annexure b handover

8/12/2019 Annexure B Handover

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Wireless Curriculum Development Section

ISSUE

OMF010002 Handover

1.5


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Summary of Handover

HO Algorithm process

HO Data Configuration

HO Signaling process

Course Contents


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Summary of HOPurposes of HO

Purposes of HO

To keep a continuous communication with a moving MS

To improve network service performance

To reduce the call drop rate

To reduce the congestion rate


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Classification of HO:

Emergency HO

Timing Advance (TA) Emergency HO

Bad quality (BQ) Emergency HO

Rx_Level_Drop Emergency HO

Interference Emergency HO

load HO

Normal HO

Edge HO Layer HO

Power Budget (PBGT) HO

Speed-sensitive HO (Fast moving MS HO)

Concentric Cell HO

Summary of HOClassification of HO


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Summary of Handover (HO)




Course Contents


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General HO process

Measurement report preprocessing

Penalty processing

Basic ranking and Secondary ranking

HO judgment



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General process of HO Algorithm

M.R.

preprocessing

Penaltyprocessing

Basic ranking

Secondaryranking

HO judgement

TA emergency HO

BQ emergency HO

RSD emergencyHO

Interf. emergency HO

Load Sharing HO

Edge HO

Layer HO

PBGT HO

Processingprogram

OM forced HO

Directed retry

Overlaid/underlaid HO

Fast moving MS

HO

1

1


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General HO process


Penalty processing

Basic ranking and secondary ranking

HO judgment


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Measurement Report Preprocessing

Measurement Report (MR):

Uplink MR includes uplink receiving level and quality.

Downlink MR includes downlink receiving level, downlink

receiving quality of the serving cell and other downlink receiving

levels from the neighbor cells.

Serving cell Neighbour cell

The downlinkmeasurement report of theneighbour cell (BCCH)

The downlinkmeasurement report

of the serving cell

The uplinkmeasurement report of

MS


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Measurement Report Preprocess

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.


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How to interpolate MR?

MRMR

MR MRMR

Measurementreport No. n

Measurement rNo. n+4

ContinuousMR

flow

Measurement Report Preprocess


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General HO process


Penalty processing


HO judgment



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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 HO attempt is prohibited within the penalty time after anoverlaid/underlaid HO fails.


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BTS

HO failure

BSC

Cell A

Cell B

Penalty Processing

Penalty on the target cell:

Punish the target cell when a HO fails. This is to avoid the MS

to select this cell again in next HO judgment.


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BTS

BQ& TA HO

BSC

Cell A

Cell B

Penalty Processing

Penalty on the serving cell:

Punish the original serving cell when an emergency HO ( due to

BQ and TA) occurs.


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Back? No way!

Umbrella

Micro cell

Penalty Processing

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.


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Underlaid

Overlaid Do not

attemptagain after a

failed HO!

Penalty Processing

A new Overlaid/underlaid HO is prohibited within a penalty

time after an Overlaid/Underlaid HO failure.


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General HO process


Penalty processing


HO judgment


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Basic Ranking and Secondary 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))

i.e : RX_LEV(o)MSRXMIN(o)-MAX(0,Pa(o))> 0 .. ( 1 )

For Neighbor cell: RX_LEV (n) > MSRXMIN(n)+ MAX(0,Pa(n))+ OFFSET

i.e : Having the same formula as above

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



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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.



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The 16bits rule

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.

16 912345 1



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

layer ) hysteresis.

The 4th bit of the serving cell is always 0,

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

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

bit 4th is set to 0.

The receiving level of the neighbor cell < The receiving level of the

serving cell + Inter-cell HO ( of the same layer ) hysteresis, bit 4th is

set to 1.

Note: In PBGT HO, whichever the greater of the inter-cell ( of the same

layer ) hysteresis and PBGT threshold, that value will be used in the

PBGT HO.

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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.

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GSM900

Cell

Micro Cell

Umbrella

CellGSM 900

GSM1800 GSM1800GSM1800

GSM 900 GSM 900 GSM 900

GSM900GSM900

GSM1800GSM1800

GSM900 GSM900

GSM1800 GSM1800

GSM1800

Cell

Hierarchical cell structure



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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 celllist.

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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: Layer HO threshold adjustment bit

Serving cell criterion:

Receive level >= layer HO threshold layer HO hysteresis, bit 14th is set

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

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

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

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Neighbor cell criterion:

Receive level >=layer HO threshold + layer HO hysteresis, bit 14th is

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

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

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

note :

The layer HO threshold and hierarchical hysteresis correspond to the

value of that individual cellsvalue.

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

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

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

hierarchical layers of the cell.

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

Serving cell or Neighbor cells:

When cell type is extension cell1.

When cell type is normal cell0.

The 16th bit: Reserved bit

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General HO process


Penalty processing


HO judgment



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HO Algorithm

Initializing

M rule

K rule

16bits rule

Emergency HO judgment

Load-HO judgment

Normal HO judgment

Fast moving HO judgment

Layer HO judgment

PBGT HO judgment

Send HO command

Send HO command

Send HO command

Overlaid/under laid HO

judgment

Edge HO judgment

Forced HO Direct re-tryO&M reason


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Types of HO

Types of HO :

Emergency HO

TA & 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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Emergency HO

TA HO criterion :

TA of the serving cell > TA Thrsh.

BQ HO criterion :

The average value of the uplink quality of the serving cell >UL Qual. Thrsh.

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

DL Qual. Thrsh.

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

of HO):

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

value.


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Emergency HO

Rx_Level_Drop HO:

Due to downlink signal level drop

Triggered upon detecting rapid level drop during MS busy mode.

Requirements for the target cell: The target cell is the first cell in the neighbor cell list.


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Emergency HO

Interference HO (DL&UL) :

When the receiving level > receiving threshold level. But

Receiving quality < threshold of quality interference.

Requirements for the target cell:

The target cell is in the cell list.


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Cell Load HO

Cell Load HO Criterions :

System load of BSC < Permissible load of HO threshold

Load of serving cell > Load HO threshold

Requirements for the target cell

Load of target cell < Load HO threshold

BTS

BSC


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Normal HO

Edge HO Criterion:

In N seconds, when there are P seconds that neighbor cellsDL

or MSs UL signal level is lower than the Edge HO threshold.

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

utilizes the P/N rule.

Requirements for the target cell:

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


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Normal HO

Layer HO criterions:

Serving cell :

No requirement.

Target cell :

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

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

hysteresis.

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

of target cell should be higher than the serving cells.


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PBGT HO Criterions :

Target cellspath loss is smaller than the serving cellspath loss

by the PBGT threshold value.

Satisfying the P/N rule.

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

Note :

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

system permits PBGT HO for the cell, PBGT HO can occur ineither inter-BSC or inter-MSC.

PBGT HO


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Fast-Moving HO

When the serving cell is micro cell :

When the MS has traveled through P numbers of cell, and there

are Q (=


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underlaid

overlaid

Overlaid/ underlaid :

Division of underlaid and overlaid is decided by MS downlink

receive level and TA value.

Overlaid/Underlaid HO


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Criterion for HO from overlaid to underlaid:

TA value => TA threshold + TA hysteresis Or

RX_LEV


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Question

Can you list the function of each bit in 16bit ranking?

What is the period of measurement report?


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Course 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]

HO data lookup process


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[Handover Control Table] -1Parameter

nameMeaning Value range Recommen

ded value

Co-BSC/MSCAdj.

It means whether the 12th

and 13th

bits acts in the 16bit order.Yes means handover in the same BSC/MSC is preferred.No means that the 12

thand 13

thbits are shielded and set to

0.

Yes, No Yes

Penaltyallowed

It determines whether to punish the target cell of handoverfailure, or the original served cell of handover upon too big TA

or bad quality. The penalty measures can apply to cells in orout of the same BSC.

Yes, No No

Load HOallowed

It determines whether to perform the handover to share trafficload. Load sharing can lower the channel assignment failureratio caused by cell congestion, so as to make evenerallocation of the service in respective cells, and lower the cellcongestion rate , and improve network performance. It on lyapplies in the same BSC or cells at the same level.

Yes, No No

MS Fastmoving HO

allowed

It determines whether to handle the fast moving MS with thealgorithm. It is only recommended in special a reas (such as a

highway), to lower CPU load. This algorithm should only beused in suitable conditions, and usually it is not applied.

Yes, No No


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[Handover Control Table] -2

Parameter name Meaning Value range Recommendedvalue

RX_Level_DropHO allowed

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 itis not used. To apply the handover algorithm, BSC

must have original measurement report.

Yes, No No

PBGT HOallowed

It means whether PBGT handover algorithm isallowed. PBGT handover algorithm currently isprocessed on LAPD board. To avoid Ping -panghandover, PBGT handover is only performed betweencells at the same layer and with the same priority, andmeanwhile it is only triggered on TCH.

Yes, No Yes

MS powerprediction afterHO

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

Yes, No Yes


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Parametername

Meaning Value range Recommendedvalue

MR.Preprocessing

Yes means perform measureme nt reportpreprocessing on BTS; No means preprocessing onBSC, then the two parameters of Send originalmeasurement report and Send BS/MS power level do not act. Yes means decreasing of Abis interfacesignaling and BSC load, and improving of network

response time performance. The switch determineswhere to perform power control. When it is set toYes, power control is performed at BTS side. Whenit is set to No, power control is performed at BSCside. When setting this parameter, first be clearwhether BTS supports the power control algorithm toset or not.

Yes, No Yes

[Handover control table] -3


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Parametername


Transferoriginal MR.

It means whether to send the original measurementreport to BSC after measurement report preprocessingon BTS. When it is set to Yes, BTS sends not onlyprocessed measurement rep ort but also originalmeasurement report to BSC.

Yes, No No

TransferBS/MS powerclass

It means whether to send BS/MS power level from BTSto BSC. This function is used to view the effect of powercontrol on BTS. Meanwhile, when preprocessing isavailable, if BS/MS power level is not reported, the uplinkand downlink balance measurements will be affected,and handover types such as PBGT handover andoverlaid/underlaid handover needing powercompensation will be abnormal.

Yes, No Yes



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Parametername


Sent Freq. ofpreprocessedMR.

It indicates the time interval at which a measurement reportis preprocessed at B TS side and sent to BSC thePreprocessed measurement report. This parameter actsonly whenMeasurement report pre-processing is enabled .For 15:1 link configuration, the report frequency should be

as low as once per second due to limited link resource. Atthis time, for handover nee ding P/N judgment such as edgehandover, layer handove r, PBGT handover andoverlaid/underlaid handover,

Twice persecond, Onceper second

According toconcreteconditions



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Parametername

Meaning Valuerange

Recommendedvalue

Layer of thecell

Huwei hierarchical network structure is divided into 4 layers. 16priorities 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 900layer, Micro layer is the major 1800 layer, Pico is the 900 and1800 micro cell layer. The smaller layer value, the higherpriority.

The1st~4thlayers

M900: the 3 rd

layer

M1800: the 2 ndlayer

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

1~16priorities

1

Layer HOThrsh.

It affects the value of the 14th bit in the 16bit ranking, and it isalso the level requirement on the target cell for int erferencehandover, layer handover and load handover. Then su ch levelshould be higher than layer h andover threshold + layer

handover hysteresis. The layer handover threshold should beset >= Edge handover threshold + Inter -cell handoverhysteresis.

0~63 25

Layer HOhysteresis

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


[Cell Description Table] -1


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Parametername


Penalty onMS Fastingmoving HO

It is valid when the fast m oving handover algorithm isenabled. It is the signal level penalty value on the otherneighbor cells when MS moves fast and is handed over

to umbrella cell. The paramete r is only valid within thepenalty time.

0~63dB 30

PenaltyTime on MSFastingmoving HO

It means that within this tim e, the penalty on the otherneighbor cells will be exerted a fter MS is handed overto umbrella cell by fast moving HO.

0~255seconds

40

Min DL level

0ncandidatecell

This is the min signal level requirement for the cell itself

to be a candidate cell . Too low configuration may easilycause call drops, while too high a configuration mightturn handover too hard to occur.

0~63 15


[Cell Description Table] -2


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Parametername


Ncell ID Neighbor cell ID index. 0~255 forinternal cell;0~799 forexternal cell

Min accesslevel offset

This offset is based on Min downlink level of handovercandidate cell. Different offsets can be defined for differentadjacent cells, and to enter the can didate cell list, thecorresponding adjacent cell rec eiving signal level must behigher tha n the sum of Mi n downlink level of handover

candidate cell and Min. Access level offset.

0~63 0


[Adjacent Cell Relation Table] -1


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Parametername


PBGT HOThrsh.

It means that PBGT handover is performed when thedifference between the target cell downlink path loss and theserving cell downlink path loss is bigger than PBGT handoverthreshold. Whe n PBGT handover is enabled , and Inter -cellhandover hysteresis > PBGT handover threshold

(corresponding dB value), Inter -cell handover hysteresistakes place of PBGT handover threshold to act. . PBGThandover threshold also needs to be adjusted acc ording tohandover performance statistics result.

0~127,corresponding to--64~63dB

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

Inter-cell HOhysteresis

Handover hysteresis between an adjacent cell and the servingcell. It is set to reduce Ping -pang HO. The hysteresis valuealso needs to be adjusted according to the handoverperformance statistics result and live network. Flexible

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

0~63db It is around 4 in thedensely populateddowntown, andaround 8 on the

outskirts.

[Adjacent Cell Relation Table] -2


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[Penalty Table] -1

Parametername


Penalty levelafter HO fail

The signal level value in dB, to punish the target cellwhich has caused a HO failure due to problems suchas congestion , to prevent MS from a handover

re-attempt to that ce ll again. This value is only validwithin the penalty time for handover failure.

0~63dB 30

Penalty timeafter HO fail

Penalty time on the corresponding target cell afterhandover failure

0~60 seconds 10

Penalty levelafter BQ HO

fail

The signal level pen alty value for the original servingcell, to avoid Ping -pang handover after emergency

handover upon bad quality. It is only valid within thepenalty time for BQ HO.

0~63dB 63

Penalty timeafter BQ HOfail

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


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[Penalty Table] -2

Parametername


Penaltylevel afterTA HO fail

The signal strength penalty value for the original serving cell,to avoid Ping -pang handover after TA emergencyhandover. It is only valid within the penalty time for tahandover.

0~63dB 63

Penalty timeafter TA HOfail

Penalty time for the original serving cell after TA emergencyhandover.

0~60Seconds 10

Penalty time

after IUOHO fail

After an overlaid/underlaid handover failure (big circle hands

over to small circle o r vice versa), within certain time (thisparameter configuration value) overlaid/und erlaid handoveris forbidden for the same call.

0~16Seconds 10


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[Emergency Handover Table] -1

Parameter

name

Meaning Value range Recommended

value

TA Thrsh. When TAthis value, emergency handover is

triggered

0~63 bit

period

63

DL QUAL.

Thrsh

The downlink receiving quality threshold for BQ

emergency handover. When frequency hopping orDTX is enabled, RQ becomes worse (normal

phenomenon), this value should be set to 70. The

adjustment should also base on the current network

quality and handover statistics. When triggering

emergency handover, the first to select is the inter-

cell handover, the intra-cell handover is only

triggered when there is no candidate cell and the

intra-cell handover is allowed in the serving cell.

0~70,

corresponding to BQ levels

of 0~7

60

UL QUAL.

Thrsh.

The uplink receiving quality threshold for BQ

emergency HO.

correspondin

g to BQ levels

of 0~7

60


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Parametername


ULQual.Thrsh.for interf.HO

Uplink receiving quality threshold in the serving cell forinterference handover. When frequency hopping or DTX isenbaled, RQ becomes worse (normal phenomenon), thisvalue should be set to 60. The adjustment should also baseon the current network quality and handover statistics. Whentriggering interference handover. If the serving cell is in thefirst position and intra-cell handover is permitted, performintra-cell handover. Otherwise select the second candidatecell to perform inter-cell handover.

correspondingto BQ levels of0~7

50, interferencequality thresholdmust be better thanthe emergencyquality threshold

DL Qual.Thrsh. Forinterf HO.

Downlink receiving quality threshold in the serving cell forinterference handover.

0~70,correspondingto BQ levels of0~7

50


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Paramete

r name


value

UL

RX_LEV

Thrsh. for

interf.HO

Min uplink receiving power threshold from the serving cell

required for interf. HO, when interference handover is

triggered if the uplink quality is worse than quality thr eshold

and at this time the uplink signal level is higher than the signalthreshold. When triggering interference handover, If the

serving cell is in the first posi tion in the cell list, and intra-cell

handover permitted, then start intra -cell HO. Otherwise select

the second cell to perform inter-cell HO.

0~63 25

DL

RX_LEV

Thrsh. for

interf HO.

Min downlink receiving power threshold from the serving cell

required for interf. HO.

0~63 30


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Parametername


Filterparameters

A1~A8

Used for configuration of filter for rapid signaldrop judgment, and together with filter parameterB, they are 9 parameters for a filter. Thecorresponding formula is (in the program, A1~A8

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

C1(nt)=A1C(nt)+A2C(nt-t)+A3C(nt 2t)+

+A8C(nt-7t)Where, C (nt) is the receiving signal level in theuplink measurement report of the serving cellsent at the time of nt. If C1 (nt) < B, and C (nt) isbelow the edge handover threshold, then the

signal level is considered to be of rapid drop.

0~20 10

Filterparameter B

Used for configuration of filter for rapid signaldrop judgment. Please refer to the explanationfor A1~A8 of filter.

0~255 0


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[Load Handover Table] -1

Parametername


System fluxThrsh. for

load HO

The pre-condition for load HO is that the system flow (signalingflow) is lower the threshold. This value can not be set too high

because load handover upon max threshold may cause seriouseffect to the system.

0, 8~11 systemflow levels,

correspondingto 0, 70, 80, 90and 95.

10

Load HOThrsh

Load handover is triggered when the serving cell load is higherthan the threshold, TCH seized in the cell has reaching thecorresponding percentage.

0~7 cell loadlevels,correspondingto 0, 50, 60, 70,75, 80, 85, 90

5

Load Req. oncandidate cell

The Load threshold for the ta rget cells that can accept MS fromserving cell in load HO, i.e. when the TCH under Idle mode inthe neigh bor cell is lower than the corresponding percentage ,the cell refuses to accept MS from serving cell handed over dueto the load reason.

0~7,correspondingto 0, 50, 60, 70,75, 80, 85, 90

2


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[Load Handover Table] -2

Parametername


Load HObandwidth

This config uration is related to the edge handoverthreshold. Load handover is only allowed when the MSreceiving level from the serving cell is within the range of

margin handover threshold, margin handover threshold +load handover bandwidth.

0~63db 25

Load HO stepperiod

When a cell is up to conditions for load handover, all callswithin the serving cell will send handover request at thesame time, this will cause abrupt increase on processorload, and under certain conditions this will cause the

target cell congestion and result in call drops. Thereby,step by step load handover algorithm is used to controlhandover. The cycle is the time needed for handovers ofeach step.

1~60 seconds 10

Load HO steplevel

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

1~63db 5

j O C fi i


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[Normal Handover Table] -1

Parametername

Meaning Value range Recommended value

Edge HO UL

RX_LEV

Thrsh.

During the statistics time, if the time in which the uplinkreceiving level is lower than the value is longer thancertain time called continuous time, edge handoverwill be performed. If PBGT handover is enabled,Corresponding edge handover threshold will be set lower.

0~63 25 (without PBGThandover, downtown),15 (single station onoutskirts), 15 (withPBGT handover,downtown)

Edge HO DL

RX_LEV

Thrsh.

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

M j HO P C fi i


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Parametername


Edge HOwatch time

It means that within the time statistics, if thetime in which the signal level is lower thanthreshold is higher than the continuous time,then margin HO is to be triggered.

1~16 seconds 5

Edge valid

time

See the above. 1~16 seconds 4

M j HO P C fi i


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Parametername


PBGT watch

time

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

PBGT validtime

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

M j HO P t C fi ti


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[Normal Handover Table] -4Parameter

nameMeaning Value range Recommended

value

Layer HOwatch time

Statistics time for Layer HO judgment 1~16 seconds 5

Layer HOvalid time Continuous time for Layer HO judgment. 1~16 seconds 4

M j HO P t C fi ti


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[Fast-Moving Handover Table]Parameter

nameMeaning Value range Recommended

value

MSFast-movingwatch cells

The cell sum P for judge whether MS is fast moving.The value, if too large, may cause abrupt increase ofsystem flow, while too small value may causeinaccurate judgment for fast moving MS.

1~10 3

MSFast-movingvalid cells

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

1~10 2

MSFast-movingtime Thrsh.

The time threshold (2r/v) determined by the cell radius(r) and moving speed (v). If the time in which MSpasses the cell is smaller than the threshold, then MSis judged to quickly pass the cell.

0~255seconds

15

M j HO P t C fi ti


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[Concentric Cell Handover Table] -1

Parameter

name

Meaning Value range Recommended value

UO signal

intensity

difference

BTS transmitting Power difference between

underlaid and overlaid may cause MS receiving

signal intensity difference in underlaid and overlaid .

The parameter uaually indicates the antenna EIRPdifference in dB between underlaid cell and overlaid

cell. According to field measurement, multi-point

measurement is necessary if the underlaid and

overlaid use different antenna.

0~63db Set according to

actual conditions

M j HO P t C fi ti


70/94


[Concentric Cell Handover Table] -2Parameter

name


value

RX_LEV

Thrsh

Rx level hysteresis, 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 betweenunderlaid and overlaid .

0~63 25

RX_LEV

hysteresis

Works with Rx threshold. 0~63 5

TA Thrsh. It must be bigger than TA emergency handover

threshold.

0~63 bit period,

with 1 bit period

corresponding to

0.55km

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



71/94


[Concentric Cell Handover Table] -3Parameter name Meaning Value

rangeRecommended

value

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

5

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

4

M j HO P t C fi ti


72/94


[Concentric Cell Handover Table] -4Parameter

name


value

Assign

optimum

layer

In Overlaid/Underlaid, the following selection are available

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

the measurement report on SDCCH and assign to the

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

assignment. (3) Select the underlaid first for TCHassignment. (4) Do not give extra priority.

System

optimization,

overlaid ,

underlaid , no

preferential

System optimization

Assign-

optimum

level Thrsh.

If system optimization is selected, estimate (interpolate,

filter) current SDCCH level value through uplink

measurement value in the former SDCCH measurement

report, and compare with Assign-optimum Level

threshold, so as to assign overlaid or underlaid channel.

If SDCCH is in the overlaid : edge handover threshold +

signal intensity difference between underlaid and overlaid+ uplink and downlink balance allowance + SDCCH and

TCH difference allowance. If SDCCH is in the underlaid :

edge handover threshold + uplink and downlink balance

allowance + SDCCH and TCH difference allowance.

0~63



73/94


[Concentric Cell Handover Table] -5

Parameter

name

Meaning Value

range

Recommended

value

Pref. subcell

in HO of

intra-BSC

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

are two processing methods for incoming handover request

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

(2) Add BCCH signal level value of the target cell in inter-cell handover request message to BSC to make BSC

allocate optimum channel for MS from underlaid or

overlaid .

Yes, No Yes

Incoming-to-

BSC HO

optimum

layer

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

Overlaid/Underlaid, then, this parameter will show which

layer is preferred to provide service for the MS.

overlaid ,

underlaid ,

none

None

HO Parameters Configuration


74/94

HO Parameters Configuration


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.

Summary of BSC HO


75/94


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

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

sends HO request messages containing the target CGI to MPU

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

the cell from Cell Module Information Table.

MPU sends a HO command message to the target module and

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

Summary of BSC HO

Course Contents


76/94





Course Contents



77/94


Intra BSC Handover

Intra MSC Handover

Inter MSC Handover

Intra-BSC Handover Signaling process


78/94

Intra BSC Handover Signaling process

MS MSBTS1 BTS2BSC MSC

Measurement Report from MS

Channel_Active

Channel_Active ACK

HANDOVER COMMAND

Handover AccessHandover_Detect

PHY INFO

First SABM

Establish_IND

PHY INFO

Handover Complete

Handover_Performed



79/94


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.



80/94

MS BTS BTSBSC MSC

Measurement ReportMeasurement Report

Channel_Activate

Channel_Activate ACK

Handover Command (Old FACCH)

Handover Access (New FACCH)

Handover Complete (New FACCH)

RF Channel ReleaseHandover Performed

T09++

T12++

T10++

T13++

Attempted outgoing internal inter cell handovers

Attempted incoming internal inter cell handovers

Successful incoming internal inter cell handovers

Successful outgoing internal inter cell handovers

(Original) (Target)


Measurement Points of Intra BSC Handover


81/94

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



82/94


Intra BSC Handover

Intra MSC Handover

Inter MSC Handover

Intra-MSC HO Signaling process


83/94

MS BTS BTSBSC1 BSC2MSC(original) (Target)

Measurement Report

Measurement ReportHandover Required

Handover Request

Channel_Active

Channel_Active_ACK

Handover_Request_ACKHandover 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

Signaling intra MSC

Intra MSC HO Signaling process



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O S g g p ocess

Intra BSC Handover

Intra MSC Handover

Inter MSC Handover

Measurement Points of Inter-BSC Handover


85/94

Signaling process between MSC

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-CommandClear-Complete

MAP_Send_End_Signal_ACK

Some intermediate steps are omitted

IAI

ACM

Measurement Points of Inter-BSC Handover


86/94

Signalingprocess between MSC

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

HO-REQUIREDMAP_Prepare_HO

MAP_Prepare_HO_ACK

MAP_Allocate_HO_NUM

MAP_Send_HO_Report

MAP_Send_HO_Report_ACK

MS

HO-REQUEST

HO-REQUEST-ACK

HO-Command

MS

HO-AccessMAP_Process_Access_Signalling

HO-Complete

MAP_Send_End_SignalClear-Command

Clear-Complete

MAP_Send_End_Signal_ACK

Some intermediate steps are omitted

IAI

ACM


87/94

Inter MSC HOSubsequent HO process


88/94

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

q p

Inter MSC HOSubsequent HO process


89/94

Highway

MSC-AMSC-C

MSC-B MSC-C

q p

Subsequent HO

Inter MSC HO Signaling process


90/94

g g p

Statistics countersame as

Intra MSC HO, Statistics is

handled by BSC

HO formula-- same as Intra

MSC HO

Basic process of HO Signaling process


91/94

p g g p

1. There is no HOrequestinformation for intra-BSC HO, and all of the HO are analyzedand processed in BSC. Once the target cell as required is found in the BSC, Channel

activationinformation is sent to it directly.

2. 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-Requestto the BSC of the target

cell, and the target BSC activates the target cell channel to complete the following

procedure.

3. 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-HOmessage 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.

Intra-BSC HO and Inter-BSC HO


92/94

Major differences:

Inter BSC HO transfers HO-REQmessage through MSC, with

CGI of the serving cell and target cell carried in the message.

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

handled inside BSC.

Intra BSC HO only sends HO-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 .

Question


93/94

What is the content of PHY INFO? When will the system

send this message to MS?

Why Internal inter cell radio handover success rate >=

Internal inter cell handover success rate?


94/94

annexure b handover

Documents