omf810002 gsm handover algorithm issue2.0

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Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved.

GSM Handover Algorithm

Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. Page2

Foreword

Handover is a key technology of mobile communication

system and make continued conversation possible.

Handover algorithm in Huawei product is flexible and

powerful.


Objectives

Upon completion of this course, you will be able to:

Outline the types of handover

Master handover judgment flow

Understand algorithm of different handovers

Explain HO data configuration


Contents

1. Introduction of Handover

2. HO Algorithm Process


Contents




Purposes of HO

To keep a continuous communication with a moving MS

To improve network service performance

To reduce the call drop rate

To reduce the congestion rate


Classification by Reason

No DL MR Emergency HOTiming Advance (TA) HOInterference HORx_Level_Drop HOBad Quality (BQ) HO

Emergency HO

Enhanced Dual Band HO

Load HO

Normal HO

1

2

3

4

Classification by

ReasonEDGE HO PBGT HOLayer HO MS Fast Moving HOConcentric Cell HOAMR HO


Classification by Synchronization

CELL

Case 1

Synchronous Handover: the target BTS shall not send PHY INFO message

Case 2

Asynchronous Handover: the target BTS shall send PHY INFO message

Case 3 Case 4Case 5

MSC

BSC

BTS

BSC BSC

MSC

BTS BTSBTS

BTS

NSS Network


Classification by Equipment and Channel

SDCCH → TCHSDCCH → TCH(Direct Retry)(Direct Retry)

SDCCH → SDCCHSDCCH → SDCCH

Intra – Cell HOIntra – Cell HO ( HR( HR↔FR…↔FR…))

Inter – Cell HOInter – Cell HO

Intra – BSC HOIntra – BSC HO

Intra – MSC HOIntra – MSC HO

Inter – MSC HOInter – MSC HO

TCH TCH → TCH→ TCH


Contents




Contents


2.1 General HO Process

2.2 Measure and Measurement Result Report

2.3 Measurement Report Preprocessing

2.4 Handover Judgment

2.5 Handover Implementation


General HO Process

MS Goes into New Dedicated

Mode

MS Goes into Dedicated

Mode

Measure and Measurement Result

Report1

Measurement Report

Preprocessing2

Handover

Judgment3

Handover

Implementation4


General HO Process


Mode


Mode


Report1

Measurement Report

Preprocessing2

Handover

Judgment3

Handover

Implementation4


The downlink measurement reportof the neighbor cell (BCCH)

Measurement Report

Uplink MR includes uplink receiving level and quality.

Downlink MR includes downlink receiving level, downlink

receiving quality of the serving cell and other downlink

receiving levels from the neighbor cells.

Serving cell

Neighbor cell

The uplink MR

The downlink MR


Measurement Report


Period of Measurement Report

The downlink MR is sent to BTS in SACCH uplink

The interval is 480ms/per time when MS is on TCH

The interval is 470ms/per time when MS is on SDCCH

12TCH 12TCH1SACCH 1 Idle

480ms 4 TCH Multi-frames


General HO Process


Mode


Mode

Measurement Report

Preprocessing

Handover

Judgment3

Handover

Implementation4


Report1

2


MR Preprocessing

MR Preprocessing

Interpolation Recover the lost

measurement report

Filtering Smooth the

instantaneous fading

point


MR Interpolation

MR

MR

No. n

No. n+4

Continuous MR Flow

MRMR

MR

Missing by some reasons

…

…


MR Filtering

MR

MRContinuous MR Flow

MRMR

MR

…

…Filter----Average several consecutive MRs

MR


Data Configuration of MR Preprocessing


General HO Process

MS Goes into New Dedicated Mode

MS Goes intoDedicated Mode

Measure and Measurement Result Report1

MR. Preprocessing2

Handover Judgment3

Handover Implementation4

TA HO

Interference HO

Rx_Level_Drop HO

Bad Quality HO

Load HO

Edge HO

Layer HO

PBGT HO

AMR HO

No DL MR HO

Concentric Cell HO

MS Fast Moving HO


Penalty Processing

Ranking Processing

OM Forced HO

Direct Retry

Emergency HO

Normal HO


Penalty Processing

Intra-cell HO

HO FailsEmergency (TA&BQ)HO

MS Fast Moving

HO

Concentric Cell HO

Penalty

Punish on the target

cell

Punish on the original cell

Punish on other high priority layer

cells

AMR HOFails


Penalty for Handover Failure

Punish the target cell when a HO fails.

This is to avoid the MS to select this cell again in next HO

judgment.

Cell A

BTS

HO Fail

BSC

Cell B

BTS


Data Configuration of Penalty for Handover Failure


Cell A

Cell B

BTSBQ&TA HO

BSC

Penalty for Emergency Handover Punish the original cell when an emergency HO ( due to

BQ and TA) occurs.


Data Configuration of Penalty for Emergency Handover


Back? No way!Back? No way!

Umbrella

Micro cell

Penalty for MS Fast-moving Handover Giving penalty on the other three layers(Non-umbrella Layer )

after MS handovers to Umbrella cell by fast-moving-HO.

This is to keep MS staying in the umbrella cell and avoid

frequent HO.


Data Configuration of Penalty for MS Fast-moving Handover


Underlaid

Overlaid Do not attempt again during penalty time

after one failed HO(O->U)!

Penalty for Concentric Cell

A new concentric cell HO is prohibited within a penalty

time after a concentric cell HO failure.

Do not attempt again after N failed

HO(U->O)!


Data Configuration of Penalty for Concentric Cell


Underlaid

OverlaidDo not

attempt back too fast!

Penalty for Enhanced Concentric Cell A new UO HO is prohibited within a penalty time

after a OU HO is performed successfully.


Data Configuration of Penalty for Enhanced Concentric Cell


Penalty for Intra-cell HO A new intra-cell HO is prohibited if it occurs too frequently.

3 7 12 32 T (s)0

Penalty time

Intra-cell HO Time

2nd.3rd.

4th.

Max. consecutive HO times: 3

Forbidden time after Max. times: 20s

Interval for consecutive HO Jud: 6s

1st.


Data Configuration of Penalty for Intra-cell HO


Data Configuration of Penalty for AMR FRHR Handover Failure


General HO Process




MR. Preprocessing2

Handover Judgment3


TA HO

Interference HO

Rx_Level_Drop HO

Bad Quality HO

Load HO

Edge HO

Layer HO

PBGT HO

AMR HO

No DL MR HO

Concentric Cell HO

MS Fast Moving HO


Penalty Processing

Ranking Processing

OM Forced HO

Direct Retry

Emergency HO

Normal HO


Ranking Processing

M rule

K rule

Basic ranking

16 bits ranking

Network feature adjustment

The ranking result: target cell selection of handover


M Rule Begin

Finish to all neighbor cells?

An BSC external neighboring

cell& the current channel is SDCCH ?

No

Yes

Direct retry? [Inter-BSC SDCCH HO Allowed] is Yes?

Delete the cell from the cell list?

If the cell flow is overload ?

Yes No

Yes

No

RX_LEV_DL(n) < [Min DL Power

on HO Candidate Cell](n)+ [Min Access Level Offset]

(s)?

RX_LEV_UL(n) < [Min UP Power on HO Candidate Cell](s)+

[Min Access Level Offset](s)?

Delete this cell from the cell list

Yes

No

No

No

No

Yes

End

For service cell: Min Access Level Offset=0 M rule will remove the

neighbor cells from the candidate

cell listaccording to the flow.

Yes

Yes


Data Configuration of M Rule


K Rule Flow of calculating K value.

Begin

Finish to calculate value K to all cells?

Serving cell?

K=0

No

K = RX_LEV (n) – RX_LEV

(s)

Yes

End

No

Yes

All the candidate cells are ranked in descending order according to the K value

A

F

E

D BC

Serving Cell

Receiving Level

Cell

Serving Cell

Cell ACell B

Cell C

Cell D

Cell E

Cell F


Network Feature Adjustment After network feature adjustment, all the candidate cells

have their own 16 bits value.

The smaller the value is, the higher the handover priority

and position of the cell are in the candidate cell list, then it

is possible to be the candidate cell.

The Lowest

Weight

The Highest

Weight16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1


Network Feature Adjustment The 1st~3rd bits

The bit value indicates the priority of downlink receiving level

according to the cell signal level and the penalty process

taking place beforehand.

The values come from max. 6 candidate cells and 1

serving cell according to the level ranges from 000~110.

The value for the cell with the strongest signal level is

000.

16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1


Network Feature Adjustment The 4th bit: Inter-cell HO hysteresis bit.

Note: In PBGT HO, whichever the greater of the inter-cell ( of

the same layer ) hysteresis and PBGT threshold, that value

will be used in the PBGT HO.

16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1

Is serving cell?

Always set to

0

No

RX_LEV_DL (n) >= RX_LEV_DL (s) +

[Inter-cell HO hysteresis]

Yes

Set to 0Yes

Set to1

No


Data Configuration of Inter-cell HO Hysteresis


Network Feature Adjustment

The 5th~10th bits

The bit value is decided according to their position in Huawei

hierarchical network structure.

Huawei cell layers can be divided into 4 layers and each layer

can be further divided into 16 different priorities.

So there are 64 different priorities in Huawei hierarchical cell

structure.

16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1


Hierarchical Cell Structure

GSM900 Cell

Micro Cell

Umbrella Cell GSM 900

GSM1800 GSM1800GSM1800

GSM 900

GSM900GSM900

GSM1800GSM1800

GSM1800 Cell

GSM 900

GSM900GSM900

GSM1800GSM1800

Layer 4（ low ）

Layer 3

Layer 2

Layer 1（ high ）


Data Configuration of Cell Hierarchical Network Structure


Network Feature Adjustment The 11th bit: The bit value is decided by cell-load-sharing

criterion.

This bit is affected by 14th bit.

16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1

System load>=[System Flux Threshold for Load HO] or [Load HO Allowed ] =No ?

Yes 11th bit is turned off

Is serving cell?

set to 0

NoYes

Cell load >= [Load HO Threshold](s)?

set to 1 set to 1

cell load >=[ Load Rep.

on Candidate Cell](n)?

set to 0

Yes

No

Yes

No

No


Data Configuration of Cell-load-sharing


Network Feature Adjustment 12th bit and 13th bit: Whether share the same BSC or MSC.

16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1

Is serving cell?NoYes

Both 12th and 13th set to

0

Different BSC:

12th set to 113th set to 0

Is [Co-BSC/MSC Adj] yes?

See 14th bit

Yes

No

Co-BSC?

Co-MSC?

No

Yes

Different MSC:


No

Yes

Turn off 12th &13th bit

The same BSC:



Data Configuration of Co-BSC&MSC


The 14th bit: Layer HO threshold adjustment bit.

Network Feature Adjustment

16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1

The 15th/16th bits are reserved

Is serving cell?

set to 0

NoYes

Bit 14th set to 1, and bit

5th ~13th are turned off

set to 0

Yes Yes RX_LEV_DL >= [Inter-layer HO

Threshold] – [Inter-layer HO Hysteresis]?

RX_LEV_DL >= [Inter-layer HO Threshold] + [Inter-layer HO

Hysteresis]?

No No


Data Configuration of Layer HO Threshold Adjustment


General HO Process




MR. Preprocessing2

Handover Judgment3


TA HO

Interference HO

Rx_Level_Drop HO

Bad Quality HO

Load HO

Edge HO

Layer HO

PBGT HO

AMR HO

No DL MR HO

Concentric Cell HO

MS Fast Moving HO


Penalty Processing

Ranking Processing

OM Forced HO

Direct Retry

Emergency HO

Normal HO


No DL MR HO

Serving Cell Neighboring Cell

When the quality of Um interface become worse and

worse, it is for the worse uplink quality that MS can not

deliver downlink MR, while the downlink quality is not bad

enough for MS to receive the downlink message normally.

Bad uplink quality


Position of No DL MR HO



Measure and Measurement Result Report

1

MR. Preprocessing2

Handover Judgment3


TA HO

Interference HO

Rx_Level_Drop HO

Bad Quality HO

Load HO

Edge HO

Layer HO

PBGT HO

AMR HO

Concentric Cell HO

MS Fast Moving HO


Penalty Processing

Ranking Processing

OM Forced HO

Direct Retry

Emergency HO

Normal HO

No DL MR HO


No DL MR HO Begin

Report 1 DL MR at lease?

Is [No Dl Mr. HO Allowed] Yes ?

<=[Cons.No Dl Mr.

Ho Allowed Limit]?

Is serving cell? Select the candidate cell

with the highest priority,

exluding serving cell

Trigger No DL Mr. HO

Yes

No

End

No

No

Yes

Yes

>= signal quality filter length?

Yes

signal quality filter length:For TCH:[Filter Length for TCH

Qual]For SDCCH:[Filter Length for

SDCCH Qual]

No Dl Mr. in current Mr.?

Yes

UL_Qua. (after filering)

>=[No Dl Mr.Ul Qual

HO Limit]?Yes

Only one cadidate cell?

>=[Forbidden time

after MAX Times]?

Yes

No

No

No

Yes

Yes

No

No

[Intrecell HOAllowed]?

Yes

No


Data Configuration of No DL MR HO


TA(Time Advance) HO


TA Threshold(s)

Time

TA(s)

HandoverTriggering

TA Threshold(n)

or

Handover Triggering ZoneTA(n)


TA(Time Advance) HO

Trigger TA handover

Begin

The actual TA >= [TA Threshold]?

Is [TA HO Allowed] Yes ?

Any neighbour cell

exist?

Is serving cell?

Select the cell with the highest priority in the

cadidate cell list

TA(n is in the same BTS)<=[TA Threshold](s)?

Suitable cell exist?

Yes

No

End

No

No

YesYes

No

No

Yes

Yes

Yes

No


Data Configuration of TA HO


Interference Handover

Lev_Thr

Rx_Qual

RX_Lev

Qual_Thr

InterferenceOrigin


Handover Triggering Zone


Interference HOBegin

UL or DL receiving

Quality(s)>=A?

Is [Interference HO

Allowed] Yes ?

Any neighbour cell

exist?

Is serving cell?

Select the cell with the

highest priority in the cadidate cell list

Rx_Level(n)>= [Inter-layer HO Threshold](n) +[Inter-layer HO Hysteresis](n)?

Yes

No

End

No

No

Yes No

NoYes

None AMR FR: A = RXQUALn, 1<=n<=12 AMR FR:A = RXQUAL1, n=1; A = RXQUALn + RXLEVoff,

2<=n<=12

[Intracell HO Allowed] yes

& cell not punished?

Any suitable cell exist?

Trigger interference handover

No

Yes

Yes

Yes

Yes

No


Data Configuration of Interference HO

Parameter Receiving Level(-110dBm) Receiving Quality

RXQUAL1 <=30 70

RXQUAL2 =31 60

RXQUAL3 32~35 59

RXQUAL4 36~38 58

RXQUAL5 39~41 57

RXQUAL6 42~45 40

RXQUAL7 46~48 55

RXQUAL8 49~52 54

RXQUAL9 53~55 53

RXQUAL10 56~58 52

RXQUAL11 59~62 51

RXQUAL12 >=63 50

Default Value


Data Configuration of Interference HO


Rx_Level_Drop HO


Rx_Level_Drop HOBegin

Satisfy the Formula& The lastest RX_LEV_UL(s) <

[Edge HO UL RX_LEV Threshold]?

[Rx_Level_Drop HO

Allowed] Yes ?

Any neighbour cell

exist?

Is serving cell?


highest priority in the cadidate cell list

Yes

No

End

No

No

Yes

NoYes

Formula:

Priority is higher than

serving cell?

Trigger Rx_Level_Drop

handover

Yes

Yes

BXAXAXAXA

XAXAXAXA

88776655

44332211

10101010

10101010

End No


Data Configuration of Rx_Level_Drop HO


BQ(Bad Quality) HO Begin

Is [BQ HO Allowed] Yes ?

Any neighbour cell

exist?

Is serving cell?


highest priority in the

cadidate cell list

Yes

No

End

No

No

Yes

NoYes

Yes

UL_Rx_Q(s)>=[UL Qual. Threshold] or DL_Rx_Q(s) >=[DL Qual. Threshold]?

RX_LEV_DL (n) > RX_LEV_DL (s)

+ Inter-cell HO hysteresis(s)

-BQ HO Margin(s) ?

[Intracell HO Allowed] yes

& cell not punished?


Trigger BQ

handover

Yes

Yes

Yes

No

No No


Data Configuration of BQ HO


General HO Process




MR. Preprocessing2

Handover Judgment3


TA HO

Interference HO

Rx_Level_Drop HO

Bad Quality HO

Load HO

Edge HO

Layer HO

PBGT HO

AMR HO

No DL MR HO

Concentric Cell HO

MS Fast Moving HO


Penalty Processing

Ranking Processing

OM Forced HO

Direct Retry

Emergency HO

Normal HO


Enhanced Dual Band HO Enhanced dual band cell is two different band cells which locate

a common site, and have the same azimuth.

Purpose

During the procedure of channel assignment and handover,

900M cell and 1800M cell can share their resource.

Assign the channel with low load in UL to MS preferentially.

Make MS handover from the high load cell to the low load cell.


Channel Assignment of Enhanced Dual Band HO

RX_LEV_OL>= [Incoming OL Subcell HO level Threshold(dB)] andRX_LEV_UL – RX_LEV (n) >[Distance Between Boundaries of UL and OL Subcells(dB)] Attention:RX_LEV (n): RX_LEV of the strongest neighboring cell which has the same frequency

band and layer with underlaid subcell, but locates in a different BTS. If there is no such a cell, this

value is -110dBmIf [ATCBHoSwitch] is [Close], the second condition is turn off.

A:

Begin from UL

[Assignment Optimization

of UL Subcell Allowed or not] ?

Cell load of UL > [UL Subcell General

Overload Threshold(%)]?

Yes

A

Yes

No

Any idle TCH Available in OL?

Assign TCH in OL

YesNo

Yes

Assign TCH in ULor direct retry

identificationor queuing

No

No

TCH assignment (SDCCH channel in UL)


Data Configuration of Channel Assignment


Begin from OL

[Assignment Optimization

of OL Subcell Allowed or

not ] No ? Cell load of UL< [UL Subcell Lower Load Threshold]?

Yes

Yes

No

Assign TCH in UL

Any idle TCH Available in UL?

Assign TCH in UL

Any idle TCH Available in OL?

Assign TCH in OL

Yes No

YesAssign TCH in OL

or direct retry identification

or queuing

No

No

TCH assignment (SDCCH channel in OL)

Channel Assignment of Enhanced Dual Band HO



Classification of TCH HO in enhanced dual band HO

OL to UL for low load in UL

UL to OL for high load in

UL

OL to UL for moving


Enhanced Dual Band HO(UO ) Triggering condition for TCH Load HO from UL to OL for high load in UL


Enhanced Dual Band HO(UO ) Triggering condition for TCH Load HO from UL to OL for high load in UL

Cell load of UL>=[UL Subcell Serious Overload

Threshold(%)]?

Begin

[Load HO From UL Subcell

to OL Subcell Allowed] Yes ?

Cell load of UL>=[UL Subcell General Overload

Threshold(%)]?

No

A & Satisfy P/N &not within penalty

time?

Trigger UL to OL

Yes No

Adjust HO zone basing

on HO step and HO period

Refresh cell load

per secondBB-C

YesB=[UL Subcell Load Hierarchical HO Period(s)]

C=[Modified Step Length of UL Load HO Period(s)]

Any MS in HO zone?

Yes

No

No

Yes

Yes

HO step: [Step Length of UL Subcell Load HO(dB)]HO zone: [Incoming OL Subcell HO level Threshold(dB)]~-47dBmHO Period: [UL Subcell Load Hierarchical HO Period(s)]RX_LEV_OL >= [Incoming OL Subcell HO level Threshold(dB)] andRX_LEV_UL – RX_LEV (n) > [Distance Between Boundaries of UL and OL Subcells(dB)]A:

No

End


Data Configuration of Enhanced Dual Band HO(UO )


Enhanced Dual Band HO(OU ) Triggering condition for TCH HO from OL to UL for moving

RX_LEV_OL <[Outgoing OL Subcell HO level Threshold(dB)] orRX_LEV_UL – RX_LEV (n) < [Distance Between Boundaries of UL and OL Subcells(dB)] – [Distance Hysteresis Between Boundaries of UL and OL

Subcells(dB)]

A:

Satisfy P/N?

Begin

A

Yes

End

Trigger OL to UL

Yes

Select Neighbor cellwith the highest priority

No

Ye

s

Generally, Object cell maybe UL or other neighbor

cell is

No


Data Configuration of Enhanced Dual Band HO(OU )


Enhanced Dual Band HO(OU ) Triggering condition for TCH Load HO from OL to UL for low load in UL


Enhanced Dual Band HO(OU ) Triggering condition for TCH Load HO from OL to UL for low load

in UL Begin

[Load HO of OL Subcell to UL Subcell Enable]

Yes ?

Cell load of UL <[UL Subcell

Lower Load Threshold(%)]?

Yes

No

End

Satisfy P/N?

HO zone: [Outgoing OL Subcell HO Level Threshold(dB)] ~ -47dBmHO step: [Step Length of OL Subcell Load HO(dB)]A: RX_LEV_UL >= Inter-layer HO Threshold + Inter-layer HO

Hysteresis

Yes

No

Confirm:HO zone and HO

stepRefresh cell

load per second

The object cell must be

the underlaid subcell and satisfy condition

A

Any MS in HO zone?

Yes

Trigger OL to ULNo

Yes

No


Data Configuration of Enhanced Dual Band HO(OU )


General HO Process




MR. Preprocessing2

Handover Judgment3


TA HO

Interference HO

Rx_Level_Drop HO

Bad Quality HO

Load HO

Edge HO

Layer HO

PBGT HO

AMR HO

No DL MR HO

Concentric Cell HO

MS Fast Moving HO


Penalty Processing

Ranking Processing

OM Forced HO

Direct Retry

Emergency HO

Normal HO


Load HOHandover triggering zone

Load HO Threshold

Time

Load of Serving Cell

Load Req. on Candidate Cell

Load of Neighboring Cell

Congested CellCongested Cell

Congested CellNormal Cell

Normal CellNormal Cell

Normal Cell


Cell A Cell B

Normal HO border

CONF_HO_RXLEV

CONF_HO_RXLEV+CLS_Ramp

CONF_HO_RXLEV+CLS_Offset

Load HO zone

Load HO

As load HO may trigger several HOs, we need to consider

the CPU load (system flow level) before triggering it. In

addition, load HO is executed step by step, that is, the

edge HO thrsh. raises according to certain step and

period and will stop when out of the Load HO Zone.

Load HO bandwidth Edge HO threshold

Load HO step level


Load HO

Congested Cell

Normal Cell

Normal Cell

Normal Cell


Load HO Begin

Is [Load HO Allowed] Yes ?

BSC internal cell?

Select the cell with the highest

priority in the cadidate cell list

End

No

No

Yes

NoYes

Yes

Current system flux<=[System Flux Threshold

for Load HO]?

C & D


Trigger load handover

Yes

Yes

Yes

End No

Load of service cell >=

[Load HO Threshold]?

Yes

No

Yes

Load HO timer T overflow?

Yes

Caculate

StepPeriod

T )1(

Caculate A=[Load HO Bandwidth]

B

Yes

Is serving cell?

No

No

B: [Edge HO_DL_RX_LEV Threshod]<DL_RX_Lev(s)

< [Edge HO_DL_RX_LEV Threshod]+AC: RX_LEV (n)>= [Inter-layer HO

Threshold] + [Inter-layer HO Hysteresis]D: load(n)< Load Req. on Candidate Cell Step: [Load HO Step Level]Period: [Load HO Step Period]

CNo

A=

No

Yes

Load HO timer T begin?

No

No

Star timer T

PeriodStep

TAStep )1Bandwidth] HO [Load

(0 Bandwidth] HO [LoadA T

Yes


Data Configuration of Load HO


General HO Process




MR. Preprocessing2

Handover Judgment3


TA HO

Interference HO

Rx_Level_Drop HO

Bad Quality HO

Load HO

Edge HO

Layer HO

PBGT HO

AMR HO

No DL MR HO

Concentric Cell HO

MS Fast Moving HO


Penalty Processing

Ranking Processing

OM Forced HO

Direct Retry

Emergency HO

Normal HO


Edge HandoverHandoverTriggering

P/N


P: Watch Time N: Valid Time

RX_LEV Thr

Time

RX_Lev


Edge HOBegin

Is [Fringe HO Allowed] Yes ?

End

No

Yes

Yes

UL_Rx_Lev(s) < [Edge HO UL RX_LEV Threshod]?

Yes

Any neighbor cell?No

Refreshits timer

Yes

Satisfy P/N rule(s)?

DL_Rx_Lev(s) < [Edge HO DL RX_LEV Threshod]?

N

o

Refreshits timer

Yes

Satisfy P/N rule(s)?

No

Select cell(n) whose 16 bit value is

higher than serving cell andwhose level satifys P/N rule(n)

basing on A

Trigger Edge handover

No

No

Yes

A: DL_Rx_Lev(n)> DL_Rx_Lev(s)+[Inter-cell HO

Hysteresis]


Data Configuration of Edge HO

Should be lower than the[Outgoing OL Subcell HO Level Threshold(dB)] in

enhance dual band data table

[Edge HO UL/DL RX-LEV Threshold]<[UL/DL RX_LEV Lower

Threshold] in HWII/III power control tabel


MS Fast-Moving HandoverHandover Triggering

Time Threshold

Umbrella Cell

Time

P/NP: Watch CellsN: Valid Cells

1 1 2 3

Micro Cell

Cells Number


MS Fast-Moving HandoverBegin

Is [MS Fast Moving HO

Allowed] Yes ?

End

No

Yes

Yes

Is the target cell the serving cell?

Is the serving cell on layer 4?

Is the best neighbor cell is the last original cell?

Satisfy P / N rule?No

Select the neighbor cell with the highest priority &

on the 4th layer & satisfy RX_LEV(n)>= Inter-layer

HO threshold(n) + Inter-layer HO hysterisis(n)

Any cell satisfy the condition above?

Trigger MS fast-moving handover

No

Yes

Yes

No

Yes Refresh timer(s)

No

No

Yes


Data Configuration of MS Fast-moving Handover


Layer HO

Neighboring CellServing Cell

GSM900 Cell（ Lay 3 ）

GSM1800 Cell（ Lay 2 ）


Begin

Is [Level HO Allowed] Yes ?

End

No

Yes

Yes

Any neighbor cell exit?

16 bit valu(n)<16 bit value(s)l?

A & ( layer(n)< layer(s)

or level(n)<level(s) )?

Satisfy P/N rule(n)?No

Trigger layer handover

Yes

No

Yes

No

A: RX_LEV(n)>= Inter-layer HO threshold(n)

+ Inter-layer HO hysterisis(n)

Yes

Identify the next cell

No

Layer HO


Data Configuration of Layer HO


PBGT HO


PBGT HO Threshold

Time

Path Loss (dB)

126dB 119dB

5

126-119=7dB>5dB

HandoverTriggering

P/NP: Watch Time N: Valid Time


Begin Is [PBGT HO

Allowed] Yes ?

End

No

YesIs current channel

signal channel?

Satisfy P / N rule?

No

Yes

Search next

neighborcell

layer(n)=layer(s)&level(n)=level(s)?

Path loss (s) – Path loss (n)

>PBGT HO Threshold

Refresh timer(s)

Trigger PBGT HO

Yes

No

Yes

No

Yes

No

PBGT HO


Data Configuration of PBGT HO


Concentric Cell Purposes

Maximize coverage area

Reduce interference and improve frequency reuse density

Construction methods

Different combiner loss

Different propagation loss

Modify the transmission power of TRX, the down tilt of

antennas, etc.

By HO parametersOverlaid

Underlaid


Classification and HO Judgment of Concentric Cell

Receiving level

Time advance

Quality

…

Receiving level

Time advance

Quality

ATCB

Cell load of

underlaid

…Normal concentric cell Enhance concentric cell


Data Configuration of Concentric Cell


Normal Concentric Cell HO

Division of underlaid and overlaid is decided by MS

downlink receive level ,TA value and quality.

underlaid

overlaid

Receiving Level Threshold

Receiving Level Hysteresis

Receiving Qaulityl Threshold

TA Threshold

TA Hysteresis


Normal Concentric Cell HO

U to O O to U


Normal Concentric Cell HO(OU ) Flow for TCH HO from overlaid to underlaid

Begin [Penalty Time of OtoU HO Fail(s)] overflow ? End

No

Ye

s

[RX_LEV for UO HO Allowed] Yes?

Yes

[OL to UL HO Allowed] Yes ?

NoYes

[RX_QUAL for UO HO Allowed] Yes?

Yes

Rx_Dl_Quality>=[RX_QUAL Treshold]?

Current TA>=[TA Threshold]+

[TA Hysteresis]?

[TA for UO HO Allowed] Yes?

Trigger OL to UL

P/N rule?

Yes Yes

Yes

Yes

No

No No

No No No

End

Rx_Dl_Level<=[RX_LEV thshold]

-[RX_LEV Hysteresis]


Normal Concentric Cell HO(UO ) Criterion for TCH HO from underlaid to overlaid

Begin [Penalty Time of UtoO HO Fail(s)] overflow ?

End

No

YesTime of HO failure<

[MaxRetry Time after UtoO Fail]?

Current TA<=[TA Threshold]-

[TA Hysteresis]?

No

Yes


Yes

Yes

No

No[RX_LEV for UO HO Allowed] Yes?

Rx_Dl_Level >=[RX_LEV Threshold]

+ [RX_LEV Hysteresis]

No


Rx_Dl_Qual<=[RX_QUAL Treshold]?

Yes

P/N rule?

Yes

No

No

No

Yes

Yes

No

[UL to OL HO Allowed] Yes ?

End

Yes

No

Trigger UL to OL


Data Configuration of Normal Concentric Cell HO


Enhance Concentric Cell HO

Division of underlaid and overlaid is decided by MS

downlink receive level, quality, TA value and cell load of

underlaid.

underlaid

overlaid

U to O HO Receiving Level Threshold

O to U HO Receiving Level Hysteresis

Receiving Qaulityl Threshold

TA Threshold

TA Hysteresis


Enhance Concentric Cell HO

Classification of TCH HO in enhance concentric cell HO

O to U for low load in U

U to O for high load in

U

O to U for moving


Enhance Concentric Cell HO(UO )

Begin [Penalty Time of UtoO HO Fail(s)] overflow ?

End

No

YesTime of HO failure<

[MaxRetry Time after UtoO Fail]?

Current TA<[TA Threshold]-

[TA Hysteresis]?

No

Yes

[ATCBHoSwitch] Open?


Go to the user selection

flow in the next slide

Yes

Yes

No


Rx_Dl_Level>[UtoO HO

Received Level Threshold]

No

A: RX_LEV_UL – RX_LEV (n) >[Distance Between Boundaries of UL and OL Subcells(dB)]

RX_LEV (n): RX_LEV of the strongest neighboring cell which has the same frequency band and layer

with underlaid subcell, but locates in a different BTS. If there is no such a cell, this value is -110dBm

AYes

No


Rx_Dl_Qual<[RX_QUAL Treshold]?

Yes

P/N rule?

YesNo

Flow for TCH HO from underlaid to overlaid for high load in UL

No

No

No

Yes

Yes

Yes

Yes

[UL to OL HO Allowed] Yes ?

End

Yes

No


Enhance Concentric Cell HO(UO )

Cell load of UL>=[En Iuo Out Cell Serious OverLoad Thred]?

Begin [UtoO Traffice

HO Allowed] Yes ?

Cell load of UL>=[En Iuo Out Cell General OverLoad Thred]?

Trigger UL to OL

Yes No



Refresh cell load

per second

B(B-1)/second

Yes

B=[Underlay HO Step Period(s)]HO step: [Underlay HO Step Level]HO period: B-1 or BHO zone: begin from -47dBm

Any MS in HO zone?

Yes

No

Yes

No

End

User selection flow from UL to OL for high load in UL


Enhance Concentric Cell HO(OU ) Flow for TCH HO from overlaid to underlaid for low load in underlaid

Begin [UtoO Traffice

HO Allowed] Yes ?

Cell load of UL<[En Iuo Out Cell Low Load Thred]?

No

Trigger UL to OL



Refresh cell load

per second

Yes

HO period: [En Iuo Cell Load Classification HO Period]HO step: [En Iuo Cell Load Classification HO Step]HO zone: begin from[OtoU HO Received Level Threshold] to

-47dBm

Any MS in HO zone?

Yes

No

Yes

No

End [OL to UL HO

Allowed] Yes ?

Yes


Enhance Concentric Cell HO(OU ) Flow for TCH HO from overlaid to underlaid for moving

Begin [Penalty Time of OtoU HO Fail(s)] overflow ? End

No

Ye

s

[ATCBHoSwitch]

Open?


Rx_Dl_Level>[OtoU HO

Received Level Threshold]

A

Yes

[OL to UL HO Allowed] Yes ?

NoYes


Yes

Rx_Dl_Qual>[RX_QUAL Treshold]?

Current TA>[TA Threshold]+

[TA Hysteresis]?


Trigger OL to UL

P/N rule?

Select the underlaid subcell or

the neighbour cell with the

highst priority in 16 bits list

Yes Yes Yes

Yes

No

Yes

No No No

No No

No End

A: RX_LEV_UL – RX_LEV (n) < [Distance Between Boundaries of UL and OL Subcells(dB)] －

[Distance Hysteresis Between Boundaries of UL and OL Subcells(dB)]


Data Configuration of Enhance Concentric Cell HO


Channel Assignment strategies of Concentric HO

Channel Assignment Strategies of Concentric HO

Immediate Assignment

AssignmentIntra-BSC Inter-cell

Handover

Incoming Cell

Handover


The preferred SDCCH channel in two layers is controlled by

parameter “TA pref. Of Imme-Assign Allowed ”

If "No", system prefers the channel in Underlaid subcell

If “Yes", system prefers the channel according to in

Channel Request message

TA smallerTA bigger

Immediate Assignment


Data Configuration of Immediate Assignment


Preferred assignment in the overlay or underlay

cell

Assign the channel of overlay or underlay cell

according to the Rx_level and TA in the

measurement report

TA smaller and Rx-level higher

Assignment


Data Configuration of Assignment


Intra-BSC Inter-Cell Handover In the case of intra-BSC inter-cell handover, the MS can be handed over

to the underlay or overlay cell first.

If “System Optimization” is selected, the preferred assignment is

conducted according to the level value in the measurement report.

overlaid

Underlaid

OverlaidAccording to the Rx-level


Data Configuration of Intra-BSC Inter-Cell Handover


Inter-BSC Handover For the inter-BSC Handover, if the target cell is concentric cell , the channel

of underlay cell should be assigned first.

overlaid

Underlaid

Overlaid

BSC1 BSC2

Assign underlaid first


Data Configuration of Inter-BSC Inter-Cell Handover


AMR Handover FlowBegin

Are [Intracell HO Allowed] & [Intracell F-H

HO Allowed ］ Yes ?

Yes

Is current channel TCH & version3?

No

A: Cell load > [AMR TCH/H Prior

Cell Load Threshold]

During [Penalty Time

after AMR TCHF-H HO

Fail(s)]?

Yes

Yes

current channel is FR

Satisfy P/N rule?Trigger internal

cellAMR handover

Yes

NoEnd

RQI/2 >[F2H HO th] & A

RQI/2 <[H2F HO th] End

Yes Yes

NoNo

No

No

No

Yes


Data Configuration of AMR HO


General HO Process


Mode


Mode


Report1

Measurement Report

Preprocessing2

Handover

Judgment3

Handover

Implementation4


Handover Implementation

No power control during handover in order to

make sure the handover is

successful

Begin

Is [Power boost befor HO

enabled or not ］ Yes ?

BTS(s) uses the max.

power output

Yes No

BSC send “HO Command” to

MS

HO execute

BTS(s) keeps current

power output

BTS(s) keeps current

power output For BTS


Data Configuration of Handover Implementation(BTS)


Handover Implementation

No power control during handover in order to

make sure the handover is

successful

Begin

Is [MS Power Prediction after HO ］ Yes ?

BSC predict power

Yes No

BSC send “HO Command” to

MS

HO execute

MS uses the highest power

to access For MS

MS will use this predict power in new cell after finishing this handover


Data Configuration of Handover Implementation(MS)


Summary

In this course, we have learned:

Classification of HO

HO general procedure

HO judgment algorithm

HO implementation process

HO data configuration

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Documents

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page6purposes of ho

ms ho ms hointerinter

page12general ho processms

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page17general ho processms

page25general ho processms