 monitored set

cells- Replacement

Window/4 dB

Addition Time/0 ms

AdditionReportingInterval/0.5 s

Drop time/320 ms -

Replacementtime/0 ms

ReplacementReportingInterval/

1s

Event Reporting cell status

Triggering Condition

Reporting Range/HysteresisTime to TriggerReporting

Interval

SHO Summary

• 3GPP reporting events 1A, 1B and 1C (also 6F and 6G)• CPICH Ec/Io is used as a measurement quantity rather than CPICH RSCP

• CPICH Ec/Io measurements are more accurate• 1A and 1B reporting range is defined by strongest active set cell• 1C reporting range is defined by weakest active set cell

38 © 2006 Nokia

Measurement Report Updating

• Measurement reporting criteria are cell specific

• Neighbouring cells (ADJS and HOPS parameters) are defined on a controlling cell (cell from which the call has been started or best cell in case the original cell has been deleted from the active set)

• During SHO the measurement reporting criteria are taken from the cell where the UE has started the connection

• The measurement reporting criteria are updated only when the original cell leaves the Active Set (Nokia Implementation), according to the strongest cell in the Active Set, by sending the MEASUREMENT CONTROL message, transmitted on the downlink DCCH. Standard would allow to update reporting criteria, according the current best server.

• When the UE receives a MEASUREMENT CONTROL message, the UE shall stop monitoring and measurement reporting and shall replace the measurement reporting criteria with the new information received in the MEASUREMENT CONTROL message.

39 © 2006 Nokia

Measurements Reporting Criteria Updating during Soft Handover

Cell 1 Cell 2

• Neighbour ListCell1• Addition WindowCell1• Drop WindowCell1• Drop TimeCell1

1. Idle Mode

System Information

(BCCH)

BEST Server: Cell 1

BEST Server: Cell 1

2. Connected Mode: Cell_DCH

The UE shall continue monitoring the list of

neighbor ing cells assigned in System

Information during Idle Mode

The UE shall continue monitoring the list of

neighbor ing cells assigned in System

Information during Idle Mode

Measurement Reporting Criteria

according to Cell 1


according to Cell 1

The UE shall send the MEASUREMENT REPORT message when reporting

criteria are fulfilled.

The UE shall send the MEASUREMENT REPORT message when reporting

criteria are fulfilled.

Connected Mode: Cell_DCH

3. MEASUREM

ENT REPORT (DCCH)


according to Cell 1


according to Cell 1

Intra-frequency MeasurementIntra-frequency Measurement

The measurement reporting criteria are

updated as soon as the original cell drops out from the Active Set

(Nokia Implementation).

The measurement reporting criteria are

updated as soon as the original cell drops out from the Active Set

(Nokia Implementation).

Connected Mode: Cell_DCH

4. MEASUREME

NT CONTROL (DCCH)

• Neighbour ListCell2• Addition WindowCell2 • Drop WindowCell2 • Drop TimeCell2

BEST Server: Cell 2

BEST Server: Cell 2


according to Cell 2


according to Cell 2Reporting

Criteria

Updating

40 © 2006 Nokia

Neighbour List Measurement during SHO

Cell 1 Cell 2

Intra-frequency Measurement

Intra-frequency Measurement

• Addition WindowCell1• Drop WindowCell1• Drop TimeCell1

1. System Information

(BCCH)

BEST Server: Cell 1BEST Server: Cell 1

Neighbour List Cell 1Neighbour List Cell 1


according to Cell 1


according to Cell 1

Active Set: Cell 1

Active Set: Cell 1

2

3

5

2

3

5

3. MEASUREMENT REPORT (DCCH)

1A1B6. MEASUREMENT REPORT (DCCH)

4. ACTIVE SET UPDATE

8. MEASUREMENT CONTROL (DCCH)

• Addition WindowCell2 • Drop WindowCell2 • Drop TimeCell2

BEST Server: Cell 2BEST Server: Cell 2

Measurement Reporting Criteria according to Cell 2

Measurement Reporting Criteria according to Cell 2

Neighbour List Update

1

3

4

1

3

4

Neighbour List Cell 2Neighbour List Cell 2

Active Set: Cell 2

Active Set: Cell 2Meas. Rep.

Criteria Update


according to Cell 1


according to Cell 1

3

1

4

2

5

3

1

4

2

5

Neighbour List Combination

Neighbour List Combination

Neighbour List Update

5. MEASUREMENT CONTROL (DCCH)

Active Set: Cell1 - Cell2Active Set: Cell1 - Cell2

2. Setup Call

2. Setup Call

7. ACTIVE SET UPDATE

41 © 2006 Nokia

Inter-RNC Soft HO

• Inter-RNC soft Handovers are performed if:

• RNC: IurUPSupport indicates the support of the user plane over Iur

• HOPS: EnableInterRNCsho indicates whether cell can participate in a SHO

EnableInterRNCsho

cell3 cell2

cell1

cell4

cell6

cell5

RNC RNCIurUPSupport

EnableInterRNCsho

• Otherwise, HC checks whether Hard Handover is possible

42 © 2006 Nokia

Handover Control

• Handover Types

• Intra-Frequency Handover:• Parameters Mapping• SHO Events and Measurements• Hard Handover & RRC Connection Release

• SRNS Relocation


• GSM ISHO


• Appendix

45 © 2006 Nokia

Time

Ec/Io

P CPICH 3

P CPICH 1

P CPICH 2Reporting

range

AdditionReportingInterval

1

2

HHOMarginAverageEcNoHHOMarginPeakEcNo

1A (AdditionTime = 0)

AveEcNoDownlink + HHOMarginAveEcNo < AveEcNoNcellEcNoDownlink + HHOMarginPeakEcNo < EcNONcell

Hard Handover

3

46 © 2006 Nokia

RRC Connection Release

• If difference between the best AS cell and the NS cell is too high and SHO is not performed, the RRC connection is released to avoid excessive interference

• Why might an AS update not be possible?• Excessive load in the neighbor ing cell• Hard blocking in the target BTS• Unavailability of DL spreading codes• Iub transport resources unavailable

• This function is activated by EnableRRCRelease (HOPS parameter)/0=no (def),1 =yes

• The RRC connection is released if either:

AveEcNoDownlink + ReleaseMarginForAveEcNo(n) < AvEcNoNcell(n)

EcNoDownlink + ReleaseMarginPeakEcNo(n) < EcNoNcell(n)

• ReleaseMarginForAveEcNo (HOPS) = average Eb/N0 margin [-6 … 6] dB, default 2.5dB

• ReleaseMarginPeakEcNo (HOPS) = peak Eb/N0 margin [-6 … 6] dB, default 3.5dB

• Emergency calls are exempt from RRC Connection Release process

47 © 2006 Nokia

Handover Control

• Handover Types


• SRNS Relocation

• Traffic Balancing


• GSM ISHO


• Appendix

48 © 2006 Nokia

Inter-RNC Mobility• Most of the times the UE hands over among WBTS belonging to the same RNC

(Intra-RNC Handovers)• However, what happens when the target WBTS is under a different WBTS??• 3GPP gives two different options to handle inter-RNC mobility in WCDMA

• Anchoring: the UE will be connected to the CN via the “old” RNC. It is required Iur connection between the RNCs involved

• SRNS relocation: the UE will be connected to the CN via the “new” RNC. It is the Nokia implemented method

*) SRNS relocation needs core network support; UE support mandatory in 3GPP

CN

RNCRNC

Iu Iu

Iur

CN

RNCRNC

Iu Iu

Iur

AnchoringCN

RNCRNC

Iu Iu

Iur

CN

RNCRNC

Iu Iu

Iur

SRNS relocation *)

49 © 2006 Nokia

RNCRNC

RNCRNC

RNC

RNC

RNCRNCRNC

RNC

SRNS Relocation

SRNS Relocatio

n

SRNS Relocatio

n

SRNS Relocatio

n

Call will drop

SRNC anchored

Anchor RNC (SRNC)

SRNS Anchoring

After the last branch from the SRNC has been deleted (event 1b), and all the

RL belong to the DRNC, the

Relocation is triggered

SRNS Relocation

50 © 2006 Nokia

SRNC Relocation

• The SRNC relocation is used for moving the SRNC functionality from one RNC to another RNC, that is, closer to where the UE has moved during the communication. Both the radio access network and the core network are involved

• An inter-RNC Hard Handover can be associated to the SRNS relocation, if so the relocation is UE involved, since the UE is ordered to switch to another carrier or to replace the whole active by sending a HHO command to the UE during the relocation procedure. An inter-RNC Hard Handover can be due to:

• Inter frequency HHO is needed, and the target cell is located in the DRNS• No resources (mainly Iur capacity) available between the involved RNCs (so

no inter-RNC SHO possible)• No Iur interface configured between the neighbour RNCs

51 © 2006 Nokia

UE not involved SRNC Relocation for RT UETarget RNC

SRNC Relocation Decision

SRNC operation started

CN

UP switching

User plane set -up

RANAP:Relocation Required RANAP:Relocation Request

RANAP:Relocation Request Ack

RANAP:Relocation complete

RRC:UTRAN Mobility Information

RANAP:Relocation Command

RNSAP:Relocation Commit

RANAP:Relocation Detect

RRC:UTRAN Mobility Information Confirm

RANAP:Iu Release

RANAP:Iu Release Complete

User plane release

Source RNC SRNC Relocation is initiated in the Serving RNC when all the cells of the active set belong to a different RNC. The SRNC sends a Relocation Required

• The CN evaluates if the relocation is possible and in that case, it sends a Relocation Request to the target RNC with parameters for the bearer establishment

• Relocation Command sent from CN to Source RNC with UTRAN information and bearer parameters

• After that, the Source RNC sends Relocation Commit message over Iur to the Target RNC

• When target RNC starts to act as Serving RNC, it sends a Relocation Detect message to CN. This message has no parameters

• At the same time UTRAN Mobility Information is sent to the UE, to inform that the relocation is performed

• After the confirm, the target RNC informs CN with Relocation Complete –message that the relocation procedure was successful and Iu is released from source RNC

Start RelocPrep

Stop RelocPrep

Start RelocOverall

Start RelocOverall

Stop RelocOverall

Stop RelocOverall

RelocationSupport =1

NrncRelocationSupport =1

52 © 2006 Nokia

UE involved: Combined SRNC Relocation and inter-RNC HHO for RT

UETarget RNC

SRNC Relocation Decision

L1 sync. Established between BTS and UE

CN

UP switching

User plane set -up

RANAP:Relocation Required RANAP:Relocation Request

RANAP:Relocation Request Ack

RANAP:Relocation complete

Physical Ch Reconfig Complete

RANAP:Relocation Command

Physical Channel Reconfiguration

RANAP:Relocation Detect

RANAP:Iu Release

RANAP:Iu Release Complete

User plane release

Source RNC

• Because there is no Iur interface, combined SRNS relocation and HHO are done before the UE is completely under the target RNC

• The procedure is quite similar to the not UE involved case until Relocation Command

• The only difference in the Relocation Required message, the Relocation Type IE is set to "UE involved in relocation of SRNS"

• Instead of Relocation Commit via Iur, the serving RNC sends a Physical CH Reconfiguration, after which the UE stops transmitting and receiving on the old radio links and starts on the new radio link

RelocationSupport =1

NrncRelocationSupport =1

Start RelocPrep

Stop RelocPrep

Start RelocOverall

Stop RelocOverall

Start RelocOverall

Stop RelocOverall

53 © 2006 Nokia

SRNC Relocation Parameters

• TRelocPrep : range = 1 ... 16 s, step 1 s, default = 6s• Specifies the maximum time for Relocation Preparation procedure in the source RNC. The timer

is set when a Relocation Required message is sent. The timer is stopped when a Relocation Command or a Relocation Preparation Failure message is received

• TRelocOverall : range = 1 ... 16 s, step 1 s, default = 8s• This timer is used in both source and target RNC. In the source RNC specifies the maximum time

for the protection of overall Relocation procedure. It is set in the source RNC when a Relocation Command message is received; and it is stopped when an Iu Release Command is received, or the relocation procedure is cancelled.

The timer is set in the target RNC when a Relocation Request Acknowledge message is sent. The timer is stopped when a Relocation Complete message is sent, or the relocation procedure is cancelled

• T_Reloc_Inhibit_NRT : fixed to 5s• The timer is started in source RNC when a SRNC relocation procedure is triggered for a NRT

RAB(s) in a Cell_DCH state. The SRNC relocation procedure is inhibited as long as a DCH is used for the NRT RAB(s) or this timer expires

• TDataFwd : fixed to 4s• The timer is set when a SRNS Data Forward Command message (or a Relocation Command

message) is received from the PS CN. The timer is internally stopped in the SRNC when the SRNS Data Forwarding procedure has been completed

• RelocationSupport : range = 0 (Not supported), 1 (Supported), default value = 1 • RNC object parameter, identifies whether the Core Network supports the relocation of SRNC or

not• NrncRelocationSupport : range = 0 (Not supported), 1 (Supported), default = 1

• RNC object parameter, identifies whether a neighbouring RNC supports relocation of SRNC or not

54 © 2006 Nokia

Handover Control

• Handover Types


• SRNS Relocation

• Inter-Frequency & Inter-System Handover• Measurement triggering• Inter-Frequency & Inter-System Measurements• Compressed-Mode• Inter-Frequency HO decision• Inter-System HO decision • Forced AMR voice call handover to GSM

• GSM ISHO


• Appendix

55 © 2006 Nokia

IFHO/ISHO Process Overview

HO Triggering Thresholds set in RNCHO Triggering Thresholds set in RNC

Event Triggered Coverage/Capacitybased HO fulfilled in RNC

Event Triggered Coverage/Capacitybased HO fulfilled in RNC

RNC commands selected UE(s) to startIF/IS measurements

RNC commands selected UE(s) to startIF/IS measurements

Measurements are done in Compressed Mode (CM)

Measurements are done in Compressed Mode (CM)

UE reports GSM cells withstrongest RSSI signals to RNC

UE reports GSM cells withstrongest RSSI signals to RNC

RNC makes HO decision andcommands UE to target cell

RNC makes HO decision andcommands UE to target cell

RSSI measurements and BSICverification for GSM cells

RSSI measurements and BSICverification for GSM cells

Different decision methods for IF HOOnly one decision method for IS HO

5 Coverage/Capacity HO Reasons

About 25 HO parameters

Reporting cells are active set cells (max 3) + max 6 IFHO, max 6 ISHO neighb.

Max 32 neighbours could be measured

(31 Intra-Freq neighbours)48 Inter-Freq neighbours 32 Inter-System neighbours can be measured

56 © 2006 Nokia

IFHO/ISHO measurements- difference

• IF measurements

• IS measurements

• BSIC verification required in case neighbour list includes multiple GSM neighbours using the same RF carrier

WCDMA

IS-HOMeasurement

Trigger Target Cell found

RSSI meas. BSIC verification

IS-HODecision

WCDMA

IF-HOMeasurement

Trigger Target Cell found

IF -measurements

IF-HODecision

57 © 2006 Nokia

Handover Control

• Handover Types


• SRNS Relocation

• Inter-Frequency & Inter-System Handover:• Measurement triggering• Inter-Frequency & Inter-System Measurements• Compressed-Mode• Inter-Frequency HO decision• Inter-System HO decision • Forced AMR voice call handover to GSM

• GSM ISHO


• Appendix

58 © 2006 Nokia

IF/IS Handover Measurement Triggering Reasons

4. DL DPCH approaches itsmaximum allowed powerFMCI: IFHOcauseTxPwrDLFMCG: GSMcauseTxPwrDL

5. Quality deterioration report from UL outer loop PCFMCI: IFHOcauseUplinkQualityFMCG: GSMcauseUplinkQuality

3. UE Tx power approaches itsmaximum allowed power, event 6A/6DFMCI: IFHOcauseTxPwrULFMCG: GSMcauseTxPwrUL

2 . Low measured absoluteCPICH RSCP, events 1E/1FFMCI: IFHOcauseCPICHrscp, FMCG: GSMcauseCPICHrscp

1. Low measured absolute CPICH Ec/No, event 1E/1F FMCI: IFHOcauseCPICHEcNoFMCG: GSMcauseCPICHEcNo

Measurement

Trigger

6 . Others- Load and Service based HO- IMSI based HO- Emergency ISHO

Frequency Measuring Control for Inter-Frequency = FMCIFrequency Measuring Control for Inter-System (GSM) = FMCG

59 © 2006 Nokia

1. Measurement trigger CPICH Ec/NoReporting event: 1E: A P-CPICH exceeds an absolute threshold

1F: A P-CPICH falls below an absolute threshold (HO triggered if all)

time

Cell 1 Cell 2

Cell 3

absolutethreshold

e.g

. P

-CP

ICH

Ec/N

o

1E: HHoEcNoCancel

1E: HHoEcNoCancelTime

1F: HHoEcNoThreshold

1F: HHoEcNoTimeHysteresis

64 © 2006 Nokia

Reporting Events 6A, 6B and 6D

timetime totrigger

UE T

x P

ow

er

UE Transmitted Power Tx

Threshold

6B

6A

6D

min(UEtxPowerMaxDPCH, P_MAX)

6A: The UE Tx power exceeds an absolute threshold 6B: The UE Tx power falls below an absolute threshold 6D: The UE Tx power reaches its maximum value (Not used in Nokia RAN)

InterfreqUETxPwrTimeHystGSMUETxPwrTimeHyst

68 © 2006 Nokia

4. Measurement trigger DL DPCH (DL Coverage)

Node BRNC

DCH Data Frame

IubUE

PO1TPC

Pilotbits not used

TFCIData 2 bitsData 1 bits

PO2 DL_CODE_PWR - PowerOffsetDLdpcchPilot Ptx_RL_max + DL_DPCH_TXPWR_THRESHOLD

Max Power on DPCH (e.g. 33 dBm)

Serving WCDMA cell time

It‘s time to triggerHO measurements

in the UE

e.g. Radio Link Measurement Report(e.g. Transmitted Code Power Value)

HHoMaxAllowedBitrateDL

Example Speech:Power Data Bits > 33dBm + (-3dB) +

(-1dB)Power Data Bits > 29 dBm (~1W)

Max Power on Channel

70 © 2006 Nokia

5. Measurement trigger UL QualityTa

rget

SIR

Max SIR target

Min SIR target

Actual SIR target

1st Quality deterioration report from PC to HC inside RNC

2nd Quality deterioration report (while the condition issatisfied the message is periodically repeated)

default 5s time

SIRSIR

RNC

ULQualDetRepThreshold (recommendation 2 s)

EnableULQualDetRepHHoMaxAllowedBitrateUL

RNC

71 © 2006 Nokia

Handover Control

• Handover Types

• Intra-Frequency Handover:

• SRNS Relocation


• GSM ISHO


• Appendix

72 © 2006 Nokia

Decision Algorithm

UE Tx Power (Event 6A\6B)• Threshold:InterFreqUETxPwrThrXX• L3 filter:

InterFreqUETxPwrFilterCoeff *

• Hysteresis margin (time to trigger): InterFreqUETxPwrTimeHyst *

• Data rate threshold HHOMAxAllowedBitrateUL *

UL Quality• Timer:ULQualDetRepThreshold• Data rate threshold HHOMAxAllowedBitrateUL

DL DPCH power• Threshold: InterFreqDLTxPwrThrXX• Data rate threshold HHOMAxAllowedBitrateDL

(XX=AMR,NrtPS,RtPS)

CPICH RSCP (Event 1F)• Thresholds:HHoRscpThresholdHHoRscpCancel• L3 filter:

HHoRscpFilterCoefficient *

• Time to trigger:HHoRscpTimeHysteresis *HHoRscpCancelTime *

CPICH Ec/Io (Event 1F)• Thresholds:HHoEcNoThreshold HHoEcNoCancel • L3 filter:EcNoFilterCoefficient * • Time to trigger:HHoEcNoTimeHysteresis * HHoEcNoCancelTime *

AdjiPlossMargin AdjiMinEcNo AdjiMinRSCP AdjiTxPwrDPCH AdjiEcNoMargin

InterFreqMaxMeasPeriod *InterFreqMeasRepInterval *InterFreqNcellSearchPeriod * InterFreqMinHoInterval *InterFreqMinMeasInterval * InterFreqMeasAveWindow *

Handover Triggering

Handover Execution

IF HO meas control parameters

(* = parameters already optimised)

IFHO Parameters

(in blue = parameters under study)

1 more optional trigger in RAN04:

IMSI based IFHO

73 © 2006 Nokia

IFHO measurements

• After HO triggering message is sent to RNC, a RRC message ”Measurement Control” is sent to UE containing details of the measurement that the UE must execute. Measurement reporting is periodical. Max 6 IF cells can be reported. No filtering in measurements by UE.

• Upon reception of the measurements reported by the UE, RNC applies a sliding averaging window to the CPICH Ec/No & CPICH RSCP measurements. The averaged levels are used as input to the inter-frequency decision algorithm.

• From each cell in active set (max=3) also intra-frequency measurements are done at same time

RNCRRC: ”Measurement control ” message ("carrier 2" measurements)

UE

RNC

CPICH Ec/No and CPICH RSCP measurements are reported through ”Measurement report” messages

UE

RRC: ”Measurement report”


In one measurement report there is both intra-and inter-frequency

results, no measurement filtering is used in UEAdjiMeasRepInterval

(default 0.5s)

3 neighbour info send to UE:UTRA RF channel, cell

individual offset (Ec/No) and primary scrambling code

74 © 2006 Nokia

Measurement Control Parameters: FMCI

• InterFreqMeasRepInterval: 0.5 seconds• This is the interval between measurement reports, which are sent to BTS

• InterFreqMinMeasInterval:10 s• This is Minimum Measurement Interval, wait time when the following CM starts, In

case of an unsuccessful IFHO attempt, the network will deactivate compressed mode for a time period given by this parameter, thus better value will be 2 s to speed up the reactivation of CM.

• InterFreqMeasAveWindow: 6• This is Measurement Averaging Window size, sliding window is used

• InterFreqMaxMeasPeriod: 20 reports• This is Maximum Measurement Period which determines the maximum allowed

duration of the inter-frequency measurement• If the RNC is not able to execute an inter-frequency Handover, it shall stop the inter-

frequency measurements after the UE has sent the predefined number of measurement reports to the RNC.

75 © 2006 Nokia

Measurement Control Parameters: FMCI

• Maximum allowed duration of the inter-frequency measurement is calculated:• InterFreqMeasRepInterval * InterFreqMaxMeasPeriod (0.5*20s) =10s,

• This seems to be too long time, because CM time was noticed to be about 3 seconds, so it makes senses to reduce the value of this parameter to some value about 3 seconds, otherwise, if there is failure, the network will not deactivate compressed mode until the timer of 10 seconds has expired. Thus, decreasing the parameter value will allow the UE/network to initiate a new IFHO attempt. Proposed value for GSMMaxMeasPeriod is 6

• This seems to be too long time, because the CM time was noticed to be about 3 s, thus proposed value for InterFreqMaxMeasPeriod is 6

• InterFreqNcellSearchPeriod:0 • This is neighbor cell search period parameter, IFHO is not allowed until the are

enough measurement reports given by this parameter• O means that only 1 measurement result is enough for decision making• Duration of the cell search period is calculated:

InterFreqMeasRepInterval * InterFreqNcellSearchPeriod).

76 © 2006 Nokia

Decision Algorithm

UE Tx Power (Event 6A)• Threshold:GsmUETxPwrThrXX • L3 filter:

GsmUETxPwrFilterCoeff

• Hysteresis margin: GsmUETxPwrTimeHyst

• Data rate threshold HHOMAxAllowedBitrateUL

UL Quality• Timer:ULQualDetRepThreshold• Data rate threshold HHOMAxAllowedBitrateUL

DL DPCH power• Threshold: GsmDLTxPwrThrXX• Data rate threshold HHOMAxAllowedBitrateDL

(XX=AMR,CS,NrtPS,RtPS)

CPICH RSCP (Event 1F)

• Thresholds:HHoRscpThreshold HHoRscpCancelL3 filter: HHoRscpFilterCoefficient• Timers:HHoRscpTimeHysteresisHHoRscpCancelTime

CPICH Ec/Io (Event 1F)• Thresholds:HHoEcNoThresholdHHoEcNoCancel• L3 filter:Done already for SHO• Timers:HHoEcNoTimeHysteresisHHoEcNoCancelTime

AdjgTxPwrMaxTCHAdjgRxLevMinHO (n)GsmMeasAveWindow

GsmMeasRepIntervalGsmNcellSearchPeriodGsmMinMeasIntervalGsmMaxMeasPeriod

Handover Triggering

Handover Execution2G-to-3G back prevention

GsmMinHoInterval

GSM measurement reporting

ISHO parameters

2 more optional triggers in RAN04:

IMSI based ISHO Emergency ISHO (EMISHO)

77 © 2006 Nokia

ISHO measurements

• After HO triggering message is sent to RNC, a RRC message ”Measurement Control” is sent to UE containing details of the measurement that the UE must execute. Measurement reporting is periodical. Max 6 GSM cells could be measured by UE and reported to RNC. No filtering in measurements by UE

• Upon reception of the measurements reported by the UE, RNC applies a sliding averaging window to the RXLEV measurements. The averaged levels are used as input to the IS-HO decision algorithm.

RNCRRC: ”Measurement control ” message (GSM RSSI measurements)

UE

RNC

RXLEV measurements are reported through”Measurement report” messages

UE



The first measurement report has info from the best GSM cell:

BCCH freq & RSSI, no filteringused in UE

GsmMeasRepInterval (default 0.5s)

78 © 2006 Nokia

Measurement Control Parameters: FMCG

• GSMMeasRepInterval: 0.5 seconds• This is the interval between measurement reports, which are sent to BTS• This parameter should be kept to 0.5 seconds. Increasing the reporting interval

would increase the IS-HO process delay.

• GSMMinMeasInterval:10 s• This is Minimum Measurement Interval, wait time when the following CM starts.

In case of an unsuccessful IS-HO attempt, the network will deactivate compressed mode for a time period given by this parameter, thus better value will be 2 s to speed up the reactivation of CM.

• GSMMeasAveWindow: 6• This is Measurement Averaging Window size, sliding window is used

• GSMMaxMeasPeriod: 20 reports• This is Maximum Measurement Period which determines the maximum allowed

duration of the inter-sytem measurement• If the RNC is not able to execute an inter-system Handover, it shall stop the

inter-system measurements after the UE has sent the predefined number of measurement reports to the RNC.

79 © 2006 Nokia

Measurement Control Parameters: FMCG

• Maximum allowed duration of the inter-system measurement is calculated:• GSMMeasRepInterval * GSMMaxMeasPeriod (=0.5*20s) =10s,

• This seems to be too long time, because based on field measurements BSIC and RSSI delays are about 3 seconds, so it makes senses to reduce the value of this parameter to some value about 3 seconds, otherwise, if the BSIC or RSSI measurements fail or if the IS-HO execution is not possible to due low GSM RSSI levels, the network will not deactivate compressed mode until the timer of 10 seconds has expired. Thus, decreasing the parameter value will allow the UE/network to initiate a new IS-HO attempt. Proposed value for GSMMaxMeasPeriod is 6

• GSMNcellSearchPeriod: 0 • This is neighbor cell search period parameter, ISHO is not allowed until the are

enough measurement reports given by this parameter• O means that only 1 measurement result is enough for decision making• Duration of the cell search period is calculated: • GSMRepInterval * GSMNcellSearchPeriod).

80 © 2006 Nokia

ISHO: BSIC Verification

• After the selection of the target GSM cell, the RNC sends to UE the RRC message "Measurement control” which includes details to measure ”BSIC” .

• UE stops RSSI measurements and updates the transmission gap pattern to the pattern used for BSIC decoding. The measurement reports are sent periodically to RNC.

• If the UE is unable to decode the BSIC during the given period, the BSIC measurement operation is aborted.

RNC

RRC: ”Measurement control ” message (BSIC decoding)

WCDMA

IS-HO trigger Target Cell found IS-HO command

RSSI meas. BSIC verification

• Numbers of GSM cells in the

neighbor cell list• Reporting interval• Sliding averaging

window• Transmission gap

pattern for RSSI measurements

TBSIC depends on :

• Transmission gap pattern for BSIC decoding

TRSSI depends on

81 © 2006 Nokia

Handover Control

• Handover Types


• SRNS Relocation


• GSM ISHO


• Appendix

82 © 2006 Nokia

Compressed Mode in Uplink

GSM BTS WCDMA BTS

DL

DL CM (this should be offwhen GSM is measured)

UL CM (needed to avoid interference)

During WCDMA transmissionsignal leakage will go to GSMRx also

83 © 2006 Nokia

Compressed Mode (CM)

• CM was introduced to WCDMA to allow inter-frequency (system) Handovers• CM is used to create idle periods (gaps) in the transmission during which ncell

measurements on another frequency can be made

• Gaps can be created using single or double frame approach (Nokia supports both)• Because same data amount is sent in a shorter time more power is needed during CM

(both in UE and BTS) => affects WCDMA coverage

• Fast Power control information might be lost during the gap => higher Eb/No=> affects WCDMA capacity

• Compressed frames may be lost if power control is not set correctly => affects WCDMA quality

• CM methods are Spreading Factor Halving and Higher Layer Scheduling

Normal frame Normal frame

Measurement gapMeasurement gapPower / Data Rate

CompressedMode

Normal frame

84 © 2006 Nokia

AssumptionAssumption Effect to the capacityEffect to the capacity

Required Eb/No is 1.5 dB higher during compressed frames

Required Eb/No is 1.5 dB higher during compressed frames1.5 dB = 41% more interference1.5 dB = 41% more interference

Every 3rd frame is compressedEvery 3rd frame is compressed41% /3 = 14% more interference41% /3 = 14% more interference

10% of the users are measured at the same time

10% of the users are measured at the same time14% /10 = 1.4% more interference14% /10 = 1.4% more interference

Capacity degradation < 2%

Performance of Compressed Mode: Capacity

Exact increase in Eb/N0 depends on service, multipath diversity, antenna diversity, mobile speed, uplink or downlink, measurement gap length, compressed mode

method (spreading factor), and 1.5 dB represents a typical value.

Exact increase in Eb/N0 depends on service, multipath diversity, antenna diversity, mobile speed, uplink or downlink, measurement gap length, compressed mode

method (spreading factor), and 1.5 dB represents a typical value.

85 © 2006 Nokia

Performance of Compressed Mode: Coverage

AssumptionAssumption Effect to the coverageof real time services

Effect to the coverageof real time services

Required Eb/No is 1.5 dB higher during compressed frames

Required Eb/No is 1.5 dB higher during compressed frames 1.5 dB reduced coverage1.5 dB reduced coverage

7-slot gap is used7-slot gap is used 10*log10(15/8) = 2.7 dB reduced coverage

10*log10(15/8) = 2.7 dB reduced coverage

Every 2nd frame is compressed with 20 ms interleaving (speech)

Every 2nd frame is compressed with 20 ms interleaving (speech) 4.2 dB / 2 = 2.1 dB reduced coverage 4.2 dB / 2 = 2.1 dB reduced coverage

Total coverage reduction 2.1 dB

Compressedmode

Mobile max. power

Frame error if mobile hitsits maximum power

2.7 dB + 1.5 dB more power is needed during compressed mode

• Non-real time services can reduce the bit rate during compressed frames no effect to coverage• Speech connection can switch to a lower AMR mode

86 © 2006 Nokia

Measurement Gap

Min transmitted TSs per Frame: 8

radio frame radio frame

TGL

Length of gap:3, 4, 5, 7 timeslots

Single-frame method

radio frame radio frame

TGL

Double-frame method

Length of gap:3, 4, 5, 7, 10, or 14

timeslots

87 © 2006 Nokia

Compressed mode methods

• Halving Spreading Factor, SF/2 for RT and NRT services (UL and DL)

• Doubles temporarily the physical channel data rate, possible for all services

• Needs 3 dB more UE power due to halved spreading ratio

• If new channelization code is available from code tree in DL

• WCEL: AltScramblingCodeCM/0=used (def), 1=not used

• Higher Layer Scheduling, HLS (UL and DL) • Only possible for PS services (RT or NRT)

• Does not cause extra load to the cell but reduces DCH user data

• HLS ¾ data rate or HLS ½ data rate possible

Double frame is used in case of HLS ¾ data rateSingle frame is used in case of spreading factor halving and HLS ½

data rate.

89 © 2006 Nokia

How many UEs in Compressed Mode ?

PtxTarget/PrxTarget

DL/ULtransmission power

Load

PtxOffset/PrxOffset

New UEs can be switched to CM when:

Pxx_Total < Pxx_Target & # of UEs in CM <

MaxNumbUECMcoverHO

One new UE in CM can be allowed

if the limit is not reached

No new UE can be in CM here

90 © 2006 Nokia

AMR, RT PS or CS data service

AMR, RT PS or CS data service

• Selection of the compressed mode method is performed in the following way:

SF/2 used for both UL and DLSF/2 used for both UL and DL • compressed mode trigger parameters have to be set so that there is room for power increase due to code splitting otherwise power increase is cut and quality of connection gets worse during the compressed frames

• Usage of alternative scrambling code is possible if RNP parameter AltScramblingCodeCM enables

Transmission Gap Pattern:Single frame: 7 slot gap,

variable # of normal frames



NRT PS data serviceNRT PS data service

Higher layer scheduling is used for both UL and DL

Higher layer scheduling is used for both UL and DL

Transmission Gap Pattern:Transmission Gap Pattern:

Single frame: 7 slot gap,# of normal frames

Single frame: 7 slot gap,# of normal frames

Double frame: 7 slot gap,# of normal frames

Double frame: 7 slot gap,# of normal frames

Selection between HLS ½ and HLS ¾

Selection between HLS ½ and HLS ¾

Compressed Mode Initiate Compressed Mode

Configure GSM measurements

91 © 2006 Nokia

Multi Service : AMR + PS data, AMR + CS data,

PS data + CS data

Multi Service : AMR + PS data, AMR + CS data,

PS data + CS data

• Selection of the compressed mode method is performed in the following way:

SF/2 used for both UL and DLSF/2 used for both UL and DL• also same power and

alternative scrambling code aspects as in pure AMR or CS data service casesTransmission Gap Pattern:

Single frame: 7 slot gap, variable # of normal frames



• Note that same method according to service is used for all Handover triggers• Both uplink and downlink gap patterns can be used despite of whether other direction is

compressed or not• If both directions (UL and DL) are compressed, gap pattern is chosen so that both directions support it• E.g. downlink support single frame but uplink double frame, it means that double frame shall be used

• The number of normal frames between gapped frames is defined with parameters • This solution leaves the following problem in certain multi service call

• Currently UEs of certain vendor do not support in downlink DPCCH and DPDCH slot format #15B (compressed mode code splitting when SF=4)

• This means that 320 kbps PS data + AMR does not work for these terminals • This problem can be partly avoided by denying compressed mode with that high data rate

• It can be done in downlink with RNP parameter HHOMaxAllowedBitRateDL

Compressed Mode Initiate Compressed Mode

Configure GSM measurements

93 © 2006 Nokia

Handover Control

• Handover Types


• SRNS Relocation

• Inter-Frequency & Inter-System Handover• Measurement triggering• Inter-Frequency & Inter-System Measurements• Compressed-Mode• Inter-Frequency HO decision• Inter-System HO decision • Forced AMR voice call handover to GSM

• GSM ISHO


• Appendix

94 © 2006 Nokia

It is not sufficient to have triggers, which detect that a Handover has to be done. Criteria are required to decide, whether to carry out an intra-frequency, inter-frequency, or inter-RAT Handover – if there is the possibility for a Handover at all!

Conditions shown here have to be satisfied, before an inter-frequency Handover can be conducted. The best neighbor ing cell must fulfil following criteria („best“ according to Ec/No):

• Quality Criterion in case trigger was DL DPCH Power or CPICH Ec/No:AVE_RSCP_NCELL (n) > AdjiMinRSCP(n) + max(0,

AdjiTxPwrDPCH(n) - P_MAX)Signal level from new cell > required Signal level in new cell + adjustment due to

allowed power

AVE_EcNo_NCELL (n) > AVE_CPICH_EcNo + AdjiEcNoMargin(n)EcNo on new cell better than EcNo in old cell + margin

• Pathloss Criterion in case trigger was UE Tx Power, CPICH RSCP or UL DPCH Quality:

AVE_EcNo_NCELL (n) > AdjiMinEcNo(n) EcNo on new cell better than required EcNo in new cell (default –14 dB)

CPICH_POWER - AVE_CPICH_RSCP > CPICH_POWER_NCELL (n) -

AVE_RSCP_NCELL (n) + AdjiPlossMargin(n) PathLoss in old cell > PathLoss in new cell + Margin (default 2 dB)

(continued)

IFHO Decision

95 © 2006 Nokia

RRC: MEASUREMENT CONTROL (IF meas details)

UEISHO triggered: Event 6A\1F….

RNC

RRC: MEASUREMENT REPORT (Event 6A\1F..)

RRC: MEASUREMENT REPORT (CFN, TGPS)

Radio Link Setup

Periodic IF meas Reporting

RRC: PHYSICAL CHANNEL RECONFIGURATION (Timing Indication)

RRC: PHYSICAL CHANNEL RECONFIG COMPLETE

Handover Decision

.

.

Compressed Mode

Compressed Modeparameters

There is bad quality conditions in the link ..

With the information gotten, the RNC assess the best cell, and decides to attempt a IFHO to it

IF HO Signalling

RRC: PHYSICAL CHANNEL RECONFIGURATION


IF measurement setup and Compressed Mode activation

96 © 2006 Nokia

Inter-frequency HO – Quality Criteria

HO?

a) AVE_RSCP_NCELL (n) > AdjiMinRSCP(n) + max(0, AdjiTxPwrDPCH(n) – P_MAX)b) AVE_EcNo_NCELL (n) > AVE_CPICH_EcNo + AdjiEcNoMargin(n)

AdjiMinRSCP(n)

max(0, AdjiTxPwrDPCH(n) - P_MAX)

b)

AdjiMinEcNo(n)

AdjiEcNoMargin(n)

AVE_EcNo_NCELL (n)

a)

AVE_EcNo_NCELL(n) >AVE_CPICH_EcNo + AdjiEcNoMargin(n)

97 © 2006 Nokia

Inter-frequency HO – Pathloss Criteria

a) AVE_EcNo_NCELL(n) > AdjiMinEcNo(n)b) CPICH_POWER - AVE_CPICH_RSCP

> CPICH_POWER_NCELL(n) - AVE_RSCP_NCELL(n) + AdjiPlossMargin(n)

best active setcell

AdjiPlossMargin(n)

best inter-frequencycell

b)AVE_EcNo_NCELL (n) > AdjiMinEcNo(n)

AdjiMinEcNo(n)

a)

99 © 2006 Nokia

Handover Control

• Handover Types


• SRNS Relocation


• GSM ISHO


• Appendix

101 © 2006 Nokia

AdjgRxLevMinHO(n)

max(0, AdjgTxPwrMaxTCH(n) - P_max)

AVE_RXLEV_NCell(n) > AdjgRxLevMinHO(n) + max(0, AdjgTxPwrMaxTCH(n) - P_max)

GSM cell

ISHO Decision

102 © 2006 Nokia

• BSIC verification always performed for AMR calls – no interrupt in voice call

CNUE Node B

RNC

RRC: Measurement Report

RRC: Measurement Control

NBAP: Radio Link Reconfiguration PrepareNBAP: Radio Link Reconfiguration

Ready NBAP: Radio Link Reconfiguration CommitRRC: Physical Channel

ReconfigurationRRC: Physical Channel Reconfiguration Complete NBAP: Compressed Mode

Command



NBAP: Compressed Mode Command



RRC: Handover from UTRAN Command

GSM BSIC Identification

GSM RSSI Measurement

ISHO triggering (3 reasons are possible)

Initial Compressed Mode Configuration

RANAP: Relocation Required

RANAP: Relocation Command

RANAP: IU Release Command

RANAP: IU Release Complete

ISHO 3G -> 2G - AMR Signalling Flow

103 © 2006 Nokia

• In most cases BSIC verification is not required (data interrupt as UE moves to 2G)

• PS makes use of RRC: CELL CHANGE ORDER FROM UTRAN message

UE

Node B

RNC



NBAP: Radio Link Reconfiguration Prepare

NBAP: Radio Link Reconfiguration Ready

NBAP: Radio Link Reconfiguration Commit

RRC: Physical Channel Reconfiguration

RRC: Physical Channel Reconfiguration Complete

NBAP: Compressed Mode Command


RRC: Measurement Control GSM RSSI Measurement

ISHO triggering (5 reasons are possible)

Initial Compressed Mode Configuration

CN

RANAP: SRNS Context Request

RANAP: SRNS Context Response

RANAP: IU Release Command

RANAP: IU Release Complete

RRC: Cell Change Order from UTRAN

RANAP: SRNS Data Forward Command

ISHO 3G -> 2G - PS Signalling Flow

105 © 2006 Nokia

Handover Control

• Handover Types


• SRNS Relocation


• GSM ISHO


• Appendix

106 © 2006 Nokia

Forced Handover for AMR Voice Call

• Feature can be used to push3G AMR calls to 2G

• Extreme parameter settingfor ISHO trigger cause“UE Tx power” (event 6A)

WCDMA

GSM

AMR voice call setup in 3G

forced handover

to GSM

[..]UE RNC

RRC: RadioBearerSetup

RRC: RadioBearerSetupComplete

RRC: MeasurementControl

RRC: MeasurementReport (event 6A)

FMCG: GSMcauseTxPwrUL

FMCG: GsmUETxPwrThrAMR

ISHO measurements & HO to GSM

UE immediately answers

with Measurement Report„push“ means Handover, not Directed-Retry !

107 © 2006 Nokia

Forced Handover for AMR Voice Call

• GSMcauseTxPwrUL• Range and step: 0 (False), 1 (True)• Indicates whether a handover to GSM caused by high UE TX power level is enabled.

The handover is enabled when the value of the parameter is "Used“• To enable feature, setting must be 1 (True)

• GsmUETxPwrThrAMR• Range and step: -60..0 dB• This parameter determines the UE TX power threshold for a CS voice connection. If

the handover to GSM caused by high UE TX power level is enabled, the RNC starts inter-RAT (GSM) measurements when the UE TX power reaches this threshold. The UE TX power threshold is relative to the maximum TX power level an UE can use on the DPCH in the cell (or the maximum RF output power capability of the UE, whichever is lower

• To enable feature, setting must be –60 dB

108 © 2006 Nokia

Handover Control

• Handover Types


• SRNS Relocation


• GSM ISHO• Load Based Handover to WCDMA• Cell Reselection


• Appendix

109 © 2006 Nokia

Load based Handover GSM -> WCDMA

100%

80%

0%

Load reason Handoversfor speech

Load of GSM cell

Packet Data to WCDMAregardless of GSM load

Packet Data to WCDMAregardless of GSM load

Speech to WCDMAonly with high GSM load

Speech to WCDMAonly with high GSM load

Higher bit ratesfor data users

Higher bit ratesfor data users

More capacity for

speech

More capacity for

speech

Packet BCCH parameters can be usedto push GPRS mobiles to WCDMA

Packet BCCH parameters can be usedto push GPRS mobiles to WCDMA

110 © 2006 Nokia

GSMGSM

GSMGSM

Load and Coverage Reason Handover

GSMGSM

GSM highloaded

WCDMA lowloaded

GSMGSM GSMGSM

WCDMAWCDMA WCDMAWCDMA

Load reason Handover for speech and for HSCSD

Load reason Handover for speech and for HSCSD

WCDMAWCDMA GSMGSM

Load reason Handover

Coverage reason Handover

WCDMA can be usedto relieve GSM overload

GSM can be used to extend WCDMA coverage area

WCDMA can be usedto relieve GSM overload

GSM can be used to extend WCDMA coverage area

Mobile moving

111 © 2006 Nokia

Load based Handover Process: GSM-> WCDMA

Handover Triggering Thresholds set in BSCHandover Triggering Thresholds set in BSC

Inter-RAT measurements starts in case The RXLEV of the serving cell is above or

below the given threshold Qsearch_C

Inter-RAT measurements starts in case The RXLEV of the serving cell is above or

below the given threshold Qsearch_C

Handover Decision is done in case ofLoad of the serving cell > Load_Threshold and CPICH Ec/No> min Ec/No Threshold

Handover Decision is done in case ofLoad of the serving cell > Load_Threshold and CPICH Ec/No> min Ec/No Threshold

MS selects the target UTRAN cell based on measurement results

MS selects the target UTRAN cell based on measurement results

Handover command is send to MSCHandover command is send to MSC

In the S10.5 MS is measuring the UTRAN cells continuously if they are defined as a neighbor ,

The number of GSM neighbor reported could be 3-6 depending on the set value of parameter FDD_MULTIRAT_REPORT (0,1,2=def,3).

The load is measured in the cell level by comparing the occupied TCHs to the available TCHs (20 s interval used)

Load Threshold for Speech Calls or Transparent Data inter-RAT Handover:utranHoThScTpdc (Min Traffic Load TDHO), default = 80%minEcnoThreshold (Min CPICH EC/NO Threshold), default –15 dB

Parameters are sent from the BSC to the mobilein the Measurement Information message

112 © 2006 Nokia

ISHO 2G -> 3G ParametersParameter Specification name Nokia parameter Range Default value

min traffic load for speech call LOAD_THRESHOLD_FOR_SC_IS_HO

utranHoThScTpdc (LTSC)

0-100% 80%

minimum CPICH Ec/Io level MIN_ECNO_THRESHOLD minEcnoThreshold

(MET)

-24…0.5 dB

-15 dB

min interval between unsucc ISHO attempt

MIN_INTERVAL_BETWEEN_UNSUCC_ISHO_ATTEMPT

minIntUnsuccIsHo (UMIU)

0…255 s 3 s

threshold for multi-RAT MS Qsearch_C qSearchC (QSRC) 0…15 15 (never) rec. 7 (always)

Specification name Parameter explanation Value range Note

FDD_REP_QUANT Indicates the reporting quantity for UTRAN FDD cells

0=RSCP, 1=EC/NO

Not tunable, Fixed value 1

3G_SEARCH_PRIO Indicates if 3G cells may be searched when BSIC decoding is required

0 = no, 1 = yes


FDD_MULTIRAT_REPORTING The number of cells from the access technology/mode FDD that shall be included in the measurement report

0…3 Not tunable, Fixed value 2

Qsearch_C_Initial Indicates the Qsearch value to be used in connected mode before Qsearch_C is received

0 = use Qsearch_I, 1 = ∞ (always)


Ch

an

geab

leH

idd

en

113 © 2006 Nokia

Handover Control

• Handover Types


• SRNS Relocation


• GSM ISHO• Load Based Handover to WCDMA• Cell Reselection


• Appendix

114 © 2006 Nokia

Cell Reselection List

GSM MS starts WCDMA measurements if :RLA_C< F(Qsearch_I) for 0<Qsearch_I<=7

orRLA_C> F(Qsearch_I) for 7<Qsearch_I<=15

If, for suitable UMTS cell & for a period of 5 s:

CPICH RSCP > RLA_C + FDD_Qoffset

CPICH Ec/No FDD_Qmin

no prioritiesbetween WCDMA

neighbor s

Measurement Updates:• RLC_C value of the serving cell• + least 6 strongest non serving GSM cells

at least every 5 s

check

and

WCDMA cellreselection

BCCH: FDD_Qmin, FDD_Qoffset

Fdd_Qoffset: select allways (value is -infinity)

FDD_Qmin= -13 dB

Cell Reselection 2G -> 3G

115 © 2006 Nokia

• Re-selection measurements are controlled by the parameter threshold to search WCDMA RAN cells (QSRI)

• The parameter defines a threshold and also indicates whether these measurements are performed when RLA_C (a running average of received signal level) of the serving GSM cell is below or above the threshold


GSM MS starts WCDMA measurements in case running average signal (RLA_C) level is below or above

certain threshold:RLA_C # Qsearch _I (Non GPRS)

116 © 2006 Nokia

• Triggering of the 3G cell measurementsDepending on operator´s 2G – 3G interworking strategy parameter Q_search_I should planned accordingly.

Configuration 1RLA_C<

F(Qsearch_I)

( 0<Qsearch_I<=6 )

GSM 3G

If camping in a 3G cell is priority then:

- Configuration 1 is not acceptable because camping on 3G in zones with good GSM coverage is not possible. - Configuration 2: camping on 3G is not possible in high medium&poor GSM coverage.- Configuration 3: camping on GSM/3G is possible and not constraint to other system’s coverage.Therefore, configuration 3 is the best choice at expenses of decreasing the battery lifetime of the terminal

Configuration 2RLA_C>

F(Qsearch_I)

( 7<Qsearch_I<=15 )

In the best case, 3G cell measurements are restricted to the condition: RLA_C level > –78 dBm

GSM

3G

In the best case, 3G cell measurements are possible when RLA_C level < –74 dBm

GSM

3G

Configuration 3RLA_C< (always).

(Qsearch_I=7)

Measurements for 2G -> 3G inter-system cell reselection

117 © 2006 Nokia

Cell Re-selection Parameters

• Qsearch_I and Qsearch_P define the threshold for non-GPRS/GPRS (respectively) capable UEs to measure 3G neighbour cells when a running average of the received downlink signal level (RLA_C) of the serving cell is below (0-7) or above (8-15) the threshold

Value

0 1 … 6 7 8 9 10 … 14 15

dBm -98 -94 … -74 Always

-78 -74 -70 … -54 Never

• FDD_Qoffset and FDD_GPRS_Offset the non-GPRS/GPRS (respectively) capable UEs add this offset to the RLA_C of the GSM cells. After that the UE compares the measured RSCP values of 3G cells with signal levels of the GSM cells

Value

0 1 2 3 … 8 … 14 15

dBm -always

-28 -24 -20 … 0 … 24 28

Always select irrespective of

RSCP value

Reselect in case RSCP > GSM RXLev (RLA_C)

+28dB

If RLA_C < -94 UE starts 3G

measurements

UE always measures 3G cells

If RLA_C > -70 UE starts 3G

measurements

118 © 2006 Nokia

Cell Re-selection Parameters• FDD_Qmin, defines minimum Ec/No threshold that a 3G cell must exceed, in order

the UE makes a cell reselection from 2G to 3G. This is the new mapping table

• FDD_REP_QUANT defines the reporting quantity for UTRAN cell (1=Ec/No or 0=RSCP, default 1). This parameter is hidden and it can not be tuned

• 3G_Search_PRIO parameter allows to extend the BSIC reporting interval from 10 s to 13s by checking the BSICs from non-serving BCCH carriers and also make WCDMA measurements as often as possible. Range is 0=no, 1=yes, default value .This parameter is hidden and it can not be tuned

· Defined in the SI2quater and PSI3quater if PBCCH is allocated

ParameterParameter

Name for Sys Info (SI)Name for

Sys Info (SI)

Qsearch_IQsearch_I

2quater2quater

Qsearch_PQsearch_PQsearch_PQsearch_P

2quater2quater 3quater3quater

FDD_QMinFDD_QMin

2ter2ter

FDD_(GPRS)Qoffset

FDD_(GPRS)Qoffset

2quater2quater

FDD_REP_QUANT

FDD_REP_QUANT

2ter2ter

3G_search_PRIO

3G_search_PRIO

2(3)quarter(PBCCH)

2(3)quarter(PBCCH)

Fdd_Qmin mappingAif parameter 0 1 2 3 4 5 6 7Fdd_Qmin (old) [dB] -20 -19 -18 -17 -16 -15 -14 -13Fdd_Qmin (new) [dB] -20 -6 -18 -8 -16 -10 -14 -12

119 © 2006 Nokia

Cell Re-selection Example-Weaker WCDMANon GPRS case

t

Serving GSM Cell

Neighbour WCDMA Cell

Ec/NoRSCP/RLA_C

5 sec.

Cell re-selection to WCDMA

FDD_Qmin=0(-20 dB)

FDD_Qoffset =6 (-8 dB)

Qsearch_I=0 (-98 dBm)

RLA_C

Measurements starts (serving cell)

Minimum Quality Requirement for WCDMA Ec/N0

RSCP

120 © 2006 Nokia

Cell Re-selection Example-Weaker WCDMAGPRS case

t

Serving GSM Cell (Best)

Neighbour WCDMA Cell

Ec/NoRSCP/RLA_C

5 sec.

Cell re-selection to WCDMA

FDD_Qmin=-20 dB

FDD_GPRS_Qoffset =10 (8 dB)Qsearch_P=0(-98 dBm)

RLA_P

Measurements starts (serving cell)

Minimum Quality Requirement for WCDMA

Ec/N0

RSCP

121 © 2006 Nokia


• Whilst camping in a 3G cell the UE performs intra-frequency, inter-frequency, and inter-system measurements based on the measured CPICH EcNo of the serving cell according to the following rules:

• Serving cell parameters Sintrasearch, Sintersearch and SsearchRAT are compared with Squal (CPICH Ec/No - Qqualmin) in S-criteria for cell re-selection

• UE will measure neighbor cells depending on how parameters are set & send (if parameters are not sent UE shall measure all cells)

• 1 - None (Squal > Sintrasearch )

• 2 - WCDMA intra-frequency (Sintersearch < Squal Sintrasearch)

• 3 - WCDMA intra- and inter- frequency, no inter-RAT cells (SsearchRAT < Squal Sintersearch)

• 4 - WCDMA intra- and inter-frequency and inter-RAT cells (Squal SsearchRAT )

SintrasearchSintersearchSsearchRAT

WCDMACELL

1234

122 © 2006 Nokia


First ranking of all the cells based on CPICH RSCP (WCDMA) and RSSI (GSM)

Rs = CPICH RSCP + Qhyst1Rn= Rxlev(n) - Qoffset1

Rn (GSM) > Rs (WCDMA)And

Rxlev (GSM) >QrxlevMin

YesNo

Cell re-selection to GSM

Neighbour WCDMA or GSM cell calculation with offset

parameter

Serving WCDMA cell calculation, with

hysteresis parameter

UE starts GSM measurements if CPICH Ec/No < qQualMin + sSearchRAT

SintraSearch

SinterSearch

SsearchRAT

CPICH EcNo

qQualMin

Second ranking only for WCDMA cells based on CPICH Ec/No

Rs = CPICH Ec/No + Qhyst2Rn=CPICH_Ec/No(n)-Qoffset2 Cell re-selection to

WCDMA cell of highest R value

123 © 2006 Nokia


• UE ranks the serving cell and the measured neighboring cells to find out if reselection should be made

• All the measured suitable cells (S-criteria) are included in the ranking. • Criteria for a suitable cell (S-criteria) is defined as

• WCDMA intra-frequency neighbor cell: • CPICH Ec/No > AdjsQqualmin and CPICH RSCP > AdjsQrexlevmin

• WCDMA inter-frequency cell: • CPICH Ec/No > AdjiQqualmin and CPICH RSCP > AdjiQrexlevmin

• GSM cell:• Rxlev > Qrxlevmin

• Ranking is done using Criteria R, and the UE reselects to the cell with highest R-criteria. R-criteria is defined as:

• For serving cell: Rs = Qmeas,s + Qhysts • For neighboring cell Rn = Qmeas,n – Qoffsetts,n

• Qmeas is CPICH Ec/No for WCDMA cell and RxLev for GSM cell

124 © 2006 Nokia


• There is no timer defined how long the GSM should be fulfilling the re-selection criteria

• However there is running average of 4 GSM measurements which provides some protection against ping – pong (time vice –based on DRX cycle length and as sliding window average)

• In case additional protection is needed it can be arranged by using the Qhyst1 parameter (for WCDMA serving cell RSCP) or AdjgQoffset1 (for GSM neighbor ing cell RxLev)

First ranking of all the cells based on CPICH RSCP (WCDMA) and RSSI (GSM)

Rs = CPICH RSCP + Qhyst1Rn= Rxlev(n) - Qoffset1

125 © 2006 Nokia

How to avoid ping pong ?

• When phone is camped on 3G, GSM measurements can start when CPICH Ec/Io of serving cell is below Ssearch_RAT + QqualMin.

• When phone is camped on GSM, cell reselection to 3G is possible if CPICH Ec/Io of the candidate is above FDD_Qmin.

• Therefore, to avoid ping pongs between 3G and GSM the following condition should be met:

FDD_Qmin >= QqualMin+Ssearch_RAT

QqualMin=-18 dB

Ssearch_RAT=4 dB

CPICH Ec/Io

FDD_Qmin >= -12 dB

QqualMin +Ssearch_RAT

t

Camping on 3G Camping on GSM Camping on 3G

126 © 2006 Nokia

Handover Control

• Handover Types


• SRNS Relocation


• GSM ISHO


• Appendix

127 © 2006 Nokia

HSDPA mobility

• The mobility procedures are affected by the fact that the HS-PDSCH allocation for a given UE belongs to only one of the radio links assigned to the UE

• RAS05: HSDPA mobility handling with channel type switching• When entering SHO region, HS-DSCH to DCH switch is executed• When entering region without HSDPA support, HS-DSCH to DCH switch is

executed• Packet data continues on DCH

• RAS05.1: Serving HS-DSCH Cell Change• UL/DL DCH = soft/softer HO• DL HS-DSCH = serving cell change

• Channel type switching required always before ISHO/IFHO

128 © 2006 Nokia

Chapter 7-Handover Control-

1. What characterises intra frequency WCDMA hard Handover?

2. Which Handover types are mobile evaluated Handovers?

3. What is the difference between soft and softer Handover?

4. What conditions must be met, before a cell can be added to the active set?

5. What type of situations initiate inter-frequency or inter-system Handover?

6. What is the main difference between IFHO and ISHO measurements ?

7. What is the reason for GSM ISHO ?

129 © 2006 Nokia

Handover Control – Appendix

• Handover Types• Intra-Frequency Handover• SRNS Relocation • Inter-Frequency & Inter-System Handover:• GSM ISHO• Overview – HSDPA mobility

• Appendix• IMSI Based Handover• Emergency ISHO• Load and Service based HO• Directed RRC setup (IF)

130 © 2006 Nokia

IMSI Based Handover – Solution Overview

• IMSI based Handover is optional RAN’04 feature• The purpose of the IMSI specific Handover feature is that a mobile

subscriber in a visited network can be commanded to measure selectively only specified PLMN cells and to make Handover accordingly to those specified (home or authorised) PLMNs. The input for the selective measurement control is the PLMN id that is included in the IMSI of the subscriber. IMSI = MCC + MNC + MSIN

MCC+MNC =PLMN ID

IMSI International Mobile Subscriber IdentityMCC Mobile Country CodeMNC Mobile Network CodeMSIN Mobile Subscriber Identification NumberPLMN Public Land Mobile Network• There are four kind of IMSI based Handover:

• IMSI based Intra-frequency HO• IMSI based Inter-frequency HO• IMSI based Inter-system HO• Immediate IMSI based inter-frequency/intra-frequency HO

131 © 2006 Nokia

IMSI Based HO

• There is two new Management object class related to IMSI based HO

• WANE-WCDMA authorised networks• Authorized network identifier (AuthorisedNetworkId)• List of authorized networks (AuthorisedNetworkList)• Authorised network PLMN (AuthorisedNetworkPLMN)• Technology used in the authorised network (Technology)• WANE name (WANEName)

• WSG-WCDMA Subscriber group• Subscriber home PLMN (HomePLMN)• Name of subscriber home PLMN (OperatorName)• Subscriber Group identifier (SubscriberGroupID)• Identifier of the authorised network (WSGAuthorisedNetworkId)• GSM roaming allowed (GSM roaming)

• WANE set contains PLMN ids where the UE is allowed to make Handovers• WSG object maps the subscriber (PLMN id) to certain WANE set with a

WANE id. A WSG object should be created for every subscriber (PLMN id) visiting the network.

• Max Number of WANEs is 10 and max number of WSGs is 128

132 © 2006 Nokia

WSG – Selecting the list of Authorised PLMNs

• The RNC shall select the desired list of authorised PLMNs for the selective measurement control on the basis of the PLMN Id that is included in the IMSI of the subscriber

• The RNC links the PLMN ID of the subscriber with the desired list of authorised PLMNs by means of an index table

PLMN 242 07

Authorised PLMN list #2

IMSI 24207XXX

PLMN 24207

Each IMSI has hard coded the PLMN that

belongs to.The WSG associates

one list number (WANE ID) to each

PLMN

WSG id PLMN id List id

0 24305 (Op F 3G, border country)

1

1 24201 (Op B Shared 3G)

4

… … …

7 24207 (Op A 3G) 2

8 24208 (Op B 3G) 3

… … …

127IMSI 24208XXX

PLMN 24208

PLMN 242 08

Authorised PLMN list #3

MCC MNC

133 © 2006 Nokia

WANE - Structure of the Authorised PLMN lists

• A list of authorised PLMNs shall contain the maximum of six PLMN identifiers • The radio network database shall have ten separate authorised PLMN lists (WANEs)

• It is not necessary to add the home PLMN Id of the subscriber to the list of authorised PLMNs

List # Authorised PLMNs (max. 6)

#1 24210 (Op D 3G)

…

#2 24206 (Op A GSM

24200 (Op C 3G

24201 (Op C GSM)

24305 (Op F 3G, border country)

…

#3 24209 (Op B GSM)

24201 (Op B Sh 3G)

24210 (Op D 3G)

24306 (Op G 3G, border country)

…

#4 24208 (Op B 3G)

24209 (Op B GSM)

…

… …

#0 All …

• 'All' in the list #0 indicates that all PLMNs are considered authorised PLMNs (RNC shall combine the neighbour cell list for the inter-frequency or inter-RAT (GSM) measurement from all neighbouring cells regardless of their PLMN identifiers)

134 © 2006 Nokia

Types of IMSI Based handover

There are five kind of IMSI based Handover:

• IMSI based Intra-frequency HO (IMSIBasedSHO=enabled)• IMSI based Inter-frequency HO (IMSIBasedIFHO= enabled)• IMSI based Inter-system HO (IMSIBasedGsmHO= enabled)• Immediate IMSI based Inter-frequency HO

(IMSIBasedIFHO=immediate)• Immediate IMSI based Inter-system HO

(IMSIBasedGsmHO=immediate)

135 © 2006 Nokia

IMSI based Intra Frequency HO

• If at least one of the AS cells has IMSIbasedSHO enabled, then Intra Frequency HO is possible only if the PLMN ID of the monitored cell, which needs to be added, is the same as either the home PLMN ID of the subscriber or the authorized PLMNs or an AS cell's PLMN

• If none of the AS cells has IMSIbasedSHO enabled, then the monitored cell is added into the active set regardless of the PLMN IDs

• The IMSI based Intra Frequency HO does not affect the intra frequency measurement procedure: the RNC makes the neighbour cell lists for the intra-frequency measurements regardless of the PLMN IDs of the neighbour cells

• When a cell triggers the events 1A or 1C, the RNC checks whether fulfils the PLMN requirements, in that case it is added to the AS

• If a cell, that triggers the events 1A or 1C, does not fulfil the PLMN requirements and becomes the strongest (increases the interference), the RNC may release the RRC connection

136 © 2006 Nokia

Example: IMSI based Intra Frequency HO

f1 f1f1

Op ACountry X

The RNC shall be able to perform inter-PLMN handovers (SHO and IFHO) within the RNC (otherwise it will not be possible to add the green operator cell to the active set)

f1 f1f1

RNC 1(Shared Op A - Op B)

Op BBorder Country

The IMSI Intra Frequency HO is between different PLMNs -> Intra Frequency Hard Handover (there is no Iur between those RNCs)

Example 1

Example 2

137 © 2006 Nokia

IMSI based Inter Frequency/ Inter System HO

• If at least one of the AS cells has IMSIbasedIFHO/ IMSIbasedISHO enabled, then Inter Frequency / Inter System HO is possible only if the PLMN ID of the monitored cell, which needs to be added, is the same as either the home PLMN ID of the subscriber or the authorized PLMNs

• Unlike IMSI based Intra Frequency HO, the measurement list sent by the RNC in IMSI based IF/IS HO only includes the IF/IS HO cells which fulfil the PLMN requirement

• The procedure is the same for IF/IS HO causes

1. DL DPCH approaches its maximum allowed power

2. Quality deterioration report from UL outer loop PC

3. Low measured absolute CPICH Ec/No

4. UE Tx power approaches its maximum allowed power

5. Low measured absolute CPICH RSCP

138 © 2006 Nokia

IMSI IF HO Signalling

RRC: MEASUREMENT CONTROL (IF meas details)

UEISHO triggered

RNC

RRC: MEASUREMENT REPORT (Trigger Event )

RRC: MEASUREMENT CONTROL (CFN, TGPS)

RRC: MEASUREMENT REPORT (CFN, TGPS)

Radio Link Setup

Periodic IF meas Reporting

RRC: PHYSICAL CHANNEL RECONFIGURATION (Timing Indication)


Handover Decision

.

.

Compressed Mode Activation

RNC commands measurements of the authorized IF cells

There is bad quality conditions in the link ..

With the information gotten, the RNC assess the best cell, and decides to attempt a IFHO to it

139 © 2006 Nokia

Immediate IMSI based Inter Frequency/ Inter System HO

• It is new cause that triggers the Inter Frequency or Inter System HO• If at least one of the AS cells has IMSIbasedSHO enabled and IMSIbasedIFHO/

IMSIbasedISHO is set to immediate, then RNC starts a Immediate IMSI IF/IS HO in case the RNC cannot add a cell, which triggers the event 1A or 1C, into the AS, due to it does not fulfil the requirement of home/authorised/active set PLMNs

• It is possible to monitor a cell which does not fulfil the PLMN requirements because the RNC provides information about all the intra frequency cells, regardless of the PLMN IDs

• The compress mode is started and the RNC sends in a MEASUREMENT CONTROL message only information about the inter-frequency or inter-system cells whose PLMN is the same as either the home PLMN ID of the subscriber or the authorized PLMNs

• The IF HO/ISHO takes place normally

140 © 2006 Nokia

Op A IMSI

Example 1 : IMSI Based IFHO ActivatedIMSI parameters in

all RNC 1 cells

IMSIbasedGsmHO=disabledIMSIbasedSHO=disabled

IMSIbasedIFHO=enabled

Authorised PLMNs

#1 10011

#2 10010

#3 10020

f2

f1 f1f1

RNC 1(Shared Op A - Op B)

RNC 2(Op A)

f2

WSG id

PLMN id

List id

0 10010

1

1 10020

3

2 10011

8

3 10021

2

IMSI Objects in RNC 1

Op A own cell (PLMN 10010)Op A controlled cell shared RNC(PLMN 10011)

Op B own cell (PLMN 10010)Op B controlled cell shared RNC (PLMN 10021)

Op A

Op A

Op BOp A

RNC reports all the intra-freq cells. There is no PLMN analysis since IMSIbasedSHO=disabled, so -> Intra Freq HO to Op B cell

One of the IFSO causes reaches its threshold, so IMSI IFHO triggered

(IMSIbasedIFHO=enabled) and RNC sends the list of

the allowed cells-> IFHO to Op A

Notice that an Op B IMSI

would behave differently in

the very same scenario!!!

141 © 2006 Nokia

Immediate IMSI HO cause conditions

1. If at least one of the AS cells has IMSIbasedSHO=enabled and IMSIbasedIFHO/ IMSIbasedISHO=immediate

2. The AS cell in question has one or more inter-frequency/inter-system neighbour cells whose PLMN ID equals either the home PLMN ID of the subscriber or a PLMN ID in the authorised list

3. The PLMN ID of a monitored cell (that has triggered the reporting event 1A or 1C) does not fulfil the requirement of the home/authorised/active set PLMNs (that is why IMSIbasedSHO=enabled is needed , otherwise it wouldn’t be possible to detect that the cell does not fulfil the PLMN requirement)

142 © 2006 Nokia

Summarizing ….IMSI Based Intra Freq HO

IMSI Based IFHO/ISHO

Immediate IMSI Based IFHO/ISHO

Settings in an active set cell

IMSIbasedSHO=enabled

IMSIbasedGsmHO= enabled

/IMSIbasedIFHO= enabled

IMSIbasedSHO= enabledAND

(IMSIbasedGsmHO=immediate /

IMSIbasedIFHO= immediate)

PLMN criteria (IMSI HO trigger)

Home\ Authorised \Active set

Home\Authorised

An IMSI Intra-Freq attempt to a cell that does not fulfil the Intra Freq PLMN criteria

Neighbour list sent by the RNC

All the Intra Freq cells

Only the If/IS HO cells that fulfil the PLMN criteria

Only the If/IS HO cells that fulfil the PLMN criteria

PLMN criteria applied by RNC only over a cell which is candidate to be added

in the active set

Notice the Immediate IMSI HO involves 2 cell lists: (1) To fulfil

the (IMSI Intra Freq) PLMN criteria (2)Once the Immediate IMSI is

triggered, the allowed PLMN IF/IS cells where the subscriber can

hand over to

It is not required for these cells to have the IMSI feature

enabled, in order to be included in the neighbour list. Just to have the proper

PLMN ID

143 © 2006 Nokia

IMSI Based HandoverExample Cases

• IMSI-based Handover can be used in different network sharing cases• case 1: geographical sharing• case 2: common shared RAN with gateway core• case 3: mobile virtual network operator (MVNO)

• Based on IMSI, users of each operator can be handed over to their home or authorised WCDMA network from the shared area, when coverage becomes available (cases 1 and 2)

• Based on IMSI, inter-system Handovers to the user’s home or authorised GSM network can be performed in the shared area (all cases)

- inter-frequency HO to home or authorised WCDMA cell

- inter-system HO to home or authorised GSM network

IMSI-based Handovers from the shared area:

Different neighbor cell definitions in RNC for different IMSI ranges

144 © 2006 Nokia

Case 1: IMSI Based Handover andGeographical Sharing

GSM GSM GSM

GSM

WCDMA

GSM GSM GSM

WCDMA WCDMA WCDMA

WCDMA WCDMA WCDMA WCDMA

GSM GSM GSM GSM GSM

Operator A GSM cell

Operator A own WCDMA cellOperator A controlled sharedWCDMA cell

Operator B GSM cell

Operator B own WCDMA cellOperator B controlled shared WCDMA cell

Operator A user path Operator B user path

Based on IMSI, load and service-based

inter-system HOs to their own GSM

network in shared area

Separate neighbor lists for different IMSI ranges (different PLMN users)

Based on IMSI, operator A user is handed over to its

own WCDMA network when

coverage becomes available

GSM

GSMBased on IMSI, operator B user

is handed over to its own WCDMA network when


Based on IMSI, users are handed over to their own

GSM networks when WCDMA coverage ends

145 © 2006 Nokia

Case 2: IMSI Based Handover andCommon Shared RAN

GSM GSM GSM

WCDMA

WCDMA

GSM GSM GSM

Operator A GSM cell

Operator A own WCDMA cell

Common shared WCDMA cell

Operator B GSM cell

Operator B own WCDMA cell


WCDMA WCDMA


GSM

GSM

WCDMA

GSM

GSM




Based on IMSI, operator A user is handed over to its

own WCDMA network when


Based on IMSI, operator B user

is handed over to its own WCDMA network when




146 © 2006 Nokia

Case 3: IMSI Based Handover andMobile Virtual Network Operator

GSM GSM

GSM GSM

WCDMA WCDMA


GSM

GSM

Operator A GSM cell

Operator A controlled WCDMA cell

Operator B GSM cell







147 © 2006 Nokia

Handover Control

• Handover Types• Intra-Frequency Handover:• SRNS Relocation • Inter-Frequency & Inter-System Handover:• GSM ISHO• Overview – HSDPA mobility• Appendix

• IMSI Based Handover• Emergency ISHO • Load and Service based HO• Directed RRC setup (IF)

148 © 2006 Nokia

Emergency ISHO (EMISHO)Directed Emergency Call Inter-system Handover directs emergency calls from UTRAN to GSM network in order to allow more accurate than Cell ID and RTT based location service.It is an optional feature and designed for US market to support FCC requirements.

Source UMTS RAN

Target GSM BSS

PSAP

GMLCGMLC

1. Emergency CallEstablishment 8. Location

Request9. Location

3. Handover to GSM7. Location

Route of call before handover

Route of call after handover

3G MSC

2G MSC

149 © 2006 Nokia

EMISHO Call-Flow

RANAP: Location Reporting Control

NBAP: Dedicated Measurement Init Req

RRC: Measurement Control UE Tx-Rx

NBAP: Dedicated Measurement Init Resp

RRC: Measurement Report Tx-Rx

Location Calculation based on CId and RTT

ISHO measurements & HO to GSM

Case a) ISHO to GSM is successful, no response to MSS

Case b) ISHO to GSM is not successful:RANAP: Location Report

Report Area IE: Geographical Area

Client Type IE: Emergency Call

SMLC

Radio Bearer setup

In case ISHO to GSM fails, RNC keeps location based on CI+RTT in mind

and sends RANAP:Location Report*

*

150 © 2006 Nokia

Handover Control

• Handover Types• Intra-Frequency Handover:• SRNS Relocation • Inter-Frequency & Inter-System Handover:• GSM ISHO• Overview – HSDPA mobility• Appendix


151 © 2006 Nokia

Load and Service based HO

• The target of the Load and Service based HO feature is to allow balancing of traffic between WCDMA frequencies/layers and between GSM and WCDMA

• The LSHO cab be configured to

AND/OR

Transfer UE to wanted layer based on used Service

Transfer UE to other layer in high Load based on used Service

152 © 2006 Nokia

Load based handover

Load based handover

Service based

handover

Service based

handover

Constant monitoring of loading

Periodical checking

HO trigger

s

Selection of connections to

be handed over

Measurements

Execute handove

rs

Handover

decision

Load and Service Based Handover Procedure

153 © 2006 Nokia

Load of the source cell (GSM or WCDMA)

100%

80%

0%

only Service basedhandovers

Load and Service basedhandovers according toservice priorities

Perc

en

tag

e c

om

pare

d t

o t

he t

arg

ete

d load • Effective integration of GSM

and WCDMA • WCDMA layer management

ServicePreferred

system/layer

Conv. CS speech

Conv. CS transparent data

Conv. PS speech

Conv. PS RT data

GSM

GSM

WCDMA, macro

WCDMA, micro

Streaming CS non-transp. GSM

Streaming PS RT data WCDMA, micro

Interactive PS NRT data WCDMA, micro

Example of service priority table in RNC

Background PS NRT data WCDMA, micro

Load and Service based Handovers

154 © 2006 Nokia

Load and Service based Handover – Control

• RNC configuration parameters define according to several services whether load and/or service based handover can be performed.

• SLHOUseBackgroundPSNRTData , SLHOUseConvCSSpeech , SLHOUseConvPSRTData , SLHOUseConvPSSpeech , SLHOUseInteractivePSNRTData , SLHOUseStreamCSNTData , SLHOUseStreamPSRTData

Service type UE is using Used handover type

Conversational, Circuit switched speech Eg. Load & Service HO

Conversational, Circuit switched transparent data Eg. Load & Service HO

Conversational, Packet switched speech Eg. Load HO

Conversational, Packet switched real time data Eg. Load HO

Streaming, Circuit switched non-transparent data Eg. Service HO

Streaming, Packet switched real time data Eg. Service HO

Interactive, Packet switched non-real time data Eg. None

Background, Packet switched non-real time data Eg. None

155 © 2006 Nokia


• Load based HO• Service based HO• Selection of RRC connections and Service priority• Load of the target cells• Inter-frequency and inter-RAT measurements• Handover decision• Repetitive load and service-based handover attempts

156 © 2006 Nokia

Tota

l in

terfe

ren

ce

NR

T re

jectio

n

rate

Sp

read

ing

cod

e

usag

e

HW

/ log

ical

resou

rce u

sag

e Uplink

Downlink

Tota

l pow

er

NR

T re

jectio

n

rate

Total interference

load

PS NRT capacity request rejection

rate

Lack of downlink spreading

codes

HW / logical

resource limitation

Triggers set by operator

After ONE of the reasons is fulfilled cell is in theload based handover state

Hard blocking ratio of

- BTS/WSP- AAL2

Hard blocking ratio of

- BTS/WSP- AAL2

Triggering of Load based Handovers

157 © 2006 Nokia

LHOPwrOffsetUL = - 1.5 dB relative to PrxTarget

PrxTotal > PrxTarget + LHOPwrOffsetUL

PtxTotal > PtxTarget + LHOPwrOffsetDL

LHOPwrOffsetDL = - 0.7 dB relative to PtxTarget

Headroom for CM triggering must be considered also

RNC checks based on RRI interval:

Triggering of Load based Handovers - Total interference load

PtxTotalNonHSDPA > PtxTargetHSDPA + LHOPwrOffsetDL

When HSDPA in use in the cell:

158 © 2006 Nokia

Measurement Report (e4a) Capacity Request

RNC internal Capacity Request (MAC layer)

CapaReqRejRateUL = RejectedRequestsCellUL

(AllCapacityRequestsCellUL + LHONRTTrafficBaseLoad )

CapaReqRejRateDL = RejectedRequestsCellDL

(AllCapacityRequestsCellDL + LHONRTTrafficBaseLoad )

CapaReqRejRateUL > LHOCapaRejRateUL

CapaReqRejRateDL > LHOCapaRejRateDL

RNC checks based on 1 sec intervals:

Triggering of Load based Handovers - PS NRT capacity request rejection rate

159 © 2006 Nokia

C 0 (0)=(1)

C 1 (0)=(1,1)

C1 (1)=(1,-1)

C 2 (0)=(1,1,1,1)

C 2 (1)=(1,1,-1,-1)

C 2 (2)=(1,-1,1,-1)

C 2 (3)=(1,-1,-1,1)

C3 (0)=(…)

C3 (1)=(…)

C3 (2)=(…)

C3 (3)=(…)

C3 (4)=(…)

C3 (5)=(…)

C3 (6)=(…)

C3 (7)=(…)

Code Order 0 (SF 1)

Code Order 1 (SF 2)

Code Order 2 (SF 4)

Code Order 3 (SF 8)

ReservationRateSC(SF128) = ReservedSC

NumbAvailableSC100 *

ReservationRate(SF128) > LHOResRateSCRNC checks based on RRI interval:

Triggering of Load based Handovers - Lack of downlink spreading codes

160 © 2006 Nokia

WSP capacity IuB AAL2 capacity

> LHOHardBlockingRatio NumberOfSamplesHardBlocking

(AllSamplesHWhuntDuringMeasPeriod + LHOHardBlockingBaseLoad )100 *

Triggering of Load based Handovers - HW or logical resources are limited• A load-based handover state is triggered due to HW or logical resource

(WBTS WSP capacity, IuB AAL2) congestion in the cell • Hard blocking occurs when a DCH setup attempt faces congestion of

the BTS or Iub AAL2 transmission capacity • ‘All samples’ is defined to be the number of successful and

unsuccessful BTS or Iub AAL2 transmission capacity hunts in the DCH setup attempts

161 © 2006 Nokia

Triggering of Load based Handovers – Parameters• WCEL: LHOPwrOffsetUL

• Range and step: -10..0 dB, step 0.1 dB (Default value: -0.7 dB)• WCEL: LHOPwrOffsetDL

• Range and step: -30..0 dB, step 0.1 dB (Default value: -1.5 dB)• WCEL: LHOCapaRejRateUL

• Range and step: 0..100 %, step 1 % (Default value: 70 %)• WCEL: LHOCapaRejRateDL

• Range and step: 0..100 %, step 1 % (Default value: 70 %)• WCEL: LHONRTTrafficBaseLoad

• Range and step: 0..255, step 1 (Default value: 10)• WCEL: LHOResRateSC

• Range and step: 0..100 %, step 1 % (Default value: 80 %)• WCEL: LHOHardBlockingRatio

• Range and step: 0..100 %, step 1 % (Default value: 50 %)• WCEL: LHOHardBlockingBaseLoad

• Range and step: 0..255, step 1 (Default value: 10)

162 © 2006 Nokia

t

1. Sliding window to average measurement samples when starting

load based HO state

Load based HO state triggers ON

Load based HO state "ON" indication shall be broadcasted in this point

2. Hysteresis time

Load based HOs are started if load (measured in the window 1.) rises above the threshold and stays there for the hysteresis time

3. Sliding window to average measurement samples when stopping load based HO state

Load HOs

Activation of new load basedHOs stopped

4. Timer which delays broadcasting of load based HO

state "OFF" indication

Load based HO state "OFF" indication shall be broadcasted in this point

Load based HO state triggers OFF

1.2.

3.

1.3.

4.

3.

• Load based Handover state for any cell is triggered if load exceeds load thresholds• Each load trigger reason can be switched on or off separately; one reason triggered is enough

to put the cell in Load based Handover state; state is over if all trigger reasons are below threshold

• In Load based Handover state, RNC runs RRC (UE) selection process for off-loading WCDMA cell• Averaging period for starting Load based Handover state is longer than for stopping

Processing of measurement results indicating load

163 © 2006 Nokia

Processing of measurement results indicating load

• Separate averaging window for ON (1) / OFF (3) measurement• Interference load: LHOWinSizeONInterference, LHOWinSizeOFFInterference • PS NRT CR: LHOWinSizeONCapaReqRejRate, LHOWinSizeOFFCapaReqRejRate• Lack of SCs: LHOWinSizeONResRateSC, LHOWinSizeOFFResRateSC• HW limit: LHOWinSizeONHardBlocking, LHOWinSizeOFFHardBlocking

• (2) Hysteresis time• Interference load: LHOHystTimeInterference• PS NRT CR: LHOHystTimeCapaReqRejRate• Lack of SCs: LHOHystTimeResRateSC• HW limit: LHOHystTimeHardBlocking

• (4) Delay off• Interference load: LHODelayOFFInterference• PS NRT CR: LHODelayOFFCapaReqRejRate• Lack of SCs: LHODelayOFFResRateSC• HW limit: LHODelayOFFHardBlocking

165 © 2006 Nokia

Service based handover frequency (WCEL):• ServHOPeriodInterFreq [0..120sec], step 1s, default:

30 sec; “0”= off• ServHOPeriodInterRAT [0..120sec], step 1s, default:

30 sec; “0”= off

Service based handover frequency (WCEL):• ServHOPeriodInterFreq [0..120sec], step 1s, default:

30 sec; “0”= off• ServHOPeriodInterRAT [0..120sec], step 1s, default:

30 sec; “0”= off

WCDMA cell

HO candidates

Service Based Handover Procedure

167 © 2006 Nokia

Selection of RRC connections for load and service based HO

• UE shall be selected in the set of possible candidates for the service or load based handover procedure • IF UE IS NOT in preferred RAT or hierarchical WCDMA layer• Preferred RAT or hierarchical WCDMA layer IS AVAILABLE

• Preferred layer is defined in the combined service priority list• Preferred layer is priority 1 layer in the list• Priority 2 and 3 layers are can be selected in load based HO procedure

• Availability of the target layer depends on• Definition of the target cells in the neighbour list• Load of the target layer/cell

168 © 2006 Nokia

Number of UEs to be selected

• Number of UEs that are selected in the certain cell to load based handover procedure during load based HO state

• LHOnumbUEinterFreq• Range and step: 0..32, step 1 (Default value: 0 = Not used)

• LHOnumbUEinterRAT• Range and step: 0..32, step 1 (Default value: 0 = Not used)

• Each time service based handover is started in the cell, certain number of RRC connections is selected in the procedure if possible

• ServHOnumbUEinterFreq• Range and step: 0..32, step 1 (Default value: 1)

• ServHOnumbUEinterRAT• Range and step: 0..32, step 1 (Default value: 1)

169 © 2006 Nokia

Number of UEs in CM

• RNC configuration parameter (WCEL) defines how many UEs can be simultaneously in the compressed mode in certain cell due to service or load based handover procedures

• MaxNumberUEcmSLHO

• Compressed mode measurements due to load reason have higher priority than due to service reason

• Also, quality and coverage handovers can steal capacity from this category if needed

• Measurement capability IE of certain UEs can indicate that CM is not needed i.e. UE have dual receiver capability

170 © 2006 Nokia

Load based handoverLoad based handover

1. connections which SRNC is this RNC 1. connections which SRNC is this RNC

2. connections which are not yet performing handover measurements


3. connections without previous load based handover attempts in this cellwithin a certain period

3. connections without previous load based handover attempts in this cellwithin a certain period

4. NRT connections which allocation has lasted longer than the specified period- LHOminNrtDchAllocTime (RNC)

4. NRT connections which allocation has lasted longer than the specified period- LHOminNrtDchAllocTime (RNC)

5. Multiservice connections without contradictions in the service priority definitions (target system can not be GSM/GPRS for CS+PS)


6. connections which are not in preferred RAT or WCDMA hierarchical cell layer


7. connections which cause highest load in the cell depending on the Load trigger

7. connections which cause highest load in the cell depending on the Load trigger

8. connections which does not require compressed mode


9. random selection of remaining after steps 1-8


Selection of RRC connections for load based HO

Service based handoverService based handover

1. connections which SRNC is this RNC 1. connections which SRNC is this RNC



3. connections without previous service based handover attempts in this cell within a certain period

3. connections without previous service based handover attempts in this cell within a certain period









Alw

ays

Only if MORE than defined number

171 © 2006 Nokia

Load based HO Phase 6 & Service based HO Phase 5• RRC connections which are not in preferred RAT or hierarchical WCDMA layer

according to combined service priority list• RNC shall investigate which RRC connections are not in preferred RAT or hierarchical

WCDMA layer• RNC checks if selected target is available and selects those as a candidates for the

load based handover procedure

• Selection of candidates is performed in three phasesPhase 1 – Connections with Priority 1 target layer available are selected as a

candidates for the load or service based handover procedure (if no first priority cases, no service based HO is performed)

Phase 2 – Connections with Priority 2 target layer available are selected as a candidates for the load based handover procedure

Phase 3 – Connections with Priority 3 target layer available are selected as a candidates for the load based handover procedure

• If even after 3rd phase any RRC connection can not be selected, no handover procedures are performed and finally overload control of RNC shall perform its actions if needed

172 © 2006 Nokia

Target system for the service and load-based handover• The preferred RAT or preferred hierarchical WCDMA layer of each RRC

connection in the service-based handover is determined according to combined service priority list information

• Combined service priority list defines the target system for the service and load-based handover

• The RNC produces a combined service priority list based on the Iu interface service priority information and the RNC based service priority handover profile table

173 © 2006 Nokia

Availability of the target WCDMA layers and GSM system • The RNC investigates the availability of the target WCDMA layers and

GSM system in the neighbour cell list of the UE, which is selected in the service and load-based handover procedure

• Combination of all neighbour cells of active set cells

• If one or more of the other WCDMA frequency layer cells in the neighbour cell list are marked as blocked cells in the SLHO procedure

• Parameter AdjiHandlingBlockedCellSLHO (ADJI) defines whether that layer is used as a target layer or not

• The RNC checks if the GSM inter-system neighbour cell list has any definitions which the penalty time (AdjgPenaltyTimeNCHO) is not running

• If yes, the GSM system is available for the service and load-based inter-RAT procedure

174 © 2006 Nokia

Service priority handover profile table in RNC

• RNC based service priority handover profile table is defined by RNC level and service specific parameters

Service typeService typeConversational, CS speechConversational, CS speechConversational, CS-T dataConversational, CS-T dataConversational, PS speechConversational, PS speechConversational, PS RT dataConversational, PS RT dataStreaming, CS-NT dataStreaming, CS-NT dataStreaming, PS RT dataStreaming, PS RT dataInteractive, PS NRT dataInteractive, PS NRT dataBackground, PS NRT dataBackground, PS NRT data

Preferred system/layerPreferred system/layerGSMGSMWCDMAWCDMAWCDMAWCDMAWCDMAWCDMAWCDMA macroWCDMA macroWCDMA macroWCDMA macroWCDMA microWCDMA microNot definedNot defined

SLHOprofileConvCSspeech

SLHOprofileConvCSTdata

SLHOprofileConvPSspeech

SLHOprofileConvPSRTdata

SLHOprofileStreamCSNTdata

SLHOprofileStreamPSRTdata

SLHOprofileInteractivePSNRTdata

SLHOprofileBackgroundPSNRTdata

Range and step: 0 (Not defined), 1 (GSM), 2 (WCDMA), 3 (WCDMA micro layer), 4 (WCDMA macro layer)

175 © 2006 Nokia

WCDMA Layers

• WCDMA macro cell means HCS priorities from 0 to 3. • HCS priority 0 is the highest priority for a service type that prefers macro

cells. • WCDMA micro cell means HCS priorities from 4 to 7.

• HCS priority 7 is the highest priority for a service type that prefers micro cells.

• The main principle is that an attempt is made to hand over a certain service type to the cell/layer which has the highest available priority for it

• The HCS priority of the serving cell is determined by the RNP parameter HCS_PRIO (WCEL), and the HCS priority of an inter-frequency neighbour cell is determined by the parameter AdjiHCSpriority (HOPI).

176 © 2006 Nokia

Iu interface service priority information

• Iu interface service priority information defines the target system for the service and load-based handover

• The Iu interface service priority information is RAB-based and optional

• The Service Handover IE received from the Iu interface via RANAP signalling (RANAP: RAB ASSIGNMENT REQUEST message) provides the following alternatives:

1. Handover to GSM should be performed (GSM higher priority)2. Handover to GSM should not be performed (WCDMA higher priority)3. Handover to GSM shall not be performed (only WCDMA)

• Service Handover IE is always set at (2) in Nokia SGSN• In Nokia MSC can be set based on service

• Speech , >32kbit/s CS Data, and <32kbit/s CS Data

177 © 2006 Nokia

Combined service priority list

• The RNC produces a combined service priority list

• Iu interface service priority information has a higher priority than the based table

1. Iu interface service priority information IS NOT available• RNC based service priority handover profile table is used instead

2. Iu interface service priority information IS available• Iu interface service priority information defines the target system• If both WCDMA

• RNC based service priority handover profile table can define preferred target hierarchical cell layer (macro/micro) inside WCDMA system

• If the UE is not in the preferred RAT or hierarchical WCDMA layer, and the preferred RAT or hierarchical WCDMA layer is available, the UE is selected into the set of possible candidates for the service or load -based handover procedure.

178 © 2006 Nokia

Combined service priority list – 1

• Iu interface service priority information not available

RNC-based service priority information


GSM 1. GSM

2. GSM

3. WCDMA

WCDMA 1.

2. WCDMA

3. GSM

WCDMA macro 1. WCDMA macro layer

2. WCDMA

3. GSM

WCDMA micro 1. WCDMA micro layer

2. WCDMA

3. GSM

Not defined 1.

2. WCDMA

3. GSM

Priority 1 /Preferred Layer for RAB in

• Service-based HO• 1st phase of Load-based

HO

Priority 2 Layer for RAB in• 2nd phase of Load-based

handover procedure

Priority 3 Layer for RAB in• 3rd phase of Load-based

handover procedure

179 © 2006 Nokia


• Service Handover IE: Handover to GSM should not be performed



GSM 1.

2. WCDMA

3. GSM

WCDMA 1.

2. WCDMA

3. GSM

WCDMA macro 1. WCDMA macro layer

2. WCDMA

3. GSM

WCDMA micro 1. WCDMA micro layer

2. WCDMA

3. GSM

Not defined 1.

2. WCDMA

3. GSM

180 © 2006 Nokia


• Service Handover IE: Handover to GSM should be performed



GSM 1. GSM

2. GSM

3. WCDMA

WCDMA 1. GSM

2. GSM

3. WCDMA

WCDMA macro 1. GSM

2. WCDMA macro layer

3. WCDMA

WCDMA micro 1. GSM

2. WCDMA micro layer

3. WCDMA

Not defined 1. GSM

2. GSM

3. WCDMA

181 © 2006 Nokia

Example

• Target• 1) To divert Interactive PS NRT traffic to WCDMA Micro

layer• SLHOUseInteractivePSNRTData = ‘Load and Service

based HO’• SLHOprofileInteractivePSNRTdata = ‘WCDMA micro layer’• Fixed: Service Handover IE: Handover to GSM should not

be performed

• 2) To divert Interactive PS RT traffic to WCDMA Micro layer

• SLHOUseInteractivePSRTData = ‘Load and Service based HO’

• SLHOprofileInteractivePSRTdata = ‘WCDMA micro layer’• Fixed: Service Handover IE: Handover to GSM should not

be performed

• 3) To divert AMR traffic to GSM layer due to load• SLHOUseConvCSSpeech = ‘Load based HO’• SLHOprofileConvCSspeech= ‘WCDMA micro layer’• Service Handover IE: Handover to GSM should be

performed


2. WCDMA

3. GSM


2. WCDMA

3. GSM

1. GSM

2. GSM

3. WCDMA


182 © 2006 Nokia

Example

WCDMAMacro

WCDMAMicro

GSM

PSNRT

PSRT AMR


2. WCDMA

3. GSM


2. WCDMA

3. GSM

1. GSM

2. GSM

3. WCDMA

1st1st 2nd

1) Service based HO

2) Load based HO

183 © 2006 Nokia

Example

WCDMAMacro

WCDMAMicro

GSM

PSNRT

PSRT AMR


2. WCDMA

3. GSM


2. WCDMA

3. GSM

1. GSM

2. GSM

3. WCDMA

1st3rd 3rd

Blocked/Not available

1) Service based HO

2) Load based HO

185 © 2006 Nokia

Load of the target WCDMA cell

• The RNC checks the load of the target WCDMA cell before a service-based or load-based inter-frequency handover

• Load-based handover state status information• Received from the target cell as a broadcast sent inside the RNC

• Status of the event-triggered common load measurement (if available) of the neighbour cells controlled by the DRNC

• RNC also checks whether the SLHO penalty time of that cell is running or not

• AdjiPenaltyTimeNCHO

Cell can be blocked in the SLHO procedure• Service and load-based handovers are not performed to the cell that is

blocked in the SLHO procedure

186 © 2006 Nokia

Load measurements under DRNC

• RNC does not have the load-based handover state status information from cells under DRNC

• The SRNC initiates common load measurements over Iur to certain DRNC's cells for the service and load-based handover

• Parameter AdjiComLoadMeasDRNCCellNCHO (ADJI) controls the common load measurement of an inter-frequency neighbour cell that is controlled by the DRNC

• The measurement is controlled over Iur by using RNSAP signalling• The used measurement is event-based

• “Event A” (load is over threshold) and “Event B” (load is below threshold)• Controlled by NCHOThrComLoadMeasDRNCCel,

NCHOHystComLoadMeasDRNCCell, NCHOFiltercoeffComLoadMeasDRNCCell

• Parameter SLHOHandlingOfCellLoadMeasNotAct defines whether a cell that does not have active load measurement is blocked in the service and load-based handover procedure

187 © 2006 Nokia

Load measurements under DRNC

• AdjiComLoadMeasDRNCCellNCHO (ADJI)• Range and step: 0 (Not activated), 1 (Activated)• Default value: 0 (As a default measurement is not activated)

• NCHOThrComLoadMeasDRNCCel (RNC)• Range and step: 0..100, step 1• Default value: 70 (The recommended values are from 60 to 80, which

means that only a rather high load is indicated)• NCHOHystComLoadMeasDRNCCell (RNC)

• Range and step: 0..60 s, step 0.01 s• Default value: 3 s

• NCHOFiltercoeffComLoadMeasDRNCCell (RNC)• Range and step: 0 (0), 1 (1), 2 (2), 3 (3), 4 (4), 5 (5), 6 (6), 7 (7), 8 (8), 9

(9), 11 (11), 13 (13), 15 (15), 17 (17), 19 (19)• Default value: 15 (SLHO feature requires long averaging)

188 © 2006 Nokia

Congested target WCDMA or GSM cell

• The exact load of the target GSM/GPRS cell is not checked by the source RNC in case of a service or load -based inter-RAT handover

• Target BSC checks its own load situation and rejects the handover if necessary

• If any handover to GSM cell has failed the service and load-based handovers are prevented during a certain period

• Relocation to the GSM system is unsuccessful and RANAP: Relocation Preparation Failure is received from the core network

• The period is defined with the (HOPG) parameter AdjgPenaltyTimeNCHO

• In WCDMA inter-frequency cells the penalty is set if a handover of any type (quality, coverage, etc.) fails to reserve resources from the target cell

• The penalty time is defined with the (HOPI) parameter AdjiPenaltyTimeNCHO

190 © 2006 Nokia

Inter-frequency and inter-RAT measurements

• Service and load-based inter-frequency and inter-RAT handover measurements are similar to the ones used in coverage and quality-based handovers

• Service and load-based inter-frequency handovers are performed only for RRC connections that are in the CELL_DCH state

• In case of a RT connection or a RT/NRT multiservice connection, normal inter-RAT measurements are performed

• Whether the inter-frequency measurements of the NRT connection using the compressed mode are allowed to be performed or not, is controlled with the RNP parameter SLHOCmAllowedNRT (RNC)

191 © 2006 Nokia

Measurement parameters

• Measurement parameters of the service and load-based handover are similar to the ones used in coverage and quality -based handovers

• InterFreqMinHoInterval and GsmMinHoInterval are used also in case of service and load-based handovers to define time after unsuccesful compressed mode/handver attempt

• The minimum time between successful service or load -based handovers can be limited with parameters InterFreqMinSLHOInterval (FMCI) and GsmMinSLHOInterval (FMCG)

• Prevent repetitive handovers between cells during one RRC connection• If set to zero only one (one way) service or load-based HO allowed during

RRC connection• Return of the service-based or load-based handover back to GSM is disabled

192 © 2006 Nokia

Inter-frequency and inter-RAT neighbour cell lists

• Handover to ‘GSM’• The inter-RAT neighbour cell list used is the same as in a coverage- or

quality-reason handover, but cells that are blocked in the SLHO procedure are reduced

• Handover to ‘WCDMA macro cell’: The cells of the found macro layer(s) form the neighbour cell list used in measurements

• Layer(s) where all the cells have the definition HCS = 0 … 3• Layer(s) which are not blocked in the SLHO procedure

• Handover to ‘WCDMA micro cell’: The cells of the found micro layer(s) form the neighbour cell list used in measurements

• Layer(s) where all the cells have the definition HCS = 4 … 7• Layer(s) which are not blocked in the SLHO procedure

• Handover to ‘WCDMA’: The inter-frequency neighbour cell list used is the same as in a coverage- or quality-reason handover

• Frequency layers that are blocked in the SLHO procedure are reduced

193 © 2006 Nokia

Inter-frequency and inter-RAT neighbour cell lists

• When more than one frequency to be measured• RNC selects a subset of inter-frequency neighbour cells (with the same

UTRA RF channel number) which are measured first• The measurement order is controlled with the RNP parameter

AdjiPrioritySLHO (HOPI) which is defined for each inter-frequency neighbour cell

• If the RNC is not able to define the measurement order by using the parameters, it measures least-loaded frequencies first

195 © 2006 Nokia

Load and service-based inter-frequency handover

• The measurement results of the best neighbour cell must satisfy the following equations before the service and load-based inter-frequency handover is possible

• (n) is the best neighbour cell accordint to EcNo• The sliding averaging window is controlled with the RNP parameter

InterFreqMeasAveragingWindow • RNC ranks the potential target cells according to the priority levels

AdjiPrioritySLHO (HOPI), if several neighbour cells meet the equations at the same time

a) AVE_RSCP_NCELL (n) > AdjiMinRscpNCHO (n) + max(0, AdjiTxPwrDPCH(n) – P_MAX)

b) AVE_EcNo_NCELL (n) > AdjiMinEcNoNCHO (n)

196 © 2006 Nokia

Load and service-based inter-frequency handover

• The RNC checks if the cells which are blocked in the service and load-based handover procedure are outside the soft handover range of the selected best target cell

• Handover decision cannot be performed before the UE has reported the EcNo result of all the cells which are blocked in the service and load-based handover procedure

• The following equation has to be true until a service and load-based handover to the best neighbour cell is possible:

• The RNP parameter AdjiEcNoOffsetNCHO(target) (ADJI) defines the offset for the procedure to ensure that the UE does not perform an immediate soft handover to a blocked cell in the new frequency layer

AVE_EcNo_NCELL (target) - AdjiEcNoOffsetNCHO (target) > AVE_EcNo_NCELL (blocked)

197 © 2006 Nokia

Load and service-based inter-RAT handover

• The measurement results of the best neighbour cell must satisfy the following equations before the service and load-based inter-RAT handover is possible

• (n) is the best neighbour cell accordint to EcNo• The sliding averaging window is controlled with the RNP parameter

GSMMeasAveWindow• The RNC performs the inter-RAT handover to the best GSM neighbour (target)

cell as soon as the best GSM neighbour cell meets the required radio link properties

• RNC ranks the potential target cells according to the priority levels AdjgPrioritySLHO (HOPG), if several neighbour GSM cells meet the equation at the same time

• BSIC is always verified for CS voice services• Mobile station can synchronise to the GSM cell before the handover• Verify the identification if two or more neighbour GSM cells have the same BCCH

Frequency

• For PS services BSIC is verified only if multiple neighbours with same BCCH frequency

AVE_RXLEV_NCell(n) > AdjgMinRxLevNCHO (n) + max(0, AdjgTxPwrMaxTCH (n) - P_max)

199 © 2006 Nokia

Repetitive load and service-based handover attempts• Repetitive load-based or service-based handover attempts of a RRC

connection are restricted• If the load-based or service-based HO/NCCR attempt is unsuccessful,

the next load- or service-based HO/NCCR attempt is possible after a certain period

• After the first attempt: 30 sec• After the second attempt: 60 sec• After that 120

• Parameters InterFreqMinSLHOInterval (FMCI) and GsmMinSLHOInterval (FMCG) are used to prevent repetitive handovers between cells during one RRC connection

200 © 2006 Nokia

Handover Control

• Handover Types• Intra-Frequency Handover• SRNS Relocation • Inter-Frequency & Inter-System Handover• GSM ISHO• Overview – HSDPA mobility• Appendix


201 © 2006 Nokia

Traffic Balancing

• Traffic balancing with Call setup control or during hard HO to another frequency

• Directed RRC connection setup => direct the user to the frequency with lower loading within the same sector

• A second frequency can be added for each sector/site independently as the capacity needs to be increased

f1f1 f1f1 f1f1

f2f2

f2f2 f1f1 f1f1

High capacity site

Start call on f2 Coverage reasonHandover

High capacity WCDMA sites can be utilized

High capacity WCDMA sites can be utilized

202 © 2006 Nokia

Directed RRC Connection Setup

• If either the UL or DL load of the Source cell exceed a certain threshold value, the DRRC Connection setup process is initiated.

• CurrentCellPrxTotal > PrxTarget (default 4 dB)+ DRRCprxOffset (default -1 dB)

• CurrentCellPtxTotal > PtxTarget (def. max-3 dB)+ DRRCptxOffset (default -3 dB)

• The load of the current cell (UL/DL) is compared with the load of other cells in same sector to find out cell having less load:

• CurrentCellPrxTotal > CellPrxTotal(n) – DRRCprxMargin (default -0.5 dB)• CurrentCellPtxTotal > CellPtxTotal(n) – DRRCptxMargin (default -2 dB)

• Decision of Directed RRC connection setup is done by Admission Control in RNC

• Directed RRC connection setup is used for balancing the load (UL/DL) between cells which belong to same sector

• Same sector has cells with equal primary CPICH power, PtxTarget, PtxOffset, PrxTarget and PrxOffsetvalues

• Parameter Sector Identifier tells to which sector cell belongs to

203 © 2006 Nokia

Site – Sector – Cell in 3G

f 1

1+1+1

2+2+2

f 1 f 2

Each WCDMA cell consits of:

Load Control (LC)

Admission Control (AC)

Packet Scheduler (PS) / HSDPA

3 cells covering 3 sectors. 6 cells covering 3 sectors.

Sector 1

Sector 2

Sector 3

Cell 1

Cell 2Cell 3

Sector is meant as geographical coverage area

Site A

1 site (NodeB, WBTS) with 3 cells.

high capacity-site Site B

1 site (NodeB, WBTS) with 6 cells.

Cell 1

Cell 2Cell 3

Cell 4

Cell 5

Cell 6

Sector 3Sector 2

Sector 1

204 © 2006 Nokia

RACH: RRC Connection Setup Request

Cell_2 frequency 2

Cell_1 frequency 1

FACH: RRC Connection Setup

DCCH: RRC Connection Setup Complete

Cell_1 load > Cell_2 load + load threshold-> DRRC activated

incl. UARFCN of target cell

Directed RRC Connection Setup - Signalling

205 © 2006 Nokia

Directed RRC Connection Setup

Load of Source cell Load of Target cell

0 %

60 %NoDRRCallowed

PrxTarget(4 dB)

DRRCprxOffset(-1 dB) DRRCptxOffset(-3 dB)

50 %

0 %

60 %

DRRCprxMargin(-0.5 dB) DRRCptxMargin(-2 dB)

DRRCNoDRRCneeded

CurrentCellPrxTotalCurrentCellPtxTotal

PrxTarget(4 dB)

CellPrxTotal(n)CellPtxTotal(n)

DRRC

DRRC connectionsetup

now

now

DRRC connection setup to the target cell if both of the following equations are fulfilled:CurrentCellPrxTotal (source cell) > CellPrxTotal(n) – DRRCprxMargin (default -0.5 dB)CurrentCellPtxTotal (source cell) > CellPtxTotal(n) – DRRCptxMargin (default -2 dB).

07_handovercontrol_2006_06

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