Handover Issue.ppt

7/30/2019 Handover Issue.ppt

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Handover

Issue


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Upon completion this course, you will beable 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 and target cell

belong the same BTS Asynchronous handover: source and target cell

belong the different BTS


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1.1 General HO process

1.2 Measurement report preprocessing

1.3 Penalty processing

1.4 Basic ranking and Secondary ranking

1.5 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 MSHO

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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MRMR

MR MRMR

Measurementreport No. n

Measurement rNo. n+4

ContinuousMR

flow

How to interpolate MR?


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Penalty processing There are altogether four types of

penalty process (second step of HO

algorithm process )

Penalty on the target cell when a HOfails.

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


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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 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 cell

Punish the original serving cell when an

emergency HO ( due to BQ and TA) occurs.


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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 MSstaying in the umbrella cell and avoid

frequent HO.


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Underlaid

Overlaid Do not

attemptagain after a

failed HO!

Penalty on overlaid/underlaid

cellA new Overlaid/underlaid HO is prohibited

within a penalty time after an

Overlaid/Underlaid HO failure.


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GSM900

Cell

Micro Cell

Umbrella

CellGSM 900

GSM1800 GSM1800GSM1800

GSM 900 GSM 900 GSM 900

GSM900GSM900

GSM1800GSM1800

GSM900 GSM900

GSM1800 GSM1800

GSM1800

Cell

Hierarchical cell structure


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Types of HO

Emergency HO

TA HOBQ HO

interference HO

Rx_Level_Drop HO Load HO

Normal HO

Edge HO, layer cell HO and PBGT


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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


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Rx_level_drop HO

Rx_Level_Drop HO

Due to downlink signal level drop

Triggered upon detecting rapid level dropduring MS busy mode.

Requirements for the target cell:

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


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Interference HO

Interference HO (DL&UL) :

When the receiving level > receiving

threshold level. But Receiving quality Load HO threshold

Requirements for the target cell

Load of target cell < Load HO thresholdBTS

BSC


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Edge HO Edge HO Criterion:

In N seconds, when there are P seconds that

neighbor cells DL or MSs UL signal level is

lower than the Edge HO threshold. Then thecriterion 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 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.


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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 theserving cell.

Note :

PBGT HO can only occur between same-


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Fast-moving HO

When the serving cell is micro cell :

When the MS has traveled through P

numbers of cell, and there are Q (=


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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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Overlaid/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


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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


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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


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underlaid

overlaid

:

Division of underlaid and overlaid is decidedby MS downlink receive level ,TA value and

quality.

Normal overlaid/underlaid HO

The quality boundary is elided in this figure


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1.1 Intra BSC Handover

1.2 Intra MSC Handover

1.3 Inter MSC Handover


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Intra-bsc handover signaling

processMS MSBTS1 BTS2BSC MSCMeasurement Report from MS

Channel_Active

Channel_Active ACK

HANDOVER COMMANDHandover Access

Handover_DetectPHY INFO

First SABM

Establish_IND

PHY INFO

Handover Complete

Handover_Performed


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Intra-bsc handover signaling process

Attention

In asynchronous HO, if MS could not reach

the new TCH channel after the target cell hassent 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, BSCrelease the assigned TCH channel in the

target cell .

Max resend times of physical

information*Radio link connection timer >


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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

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)

Intra-bsc handover signaling process

Measurement points of intra BSC


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Measurement 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 intercell handovers )

Internal inter cell handover success

rate

=(Successful incoming internal inter


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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


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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


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Inter-msc HO signaling process

Signaling process Abnormal 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.


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Roaming

EMS

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 COMPLETE

Send 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


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Highway

MSC-AMSC-C

MSC-B MSC-C

Inter MSC hosubsequent HO process

Subsequent HO


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Inter MSC HO signaling process

Statistics countersame as Intra MSC HO,

Statistics is handled by BSC

HO formula-- same as Intra MSC HO


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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


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Major 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.


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Summary

In this course, we have

learned:

Classify of handover

Judgment and Ranking

step

Handover Data

Configuration

Handover signaling Flow

Summary

Handover Issue.ppt

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