Hand Over

HUAWEI TECHNOLOGIES CO., LTD.

www.huawei.com

Huawei Confidential

Security Level:

英文标题 :40-47pt

副标题 :26-30pt

字体颜色 : 反白内部使用字体 :

FrutigerNext LT Medium

外部使用字体 : Arial

中文标题 :35-47pt

字体 : 黑体副标题 :24-28pt

字体颜色 : 反白字体 : 细黑体

Handover

Sanjaya Weerakoon

13/03/2008

HUAWEI TECHNOLOGIES CO., LTD. Page 2Huawei Confidential

Content

Introduction and purpose of handover

Process of Handover

Types of Handover


Introduction and Purpose of HO

Handover can maintain the communication

continuity of MS which moves across different cells

and lower the call drop rate and provide better

communication service.

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


ProcessMeasurements MS

BTS

DL Level serving cell DL Quality serving cell DL Level neighbor cells UL Level UL Quality Timing advance Measurement reporting MS → BTS

MR preprocessing

Penalty processing

Cell Ranking

Handover Judgement

BA2 table

BCCHBSIC

BTSModule numbercell number CGI

Adjacent cell Relation TableCell Description TableExternal Cell Description Table

BSC Target cell list

Handover execution

MSBTSBSCMSC


ProcessMeasurements

Measurement reporting

MR preprocessing

Penalty processing

Cell Ranking

Handover Judgement

Handover execution

RXQUAL: Function of BER (Defined by GSM 05.08)

RXLEV: Average per SACCH period

Mapped as RXLEV value


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)

Measurements


MR preprocessing

Penalty processing

Cell Ranking

Handover Judgement

Handover execution

Process

SUB → DTX

Generate by MS

Generate by BTS



MR MR MR MR MR

Measurement report No. n

Measurement report No. n+4

Continuous MR flow

Measurements


MR preprocessing

Penalty processing

Cell Ranking

Handover Judgement

Handover execution

Interpolate ---- Add MR when missing

Filter----Average several continuous MR

MR MR MR MR MR MR

Continuous MR flow

Watch Time

Valid Time

Process


Measurements


MR preprocessing

Penalty processing

Cell Ranking

Handover Judgement

Handover execution

Process



Measurements


MR preprocessing

Penalty processing

Cell Ranking

Handover Judgement

Handover execution

M rule —— received signal level → generate candidate cell list

For serving cell RX_LEV (o) >MSRXMIN(o) + MAX(0,Pa(o))For Neighbor cellRX_LEV (n) > MSRXMIN(n)+ MAX(0,Pa(n))+ OFFSET

Pa(0) : MS_TXPWR_MAX(0) – PPa(n) : MS_TXPWR_MAX(n) – PMS_TXPWR_MAX( ) : The appointed MS transmitting power by the BSS.P : Max_Power_of_MSMax_Power_of_MS : MS maximum transmitting power

K rule —— received signal level → rank candidate cell list

16 bit ranking —— calculate 16 bit value and rank

Min DL level 0n Candidate cell

Process


Process - 16 bit ranking

1st-3rd bits: bit value is decided according to the cell signal level

and the penalty process taking place beforehand.

max. 6 candidate cells and 1 serving cell

level ranges from 000~110.cell with the strongest signal level is

000.

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



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

layer ) hysteresis.

serving cell is always 0

Neighbor cell

# 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.

# 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.

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



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.

# Huawei cell layers can be divided into 4 layers and each layer can

be further divided into 16 different priorities.

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



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.

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



12th bit: bit value is decided by co-BSC criterion.Serving cell: is always set to 0.Neighbor cell: if co-BSC with the serving cell, 12th bit is set to 0,

otherwise is set to 1.When the signal level from the neighbor cell or the serving cell is

lower than layer HO threshold and hysteresis. This function is turned

off and the value is set to 0. If the parameter – “Co-BSC/MSC Adj.” in the HO control table is set to

“No”, then this function is turned off and the value is 0. 13th bit : Bit value is decided by Co-MSC parameter, having the

same concept as the 12th bit.

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



14th bit: Layer HO threshold adjustment bit

15th bit: Bit value is decided by cell type

16th bit: Reserved bit

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


Measurements


MR preprocessing

Penalty processing

Cell Ranking

Handover Judgement

Handover execution

Process


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 SABMEstablish_IND

PHY INFO

Handover Complete

Handover_Performed

Measurements


MR preprocessing

Penalty processing

Cell Ranking

Handover Judgement

Handover execution HO-REQUIRED

HO-REQUEST

Process


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&Bad Quality HO

TA HO criterion : TA of the serving cell > TA Thrsh.

BQ HO criterion : The average value of the uplink quality of the serving

cell >

UL Qual. Thrsh. The average value of the downlink quality of the serving

cell > DL Qual. Thrsh.

Requirements on the target cell Select the first cell in the neighbor cell list


Rx_Level_Drop HO

Rx_Level_Drop HO Due to downlink signal level drop Triggered upon detecting rapid level drop during MS busy

mode.

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


Interference 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.


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


Edge HO

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

DL or MS’s UL signal level is lower than the Edge HO

threshold. Then the criterion is met and Edge HO occurs.

This method utilizes the P/N rule.

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


Layer HO

Layer HO criterions: Serving cell :

No requirement.

Target cell : Layer of the target cell is lower than the serving cell. Receive level of the target cell > layer cell threshold + layer cell

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

priority of target cell should be higher than the serving cell’s.


PBGT HO

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

loss by the PBGT threshold value. Satisfying the P/N rule. Target cell should be ranked in front of the serving cell.

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

system permits PBGT HO for the cell, PBGT HO can occur in

either inter-BSC or inter-MSC.


Fast-Moving HO

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

there are Q (=<P) numbers of cell that the MS has traveled in

high speed, the criteria is satisfied. MS will be handed over to

umbrella cell.

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

penalty can be given to the micro cell for a duration of time

(penalty time). In this way, the MS will not use the micro cell.

Note :In this case, the micro cell is only used under urgency

conditions( Poor TA and BQ ).


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 Satisfying P/N rule


Thank You

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