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GSM RNO & RNP Training

1HUAWEI Mexico Training Center

www.huawei.com

Copyright 2006 Huawei Technologies Co., Ltd. All rights reserved.

Handover

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Page2Copyright 2006 Huawei Technologies Co., Ltd. All rights reserved.

Foreword

Handover is a 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 of this course, you will be able to:

Understand the types of handover.

Master handover judgment flow.

Configure handover data.

Master handover signaling flow.

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Contents

1. Introduction of Handover

2. HO Algorithm Process

3. HO Data Configuration

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

Handover can maintain the communication continuity of MS which moves across different

cells and lower the call drop rate and provide better communication service.

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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

Fast moving MS HO (Speed-sensitive 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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Contents





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Contents


2.1 General HO Process

2.2 Measurement Report Preprocessing

2.3 Penalty Processing

2.4 Basic Ranking and Secondary Ranking

2.5 Condition of Handover

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General Process of HO AlgorithmM.R.

preprocessing

Penaltyprocessing

Basic ranking

Secondaryranking

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

All the network element will be involved in the HO process, including BTS, BSC and MSC.

MS--Responsible for measurement report of the serving cell and neighbor cells.

BTS--Responsible for monitoring of uplink received level and quality of each served MS, and

monitoring of the interference level on its idle traffic channel.

BSC--Processing the measurement report and making handover judgment.

MSC--Participating in the confirmation of target cell in inter-BSC handover.

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Contents







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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 Neighbor cell

The downlinkmeasurement report

of the serving cell

The uplink measurementreport of MS

The downlink measurement reportof the neighbor cell (BCCH)

In dedicated mode, the system performs handover and power control judgment based on

measurement reports. The downlink MR are reported to the network via uplink SACCH

channel.

Downlink--In dedicated mode, MS reports MR via uplink SACCH channel periodically. The

report includes the receiving level, received quality, TA, power class and whether DTX isused. At the same time, MS will perform pre-synchronization to neighbor cell defined by the

system to obtain BCCH frequencies and BSIC, measure their received signal level and

report the six max. neighbor cells with the highest received signal level.

Uplink--The uplink measurement report is measured by BTS, including the receiving level

and receiving quality from the MS.

Both parts are sent by BTS to BSC for further processing at the same time.

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Measurement Report

There are two values in the measurement report: FULL MR and SUB MR.

FULL--Averaging 100 TCH bursts (except the four idle frames in the four 26-multiframes)

SUB--Averaging 12 bursts (four SACCH bursts and eight TCH bursts in specific position).

SUB should be selected when the Discontinuous Transmission (DTX) function is activated.

RXQUAL level in M R Huawei value BER behind

0 0 Less than 0.2%

1 10 0.2% ~ 0.4%

2 20 0.4% ~ 0.8%

3 30 0.8% ~ 1.6%

4 40 1.6% ~ 3.2%5 50 3.2% ~ 6.4%

6 60 6.4% ~ 12.8%

7 70 Greater than 12.8%

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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

SACCH is a bidirectional channel.

It sends the downlink measurement report to BTS in uplink SACCH.

It sends SYS.INFO. 5 and SYS. INFO. 6 to MS in downlink SACCH.

1. The SACCH measurement report period varies with the channel

occupied by MS in dedicated mode.

2. When associated with SDCCH, SACCH measurement period is 470ms,

this is because there is an entire SACCH message block in 2 SDCCH

51-multiframes.

3. When associated with TCH, SACCH measurement period is 480ms, this

is because there is an entire SACCH message block in 4 TCH 26-

multiframes

A complete measurement report is formed by four consecutive SACCH bursts. In SDCCH

channel the four bursts are transmitted continuously. In TCH channel there is only one

SACCH burst in each 26-multiframe, therefore only four 26-multiframe can constitute a

complete measurement report.

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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.

MR Interpolation:

The continuity of measurement report is judged by measurement result number. First-order

interpolation is employed in the interpolation algorithm for missing measurement report, i.e.,

to calculate the missing values (linear) between the measurement values at both ends of the

missing measurement reports.

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MRMR

MR MRMR

Measurementreport No. n

Measurement reportNo. n+4

Continuous MRflow

How to Interpolate MR?

Each measurement report has a serial number. If the serial numbers of received

measurement reports are not consecutive, there must be missing measurement reports, and

the system will make them up according to the interpolation algorithm.

As shown in the diagram, the network receives measurement reports n and n+4, whose

serial numbers are not consecutive, so the system will make up for the missing

measurement reports n+1, n+2 and n+3 with a certain algorithm.

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Filter----Average several continuous MR.

MRMR MRMR

MR MR

Continuous MRflow

MR Filtering

When the network receives the measurement report, it can not judge the current condition of

MS according to just one measurement report due to the signal fluctuation. Therefore,

filtering, a more suitable method is applied.

Different filters are applied in receiving level, receiving quality and TA of uplink and downlink.

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Contents







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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 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 IUO cell HO attempt is prohibited within the penalty time

after an IUO cell HO fails.

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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.

Cell A

BTS

HO failure

BSC

Cell B

When MS fails to handover to a target cell, a penalty will be given on the signal level of this

target cell during a so called handover failure penalty time period. That is, when ranking the

neighbor cells in the cell list, the corresponding neighbor cell with a failure record within the

penalty time will be penalized by cutting certain value on the reported signal level.

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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.

In case of BQ emergency handover, the original serving cell will be penalized (called signal

level penalty by BQ HO ), during BQ HO penalty time, to avoid MS to be handed back to the

original serving cell again within certain time.

It is the same for TA handover, i.e. the original serving cell is penalized (signal level penalty

by TA HO ) during TA HO penalty time.

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Back? No way!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 and avoid frequent HO.

Purpose of such penalty: When MS crosses continuously several micro cells, it handover to

the umbrella cell with lower hierarchical priority level, to avoid too frequent handovers which

will affect the communication quality between those cells. At the same time, penalty is

started to avoid handover back to original cell again. A possible example is that a fast

moving car is running on a highway.

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Underlaid

Overlaid Do notattempt

again after afailed HO!

Penalty on Overlaid/Underlaid Cell

A new Overlaid/Underlaid HO is prohibited within a penalty

time after an Overlaid/Underlaid HO failure.

HW-Overlaid/underlaid HO failure means the failure of handover from the Underlaid to the

Overlaid, or from the Overlaid to the Underlaid.

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Contents







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Procedure 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

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M Rule 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 the

BSS.

P : Max_Power_of_MS Max_Power_of_MS : MS maximum transmitting power

RX_LEV(o), RX_LEV(n)-- MS received signal level of the serving cell and the neighbor cell,

MSRXMIN(o) and MSRXMIN(n)-- Lowest MS received signal level required by the serving

cell and neighbor cell.

Pa(o)=MS_TXPWR_MAX(o)

P;

Pa(n)=MS_TXPWR_MAX(n) P;

P =MAX_POWER_OF_MS ;

MS_TXPWR_MAX(n)-- Maximum transmission power of mobile phone allowed.

MAX_POWER_OF_MS -- Maximum physical transmission power of MS.

OFFSET--Minimum access level offset

MAX(0,Pa(o))--The current algorithm takes into consideration only the lowest received power

threshold of downlink, uplink is not included.

For the uplink: If the physical maximum power of MS exceeds the maximum transmissionlevel required by BSS, then Pa is 0.

Otherwise, a compensation value will be added.

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K Rule Criterion

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.

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The 4th Bit: Determined by HO Hysteresis

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.

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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 islower 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.

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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

The handover algorithm of Huawei divides the whole network into four layers, each of which

further divided into 16 levels. The lower the layer is, the higher the handover priority level will

be. The Micro Cell layer has the highest priority level.

Relevant parameters: Handover [Cell Description Table]

Layer of the cell

Level priority

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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.141516 12345678910111213

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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.

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The 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.

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

At the same time, bit 13th, 12th and 10th5th bits are turned off.

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The 14th Bit: Determined by Layer HO

Neighbor cell criterion

RXLEV >=layer HO threshold + layer HO hysteresis0.

If the above criterion is not met1.

At the same time, bit 13th, 12th and 10th5th bits are turned off.

Note

The layer HO threshold and hierarchical hysteresis correspond to the value of

that individual cells value.

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.

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The 15th Bit: Determined by Cell Type

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

Serving cell or Neighbor cell criterion

When cell type is extension cell 1.

When cell type is normal cell 0.

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The 16th Bit: Determined by MNC HO Strategy

The 16th bit: bit value is decided by MNC HO strategy.

Serving cell: is always set to 0.

Neighbor cell criterion

When MNC HO adjustment is supported, digit 16 is valid, otherwise, it is 0.

When co-MNC HO adjustment is with priority, digit 16 of the neighboring

cell of different MNC with the service cell is 1; otherwise, it is 0.

When HO between different MNC is with priority, digit 16 is 1 if digit 14 is 1

or the neighboring cell and service cell are of the same MNC, otherwise, it

is 0.

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Contents







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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

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TA HO

Triggering condition

The actual TA > TA HO Thrsh.

Object cell selection

The cell must be of the highest priority in the candidate cell sequence

and meet the following restrictions.

Restriction

The service cell cannot be the object cell.

HO is not allowed when TA Thresh. of the neighboring cell with the

same BTS is smaller than that of the service cell.

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Bad Quality HO


UL receiving quality >=UL receiving quality thrsh. of the service cell. OR DL receiving quality >=DL receiving quality thrsh. of the service

cell.


The cells must be of the highest priority in the candidate cell sequence

and meet the following restrictions.

Restriction

Handover to the neighboring cell with the highest priority. If there is no

neighboring cell, handover to the service cell, and the channel at

different TRX is preference.

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Signal Level Rapid Drop HO


( ) ( ) ( ) ( ) ( ) ( )

( ) ( ) BXAXA

XAXAXAXAXAXA

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Interference HO


UL receiving quality>=Service cell UL receiving quality Thrsh. AND UL receiving

level>=Service cell UL receiving level Thrsh.

OR DL receiving quality>=Service cell DL receiving quality Thrsh. AND DL

receiving level>=Service cell DL receiving level Thrsh.


The cells must be of the highest priority in the candidate cell sequence and meet

the following restrictions.

Restriction

The service cell that is not in the penalty time for intra-cell handover.

The neighboring cell with the receiving level higher than the inter layer HO Thrsh.

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Load HO


The load HO switch of the service cell is enabled.

The system signaling flow is not larger than the Load HO system flow Thrsh.

The service cell traffic is larger than the Load HO Thrsh.

The DL receiving level is in the load HO zones.



The traffic of the neighboring cell must be lower than its load HO receiving thrsh.

Restriction

It is not available with SDCCH.

Load HO just occur within the same BSC.

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Cell A Cell B

Normal HO border

CONF_HO_RXLEV

CONF_HO_RXLEV+CLS_RampCONF_HO_RXLEV+CLS_Offset

Load HO zone

Load HO

As load HO may trigger more HOs, consider the CPU load

(system flow level) before triggering it. In addition, load is taken bystep, that is, the edge HO thrsh. raises according to certain step

and period and stops after without the Load HO Zone.

Load HO bandwidthEdge HO threshold

Load HO step level

A handover band is defined in load handover, in the range of edge handover threshold ~

edge handover threshold + load handover bandwidth. The handover band itself is divided

into multiple equalized handover step sizes, MS (falling within edge handover threshold +

N*handover step sizes) are handover to adjacent cells one by one from low to high. Once

load of the serving cell decreases (as lower than the load handover start threshold) or load of

the adjacent cell increases to a certain extent (as higher than the load handover receivedthreshold), the handover stops.

Load handover is an emergency measure, which mainly applicable to abnormal traffic peak

in part of the radio network. It should not be used as the major means to solve the traffic

congestion problem. If load handover always occurs to some area of a network, TRX re-

configuration and network topology re-design is the right way.

Related parameters: Handover - [Load handover table]

System flux Thrsh. for load HO

Load HO Thrsh.

Load HO Req. on candidate cell

Load handover bandwidth (dB)

Load HO step level (dB)

Load HO step period (second)

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Edge HO


The DL receiving level < Edge HO DL RX_LEV Thrsh.

OR The UL receiving level < Edge HO UL RX_LEV Thrsh.

Satisfying P/N rule.



The neighboring cell with the highest priority and whose priority

is higher than that of the service cell.

Related parameters: Handover - [Normal handover data table]

Edge HO UL RX_LEV Thrsh.

Edge HO DL RX_LEV Thrsh.

Edge HO watch time (second)

Edge HO valid time (second)

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Layer HO


The layer of the object cell is lower than that of the service cell.

The DL level of the object cell is higher than the inter layer HO

thrsh.

Satisfying P/N rule.



The neighboring cell with the highest priority and whose priority

is higher than that of the service cell.

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PBGT HO Triggering condition

The layer and level of the object cell are the same as those of theservice cell.

The DL level must be the result of the following formula.



The neighboring cell with the highest priority and whose priority is

higher than that of the service cell.

Restriction

It is not available with SDCCH.

In areas with densely distributed cells, the actual radio coverage range has become far

larger than the distance between BTS. If MS keeps the conversation within a cell, it will not

be effectively handed over to a nearby cell with low transmission power and that will lead to

over shooting, thus increasing the interference of radio environment and complicating

network planning and optimization. To solve this problem, Huawei Company develops PBGT

handover algorithm that is based on path loss.

PBGT handover algorithm is intended for the handover based on path loss, in real time, itseeks a cell with lower path loss and meeting certain system requirements, and judges

whether its necessary to perform handover.

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Fast-Moving HO


In Fast Moving Watch Time, the mobile phone moves through Qcells of P.

The layer of Q cells must be less than four (none Umbrella cell).


The neighboring cell with the highest priority and meet the

following condition.

The layer of the object cell must be no less than four, that is, the

Umbrella cell.

The receiving level of the object cell >= the inter layer HO thrsh. +

inter layer HO hysterisis.

Related parameters: Handover - [Fast-moving handover table]

MS Fast-moving watch cells - The total number of cells for judging whether a MS is fast

moving or not.

MS Fast-moving valid cells - Total N of actual cells that MS fast passes. That is, when N

equal to or more than Q cells that MS lately passes are fast passing ones, the fast moving

micro cell handover algorithm will be started.

MS Fast-moving time Thrsh. - Time threshold (2r/v) specified according to the cell radius (r)

and the moving speed (v). If the time used by MS to pass this cell is less than this threshold,

it means that MS passes the cell quickly.

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Overlaid/Underlaid Cell

Assume: 6TRX in one cell, two CDUs and one SCU are adopted

Where can we configure BCCH CH, CDU or SCU?

SCU

CDU

CDU

Antenna

TRX

TRX

TRX

TRX

TRX

TRX

Antenna

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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

Normal Overlaid/Underlaid

Enhance Overlaid/Underlaid

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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 on uplink reported by BTS

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Factor of Handover betweenOverlaid/Underlaid

Normal Overlaid/Underlaid

Receiving level

Time Advance

Quality

Enhanced Overlaid/Underlaid

Receiving level

Time Advance

Quality

Traffic Load of Underlaid

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underlaid

overlaid

Normal Overlaid/Underlaid HO

Division of underlaid and overlaid is decided by MS

downlink receive level ,TA value and quality.

The quality boundary is elided in this figure

An illustration of how to define the border between the underlaid and the overlaid.

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Normal Overlaid/Underlaid HO

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 threshold TA hysteresis AND

RX_LEV >=RX_LEV threshold + RX_LEV hysteresis AND

Qua. =

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Enhance Overlaid/Underlaid HO

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 threshold TA hysteresis AND

RX_LEV >= U to O level AND

Qua. =

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Contents





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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

This section introduces the main handover parameter configuration and the lookup process

of handover data in the program.

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No

Yes,

No

It determines whether to handle the fastmoving MS with the algorithm. It is onlyrecommended in special area (such as a

highway), to lower CPU load. This algorithmshould only be used in suitable conditions,and usually it is not applied

MS Fast

moving HOallowed

NoYes,No

It determines whether to perform thehandover to share traffic load. Load sharingcan lower the channel assignment failure ratiocaused by cell congestion, so as to makeevener allocation of the service in respectivecells, and lower the cell congestion rate , andimprove network performance. It on ly appliesin the same BSC or cells at the same level

Load HOallowed

YesYes,No

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

Penaltyallowed

YesYes,No

It means whether the 12 and 13 bits acts in

the 16bit order. Yes means handover in thesame BSC/MSC is preferred. No means thatthe 12 and 13 bits are shielded and set to0.

CoBSC/MSC

Adj.

Recommendvalue

ValuerangeMeaning

Parametername

Handover Control Table

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YesYes, No

It means after a handover whether MS is to useproper predicted transmitting power to access thenew channel. This can reduce system interferenceand improve service quality y (this parameter actswhen intra BSC handover occurs

MS powerprediction

afterHO

YesYes, No

It means whether PBGT handover algorithm isallowed. PBGT handover algorithm currently isprocessed on LAPD board. To avoid Ping -panghandover, PBGT handover is only performedbetween cells at the same layer and with the samepriority, and meanwhile it is only triggered on TCH.

PBGT HOallowed

NoYes, No

It means whether RX _ Level Drop emergencyhandover algorithm is allowed, handover the MSwhich receiving signal level is dropping quickly inadvance to avoid potential call drop. This algorithmshould be applied in suitable conditions, andusually it is not used. To apply the handoveralgorithm, BSC must have original measurementreport.

RX _LevelDrop

HO allowed

Recommendedvalue

Valuerange

MeaningParametername


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YesYes, No

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.

MR.

reprocessing

Recommended

valueValue rangeMeaning

Parameter

name


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YesYes, No

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.

Transfer

BS/MS power

class

NoYes, No

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 only

processed measurement rep ort but also original

measurement report to BSC.

Transfer

Original MR.

Recommended

value

Value

rangeMeaning

Parameter

name


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According to

Concrete

conditions

Twice

per

second,

Once

per

second

It indicates the time interval at which a measurement

report is 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

Sent Freq. of

Preprocessed

MR.

Recommended

value

Value

rangeMeaning

Parameter

name


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30 ~ 63

dBWorks together with the Layer handover threshold.

Layer HOhysteresis

250 ~ 63

It affects the value of the 14th bit in the 16bit ranking , and it is alsothe level requirement on the target cell for interference handoverand load handover. Then such level should be higher than layerhandover threshold + layerhandover hysteresis. The layer handoverthreshold should be set >= Edge handover threshold + Inter cellhandover hysteresis.

Layer HOThresh.

11 ~ 16

Each layer may have 16 priorities, used to control the handoverpriority between cells at the same layer. Usually priorities ofprioritiescells at the same layer are set the same. For cells at the same layer,the smaller the priority value, the higher the priority

Cellpriority

M900 : layer 3M1800:Laye 2

1 ~ 4

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 complexnetwork environment. Normally, Macro layer is the major 900 layerslayer, Micro layer is the major 1800 layer, Pico is the 900 and 1800micro cell layer. The smaller layer value, the higher priority.

Layer of

thecell

Recommendedvalue

Valuerange

MeaningParameter

name

Cell Description Table

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150 ~ 63

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.

Min DL level

0n

Candidate

cell

400 ~ 255 s

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.

Penalty

Time on MS

Fasting

moving HO

300~ 63 dB

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 the

penalty time.

Penalty on

MS Fasting

moving HO

Recommended

value

Value

rangeMeaning

Parameter

name

Cell Description Table

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00 ~ 63 dB

This offset is based on Min downlink level ofhandover candidate cell. Different offsets can be

defined for different adjacent cells, and to enter thecandidate cell list, the corresponding adjacent cellreceiving signal level must be higher than the sumof Min. downlink level of handover candidate celland Min. Access level offset.

Min accesslevel offset

It is around 4 in thedensely populateddowntown, and

around 8 on theoutskirts.

0 ~ 63 dB

Handover hysteresis between an adjacent cell andthe serving cell. It is set to reduce Ping pang HO.The hysteresis value also needs to be adjustedaccording to the handover performance statistics

result and live network. Flexible configuration of thevalue can effectively lead handover andtraffic between two adjacent cells.

Inter cellHO

hysteresis

It is around 68 in thedensely populateddowntown, andaround 72 on theoutskirts.

0~127corresponding to-64~63dB

It means that PBGT handover is performed when thedifference between the target cell downlink path lossand the corresponding to serving cell downlink pathloss is bigger than PBGT handover threshold. WhenPBGT handover is enabled, and Inter cell handoverhysteresis > PBGT handover threshold(corresponding dB value), Intercell handoverhysteresis takes place of PBGT handover thresholdto act. . PBGT handover threshold also needs to beadjusted according tohandover performance statistics result

PBGT HOThresh.

RecommendedvalueValue rangeMeaning

Parametername

Adjacent Cell Relation Table

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100 ~ 60 sPenalty time for the original serving cell after BQHO. seconds

Penalty time

after BQ HOfail

630 ~ 63 dB

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.

Penalty level

after BQ HO

fail

100 ~ 60 sPenalty time on the corresponding target cell after

seconds handover failure

Penalty time

after HO fail

300 ~ 63 dB

The signal level value in dB, to punish the targetcell 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.

Penalty level

after HO fail

Recommended


Parameter

name

Penalty Table

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100 ~ 16 s

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

Penalty time

after IUO

HO fail

100 ~ 60 sPenalty time for the original serving cell after TA

emergency Seconds handover

Penalty time

after TA HO

fail

630 ~ 63

dB

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

Penalty

level after

TA HO fail

Recommended

value

Value

rangeMeaning

Parameter

name

Penalty Table

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Emergency Handover Table

60

correspondi

ng to BQlevels of0~7

The uplink receiving quality threshold forBQ emergency HO.UL QUAL.Thrsh.

60

0 ~ 70,correspondi

ng to BQlevels of

0~7

The downlink receiving quality threshold forBQ emergency handover. When frequencyhopping or DTX is enabled, RQ becomesworse (normal phenomenon), this valueshould be set to 70. The adjustment shouldalso base on the current network qualityand handover statistics. When triggeringemergency handover, the first to select isthe inter-cell handover, the intra-cellhandover is only triggered when there is nocandidate cell and the intra-cell handover isallowed in the serving cell.

DL QUAL.Thrsh

630 ~ 63 bitperiod

When TAthis value, emergency handoveris triggered

TA Thrsh.

Recommendedvalue

Valuerange

MeaningParameter

name

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50

0 ~ 70,

corresponding

to BQ levels of

0~7

Downlink receiving quality threshold in the serving cell for

interference handover.

DL Qua.

Thresh.

For

interf HO

50, interference

quality threshold

must be better

than

the emergency

quality threshold

0 ~ 70,

corresponding

to BQ levels of

0~7

Uplink receiving quality threshold in the serving cell for

interference handover. When frequency hopping or DTX

is to enabled , 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 the first position and intra cell handover is

permitted, perform intra cell handover . Otherwise select

the second candidate cell to perform inter cell handover.

UL

Qua.

Thresh

for interf.

HO

Recommended


Parameter

name


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300 ~ 63Min downlink receiving power threshold from the serving

cell required for interf. HO.

DL

RX_LEV

Thresh. For

Interf. HO

250 ~ 63

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

inter-cell HO.

UL

RX_LEV

Thresh. For

interf.HO

Recommended

value

Value

rangeMeaning

Parameter

name


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00 ~ 255Used for configuration of filter for rapid signal drop

judgment. Please refer to the explanation for A1~A8 offilter.

Filterparameter B

100 ~ 20

Used for configuration of filter for rapid signaldrop judgment, and together with filter parameterB, they are 9 parameters for a filter. The correspondingformula is (in the program, A1~A8 is configuration valueminus 10 and B is the negative configuration value):

C1(nt)=A1C(nt)+A2C(nt-t)+A3C(nt 2t)++A8C(nt-7t) Where, C (nt) is the receiving signal levelin the uplink measurement report of the serving cellsent at the time of nt. If C1 ( nt ) < B, and C (nt) is belowthe edge handover threshold, then the signal level isconsidered to be of rapid drop.

FilterParameters

A1~A8

Recommendedvalue

Valuerange

MeaningParameter

name.


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2

0 ~ 7,

Corresponding

to 0 , 50 , 60 , 70 ,75, 80 , 85 , 90

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 neighbor cell is lower than the

corresponding percentage the cell refuses to accept MSfrom serving cell handed over due to the load reason

Load Req.

on

candidatecell

5

0 ~ 7

cell load levels,

Corresponding

to 0 , 50 , 60 , 70 ,

75, 80 , 85 , 90

Load handover is triggered when the serving cell load is

than the threshold, TCH seized in the cell has reaching

the corresponding percentage.

Load HO

Thresh

10

0, 8~11

system flow levels

Corresponding

0, 70, 80, 90

and 95.

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.

System

flux

Thresh.

For

load HO

Recomme

nded

value

Value rangeMeaningParameter

name

Load Handover Table

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Load Handover Table

51 ~ 63 dbThe whole load HO bandwidth will be divided into severalSub-bands by this parameter.

Load HO

steplevel

101~60 s

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 control

handover. The cycle is the time needed for handovers of

each step.

Load HO

step

period

250~ 63 db

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 of

margin handover threshold, margin handover threshold +

load handover bandwidth

Load HO

bandwidth

Recomm

ended

value


name

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Normal Handover Table

30 (without PBGT

handover, downtown),

20 (single station on

outskirts), 20 (with

PBGT handover,

downtown)

0 ~ 63Downlink consideration for edge HO

Edge HO DL

RX_LEV

Thresh.

25 (without PBGT

handover, downtown),

15 (single station on

outskirts), 15 (with

PBGT handover,

downtown)

0 ~ 63

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

receiving level is lower than the value is longer than

certain time called continuous time, edge handover

will be performed. If PBGT handover is enabled,

Corresponding edge handover threshold will be set

lower

Edge HO UL

RX_LEV

Thresh.

Recommended

value

Value

rangeMeaning

Parameter

name

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41 ~16See the above.Edge valid

time

51 ~16 s

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

Edge HO

watch time

Recommendedvalue

Value rangeMeaningParametername

After MR preprocessing switch is turned on, the reporting frequency of MR will affect the

handover speed.

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51 ~ 16 sstatistics time for Layer HO judgmentLayer HO

watch time

41 ~ 16 sContinuous time for Layer HO judgmentLayer HO

valid time

41 ~ 16 s

Continuous time for PBGT HO signal level

judgment.PBGT valid

time

51 ~ 16 sStatistics time for PBGT HO signal level

judgment.

PBGT watch

time

Recommended

value


name

PBGT handover should satisfy P/N judgment.

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151 ~ 225

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 MS is judged to quickly pass the cell.

MS

Fast

moving

Time Thresh.

21 ~ 10

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.

MS

Fast

moving

valid cells

31 ~ 10

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.

MS

Fast -moving

watch cells

Recommended

value

Value

rangeMeaning

Parameter

name

This table is valid only when MS Fast-moving HO allowed is turned on. It is usually unused,

and is suggested to be applied in special places such as highway.

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Common Concentric Data

0 ~ 63

If system optimization is selected, estimate(interpolate, filter) current SDCCH level valuethrough uplink measurement value in the formerSDCCH measurement report, and compare with Assign-optimum Level threshold, so as toassign overlaid or underlaid channel.If SDCCH is in the overlaid : edge handoverthreshold + signal intensity difference betweenunderlaid and overlaid + uplink and downlinkbalance allowance + SDCCH and TCH differenceallowance. If SDCCH is in the underlaid : edge

handover threshold + uplink and downlink balanceallowance + SDCCH and TCH differenceallowance.

Assign-optimumlevelThresh.

Systemoptimization

Systemoptimization,overlaid ,underlaid , nopreferential

In Overlaid/Underlaid, the following selection areavailable for TCH assignment: (1) The system

judges according to the measurement report onSDCCH and assign to the best sub-cell. (2) Selectthe overlaid first for TCH assignment. (3) Selectthe underlaid first for TCH assignment. (4) Do notgive extra priority.

Assignoptimumlayer

Recommendedvalue

Value rangeMeaningParamete

r name

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None

overlaid ,

underlaid ,

none

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.

Incoming-

to-BSC HO

optimum

layer

YesYes, No

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

Pref.

subcell in

HO of intra-

BSC

Recommended

value

Value

rangeMeaning

Parameter

Name

Precautions in Incoming to BSC HO optimum layer configuration:

1. BCCH TRX should be configured on the underlaid

2. SDCCH should be configured on the underlaid

3. If the receiving level threshold and receiving level hysteresis, or TA threshold and TA

hysteresis are configured as 63 and 63, the handover between the underlaid and overlaid

will be disabled.

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600 ~ 70In case of Qua. Is worse than this value, MShandover from overlay to underlayRX_QUALThresh.

50 ~ 16 sP/N judgment statistics time for U/O HOjudgment.

UO HOwatch time

40 ~ 16 sP/N judgment continuous time for U/O HO

judgment.UO HOvalid time

According concretecondition

0 ~ 63TA is more than this value, TCH in underlaywill be allocated

TA thresh.OfAssignmentPref.

According concretecondition

0 ~ 63TA is more than this value, SDCCH in underlaywill be allocated

TA Thresh.Of IMM-Assign Pref.

According concreteconditionYes, NoTA attend allocation of SDCCH or not

TA Prefer

Of IMM-AssignAllowed

RecommendedvalueValue rangeMeaning

Parametername

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50 ~ 16 sP/N judgment statistics time for U/O HO

judgment.

UO HO

watch time

40 ~ 16 sP/N judgment continuous time for U/O HO

judgment.

UO HO

valid time

0 ~ 63 bit

periodWorks with TA threshold.

TA

hysteresis

0 ~ 63 bit

period, with 1

bit period

corresponding

to 0.55km

It must be bigger than TA emergency handover

threshold.TA Thresh.

Recommended


Parameter

name

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Normal Concentric Data

50 ~ 63Works with Rx threshold.RX_LEV

hysteresis

250 ~ 63

Rx level hysteresis, Receiving Quality

Thrsh.,TA threshold and TA hysteresisjointly define underlaid area and overlaidarea. It must be bigger than edge handoverthreshold, and the recommended value is:edge handover threshold + signal intensitydifference between underlaid and overlaid .

RX_LEVThresh

Set according toactual conditions

0 ~ 63 dB

Transmitting Power at antenna differencebetween underlaid and overlaid may causeMS receiving signal intensity difference inunderlaid and overlaid . The parameterusually indicates the antenna EIRPdifference in dB between underlaid cell andoverlaid cell. According to field

measurement, multi-point measurement is

necessary if the underlaid and overlaid usedifferent antenna.

UO signalintensity

difference

Recommendedvalue


name

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Enhance IUO Data

350 ~ 63

In case of receiving level in underlay is more

than this value, and traffic in underlay is more

than Traffic Thresh. Of Underlay, HO occurs

from underlay to overlay

UtoO HO

Received

Level Thresh.

250 ~ 63In case of receiving level in overlay is less than

this value, HO occurs from overlay to underlay

OtoU HO

Received

Level Thresh.

Set according to

actual

conditionsYes, NoEnable traffic to be one condition of HO or not

UtoO Traffic

HO Allowed

Set according to

actualconditions

Yes, NoEnable function of Enhance IUO or notEnhance

IUO Allowed

Recommended

value

Value

rangeMeaning

Parameter

name

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Concentric Cell Handover Table

800 ~ 100 %If the traffic in underlay is over this value,

MS will handover from under to overlay

TrafficThresh. OfUnderlay

51 ~ 255 s

If there are some handover requests fromunder to overlay at the same time, systemwill handover the call with level firstly. Thisvalue determine period per step

Underlay HOStep Period

51 ~ 63 dB

It is the step that handover banddecreases, used to control the grade bygrade handover band from underlay tooverlay with underlay HO step level

Underlay HOStep Level

101 ~ 255 s

To prevent ping-pong handover, the callcant be handed over back within penaltytime when a call is handed over from

underlay to overlay

Penalty Timeof UtoO HO

Recommended

value

Value

range

MeaningParameter

name

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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 andsystem 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.

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HO Data Lookup Process

BSC performs HO judgment process, such as basic rank of

cells (completed in LAPD board). When BSC finds suitabletarget, 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.

Precautions:

1. The module No., cell No. and CGI of all neighbor cells should be found before BSC

performs basic cell ranking

2. In adjacent cell relation table: If there are cells with the same frequency and BSIC in

neighbor cells, BSC will fail to identify the right target cell. As a result, the handover

command may be sent incorrectly, thus the handover successful rate will be affected.

3. Cell ranking and HO judgment are performed in LAPD board. The handover request

message is sent via MPU, therefore the connection between LAPD and MPU is Cell module

information table, with CGI as index.

4. Once there is no CGI find in the Cell module information table, MPU may regard the

target cell as an outer BSC cell. It will send HO-Request to MSC, and count it as an

Outgoing-BSC handover request.

5. In case of incorrect module No. in Cell module information table, the handover request

will be sent to wrong modules and the handover will fail. However, BSC will still count it as

an inter-cell handover request.

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Contents





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Contents


4.1 Intra BSC Handover

4.2 Intra MSC Handover

4.3 Inter MSC Handover

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Intra-BSC Handover Signaling Process

MS MSBTS1 BTS2BSC MSC

Measurement Report from MS

Channel_Active

Channel_Active ACK

HANDOVER COMMAND

Handover Access

Handover_DetectPHY INFO

First SABM

Establish_IND

PHY INFO

Handover Complete

Handover_Performed

After receiving the SABM frame reported by MS, BTS will report

Establish_IND to BSC, and respond UA frame to MS hereafter. Not until

the UA frame is received, MS will send HO-Complete message to the

network. SABM and UA, corresponding to each other, are link creation

frames of Layer 2 of Um interface. In poor radio environment (weak signal or

interference), the network can not receive the SABM frame sent by MS, or

MS can not receive UA frame. Either condition will lead to handover failure,

and the failure cause value is radio link failure.

For synchronous handover in BSC, i.e. When BTS1 and BTS2 is the same

BTS, there will be no PHY INFO message. MS reports SABM connection

frame right after report of Handover Access message.

After receiving the HO-Complete message, BSC will send first HO-Performed message to MSC, and will release the radio channel resource of

old BTS. The old BTS1 will respond RF-Channel-ACK to BSC.

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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 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.

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Intra-BSC Handover Signaling ProcessIntra-BSC Handover Signaling Process

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)

The above process include the counter for incoming of target cell and outgoing of original

cell.

The measurement points of key counter are as follows:

1. Before sending "Channel-Activation" to the target BTS, BSC measures "Request times of

in-cell handover in BSC" The number of times of request intra-BSC incoming cell handover

and "Request times of out-cell handover in BSC" The number of times of request intra-BSC

outgoing cell handover.

2. After sending "HO-Command" to MS, BSC measures "Request times of in-cell handover

in BSC" The number of times of request intra-BSC incoming cell handover and "Request

times of out-cell handover in BSC". The number of times of request intra-BSC outgoing cell

handover.

3. After receiving "HO-Complete" from MS, BSC measures "Success times of in-cell

handover in BSC" The number of times of successful intra-BSC incoming cell handover and

"Success times of out-cell handover in BSC". The number of times of successful intra-BSC

outgoing cell handover.

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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 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

Difference between "Internal inter cell handover success rate " and "Cell radio handover

success rate " :

As viewed from formulas, both numerators are success times of handover, while the

denominators are different. While viewed from the measurement points of the counter,

Attempted inter cell handovers >= inter cell handovers, so intra BSC handover success rate

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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

Intra-MSC HO Signaling ProcessIntra-MSC HO Signaling Process

The key measurement points are as follows, same as those of intra BSC handover:

1. After sending "HO-REQUIRED", the original BSC measures "Attempted outgoing inter BSC

inter cell handovers".

2. After receiving "HO-REQUEST", the target BSC measures "Attempted incoming inter BSC

handovers".

3. After sending "HO-REQUEST ACK", the target BSC measures "incoming inter BSC handovers".

4. After receiving "HO-Command" , the original BSC measures "outgoing inter BSC handovers".

5. After receiving "HO-Complete", the target BSC measures "Successful incoming inter BSC

handover"

6. After receiving "Clear-COM" and the cause value is "HO-Successful", the original BSC

measures "Successful outgoing inter BSC inter cell handover".

The difference between "handover times" and "handover request times":

Handover times - After "HO-COM" is received or "HO-REQ-ACK" is sent

Handover request times - After "HO-REQUIRED" is sent or "HO-REQUEST" is received

Therefore, inter BSC inter cell radio handover success rate >= inter BSC inter cell handover

success rate.

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Channel Release Process

MS BTS BSC MSCDisconnect

Release

Release Complete

Clear_CMD

Clear_CMPChannel Release

Deactive_SACCH

First DISC

UA

Release_IND

RF_Release_REQ

RF_Release_REQ_ACK

Note:

This release is originated from the network side. For the release is originated actively by MS,

the signaling process is the same except the three transparent transmission direction

mentioned above is reversed.

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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 MSC

Note: Signaling process of A interface and Abis interface of inter MSC handover is the same as that of intra

MSC handover, only the signaling between two MSC is particular for the inter-MSC handover. As shown in

above figure the signaling with "MAP" is of the MAP layer, and signaling of A and Abis interfaces are

omitted.

After receiving "HO-REQUIRED" of BSC-A (the request message includes CGI of the original cell and

target cell), if MSC-A finds that LAC of the target cell doesnt belong to this MSC, MSC-A will query the

"REMOT LAC Table (including the LAC and route of the adjacent MSC), and send "Prepare-HO"

message to MSC-B according to the route. CGI of the target cell and the indicator of whether to allocate the

handover number are included in this Prepare-HO message.

According to the received "Prepare-HO" message, if the handover number needs allocating, MSC-B will

request the local VLR to allocate the handover number. If VLR has the free handover number, the handover

number will be sent to MSC-B through "Send-HO-Report". If no handover number is needed, proceed to the

next step.

After SCCP link between MSC-B and BSC-B is established, MSC-B sends "HO-REQUEST" to BSC-B.

After that, BSC-B activates the target cells channel, and returns "HO-REQUEST ACK" to MSC-B afterreceiving the channel activation acknowledgement. According to this message, MSC-B sends "Prepare-HO

ACK" to MSC-A.

MSC-A establishes the route to MSC-B according to the handover number, and sends "Initialize-Address"

(IAI) to MSC-B to help the latter to identify which voice channel is reserved for MS. While MSC-B returns

"Address-Complete" (ACM) to MSC-A.

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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

IAIACM

Signaling Process between MSC

After receiving the ACM message, MSC-A sends "HO-Command" to MS. After that MS

handover access is performed in the new channel. If its successful, UA frame from BTS-B

will be received, and "HO-Complete" will be sent to MSC-B.

MSC-B sends "Send-End-Signal" to notify MSC-A to release the orig

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