huawei gsm handover algorithm i

Huawei Confidential. All Rights Reserved

OMF010002 Handover

ISSUE 2.0

2 Internal Use

Handover is key technology of Mobile

communication system and make

continued conversation possible.

Handover algorithm in Huawei product

is flexible and powerful

3 Internal Use

ObjectivesObjectives

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

4 Internal Use

Chapter 1 Chapter 1 Introduction of HandoverIntroduction of Handover

Chapter 2 HO Algorithm process

Chapter 3 HO Data Configuration

Chapter 4 HO Signaling process

5 Internal Use

Purposes of HOPurposes of HO

To keep a continuous communication with a moving MS To improve network service performanceTo reduce the call drop rateTo reduce the congestion rate

6 Internal Use

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 ReasonClassification by ReasonClassification by ReasonClassification by Reason

7 Internal Use

Classification by SynchronizationClassification by Synchronization

Synchronous handover: source and target cell belong the same BTS

Asynchronous handover: source and target cell belong the different BTS

8 Internal Use

Chapter 1 Introduction of Handover

Chapter 2 Chapter 2 HO Algorithm processHO Algorithm process



9 Internal Use


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

10 Internal Use

General process of HO AlgorithmGeneral process of HO Algorithm

M.R.preprocessing

Penalty processing

Basic ranking

Secondary ranking

HO judgment

TA emergency HO

BQ emergency HO

RSD emergency HO

Interf. emergency HO

Load Sharing HO

Edge HO

Layer HO

PBGT HO

Processing program

OM forced HO

Directed retry

Overlaid/underlaid HO

Fast moving MS HO

1

1

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12 Internal Use

Measurement ReportMeasurement 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 downlink measurement report of the serving cell

The uplink measurement report of MS

The downlink measurement reportof the neighbour cell (BCCH)

13 Internal Use

Measurement ReportMeasurement Report

14 Internal Use

Period of 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

15 Internal Use

MR interpolation 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 MR amount is within the allowed range, then recovers the lost MR according to the algorithm.

16 Internal Use

MR MR MR MR MR

Measurement report No. n

Measurement report No. n+

Continuous MR flow

How to interpolate MR?How to interpolate MR?

17 Internal Use

Filter----Average several continuous MR.

MR MR MR MR MR MR

Continuous MR flow

filteringfiltering

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19 Internal Use

Penalty ProcessingPenalty Processing

There are altogether four types of penalty process (second step of HO 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 HO

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

overlaid/underlaid HO fails.

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BTS

HO failure

BSC

Cell A

Cell B

Penalty on the Target Cell Penalty on the Target Cell

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

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BTS

BQ& TA HO

BSC

Cell A

Cell B

Penalty on the Source CellPenalty on the Source Cell

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

22 Internal Use

Back? No way!Back? No way!

Umbrella

Micro cell

penalty on Non-umbrella Layer 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 and avoid frequent HO.

23 Internal Use

Underlaid

Overlaid Do not attempt

again after a failed HO!

Penalty on Overlaid/underlaid CellPenalty 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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25 Internal Use

Procedure of RankingProcedure of Ranking

Basic ranking and secondary ranking of cells are major parts of the HO 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

26 Internal Use

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))+ OFFSETPa(0) : MS_TXPWR_MAX(0) – PPa(n) : MS_TXPWR_MAX(n) – PMS_TXPWR_MAX( ) : The appointed MS transmitting power by

the BSS.P : Max_Power_of_MSMax_Power_of_MS : MS maximum transmitting power

M rule M rule

27 Internal Use

After the M rule , the serving cell and candidate neighbor cells are ranked in 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 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.

K rule CriterionK rule CriterionK rule CriterionK rule Criterion

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

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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 of the 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 hysteresisThe 4th bit: determined by HO hysteresisThe 4th bit: determined by HO hysteresisThe 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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The 5th—10th bit: determined by Layer The 5th—10th 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

30 Internal Use

GSM Cell

Micro Cell

Umbrella Cell GSM

GSM GSMGSM

GSM GSM GSM

GSMGSM

GSMGSM

GSMGSM

GSMGSM

GSM Cell

Hierarchical cell structureHierarchical cell structure

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The 11th bit: determined by The 11th bit: determined by loadload

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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The 12th/13th bit: determined by The 12th/13th bit: determined by co-BSC/MSCco-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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The 14th bit: determined by Layer HOThe 14th bit: determined by Layer HO

The 14th bit: Layer HO threshold adjustment bit Serving cell criterion

Receive level >= layer HO threshold – layer HO hysteresis, bit 14th is set to 0. At the same time, bit 13th, 12th and 10th—5th 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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The 14th bit: determined by Layer HOThe 14th bit: determined by Layer HO

Neighbor cell criterion Receive level >=layer HO threshold + layer HO hysteresis, bit 14th is set

to 0. At the same time, bit 13th, 12th and 10th—5th 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 the

value of that individual cell’s value. Usual situation : When the neighbor cells are of the same layer, each of

the neighbor cell’s 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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The 15th bit: determined by Cell TypeThe 15th bit: determined by Cell Type

The 15th bit: Bit value is decided by cell typeServing cell or Neighbor cells:When cell type is extension cell 1.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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37 Internal Use

Types of HOTypes 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

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TA&Bad Quality HOTA&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.

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Rx_Level_Drop HORx_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.

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Interference HOInterference 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.

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Cell Load HOCell 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

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Edge HOEdge HO

Edge HO Criterion: In N seconds, when there are P seconds that neighbor cell’s

DL or MS’s UL 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.

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Layer HOLayer 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 cell’s.

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PBGT HOPBGT HO

PBGT HO Criterions : Target cell’s path loss is smaller than the serving cell’s 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.

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Fast-Moving HOFast-Moving HO

When the serving cell is micro cell : When the MS has traveled through P numbers of cell, and there

are Q (=<P) numbers of cell that the MS has traveled in high speed, the criteria is satisfied. MS will be handed over to umbrella cell.

When the serving cell is umbrella cell : When the MS is traveling high speed in umbrella cell, a greater

penalty can be given to the micro cell for a duration of time (penalty time). In this way, the MS will not use the micro cell. Note :In this case, the micro cell is only used under urgency conditions( Poor TA and BQ ).

46 Internal Use

Overlaid/Underlaid CellOverlaid/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

47 Internal Use

Overlaid/Underlaid CellOverlaid/Underlaid Cell

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

48 Internal Use

How to Allocate SDCCH/TCH?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

49 Internal Use

Factor of Handover between Under/OverlaidFactor 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

50 Internal Use

underlaid

overlaid

:

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

Normal Overlaid/Underlaid HONormal Overlaid/Underlaid HONormal Overlaid/Underlaid HONormal Overlaid/Underlaid HO

The quality boundary is elided in this figure

51 Internal Use

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

RX_LEV <= RX_LEV threshold － RX_LEV hysteresis OR

Qua. =>Qua. threshold Satisfying P/N rule

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

RX_LEV >=RX_LEV threshold + RX_LEV hysteresis AND

Qua. =<Qua. threshold Satisfying P/N rule

Normal Overlaid/Underlaid HONormal Overlaid/Underlaid HONormal Overlaid/Underlaid HONormal Overlaid/Underlaid HO

52 Internal Use

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

RX_LEV <= O to U level OR

Qua. =>Qua. threshold Satisfying P/N rule

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

RX_LEV >= U to O level AND

Qua. =<Qua. Threshold If the box “U to O HO traffic threshold” is checked, just in the

condition that underlaid load is more than this threshold, U to O handover based on previous conditions can be triggered

Satisfying P/N rule

Enhance Overlaid/Underlaid HOEnhance Overlaid/Underlaid HOEnhance Overlaid/Underlaid HOEnhance Overlaid/Underlaid HO

53 Internal Use



Chapter 3 Chapter 3 HO Data ConfigurationHO Data Configuration


54 Internal Use

Major HO Parameters ConfigurationMajor 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

55 Internal Use

Parametername

Meaning Value range

Recommend value

Co BSC/MSCAdj.

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 to”0.

Yes, No Yes

Penaltyallowed

It determines whether to punish the target cell of handover failure, or the original served cell of handover upon too big TA or bad quality. The penalty measures can apply to cells in or out of

the same BSC

Yes, No Yes

Load HOallowed

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, No No

MS Fastmoving 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, No No

Handover Control TableHandover Control Table

56 Internal Use

Parameter name Meaning Value range Recommended value

RX _L evel DropHO allowed

It means whether RX _ Level Drop emergencyhandover algorithm is allowed, handover the MSwhich receiving signal level is dropping quickly in

advance to avoid potential call drop. This algorithmshould 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 HOallowed

It means whether PBGT handover algorithm is allowed. PBGT handover algorithm currently is processed on LAPD board. To avoid Ping -pang

handover, PBGT handover is only performed betweencells at the same layer and with the same priority, and

meanwhile it is only triggered on TCH.

Yes, No Yes

MS powerprediction after

HO

It means after a handover whether MS is to use proper predicted transmitting power to access thenew channel. This can reduce system interferenceand improve service quality y (this parameter acts

when intra BSC handover occurs

Yes, No Yes


57 Internal Use

Parameter name

Meaning Value range Recommended value

MR.reprocessing

“Yes” means perform measurement reportpreprocessing 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 interfacesignaling 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. Whenit is set to “No”, power control is performed at BSC

side. When setting this parameter, first be clearwhether BTS supports the power control algorithm to

set or not.

Yes, No Yes


58 Internal Use

Parametername

Meaning Value range Recommendedvalue

TransferOriginal MR.

It means whether to send the original measurementreport 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

TransferBS/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 isavailable , 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


59 Internal Use

Parametername


Sent Freq. ofPreprocessed

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 enabledFor 15:1 link configuration, the report frequency should beas 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 persecond, Once

per second

According to Concreteconditions


60 Internal Use

Parametername

Meaning Valuerange

Recommended value

Layer of thecell

Huawei hierarchical network structure is divided into 4 layers. 16 Thepriorities 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 higherpriority.

1 ~4 M900 : layer 3M1800: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 HOThrsh.

It affects the value of the 14th bit in the 16bit ranking , and it isalso 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 beset >= Edge handover threshold + Inter cell handover

hysteresis.

0 ~ 63 25

Layer HOhysteresis

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

Cell Description TableCell Description Table

61 Internal Use

Parametername


Penalty onMS Fastingmoving HO

It is valid when the fast moving handover algorithm isenabled . It is the signal level penalty value on the otherneighbor cells when MS moves fast and is handed overTo umbrella cell. The parameter is only valid within the

penalty time.

0~ 63dB 30

PenaltyTime on MS

Fastingmoving HO

It means that within this time, the penalty on the otherneighbor cells will be exerted after MS is handed over

to umbrella cell by fast moving HO.

0 ~ 255seconds

40

Min DL level 0n

Candidatecell

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 mightturn handover too hard to occur.

0 ~ 63 15

Cell Description TableCell Description Table

62 Internal Use

Parametername


Min accesslevel 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 HOthrsh

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

corresponding toserving 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 thedensely populated

downtown, andaround 72 on the

outskirts.

Inter cell HOhysteresis

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 handoverperformance statistics result and live network. Flexible

configuration of the value can effectively lead handover andtraffic between two adjacent cells.

0 ~ 63db It is around 4 in the densely populated

downtown, andaround 8 on the

outskirts.

Adjacent Cell Relation TableAdjacent Cell Relation Table

63 Internal Use

Parameter name


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 handoverattempt to that cell again. This value is only valid

within the penalty time for handover failure.

0 ~ 63 dB 30

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 timeafter BQ HO

fail

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

Penalty TablePenalty Table

64 Internal Use

Parameter name

Meaning Value range Recommended

value

Eenaltylevel afterTA 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 ~ 60second 10

Penalty time after IUOHO 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 ~ 16second 10

Penalty TablePenalty Table

65 Internal Use

Emergency Handover Table Emergency Handover Table

Parameter name


TA Thrsh. When TA≥this 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, RQ

becomes 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 of 0~7

60

66 Internal Use

Parametername


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), this value 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 thefirst 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, interferencequality threshold

must 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

Emergency Handover TableEmergency Handover Table

67 Internal Use

Parameterr name


ULRX_LEV Thrsh. Forinterf.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 theserving 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

DLRX_LEV Thrsh. Forinterf HO.

Min downlink receiving power threshold from the serving cell required for interf. HO.

0 ~ 63 30


68 Internal Use

Parametername.


FilterParameters

A1~A8

Used for configuration of filter for rapid signaldrop judgment, and together with filter parameter

B, they are 9 parameters for a filter. Thecorresponding formula is (in the program, A1~A8

is configuration value minus 10 and B is thenegative configuration value):

C1(nt)=A1×C(nt)+A2×C(nt-t)+A3×C(nt － 2t)++A8×C(nt-7t)

Where, C (nt) is the receiving signal level in theuplink measurement report of the serving cell

sent at the time of nt. If C1 ( nt ) < B, and C (nt) isbelow the edge handover threshold, then thesignal level is considered to be of rapid drop.

0 ~ 20 10

Filterparameter B

Used for configuration of filter for rapid signaldrop judgment. Please refer to the explanation

for A1~A8 of filter.

0 ~255 0


69 Internal Use

Parametername


System flux Thrsh. Forload 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 seriouseffect to the system.

0, 8~11 system flow levels, to

corresponding 0, 70, 80, 90

and 95.

10

Load HOThrsh

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,

Correspondingto 0 , 50 , 60 , 70 ,

75, 80 , 85 , 90

5

Load Req. oncandidate 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 TableLoad Handover Table

70 Internal Use

Load Handover TableLoad Handover Table

Parametername

Meaning Value range Recommended

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 stepperiod

When a cell is up to conditions for load handover, all calls within the serving cell will send handover request at thesame time, this will cause abrupt increase on processor

load, and under certain conditions this will cause thetarget cell congestion and result in call drops. Thereby,step by step load handover algorithm is used to control

handover. The cycle is the time needed for handovers ofeach step.

1~60 seconds 10

Load HO steplevel

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

1~ 63db 5

71 Internal Use

Normal Handover TableNormal Handover Table

Parametername

Meaning Value range

Recommended value

Edge HO UL RX_LEV Thrsh.

During the statistics time, if the time in which the uplinkreceiving 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 PBGThandover, downtown),15 (single station onoutskirts), 15 (withPBGT handover,

downtown)

Edge HO DLRX_LEV Thrsh.

Downlink consideration for edge HO 63 30 (without PBGThandover, downtown),20 (single station onoutskirts), 20 (withPBGT handover,

downtown)

72 Internal Use

Normal Handover Table Normal Handover Table

Parameter name


Edge HOwatch 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 validtime

See the above. 1 ~16 seconds 4

73 Internal Use


Parametername


Layer HOwatch time

statistics time for Layer HO judgment 1 ~ 16 seconds 5

Layer HOvalid time

Continuous time for Layer HO judgment 1 ~ 16 seconds 4

PBGT watchtime

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

PBGT validtime

Continuous time for PBGT HO signal level judgment. 1 ~ 16 seconds 4

74 Internal Use


Parametername


MSFast -movingwatch 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 causeinaccurate judgment for fast moving MS.

1~ 10 3

MS Fast –moving

valid cells

The cell sum N by which MS actually quickly passes. If within P cells that MS continuously past, the number ofcells by which the MS is judged to pass quickly is equalto or more than N, then the MS will be judged as a fast

moving MS.

1~ 10 2

MS Fast –movingTime Thrsh.

The time threshold (2r/v) determined by the cell radius (r) and moving speed (v). If the time in which MS seconds

passes the cell is smaller than the threshold, then MSis judged to quickly pass the cell.

1~ 225 15

75 Internal Use

Common Concentric Data Common Concentric Data

Parameter name


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 and TCH difference allowance. If SDCCH is in the underlaid : edge

handover threshold + uplink and downlink balance allowance + SDCCH and TCH difference allowance.

0~63

76 Internal Use

Common Concentric DataCommon Concentric Data

Parametername


Pref. subcell in 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

optimum layer

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

77 Internal Use



RX_QUAL Thrsh. In case of Qual. Is worse than this value, MS handover from overlay to underlay

0--70 60

UO HO watch time

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

UO HO valid time

P/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 allocated 0--63 According concrete condition

TA Thrsh. Of Imme-Assign Pref.

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

0--63 According concrete condition

TA Prfe. Of Imme-Assign Allowed

TA attend allocation of SDCCH or not Yes, No According concrete condition

78 Internal Use



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 time

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

UO HO valid time

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

79 Internal Use

Normal Concentric DataNormal Concentric Data

Parameter name


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 hysteresis

Works with Rx threshold. 0~63 5

UO signal intensity

difference

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.

0~63dB Set according to actual conditions

80 Internal Use

Enhance IUO DataEnhance IUO Data

Parameter name


Enhance IUO Allowed

Enable function of Enhance IUO or not Yes, No Set according to actual conditions

UtoO Traffic HO Allowed

Enable 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 underlay

0--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 overlay

0—63 35

81 Internal Use

Concentric Cell Handover TableConcentric Cell Handover Table


Traffic Thrsh. Of Underlay

If the traffic in underlay is over this value, MS will handover from under to overlay

0—100% 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

1—255s 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”

1—63dB 5

Penalty Time of UtoO HO

To prevent ping-pong handover, the call can’t be handed over back within penalty time when a call is handed over

from underlay to overlay

0—255s 10

82 Internal Use

HO data lookup process HO data lookup process

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.

83 Internal Use

HO data lookup processHO data lookup process

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 request’ counter by one.

84 Internal Use




Chapter 4 Chapter 4 HO Signaling processHO Signaling process

85 Internal Use


Section 1 Intra BSC Handover

Section 2 Intra MSC Handover

Section 3 Inter MSC Handover

86 Internal Use

Intra-BSC Handover Signaling processIntra-BSC Handover Signaling process

MS MSBTS BTSBSC MSC

Measurement Report from MS

Channel_Active

Channel_Active ACK

HANDOVER COMMAND

Handover Access

Handover_DetectPHY INFO

First SABMEstablish_IND

PHY INFO

Handover Complete

Handover_Performed

87 Internal Use

Intra-BSC Handover Signaling processIntra-BSC Handover Signaling process

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.

88 Internal Use

MS BTS BTSBSC MSCMeasurement Report

Measurement Report

Channel_Activate

Channel_Activate ACK

Handover Command (Old FACCH)

Handover Access (New FACCH)

Handover Complete (New FACCH)

RF Channel ReleaseHandover Performed

T ++T ++

T ++T ++

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)

Intra-BSC Handover Signaling processIntra-BSC Handover Signaling processIntra-BSC Handover Signaling processIntra-BSC Handover Signaling process

89 Internal Use

Measurement Points of Intra BSC HandoverMeasurement Points of Intra BSC Handover

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 + Successful

outgoing 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

90 Internal Use





91 Internal Use

MS BTS BTSBSC BSCMSC(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 ReleaseClear Complete

Attempted outgoing interBSC inter cell handovers

Attempted incoming interBSC inter cell handovers

Successful incoming inter BSC handovers

Successful outgoing interBSC inter cell handovers

Intra-MSC HO Signaling processIntra-MSC HO Signaling process

92 Internal Use

Channel Release processChannel Release process

MS BTS BSC MSCDisconnect

Release

Release Complete

Clear_CMD

Clear_CMPChannel Release

Deactive_SACCHFirst DISC

UA

Release_IND

RF_Release_REQ

RF_Release_REQ_ACK

93 Internal Use





94 Internal Use

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

HO-REQUIRED MAP_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

IAIACM

Signaling process between MSCSignaling process between MSC

95 Internal Use

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

HO-REQUIRED MAP_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

IAIACM

Signaling process between MSCSignaling process between MSCSignaling process between MSCSignaling process between MSC

96 Internal Use

Inter-MSC HO Signaling processInter-MSC HO Signaling process

Signaling process – Abnormal conditions The following conditions will cause HO failureMSC-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.

97 Internal Use

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 HO—Subsequent HO processInter MSC HO—Subsequent HO process

98 Internal Use

Highway

MSC-AMSC-C

MSC-B MSC-C

Inter MSC HO—Subsequent HO processInter MSC HO—Subsequent HO process

Subsequent HO

99 Internal Use

Inter MSC HO Signaling processInter MSC HO Signaling process

Statistics counter—same as Intra MSC HO, Statistics is handled by BSC

HO formula-- same as Intra MSC HO

100 Internal Use

Major differences Major differences

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, “Channel activation” information is sent to it directly.

When the target cell is not in the same BSC, BSC reports CGI numbers of the 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 the adjacent 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-Request” message 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-Request acknowledgement”, to execute the next procedure.

101 Internal Use

Major differencesMajor differences

Inter BSC HO transfers “HO-REQ” message 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-Performed” to MSC upon completion of HO, and MSC is not involved before that time.

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

102 Internal Use

SummarySummary

In this course, we have learned: Classify of handover Judgment and Ranking step Handover Data Configuration Handover signaling Flow

SummarySummary

huawei gsm handover algorithm i

Documents

ho algorithm processchapter

general ho processsection

ho data configuration

handover algorithm

internal usehandover

flow4 internal usechapter

ms ho1111 internal usechapter

handover data master