Microsoft Power Point - 4 OMF010002 Handover ISSUE2

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

Handover


Foreword

� Handover is a key technology of mobile communication

system and make continued conversation possible.

� Handover algorithm in Huawei product is flexible and

powerful.


Objectives

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

� Understand the types of handover.

� Master handover judgment flow.

� Configure handover data.

� Master handover signaling flow.


Contents

1. Introduction of Handover

2. HO Algorithm Process

3. HO Data Configuration

4. HO Signaling Process


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


� 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


Classification by Synchronization

� Synchronous handover

� Source and target cell belong the same BTS

� Asynchronous handover

� Source and target cell belong the different BTS


Contents






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


General Process of HO AlgorithmM.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


Contents








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 downlink measurement report

of the serving cell

The uplink measurement

report of MS

The downlink measurement reportof the neighbor cell (BCCH)


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


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 MR MR MR MR

Measurement report No. n

Measurement report No. n+4

Continuous MR flow

How to Interpolate MR?


Filter----Average several continuous MR.

MR MR MR MR MR MR

Continuous MR flow

MR Filtering


Contents








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.


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


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.


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.


Underlaid

Overlaid Do not attempt

again after a failed HO!

Penalty on Overlaid/Underlaid Cell

� A new Overlaid/Underlaid HO is prohibited within a penalty

time after an Overlaid/Underlaid HO failure.


Contents








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


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

� MSRXMIN(o) and MSRXMIN(n)-- Lowest MS received signal level required

by the serving cell and neighbor cell.

� 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 : MS maximum transmitting power


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.

141516 12345678910111213


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.

141516 12345678910111213


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.

141516 12345678910111213


GSM900

Cell

Micro Cell

Umbrella

Cell GSM 900

GSM1800 GSM1800GSM1800

GSM 900 GSM 900 GSM 900

GSM900GSM900

GSM1800GSM1800

GSM900 GSM900

GSM1800 GSM1800

GSM1800

Cell

Hierarchical Cell Structure


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


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.

141516 12345678910111213


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 10th—5th bits are turned off.

141516 12345678910111213


The 14th Bit: Determined by Layer HO

� Neighbor cell criterion

� RXLEV >=layer HO threshold + layer HO hysteresis�0.

� If the above criterion is not met �1.

� At the same time, bit 13th, 12th and 10th—5th bits are turned off.

� 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.

141516 12345678910111213


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.

141516 12345678910111213


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.

141516 12345678910111213


Contents








Types of HO

� Emergency HO

� TA HO

� BQ HO

� Interference HO

� Rx_Level_Drop HO

� Load HO

� Normal HO

� Edge HO, layer cell HO and PBGT HO

� Fast moving HO

� Overlaid/Underlaid HO


TA 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.


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.


Signal Level Rapid Drop HO


� Due to downlink signal level drop

� Triggered upon detecting rapid level drop during MS busy mode


� The neighboring cell with the highest priority and whose priority is

higher than that of the service cell in the candidate cell group.

� Restriction



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.


Interference Handover

Lev_Thr

Rx_Qual

RX_Lev

Qual_Thr

InterferenceOrigin

Serving Cell Neighboring Cell

Handover Triggering Zone


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.

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

Thrsh.

� Restriction

� It is not available with SDCCH.

� Load HO just occur within the same BSC.


Load HandoverHandover triggering

zone

Load HO Thr

Time

Traffic of Serving Cell

Receiving Threshold

Traffic of Neighboring Cell

Congested CellCongested Cell

Congested Cell


Cell A Cell B

Norm al HO border

CONF_HO_RXLEV

CONF_HO_RXLEV+CLS_Ram p

CONF_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 by

step, that is, the edge HO thrsh. raises according to certain step

and period and stops after without the Load HO Zone.

Load HO bandwidth Edge HO threshold

Load HO step level


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.


Edge HandoverHandoverTriggering

P/N

Serving Cell Neighboring Cell

P: Watch TimeN: Valid Time

RX_LEV Thr

Time

RX_Lev


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.




higher than that of the service cell.


PBGT HO� Triggering condition

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

service cell.

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




higher than that of the service cell.

� Restriction

� It is not available with SDCCH.


Fast-Moving HO


� In Fast Moving Watch Time, the mobile phone moves through Q

cells 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.


MS Fast-Moving Handover

Handover Triggering

Time Thr

Umbrella Cell

Time

P/N

P: Watch CellsN: Valid Cells

1 1 2 3

Micro Cell

Cells Number


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


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


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


Factor of Handover between Overlaid/Underlaid

� Normal Overlaid/Underlaid

� Receiving level

� Time Advance

� Quality

� Enhanced Overlaid/Underlaid

� Receiving level

� Time Advance

� Quality

� Traffic Load of Underlaid


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


Normal Overlaid/Underlaid HO

� 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



Enhance Overlaid/Underlaid HO

� Criterion for HO from overlaid to underlaid:

� TA value => TA threshold + TA hysteresis OR

� RX_LEV <= O to U level OR

� Qua. =>Qua. threshold


� 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



Contents






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


NoYes, No

It determines whether to handle the fast moving MS with the algorithm. It is only recommended in special area (such as a highway), to lower CPU load. This algorithm should only be used in suitable conditions, and usually it is not applied

MS Fast

moving HO

allowed

NoYes, No

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

Load HO

allowed

YesYes, No

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

Penalty

allowed

YesYes, No

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.

Co BSC/MSC

Adj.

Recommendvalue

Value rangeMeaning

Parametername

Handover Control Table


YesYes, No

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

MS powerprediction

afterHO

YesYes, No

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 between cells at the same layer and with the same priority, 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, and usually it is not used. To apply the handover algorithm, BSC must have original measurement report.

RX _Level Drop

HO allowed

Recommended value

Value range

MeaningParameter name



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

value Value rangeMeaning

Parameter

name



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 measurement

report 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



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



30 ~ 63

dBWorks together with the Layer handover threshold.

Layer HOhysteresis

25

0 ~ 63

(-110~-47dBm)

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

Layer HOThresh.

11 ~ 16

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

Cell priority

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 room of network planning for the operator to adapt to various complexnetwork environment. Normally, Macro layer is the major 900 layers layer, Micro layer is the major 1800 layer, Pico is the 900 and 1800 micro cell layer. The smaller layer value, the higher priority.

Layer of thecell

Recommended value

Valuerange

MeaningParameter

name

Cell Description Table


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


00 ~ 63 dB

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”.

Min accesslevel offset

It is around 4 in the densely populateddowntown, andaround 8 on theoutskirts.

0 ~ 63 dB

Handover hysteresis between an adjacent cell and the serving cell. It is set to reduce “Ping pang” HO. The hysteresis value also needs to be adjusted according to the handover performance statistics result and live network. Flexible configuration of the value can effectively lead handover andtraffic between two adjacent cells.

Inter cell HOhysteresis

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

0~127 corresponding to-64~63dB

It means that PBGT handover is performed when thedifference between the target cell downlink path loss and the corresponding to serving cell downlink path loss is bigger than PBGT handover threshold. When PBGT handover is enabled, and “Inter cell handover hysteresis” > “PBGT handover threshold (corresponding dB value)”, “Intercell handover hysteresis” takes place of “PBGT handover threshold”to act. . PBGT handover threshold also needs to be adjusted according to handover performance statistics result

PBGT HOThresh.

RecommendedvalueValue rangeMeaningParameter

name

Adjacent Cell Relation Table


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

HO. seconds

Penalty time

after BQ HO

fail

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 target

cell which has caused a HO failure due to problems

such as congestion , to prevent MS from a

handover attempt to that cell again. This value is

only valid within the penalty time for handover

failure.

Penalty level

after HO fail

Recommended

valueValue rangeMeaning

Parameter

name

Penalty Table


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


Emergency Handover Table

60

corresponding to BQ levels of

0~7

The uplink receiving quality threshold for BQ emergency HO.

UL QUAL. Thrsh.

60

0 ~ 70, correspondi

ng to BQ levels of

0~7

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.

DL QUAL. Thrsh

630 ~ 63 bit

periodWhen TA≥this value, emergency handover is triggered

TA Thrsh.

Recommended value

Value range

MeaningParameter

name


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



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



00 ~ 255Used for configuration of filter for rapid signal drop judgment. Please refer to the explanation for A1~A8 of filter.

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 corresponding formula is (in the program, A1~A8 is configuration value minus 10 and B is the negative 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 the uplink measurement report of the serving cellsent at the time of nt. If C1 ( nt ) < B, and C (nt) is below the edge handover threshold, then the signal level is considered to be of rapid drop.

FilterParameters

A1~A8

Recommendedvalue

Value range

MeaningParameter

name.



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 MS

from serving cell handed over due to the load reason

Load Req.

on

candidate

cell

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


Load Handover Table

51 ~ 63 dbThe whole load HO bandwidth will be divided into several

Sub-bands by this parameter.

Load HO

step

level

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


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



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

Recommended


Parameter

name



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


Parameter

name



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


Common Concentric Data

0 ~ 63

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.

Assign-optimum level Thresh.

System optimization

System optimization, overlaid , underlaid , no preferential

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.

Assign optimum layer

Recommended value

Value rangeMeaningParamete

r name



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



600 ~ 70In case of Qua. Is worse than this value, MS handover from overlay to underlay

RX_QUAL Thresh.

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

According concrete condition

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

TA thresh. Of Assignment Pref.

According concrete condition

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

TA Thresh. Of IMM-Assign Pref.

According concrete conditionYes, NoTA attend allocation of SDCCH or not

TA Prefer Of IMM-Assign Allowed

Recommended valueValue rangeMeaningParameter

name



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


Normal Concentric Data

50 ~ 63Works with Rx threshold.RX_LEV

hysteresis

250 ~ 63

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 .

RX_LEV Thresh

Set according to actual conditions

0 ~ 63 dB

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.

UO signal intensity

difference

Recommended value


name


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

actual

conditionsYes, NoEnable function of Enhance IUO or not

Enhance

IUO Allowed

Recommended

value

Value

rangeMeaning

Parameter

name


Concentric Cell Handover Table

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

MS will handover from under to overlay

Traffic Thresh. Of Underlay

51 ~ 255 s

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

Underlay HO Step Period

51 ~ 63 dB

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”

Underlay HO Step Level

101 ~ 255 s

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

Penalty Time of UtoO HO

Recommended value


name


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.


HO 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.


Contents






Contents


4.1 Intra BSC Handover

4.2 Intra MSC Handover

4.3 Inter MSC Handover


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


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.


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)


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


Contents






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


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


Contents






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


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.


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 Process


Highway

MSC-AMSC-C

MSC-B MSC-C

Inter MSC HO—Subsequent HO Process

� Subsequent HO


Inter MSC HO Signaling Process

� Statistics counter—same as Intra MSC HO, Statistics is

handled by BSC

� HO formula-- same as Intra MSC HO


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.


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.

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


Summary

� In this course, we have learned:

� Classify of handover

� Judgment and ranking step

� Handover data configuration

� Handover signaling flow

Thank youwww.huawei.com

Microsoft Power Point - 4 OMF010002 Handover ISSUE2

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