huawei gsm handover algorithm i 20100625

5/25/2018 Huawei GSM Handover Algorithm I 20100625

1/99Huawei Confidential. All Rights Reserved

OMF010002 Handover

ISSUE 2.0


2/99Internal Use2

Handover is key technology of Mobile

communication system and make

continued conversation possible.

Handover algorithm in Huawei product

is flexible and powerful


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Objectives

Upon completion this course, you will be

able to:

Understand the type of handover.

Master handover judgment flow

Configure handover data

Master handover signaling flow


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Chapter 1 Introduction of Handover

Chapter 2 HO Algorithm process

Chapter 3 HO Data Configuration

Chapter 4 HO Signaling process


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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


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Emergency HO Timing Advance (TA) Emergency HO

Bad quality (BQ) Emergency HO

Rx_Level_Drop Emergency HO

Interference Emergency HO

load HO Normal HO

Edge HO

Layer HO

Power Budget (PBGT) HO

Speed-sensitive HO (Fast moving MS HO)

Concentric Cell HO

Classification by Reason


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Classification by Synchronization

Synchronous handover: source andtarget cell belong the same BTS

Asynchronous handover: source and

target cell belong the different BTS


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Section 1 General HO process

Section 2 Measurement report preprocessing

Section 3 Penalty processing

Section 4 Basic ranking and Secondary ranking

Section 5 Condition of handover


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General process of HO Algorithm

M.R.preprocessing

Penaltyprocessing

Basic ranking

Secondaryranking

HO judgment

TA emergency HO

BQ emergency HO

RSD emergencyHO

Interf. emergency HO

Load Sharing HO

Edge HO

Layer HO

PBGT HO

Processingprogram

OM forced HO

Directed retry

Overlaid/underlaid HO

Fast moving MS

HO

1

1


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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 Neighbour cell

The downlinkmeasurement report

of the serving cell

The uplink measurement

report of MSThe downlink measurement reportof the neighbour cell (BCCH)


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Internal Use15

MR interpolation

Every time BSC receives a measurement report, there will be

an update to the basic rank of the cells.

BTS may fail to receive the measurement report from MS.

Before the rank-update, BSC needs to recover the lost

measurement reports according to Filter Table. If the lost MRamount is within the allowed range, then recovers the lost MR

according to the algorithm.


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Internal Use16

MRMR

MR MRMR

Measurementreport No. n

Measurement rNo. n+4

ContinuousMR

flow

How to interpolate MR?


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Internal Use18








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Internal Use19

Penalty Processing

There are altogether four types of penalty process (second step ofHO algorithm process )

Penalty on the target cell when a HO fails.

Penalty on the original serving cell when an emergency HO

( base on BQ and TA ) is performed.

Penalty on other high priority layer cells after a fast moving HOis performed.

A new HO attempt is prohibited within the penalty time after an

overlaid/underlaid HO fails.


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Internal Use20

BTS

HO failure

BSC

Cell A

Cell B

Penalty on the Target Cell

Punish the target cell when a HO fails. This is to avoid the MS to selectthis cell again in next HO judgment.


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Internal Use21

BTS

BQ& TA HO

BSC

Cell A

Cell B

Penalty on the Source Cell

Punish the original serving cell when an emergency HO ( due to BQand TA) occurs.


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Internal Use22

Back? No way!

Umbrella

Micro cell

penalty on Non-umbrella Layer

Giving penalty on the other three layers after MS handovers to Umbrella cell

by fast-moving-HO. This is to keep MS staying in the umbrella cell andavoid frequent HO.


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Internal Use23

Underlaid

Overlaid Do not

attemptagain after a

failed HO!

Penalty on Overlaid/underlaid Cell

A new Overlaid/underlaid HO is prohibited within a penalty time after an

Overlaid/Underlaid HO failure.


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Internal Use24








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Internal Use25

Procedure of Ranking

Basic ranking and secondary ranking of cells are major parts of theHO judgment. Ranking is made through 16bits-algorithm. The

serving cell and the neighbor cells will be listed in a cell list

according to their 16bits value. The ranking processes include:

M rule

K rule 16bits ranking


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Internal Use26

Only the cells with received signal level satisfy the following conditions

can be put into the candidate cell list.

For serving cell

RX_LEV (o) >MSRXMIN(o) + MAX(0,Pa(o))

For Neighbor cell

RX_LEV (n) > MSRXMIN(n)+ MAX(0,Pa(n))+ OFFSET

Pa(0) : MS_TXPWR_MAX(0)P

Pa(n) : MS_TXPWR_MAX(n)P

MS_TXPWR_MAX( ) : The appointed MS transmitting power by theBSS.

P : Max_Power_of_MS

Max_Power_of_MS : MS maximum transmitting power

M rule

K l C it i


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Internal Use27

After the M rule , the serving cell and candidate neighbor cells are rankedin descending order according to the receiving level only

Both the serving cell and the neighbor cells have their own 16bits value.

The smaller the value is, the higher the priority and position the cell is in

the cell list.

The 1st-3rd bits: bit value is decided according to the cell signal level andthe 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.

K rule Criterion

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

The 4th bit: determined by HO hysteresis


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Internal Use28

The 4th bit: bit value is determined by inter-cell HO ( of the same

layer ) hysteresis. The 4th bit of the serving cell is always 0,

The receiving signal level of the neighbor cell >= The receiving

level of the serving cell + Inter-cell HO ( of the same layer )

hysteresis, bit 4th is set to 0.

The receiving level of the neighbor cell < The receiving level ofthe serving cell + Inter-cell HO ( of the same layer ) hysteresis,

bit 4th is set to 1.

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.

The 4th bit: determined by HO hysteresis

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


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Internal Use29

The 5th10th bit: determined by Layer

The 5th-10th bits: bit value is decided according to their position in Huawei

hierarchical network structure. When the signal level of the neighbor cells or the serving cell is lower than

the layer HO threshold and hysteresis, this function is turned off and all bits

are set to 0.

That is to say only when the above criterions are met, then this function

take effect.

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


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Internal Use30

GSM900

Cell

Micro Cell

Umbrella

Cell GSM 900

GSM1800 GSM1800GSM1800

GSM 900 GSM 900 GSM 900

GSM900GSM900

GSM1800GSM1800

GSM900 GSM900

GSM1800 GSM1800

GSM1800

Cell

Hierarchical cell structure


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Internal Use31

The 11th bit: determined by load

The 11th bit: bit value is decided by cell-load-sharing criterion.

Serving cell: if Cell Load>= Start threshold of load HO, bit 11th is set to 1,otherwise is set to 0.

Neighbor cell: if Cell Load>=Receive threshold of load HO, bit 11th is set to 1,

otherwise is set to 0.

Refer to Load HO Table for the load HO threshold and load req. on

candidate cell. Clue : When the cell load is higher than the threshold, then the bit 11th is

set to 1.This is done in order to put the cell in a lower part of the cell list.

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


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Internal Use32

The 12th/13th bit: determined by co-BSC/MSC

12th bit: bit value is decided by co-BSC criterion.

Serving cell: is always set to 0. Neighbor cell: if co-BSC with the serving cell, 12th bit is set to 0,

otherwise is set to 1.

When the signal level from the neighbor cell or the serving cell is lower

than layer HO threshold and hysteresis. This function is turned off and

the value is set to 0. If the parameter Co-BSC/MSC Adj. in the HO control table is set to

No,then this function is turned off and the value is 0.

13th bit : Bit value is decided by Co-MSC parameter, having the same

concept as the 12th bit.

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


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Internal Use33

The 14th bit: determined by Layer HO

The 14th bit: Layer HO threshold adjustment bit

Serving cell criterion

Receive level >= layer HO thresholdlayer HO hysteresis, bit 14th is set to 0.

At the same time, bit 13th, 12th and 10th5th bits are set to 0.

If the above criterion is not met, then bit 14th is set to 1.

Example : 20-5 = 15 ( -95 dBm)

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


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Internal Use34

The 14th bit: determined by Layer HO

Neighbor cell criterion

Receive level >=layer HO threshold + layer HO hysteresis, bit 14th is setto 0. At the same time, bit 13th, 12th and 10th5th bits are set to 0

If the above criterion is not met, then bit 14th is set to 1.

Example : 20+5 = 25 ( -85 dBm )

note

The layer HO threshold and hierarchical hysteresis correspond to thevalue of that individual cellsvalue.

Usual situation : When the neighbor cells are of the same layer, each of

the neighbor cells layer HO threshold value will be the same. Same

concept goes for the layer HO hysteresis. This can maintain the entire

hierarchical layers of the cell.

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


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Internal Use35

The 15th bit: determined by Cell Type

The 15th bit: Bit value is decided by cell type

Serving cell or Neighbor cells:

When cell type is extension cell1.

When cell type is normal cell 0.

The 16th bit: Reserved bit

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


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Internal Use36







T f HO


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Internal Use37

Types of HO

Emergency HO

TA HO

BQ HO

interference HO

Rx_Level_Drop HO

Load HO

Normal HO

Edge HO, layer cell HO and PBGT HO

Fast moving HO

Overlaid/underlaid HO

TA&B d Q lit HO


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Internal Use38

TA&Bad Quality HO

TA HO criterion : TA of the serving cell > TA Thrsh.

BQ HO criterion :

The average value of the uplink quality of the serving cell >

UL Qual. Thrsh.

The average value of the downlink quality of the serving cell >DL Qual. Thrsh.

Requirements on the target cell (same as the above two types of

HO)

Select the first cell in the neighbor cell list i.e. lowest 16bits

value.

R L l D HO


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Internal Use39

Rx_Level_Drop HO

Rx_Level_Drop HO Due to downlink signal level drop

Triggered upon detecting rapid level drop during MS busy

mode.

Requirements for the target cell:

The target cell is the first cell in the neighbor cell list.

I t f HO


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Internal Use40

Interference HO

Interference HO (DL&UL) : When the receiving level > receiving threshold level. But

Receiving quality < threshold of quality interference.

Requirements for the target cell:

The target cell is in the cell list.

C ll L d HO


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Internal Use41

Cell Load HO

Cell Load HO Criterions :

System load of BSC < Permissible load of HO threshold

Load of serving cell > Load HO threshold Requirements for the target cell

Load of target cell < Load HO threshold

BTS

BSC

Ed HO


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Internal Use42

Edge HO

Edge HO Criterion: In N seconds, when there are P seconds that neighbor cells

DL or MSsUL signal level is lower than the Edge HO threshold.

Then the criterion is met and Edge HO occurs. This method

utilizes the P/N rule.

Requirements for the target cell: The target cell should be ranked in front of the serving cell.

L HO


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Internal Use43

Layer HO

Layer HO criterions: Serving cell :

No requirement.

Target cell :

Layer of the target cell is lower than the serving cell.

Receive level of the target cell > layer cell threshold + layer

cell hysteresis.

Target cell should be ranked in front of the serving cell. The

priority of target cell should be higher than the serving cells.

PBGT HO


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Internal Use44

PBGT HO

PBGT HO Criterions : Target cells path loss is smaller than the serving cells path

loss by the PBGT threshold value.

Satisfying the P/N rule.

Target cell should be ranked in front of the serving cell.

Note : PBGT HO can only occur between same-priority cell. If the

system permits PBGT HO for the cell, PBGT HO can occur in

either inter-BSC or inter-MSC.

Fast Moving HO


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Internal Use45

Fast-Moving HO

When the serving cell is micro cell :

When the MS has traveled through P numbers of cell, and thereare Q (=


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Internal Use46

Overlaid/Underlaid Cell

Assume, 6TRX in one cell, one CDU and one SCU are adopted

Where can we configure BCCH CH? CDU or SCU?

SCU

CDU

Antenna

Antenna

TRX

TRX

TRX

TRX

TRX

TRX



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Internal Use47


Purpose

Maximize coverage area Reduce interference and improve frequency reuse density

Construct method

Different combiner loss

Decrease the power of TRX

By HO parameter, it is called IUO Classify

Normal Underlaid/Overlaid

IUO: Enhance Underlaid/Overlaid

How to Allocate SDCCH/TCH?


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Internal Use48

How to Allocate SDCCH/TCH?

SDCCH

SDCCH are always allocated in Underlaid Layer is allocated according the transmission delay of access burst

TCH

The receiving level

TA

They are included in MR of SDCCH CH on uplink reported by BTS

Factor of Handover between Under/Overlaid


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Internal Use49

Factor of Handover between Under/Overlaid

Normal Underlaid/Overlaid

Receiving level Time Advance

Quality

Enhanced Underlaid/Overlaid

Receiving level

Time Advance Quality

Traffic Load of Underlaid

Normal Overlaid/Underlaid HO


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Internal Use50

underlaid

overlaid

:

Division of underlaid and overlaid is decided by MS downlink receivelevel ,TA value and quality.


The quality boundary is elided in this figure



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Internal Use51

Criterion for HO from overlaid to underlaid: TA value => TA threshold + TA hysteresis OR

RX_LEV Qua. threshold

Satisfying P/N rule

Criterion for HO from underlaid to overlaid: TA value =< TA thresholdTA hysteresis AND

RX_LEV >=RX_LEV threshold + RX_LEV hysteresis AND

Qua. =


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Internal Use52

Criterion for HO from overlaid to underlaid: TA value => TA threshold + TA hysteresis OR

RX_LEV Qua. threshold

Satisfying P/N rule

Criterion for HO from underlaid to overlaid: TA value =< TA thresholdTA hysteresis AND

RX_LEV >= U to O level AND

Qua. =


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Internal Use53





Major HO Parameters Configuration


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Internal Use54

Major HO Parameters Configuration

Major HO parameter configuration

1.[Handover Control Table]

2.[Cell Description Table]

3.[Adjacent Cell Relation Table]

4.[Penalty Table]

5.[Emergency Handover Table]

6.[Load Handover Table]

7.[Normal Handover Table]

8.[Fast-Moving Handover Table]

9.[Concentric Cell Handover Table

Handover Control Table


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Internal Use55

Parameter

nameMeaning

Value

range

Recommend

value

Co BSC/MSC

Adj.

It means whether the 12 and 13 bits acts in the 16bit order.

Yes means handover in the same BSC/MSC is preferred.

No means that the 12 and 13 bits are shielded and set to0.

Yes,

NoYes

Penaltyallowed

It determines whether to punish the target cell of handover

failure, or the original served cell of handover upon too big TAor bad quality. The penalty measures can apply to cells in or

out of the same BSC

Yes,No

Yes

Load HO

allowed

It determines whether to perform the handover to share traffic

load. Load sharing can lower the channel assignment failure

ratio caused by cell congestion, so as to make evener

allocation of the service in respective cells, and lower the cell

congestion rate , and improve network performance. It on ly

applies in the same BSC or cells at the same level

Yes,

NoNo

MS Fast

moving HO

allowed

It determines whether to handle the fast moving MS with the

algorithm. It is only recommended in special a reas (such as a

highway), to lower CPU load. This algorithm should only be

used in suitable conditions, and usually it is not applied

Yes,

NoNo




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Internal Use56

Parameter

name

MeaningValue range

Recommended

value

RX _L evel Drop

HO allowed

It means whether RX _ Level Drop emergency

handover algorithm is allowed, handover the MS

which receiving signal level is dropping quickly in

advance to avoid potential call drop. This algorithm

should be applied in suitable conditions, and usually it

is not used. To apply the handover algorithm, BSC

must have original measurement report.

Yes, No No

PBGT HO

allowed

It means whether PBGT handover algorithm isallowed. PBGT handover algorithm currently is

processed on LAPD board. To avoid Ping -pang

handover, PBGT handover is only performed between

cells at the same layer and with the same priority, and

meanwhile it is only triggered on TCH.

Yes, No Yes

MS power

prediction afterHO

It means after a handover whether MS is to use

proper predicted transmitting power to access the

new channel. This can reduce system interferenceand improve service quality y (this parameter acts

when intra BSC handover occurs

Yes, No Yes




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Internal Use57

Parameter

nameMeaning

Value

range

Recommended

value

MR.

reprocessing

Yes means perform measurement report

preprocessing on BTS No means preprocessing on

BSC, then the two parameters of Send original

measurement report and Send BS/MS power level

do not act. Yes means decreasing of Abis interface

signaling and BSC load, and improving of network

response time performance. The switch determines

where to perform power control. When it is set to

Yes, power control is performed at BTS side. When

it is set to No, power control is performed at BSC

side. When setting this parameter, first be clear

whether BTS supports the power control algorithm to

set or not.

Yes, No Yes




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Internal Use58

Parameter

nameMeaning

Value range

Recommended

value

TransferOriginal MR.

It means whether to send the original measurement

report to BSC after measurement report preprocessing

on BTS. When it is set to Yes, BTS sends not onlyprocessed measurement rep ort but also original

measurement report to BSC.

Yes, No No

Transfer

BS/MS power

class

It means whether to send BS/MS power level from BTS

to BSC. This function is used to view the effect of power

control on BTS. Meanwhile, when preprocessing is

available , if BS/MS power level is not reported, the uplink

and downlink balance measurements will be affected,and handover types such as PBGT handover and

overlaid/underlaid handover needing power

compensation will be abnormal.

Yes, No Yes




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Internal Use59

Parameter

name Meaning

Value

range

Recommen

ded

value

Sent Freq. of

Preprocessed

MR.

It indicates the time interval at which a measurement reportis preprocessed at B TS side and sent to BSC the

Preprocessed measurement report. This parameter acts

only when Measurement t report preprocessing is enabled

For 15:1 link configuration, the report frequency should be

as low as once per second due to limited link resource. At

this time, for handover nee ding P/N judgment such as edge

handover, layer handover, PBGT handover and

overlaid/underlaid handover

Twice per

second,

Once

per

second

According to

Concrete

conditions


Cell Description Table


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Internal Use60

Parameter

nameMeaning

Value

range

Recommended

value

Layer of the

cell

Huawei hierarchical network structure is divided into 4 layers. 16 The

priorities can be set for each layer, which provides enough roomof network planning for the operator to adapt to various complex

network environment. Normally, Macro layer is the major 900 layers

layer, Micro layer is the major 1800 layer, Pico is the 900 and

1800 micro cell layer. The smaller layer value, the higher

priority.

1 ~4M900 : layer 3

M1800:Laye 2r

Cell priority

Each layer may have 16 priorities, used to control the handover

priority between cells at the same layer. Usually priorities of priorities

cells at the same layer are set the same. For cells at the samelayer, the smaller the priority value, the higher the priority

1~16 1

Layer HO

Thrsh.

It affects the value of the 14th bit in the 16bit ranking , and it is

also the level requirement on the target cell for interference

handover and load handover. Then such level

should be higher than layer handover threshold + layer

handover hysteresis. The layer handover threshold should be

set >= Edge handover threshold + Inter cell handover

hysteresis.

0 ~ 63 25

Layer HO

hysteresisWorks together with the Layer handover threshold. 0 ~ 63dB 3




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Internal Use61

Parameter

nameMeaning

Value

rangeRecommended

value

Penalty on

MS Fasting

moving HO

It is valid when the fast moving handover algorithm is

enabled . It is the signal level penalty value on the other

neighbor cells when MS moves fast and is handed over

To umbrella cell. The parameter is only valid within thepenalty time.

0~ 63dB 30

Penalty

Time on MS

Fasting

moving HO

It means that within this time, the penalty on the other

neighbor cells will be exerted after MS is handed over

to umbrella cell by fast moving HO.

0 ~ 255

seconds40

Min DL level

0n

Candidate

cell

This is the min signal level requirement for the cell itself

to be a candidate cell low configuration may easily

cause call drops, while too high a configuration might

turn handover too hard to occur.

0 ~ 63 15


Adjacent Cell Relation Table


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Internal Use62

Parameter

nameMeaning Value range

Recommended

value

Min access

level offset

This offset is based on Min downlink level of handover

candidate cell. Different offsets can be defined for different

adjacent cells, and to enter the candidate cell list, the

corresponding adjacent cell receiving signal level must be

higher than the sum of Min. downlink level of handover

candidate cell and Min. Access level offset.

0 ~ 63dB 0

PBGT HO

thrsh

It means that PBGT handover is performed when thedifference between the target cell downlink path loss and the

corresponding to

serving cell downlink path loss is bigger than PBGT handover

threshold. When PBGT handover is enabled, and Inter cell

handover hysteresis > PBGT handover threshold

(corresponding dB value), Intercell handover hysteresis

takes place of PBGT handover threshold to act. . PBGT

handover threshold also needs to be adjusted according to

handover performance statistics result

0~127

corresponding

--64~63dB

It is around 68 in the

densely populated

downtown, and

around 72 on the

outskirts.

Inter cell

HO

hysteresis

Handover hysteresis between an adjacent cell and the serving

cell. It is set to reduce Ping pang HO. The hysteresis value

also needs to be adjusted according to the handover

performance statistics result and live network. Flexible

configuration of the value can effectively lead handover and

traffic between two adjacent cells.

0 ~ 63db

It is around 4 in the

densely populated

downtown, and

around 8 on the

outskirts.

Adjacent Cell Relation Table

Penalty Table


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Internal Use63

Parametername Meaning Value range Recommendedvalue

Penalty level

after HO fail

The signal level value in dB, to punish the target cell

which has caused a HO failure due to problems such

as congestion , to prevent MS from a handover

attempt to that cell again. This value is only valid

within the penalty time for handover failure.

0 ~ 63 dB30

Penalty timeafter HO fail Penalty time on the corresponding target cell after secondshandover failure 0 ~ 60second 10

Penalty level

after BQ HO

fail

The signal level penalty value for the original serving

cell, to avoid Ping- pang handover after emergency

handover upon bad quality. It is only valid within the

penalty time for BQ HO.

0 ~ 63d B 63

Penalty time

after BQ HO

fail

Penalty time for the original serving cell after BQ HO. seconds 0 ~ 60second 10

Penalty Table

Penalty Table


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Internal Use64

Parameter

nameMeaning

Value

range

Recomm

ended

value

Eenalty

level after

TA HO fail

The signal strength penalty value for the original serving cell,

to avoid Ping - pang handover after TA emergency

handover. It is only valid within the penalty time for ta

handover

0 ~ 63d B 63

Penalty time

after TA HO

fail

Penalty time for the original serving cell after TA emergency

Seconds handover

0 ~

60second10

Penalty time

after IUO

HO fail

After an overlaid/underlaid handover failure (big circle hands Seconds over to

small circle or vice versa), within certain time (this Parameter configuration

value) overlaid/underlaid handover is forbidden for the same call

0 ~

16second10

y

Emergency Handover Table


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Internal Use65

g y

Parameter


Recommended

value

TA Thrsh. When TAthis value, emergency handover is triggered 0~63 bit period 63

DL QUAL.

Thrsh

The downlink receiving quality threshold for BQ emergency

handover. When frequency hopping or DTX is enabled, RQbecomes worse (normal phenomenon), this value should be

set to 70. The adjustment should also base on the current

network quality and handover statistics. When triggering

emergency handover, the first to select is the inter-cell

handover, the intra-cell handover is only triggered when there

is no candidate cell and the intra-cell handover is allowed in

the serving cell.

0~70,

corresponding

to BQ levels of

0~7

60

UL QUAL.Thrsh.

The uplink receiving quality threshold for BQ emergency HO.

corresponding

to BQ levels of0~7

60



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Internal Use66

Parameter


Recommended

value

ULQual.

Thrsh

for interf.

HO

Uplink receiving quality threshold in the serving cell for interference

handover. When frequency hopping or DTX is to enbaled , RQ

becomes worse (normal phenomenon), thisvalue should be set to 60. The adjustment should also base

on the current network quality and handover statistics. When

triggering interference handover. If the serving cell is in the

first position and intra cell handover is permitted, perform

intra cell handover . Otherwise select the second candidate

cell to perform inter cell handover.

corresponding

to BQ levels of

0~7

50, interference

quality thresholdmust be better

than

the emergency

quality threshold

DL Qual.

Thrsh. For

interf HO

Downlink receiving quality threshold in the serving cell for

interference handover.

0~70,corresponding

to BQ levels of

0~7

50

g y



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Internal Use67

Parameter

r nameMeaning

Value

rangeRecommended

value

ULRX_LEV

Thrsh. For

interf.HO

Min uplink receiving power threshold from the serving cell

required for interf. HO, when interference handover is

triggered if the uplink quality is worse than quality thresholdand at this time the uplink signal level is higher than the signal

threshold. When triggering interference handover, If the

serving cell is in the first position in the cell list, and intra cell

handover permitted , then start intra cell HO. Otherwise select

the second cell to perform intercell HO.

0 ~ 6 3 25

DL

RX_LEV

Thrsh. For

interf HO.

Min downlink receiving power threshold from the serving cell

required for interf. HO.0 ~ 63 30

g y



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Internal Use68

Parametername.

Meaning Valuerange

Recommen

dedvalue

Filter

ParametersA1~A8

Used for configuration of filter for rapid signal

drop judgment, and together with filter parameter

B, they are 9 parameters for a filter. The

corresponding formula is (in the program, A1~A8

is configuration value minus 10 and B is the

negative configuration value):

C1(nt)=A1C(nt)+A2C(nt-t)+A3C(nt2t)+

+A8C(nt-7t)

Where, C (nt) is the receiving signal level in the

uplink measurement report of the serving cell

sent at the time of nt. If C1 ( nt ) < B, and C (nt) is

below the edge handover threshold, then the

signal level is considered to be of rapid drop.

0 ~ 20 10

Filter

parameter B

Used for configuration of filter for rapid signal

drop judgment. Please refer to the explanation

for A1~A8 of filter.

0 ~255 0

g y

Load Handover Table


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Internal Use69

Parameter


Recommended

value

System flux

Thrsh. For

load HO

The pre condition for load HO is that the system flow (signaling

flow) is lower the threshold. This value can not be set too high

because load handover upon max threshold may cause serious

effect to the system.

0, 8~11 system

flow levels, to

corresponding

0, 70, 80, 90and 95.

10

Load HO

Thrsh

Load handover is triggered when the serving cell load is

than the threshold, TCH seized in the cell has reaching the

corresponding percentage.

0~7 cell load

levels,

Corresponding

to 0 , 50 , 60 , 70 ,

75, 80 , 85 , 90

5

Load Req.

on

candidate

cell

The Load threshold for the target cells that can accept MS from

serving cell in load HO, i.e. when the TCH under Idle mode in

the neigh bor cell is lower than the corresponding percentage

the cell refuses to accept MS from serving cell handed over due

to the load reason

0~7,

Corresponding

to 0 , 50 , 60 , 70 ,

75, 80 , 85 , 90

2

Load Handover Table


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Internal Use70

Parameter


Recomme

nded

value

Load HO

bandwidth

This configuration is related to the edge handover

threshold. Load handover is only allowed when the MS

receiving level from the serving cell is within the range ofmargin handover threshold, margin handover threshold +

load handover bandwidth

0~ 63db 25

Load HO

step

period

When a cell is up to conditions for load handover, all calls

within the serving cell will send handover request at the

same time, this will cause abrupt increase on processor

load, and under certain conditions this will cause the

target cell congestion and result in call drops. Thereby,

step by step load handover algorithm is used to controlhandover. The cycle is the time needed for handovers of

each step.

1~60 seconds 10

Load HO

step

level

The whole load HO bandwidth will be divided into several Sub-bands by

this parameter.1~ 63db 5

Normal Handover Table


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Internal Use71

Parameter

nameMeaning

Value

rangeRecommended value

Edge HO ULRX_LEV

Thrsh.

During the statistics time, if the time in which the uplink

receiving level is lower than the value is longer thancertain time called continuous time, edge handover

will be performed. If PBGT handover is enabled,

Corresponding edge handover threshold will be set

lower

0 ~ 63

25 (without PBGT

handover, downtown),15 (single station on

outskirts), 15 (with

PBGT handover,

downtown)

Edge HO DL

RX_LEV

Thrsh.

Downlink consideration for edge HO 63

30 (without PBGT

handover, downtown),

20 (single station onoutskirts), 20 (with

PBGT handover,

downtown)



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Internal Use72

Parameter


Recommended

value

Edge HO

watch time

It means that within the time statistics, if the

time in which the signal level is lower than

threshold is higher than the continuous time,

then margin HO is to be triggered

1 ~16 seconds 5

Edge valid

timeSee the above. 1 ~16 seconds 4



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Internal Use73

Parameter

name

Meaning Value rangeRecommended

value

Layer HO

watch timestatistics time for Layer HO judgment 1 ~ 16 seconds 5

Layer HO

valid time

Continuous time for Layer HO judgment 1 ~ 16 seconds 4

PBGT watch

timeStatistics time for PBGT HO signal level judgment. 1 ~ 16 seconds 5

PBGT valid

time

Continuous time for PBGT HO signal level judgment. 1 ~ 16 seconds4



71/99

Internal Use74

Parameter


Recommended

value

MS

Fast -moving

watch cells

The cell sum P for judge whether MS is fast moving.

The value, if too large, may cause abrupt increase of

system flow, while too small value may cause

inaccurate judgment for fast moving MS.

1~ 10 3

MS

Fastmoving

valid cells

The cell sum N by which MS actually quickly passes. If

within P cells that MS continuously past, the number of

cells by which the MS is judged to pass quickly is equal

to or more than N, then the MS will be judged as a fast

moving MS.

1~ 10 2

MSFastmoving

Time Thrsh.

The time threshold (2r/v) determined by the cell radius

(r) and moving speed (v). If the time in which MS secondspasses the cell is smaller than the threshold, then MS

is judged to quickly pass the cell.

1~ 225 15

Common Concentric Data


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Internal Use75

Parameter


Recommended

value

Assign

optimum

layer

In Overlaid/Underlaid, the following selection are available

for TCH assignment: (1) The system judges according to

the measurement report on SDCCH and assign to the

best sub-cell. (2) Select the overlaid first for TCH

assignment. (3) Select the underlaid first for TCH

assignment. (4) Do not give extra priority.

System

optimization,

overlaid ,

underlaid , no

preferential

System optimization

Assign-

optimum

level Thrsh.

If system optimization is selected, estimate (interpolate,

filter) current SDCCH level value through uplink

measurement value in the former SDCCH measurement

report, and compare with Assign-optimum Level

threshold, so as to assign overlaid or underlaid channel.

If SDCCH is in the overlaid : edge handover threshold +

signal intensity difference between underlaid and overlaid

+ uplink and downlink balance allowance + SDCCH andTCH difference allowance. If SDCCH is in the underlaid :

edge handover threshold + uplink and downlink balance

allowance + SDCCH and TCH difference allowance.

0~63



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Internal Use76

Parameter

nameMeaning

Value

range

Recommended

value

Pref. subcellin HO of

intra-BSC

When the cell is configured into a Overlaid/Underlaid, there

are two processing methods for incoming handover request

in BSC: (1) No special processing for channel assignment.

(2) Add BCCH signal level value of the target cell in inter-

cell handover request message to BSC to make BSC

allocate optimum channel for MS from underlaid or overlaid

Yes, No Yes

Incoming-to-

BSC HO

optimumlayer

If there is a incoming BSC HO, and the target cell is a

Overlaid/Underlaid, then, this parameter will show which

layer is preferred to provide service for the MS.

overlaid ,

underlaid ,

none

None



74/99

Internal Use77

Parameter

nameMeaning Value range Recommended value

RX_QUAL

Thrsh.

In case of Qual. Is worse than this value, MS handover

from overlay to underlay0--70 60

UO HO watch

timeP/N judgment statistics time for U/O HO judgment. 0 ~ 16 seconds 5

UO HO valid

timeP/N judgment continuous time for U/O HO judgment. 0 ~ 16 seconds 4

TA thrsh. Of

Assignment

Pref.

TA is more than this value, TCH in underlay will be

allocated0--63

According concrete

condition

TA Thrsh. OfImme-Assign

Pref.

TA is more than this value, SDCCH in underlay will be

allocated0--63

According concretecondition

TA Prfe. Of

Imme-Assign

Allowed

TA attend allocation of SDCCH or not Yes, No

According concrete

condition



75/99

Internal Use78

Parameter

nameMeaning Value range Recommended value

TA Thrsh.It must be bigger than TA emergency handover

threshold.

0~63 bit period,

with 1 bit period

corresponding to

0.55km

TA hysteresis Works with TA threshold. 0~63 bit period

UO HO watch

timeP/N judgment statistics time for U/O HO judgment. 0 ~ 16 seconds 5

UO HO valid

timeP/N judgment continuous time for U/O HO judgment. 0 ~ 16 seconds 4

Normal Concentric Data


76/99

Internal Use79

Parameter

name Meaning Value range Recommended value

RX_LEV

Thrsh

Rx level hysteresis, Receiving Quality Thrsh.,TA

threshold and TA hysteresis jointly define underlaid

area and overlaid area. It must be bigger than

edge handover threshold, and the recommended

value is: edge handover threshold + signal intensity

difference between underlaid and overlaid .

0~63 25

RX_LEV

hysteresisWorks with Rx threshold. 0~63 5

UO signal

intensitydifference

Transmitting Power at antenna difference between

underlaid and overlaid may cause MS receiving

signal intensity difference in underlaid and overlaid .

The parameter usually indicates the antenna EIRP

difference in dB between underlaid cell and overlaid

cell. According to field measurement, multi-point

measurement is necessary if the underlaid and

overlaid use different antenna.

0~63dBSet according to actual

conditions

Enhance IUO Data


77/99

Internal Use80

Parameter


Recommended

value

Enhance IUO

AllowedEnable function of Enhance IUO or not Yes, No

Set according to

actual conditions

UtoO Traffic

HO AllowedEnable traffic to be one condition of HO or not Yes, No

Set according to

actual conditions

OtoU HO

Received

Level Thrsh.

In case of receiving level in overlay is less than this

value, HO occurs from overlay to underlay0--63 25

UtoO HO

Received

Level Thrsh.

In case of receiving level in underlay is more than this

value, and traffic in underlay is more than Traffic Thrsh.

Of Underlay, HO occurs from underlay to overlay063 35

Concentric Cell Handover Table


78/99

Internal Use81

Parameter name Meaning Value rangeRecomm

ended

value

Traffic Thrsh. Of

Underlay

If the traffic in underlay is over this value, MS will

handover from under to overlay0100% 80

Underlay HO Step

Period

If there are some handover requests from under to

overlay at the same time, system will handover the call

with level firstly. This value determine period per step

1255s 5

Underlay HO Step

Level

It is the step that handover band decreases, used to

control the grade by grade handover band from underlay

to overlay with underlay HO step level

163dB 5

Penalty Time of

UtoO HO

To prevent ping-pong handover, the call cant be handed

over back within penalty time when a call is handed over

from underlay to overlay

0255s 10

HO data lookup process


79/99

Internal Use82

BA2 table defines BCCH frequencies of all neighbor cells. It is sent

to MS by system message 5, system message 5-bis and system

message 5ter on SACCH channel.

MS reports the serving cell and BCCH, BSIC and signal levels of 6

strongest neighbor cells to BSS. This is done through SACCH.

MR pre-process is done in BTS. Module number, cell number and

CGI of all neighbor cells are derived from Adjacent cell Relation

Table, and Cell Description Table (or External Cell Description

Table) through BCCH and BSIC in the MR.

HO data lookup process


80/99

Internal Use83

BSC performs HO judgment process, such as basic rank of cells

(completed in LAPD board). When BSC finds suitable target, It

sends HO request messages containing the target CGI to MPU of

BSC. According to CGI, MPU derive the module number of the cell

from Cell Module Information Table.

MPU sends a HO command message to the target module and

step up the inter-cell/ intra-cell HO requestcounter by one.


81/99

Internal Use84






82/99

Internal Use85


Section 1 Intra BSC Handover

Section 2 Intra MSC Handover

Section 3 Inter MSC Handover

Intra-BSC Handover Signaling process


83/99

Internal Use86

MS MSBTS1 BTS2BSC MSC

Measurement Report from MS

Channel_Active

Channel_Active ACK

HANDOVER COMMAND

Handover AccessHandover_Detect

PHY INFO

First SABM

Establish_IND

PHY INFO

Handover Complete

Handover_Performed



84/99

Internal Use87

Attention In asynchronous HO, if MS could not reach the new TCH

channel after the target cell has sent PHY INFO up to max

times, the target cell reports CONN FAIL IND to BSC with the

reason: HO access failure.

After the above message is received, BSC release the assigned

TCH channel in the target cell .

Max resend times of physical information*Radio link connection

timer > Time interval between EST IND and HO DETECT

(120~180ms). This is to make sure that the physical information

reach MS.



85/99

Internal Use88

MS BTS BTSBSC MSC

Measurement ReportMeasurement Report

Channel_Activate

Channel_Activate ACK

Handover Command (Old FACCH)

Handover Access (New FACCH)

Handover Complete (New FACCH)

RF Channel ReleaseHandover Performed

T09++

T12++

T10++

T13++

Attempted outgoing internal inter cell handovers

Attempted incoming internal inter cell handovers

Successful incoming internal inter cell handovers

Successful outgoing internal inter cell handovers

(Original) (Target)

Measurement Points of Intra BSC Handover


86/99

Internal Use89

Handover formula definition Internal inter cell radio handover success rate

=(Successful incoming internal inter cell handovers + Successful

outgoing internal inter cell handovers) / (Incoming internal inter cell

handovers + Outgoing internal inter cell handovers )

Internal inter cell handover success rate

=(Successful incoming internal inter cell handovers + Successfuloutgoing internal inter cell handovers) / (Attempted incoming internal

inter cell handovers + Attempted outgoing internal inter cell handovers)

Internal inter cell radio handover success rate >= Internal inter cell

handover success rate


87/99

Internal Use90





Intra-MSC HO Signaling process


88/99

Internal Use91

MS BTS BTSBSC1 BSC2MSC(original) (Target)

Measurement Report

Measurement ReportHandover Required

Handover Request

Channel_Active

Channel_Active_ACKHandover_Request_ACK

Handover Command

Handover Access

Handover Detect

Handover Complete

Handover Complete

Clear Command (HO Successful)

RF Channel Release

Clear Complete

Attempted outgoing interBSC inter cell handovers

Attempted incoming interBSC inter cell handovers

Successful incoming inter BSC handovers

Successful outgoing interBSC inter cell handovers


89/99

Internal Use93





Signaling process between MSC


90/99

Internal Use94

MSC-BMSC-A VLR-BBSC-A BSC-B

HO-REQUIREDMAP_Prepare_HO

MAP_Prepare_HO_ACK

MAP_Allocate_HO_NUM

MAP_Send_HO_Report

MAP_Send_HO_Report_ACK

MS

HO-REQUEST

HO-REQUEST-ACK

HO-Command

MS

HO-AccessMAP_Process_Access_Signalling

HO-CompleteMAP_Send_End_Signal

Clear-Command

Clear-Complete

MAP_Send_End_Signal_ACK

Some intermediate steps are omitted

IAI

ACM

Signaling process between MSC


91/99

Internal Use95

MSC-BMSC-A VLR-BBSC-A BSC-B

HO-REQUIREDMAP_Prepare_HO

MAP_Prepare_HO_ACK

MAP_Allocate_HO_NUM

MAP_Send_HO_Report

MAP_Send_HO_Report_ACK

MS

HO-REQUEST

HO-REQUEST-ACK

HO-Command

MS

HO-AccessMAP_Process_Access_Signalling

HO-Complete

MAP_Send_End_SignalClear-Command

Clear-Complete

MAP_Send_End_Signal_ACK

Some intermediate steps are omitted

IAI

ACM

Inter-MSC HO Signaling process


92/99

Internal Use96

Signaling processAbnormal conditions The following conditions will cause HO failure

MSC-B fails to identify the target cell.

MSC-B does not allow HO to the indicated target cell.

The target cell has no channel available.

VLR-B has no HO number available.HO error or unsuitable data.

Inter MSC HOSubsequent HO process


93/99

Internal Use97

Roaming

E

MS

MSCa MSCbMSCb'

VLRbVLRb'

BSS2

BSS2'

Radio transmission signal measurementHO REQUIRED (target cell table)

Perform subsequent HO(MAP) (target cell ID, serving cell ID, MSC number)

Perform HO

(target cell ID, serving cell ID, channel type)HO REQUEST (PCM&Channel type)

HO REQUEST ACKNOWLmargin (including New TCH number and HO number)

Allocate HO number

Send HO report(HON)Radio channel ack. (MAP) (includes New TCH number and HON)

IAI

ACM

Subsequent HO ack.

HO COMMAND HO DETECT

HO COMPLETESend end signal (MAP)

ANS

End signal (MAP)Release HO report Release HON

CLEAR COMMAND

CLEAR COMPLETERelease (TUP)

Cut physical connection between MSCa and MSCb

End signal (MAP)

Release (TUP/ISUP)

Release HO report Release HON

Cut physical connection between MSCAa and MSCb'

~~~~

MS

Inter MSC HOSubsequent HO process


94/99

Internal Use98

Highway

MSC-AMSC-C

MSC-B MSC-C

Subsequent HO

Inter MSC HO Signaling process


95/99

Internal Use99

Statistics countersame asIntra MSC HO, Statistics is

handled by BSC

HO formula-- same as Intra

MSC HO

Major differences


96/99

Internal Use100

There is no HO request information for intra-BSC HO, and all of the HO

are analyzed and processed in BSC. Once the target cell as required is

found in the BSC, Channelactivationinformation is sent to it directly.

When the target cell is not in the same BSC, BSC reports CGI numbers ofthe serving cell and target cell, and HO cause to MSC through Ho-

Required. When MSC finds the LAC of the target cell is in the MSC, it

sends Ho-Request to the BSC of the target cell, and the target BSC

activates the target cell channel to complete the following procedure.

When MSC finds that the target cell LAC does not belong to the MSC, it will

query its LAI and GCI Table (including LAC and router address of theadjacent MSC), and send Prepare-HO message to the target MSC-B

according to the router address. The message includes CGI of the target

cell and indication whether or not to allocate HO number, etc. According to

the message, the target MSC-B sends HO-Requestmessage to the target

BSC-B after demanding HO number (unless it is not required in the

indication) from VLR-B, and sends Prepare-HO acknowledgement to

serving MSC after received HO-Requestacknowledgement,to execute thenext procedure.

Major differences


97/99

Internal Use101

Inter BSC HO transfers HO-REQmessage through MSC, with CGI of the

serving cell and target cell carried in the message.

Intra BSC HO does not have any CGI in any messages, it is handled inside

BSC.

Intra BSC HO only sends HO-Performedto MSC upon completion of HO,

and MSC is not involved before that time.

In inter BSC HO, MSC is involved since the HO request .

Summary


98/99

Internal Use102

In this course, we have learned:

Classify of handover

Judgment and Ranking step Handover Data Configuration

Handover signaling Flow

Summary


99/99

huawei gsm handover algorithm i 20100625

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