OMF810002 GSM Handover Algorithm ISSUE2.01

GSM Handover Algorithm N-1

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Copyright 2009 Huawei Technologies Co., Ltd. All rights reserved.

GSM Handover Algorithm



Page2Copyright 2009 Huawei Technologies Co., Ltd. All rights reserved.

Foreword

z Handover is a key technology of mobile communication system and

make continued conversation possible.

z Handover algorithm in Huawei product is flexible and powerful.




Objectives

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

Outline the types of handover

Master handover judgment flow

Understand algorithm of different handovers

Explain HO data configuration




Contents

1. Introduction of Handover

2. HO Algorithm Process




Contents






Purposes of HO

z To keep a continuous communication with a moving MS

z To improve network service performance

To reduce the call drop rate

To reduce the congestion rate

Handover can maintain the communication continuity of MS which moves across different cells and lower the call drop rate and provide better communication service.




Classification by Reason

No DL MR Emergency HOTiming Advance (TA) HOInterference HORx_Level_Drop HOBad Quality (BQ) HO

Emergency HO

Enhanced Dual Band HO

Load HO

Normal HO

1

2

3

4

Classification by

ReasonEDGE HO PBGT HOLayer HO MS Fast Moving HOConcentric Cell HOAMR HO




Classification by Synchronization

CELL

Case 1

Synchronous Handover: the target BTS shall not send PHY INFO message

Case 2

Asynchronous Handover: the target BTS shall send PHY INFO message

Case 3 Case 4 Case 5

MSC

BSC

BTS

BSC BSC

MSC

BTS BTS BTS BTS

NSS Network

Synchronous handover: source and target cell belong the same BTS

Asynchronous handover: source and target cell belong the different BTS




Classification by Equipment and Channel

SDCCH SDCCH TCHTCH(Direct Retry)(Direct Retry)

SDCCH SDCCH SDCCHSDCCH

Intra Intra Cell HOCell HO

Inter Inter Cell HOCell HO

Intra Intra BSC HOBSC HO

Intra Intra MSC HOMSC HO

Inter Inter MSC HOMSC HO

TCH TCH TCHTCH




Contents






Contents


2.1 General HO Process

2.2 Measure and Measurement Result Report

2.3 Measurement Report Preprocessing

2.4 Handover Judgment

2.5 Handover Implementation




General HO Process

MS Goes into New Dedicated Mode

MS Goes into Dedicated Mode

Measure and Measurement Result Report1

Measurement Report Preprocessing2

Handover Judgment3

Handover Implementation4




General HO Process




Measurement Report Preprocessing2

Handover Judgment3





The downlink measurement reportof the neighbor cell (BCCH)

Measurement Report

z Uplink MR includes uplink receiving level and quality.

z 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 uplink MR

The downlink MR

In dedicated mode, the system performs handover and power control judgment based on measurement reports. The downlink MR are reported to the network via uplink SACCH channel.

Downlink--In dedicated mode, MS reports MR via uplink SACCH channel periodically. The report includes the receiving level, received quality, TA, power class and whether DTX is used. At the same time, MS will perform pre-synchronization to neighbor cell defined by the system to obtain BCCH frequencies and BSIC, measure their received signal level and report the six max. neighbor cells with the highest received signal level.

Uplink--The uplink measurement report is measured by BTS, including the receiving level and receiving quality from the MS.

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




Measurement Report

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

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

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

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

RXQUAL level in MR Huawei value BER behind 0 0 Less than 0.2% 1 10 0.2% ~ 0.4% 2 20 0.4% ~ 0.8% 3 30 0.8% ~ 1.6% 4 40 1.6% ~ 3.2% 5 50 3.2% ~ 6.4% 6 60 6.4% ~ 12.8% 7 70 Greater than 12.8%




Period of Measurement Report

z The downlink MR is sent to BTS in SACCH uplink

z The interval is 480ms/per time when MS is on TCH

z The interval is 470ms/per time when MS is on SDCCH

12TCH 12TCH1SACCH 1 Idle

480ms 4 TCH Multi-frames

SACCH is a bidirectional channel.It sends the downlink measurement report to BTS in uplink SACCH.It sends SYS.INFO. 5 and SYS. INFO. 6 to MS in downlink SACCH.

1. The SACCH measurement report period varies with the channel occupied by MS in dedicated mode.

2. When associated with SDCCH, SACCH measurement period is 470ms, this is because there is an entire SACCH message block in 2 SDCCH 51-multiframes.

3. When associated with TCH, SACCH measurement period is 480ms, this is because there is an entire SACCH message block in 4 TCH 26-multiframes

A complete measurement report is formed by four consecutive SACCH bursts. In SDCCH channel the four bursts are transmitted continuously. In TCH channel there is only one SACCH burst in each 26-multiframe, therefore only four 26-multiframe can constitute a complete measurement report.




General HO Process



Measurement Report Preprocessing

Handover Judgment3



2




MR Preprocessing

MR Preprocessing

z Interpolation

Recover the lost

measurement report

z Filtering

Smooth the instantaneous

fading point

MR preprocessing consists of two steps: interpolation and filtering.




MR Interpolation

MR

MR

No. n

No. n+4

Continuou

s MR Flow

MRMR

MR

Missing by some reasons

MR Interpolation recover the lost measurement report

BTS may fail to receive the MR from MS, and it needs to recover the lost measurement reports. If the lost MR amount is within the allowed range (Allowed MR Number Lost), then recovers the lost MR according to the specific algorithm.

zService cell: linear algorithm

zNeighboring cell: the lowest value defined in GSM specification (-110dBm)

The continuity of measurement report is judged by measurement report number. Each measurement report has a serial number. If the serial numbers of received measurement reports are not consecutive, there must be missing measurement reports, and the system will make them up according to the interpolation algorithm.

As shown in the diagram, the network receives measurement reports n and n+4, whose serial numbers are not consecutive, so the system will make up for the missing measurement reports n+1, n+2 and n+3 with a certain algorithm.




MR Filtering

MR

MRContinuou

s MR Flow

MR

MR

MR

Filter----Average several consecutive MRs

MR

Filtering smooth the instantaneous fading point

zCalculate the average value within the filter window

When the network receives the measurement report, it can not judge the current condition of MS according to just one measurement report due to the signal fluctuation. Therefore, filtering, a more suitable method is applied.

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




Data Configuration of MR Preprocessing

[MR Preprocessing]

Value Range: Yes, No

Default Value: No

Description: This parameter indicates whether the BTS pre-processes the MR.

z This parameter determines the location where power control is performed. If this parameter is set to Yes, power control is performed by the BTS. Otherwise, the power control is performed by the BSC.

z When this parameter is set to No, the MR is processed by the BSC, in which case, both Transfer original MR, Transfer BS/MS power class and Sent Freq of preprocessed MR are invalid.

z When this parameter is set to Yes, the load over Abis interface and that over the BSC are reduced, thus shortening the response time and improving the network performance.

[Transfer Original MR]


Default Value: No

Description: This parameter indicates whether the original MR is transferred to the BSC after the BTS pre-processes the MR.

z When the parameter is set to Yes, the BTS transfers to the BSC both the processed MR and the original MR.

Remarks:In case of 4:1 configuration, this parameter must be set to No if SDCCH/8 is greater than 2.





[Transfer BS/MS Power Class]


Default Value: Yes

Description: This parameter indicates whether the original BS/MS power class is transferred to the BSC.

Remarks:When MR pre-processing is enabled, uplink and downlink balance measurement is affected if this parameter is set to No. In addition, power compensation handovers, such as PBGT handovers, load handovers, and Concentric Cell handovers, may become abnormal.

[Sent Freq of Preprocessed MR]

Value Range: Do not Report, Twice every second, Once every second, Once every two seconds, Once every four seconds

Default Value: Twice every second

Description: This parameter indicates the frequency that the BTS transfers the preprocessed MR to the BSC. After the MR is preprocessed by BTS, the BTS transfers the preprocessed MR to the BSC. For example, if this parameter is set to Twice every second, the BTS transfers the preprocessed MR to the BSC twice per 0.5 second.





[Allowed MR Number Lost]

Value Range: 0~31

Default Value: 4

Description: This parameter indicates the number of MRs allowed to be lost in succession. When this threshold is not reached, the lost MR is estimated via the linear interpolation basing on the first and the last MRs received. When this threshold is reached, all previous MRs are discarded, and calculations are made again when new MRs are received.

Remarks: MRs fail to be decoded correctly when the signal strength in the serving cell is poor. When this threshold is reached, all previous MRs are discarded and handover may fail. Thus, it is advised to assign this parameter with a greater value to enable emergency handover.

[Filter Length for TCH Level]

Value Range: 1~31

Default Value: 4

Description: This parameter indicates the number of MRs used for averaging the TCH signal strength.

z This parameter helps to avoid sharp drop of signal levels caused by Raileigh Fading and to ensure correct handover decisions.

Remarks: When this parameter is too large, the impact of sudden changes is reduced, and the response is delayed, thus affecting the network performance.

[Filter Length for TCH Qual]

Value Range: 1~31

Default Value: 4

Description: This parameter indicates the number of MRs used for averaging the TCH signal quality.





[Filter Length for SDCCH Level]

Value Range: 1~31

Default Value: 2

Description: This parameter indicates the number of MRs used for averaging the SDCCH signal strength.

z It is recommended that you assign this parameter with a lower value because the SDCCH occupation time is shorter than the TCH occupation time.

[Filter Length for SDCCH Qual]

Value Range: 1~31

Default Value: 2

Description: This parameter indicates the number of MRs used for averaging the SDCCH signal quality.

z It is recommended that you assign this parameter with a lower value because the SDCCH occupation time is shorter than the TCH occupation time.

[Filter Length for Ncell RX_LEV]

Value Range: 1~31

Default Value: 4

Description: This parameter indicates the number of MRs used for averaging the signal strength in neighboring cells. This parameter helps to avoid sharp drop of signal levels and to ensure correct handover decisions.

Remarks: When this parameter is too large, the impact of sudden changes is reduced, and the response is delayed, thus affecting the network performance.

[Filter Length for TA]

Value Range: 1~31

Default Value: 4

Description: This parameter indicates the number of MRs used for TA averaging.




General HO Process


MS Goes intoDedicated Mode


MR. Preprocessing2

Handover Judgment3


TA HO

Interference HO

Rx_Level_Drop HO

Bad Quality HO

Load HO

Edge HO

Layer HO

PBGT HO

AMR HO

No DL MR HO

Concentric Cell HO

MS Fast Moving HO


Penalty Processing

Ranking Processing

OM Forced HO

Direct Retry

Emergency HO

Normal HO




Penalty Processing

Intra-cell HO

HO Fails Emergency (TA&BQ)HO

MS Fast Moving

HO

Concentric Cell HO

Penalty

Punish on the target cell

Punish on the original cell

Punish on other high priority layer cells

AMR HOFails

There are several kinds of penalty process

z Penalty on target cell when a HO fails.

z Penalty on source cell when an emergency HO (BQ and TA ) is performed.

z Penalty on other high priority layer cells after fast moving HO is performed.

z Penalty for concentric cell HO

z Penalty for intra-cell HO

z Penalty for AMR HO




Penalty for Handover Failure

z Punish the target cell when a HO fails.

z This is to avoid the MS to select this cell again in next HO judgment.

Cell A

BTSHO Fail

BSC

Cell B

BTS

When MS fails to handover to a target cell, a penalty will be given on the signal level of this target cell during a so called handover failure penalty time period. That is, when ranking the neighbor cells in the cell list, the corresponding neighbor cell with a failure record within the penalty time will be penalized by cutting certain value on the reported signal level.




Data Configuration of Penalty for Handover Failure

[Penalty Level after HO Fail]

Value Range: 0~63

Unit: dB

Default Value: 30

Description: This parameter indicates the penalty level given to a target cell. A penalty level is given to a target cell to avoid further attempts when a handover fails due to any of the following reasons:

z Cell congestion

z A message indicating internal handover refusal is received.

z A message indicating Um interface handover failure is received during out-going BSC handover.

z A message indicating Um interface handover failure is received during internal handover.

Remarks: This parameter is valid only before the penalty time of handover failure expires.




Data Configuration of Penalty for Handover Failure

[RscPenaltyTimer]

Value Range: 0~255

Unit: Seconds

Default Value: 5

Description: This parameter indicates the length of the penalty timer for handover failure between adjacent cells due to cell congestion.

[UmPenaltyTimer]

Value Range: 0~255

Unit: Seconds

Default Value: 10

Description: This parameter indicates the length of the penalty timer for handover failure between adjacent cells due to failed air interface connection.

[CfgPenaltyTimer]

Value Range: 0~255

Unit: Seconds

Default Value: 255

Description: This parameter indicates the length of the penalty timer for handover failure between adjacent cells due to incorrect data configuration.




Cell A

Cell B

BTSBQ&TA HO

BSC

Penalty for Emergency Handover

z Punish the original cell when an emergency HO ( due to BQ and TA)

occurs.

In case of BQ emergency handover, the original serving cell will be penalized (called signal level penalty by BQ HO ), during BQ HO penalty time, to avoid MS to be handed back to the original serving cell again within certain time.

It is the same for TA handover, i.e. the original serving cell is penalized (signal level penalty by TA HO ) during TA HO penalty time.




Data Configuration of Penalty for Emergency Handover

[Penalty Level after BQ HO]

Value Range: 0~63

Unit: dB

Default Value: 63

Description: This parameter indicates the penalty level given to the original serving cell where emergency handover is performed due to bad quality. After emergency handover is performed due to bad quality, the receive level of the original serving cell is decreased by the penalty level. Thus, other cells are given higher priority and handover to the original serving cell is not allowed.

Remarks: This parameter is valid only before the penalty time of handover due to bad quality expires.

[Penalty Time after BQ HO (s)]

Value Range: 0~255

Unit: Seconds

Default Value: 15

Description: This parameter indicates the penalty time given to the original serving cell where emergency handover is performed due to bad quality. During the penalty time, the receive level of the original serving cell is decreased by the penalty level. Thus, other cells are given higher priority and handover to the original serving cell is not allowed.




Data Configuration of Penalty for Emergency Handover

[Penalty Level after TA HO]

Value Range: 0~63

Unit: dB

Default Value: 63

Description: This parameter indicates the penalty level given to the original serving cell where emergency handover is performed due to TA. After emergency handover is performed due to TA, the receive level of the original serving cell is decreased by the penalty level. Thus, other cells are given higher priority and handover to the original serving cell is not allowed. This parameter is valid only before the penalty time of handover due to TA expires.

[Penalty Time after TA HO(s)]

Value Range: 0~255

Unit: Seconds

Default Value:30

Description: This parameter indicates the penalty time given to the original serving cell where emergency handover is performed due to TA. During the penalty time, the receive level of the original serving cell is decreased by the penalty level. Thus, other cells are given higher priority and handover to the original serving cell is not allowed.




Back? No way!Back? No way!

Umbrella

Micro cell

Penalty for MS Fast-moving Handover

z Giving penalty on the other three layers(Non-umbrella Layer ) after MS

handovers to Umbrella cell by fast-moving-HO.

z This is to keep MS staying in the umbrella cell and avoid frequent HO.

Purpose of such penalty: When MS crosses continuously several micro cells, it handover to the umbrella cell with lower hierarchical priority level, to avoid too frequent handovers which will affect the communication quality between those cells. At the same time, penalty is started to avoid handover back to original cell again. A possible example is that a fast moving car is running on a highway.




Data Configuration of Penalty for MS Fast-moving Handover

[Penalty on MS Fast Moving HO]

Value Range: 0~63

Unit: dB

Default Value:30

Description: This parameter indicates the penalty given to the level in a neighboring cell when an MS is moving fast. Only the cells in the umbrella layer can give penalty to the cells in other three layers.

Remarks: This parameter is valid only before the penalty time of fast moving expires.

[Penalty Time on Fast Moving HO]

Value Range: 0~255

Unit: Seconds

Default Value: 40

Description: This parameter indicates the period during which penalty is performed on the neighboring cells of the fast moving MS. During this period, penalty on the neighboring cells (on only the other three layers except the umbrella layer) of fast moving MS is valid.




Underlaid

Overlaid Do not attempt again during penalty time

after one failed HO(O->U)!

Penalty for Concentric Cell

z A new concentric cell HO is prohibited within a penalty time after a

concentric cell HO failure.

Do not attempt again after N failed

HO(U->O)!

Huawei concentric cell HO failure means the failure of handover from the Underlaid to the Overlaid, or from the Overlaid to the Underlaid.




Data Configuration of Penalty for Concentric Cell

[Penalty Time after UtoO HO Fails(s)]

Value Range: 10~255 Unit: Seconds Default Value: 40

Description: After a UL to OL handover fails, no UL to OL handover request is allowed before the penalty time expires.

[Penalty Time after OtoU HO Fails(s)]


Description: After an OL to UL handover fails, no OL to UL handover request is allowed before the penalty time expires.

[MaxRetry Time after UtoO Fail]

Value Range: 0~8 Default Value: 3

Description: This parameter indicates the threshold of UL to OL handover failures. UL to OL handover is not allowed if the number of handover failures reaches this threshold.

Remarks: When this parameter is set to 0, not this threshold but the penalty time restricts the permission of handover.




Underlaid

OverlaidDo not

attempt back too fast!

Penalty for Enhanced Concentric Cell

z A new UO HO is prohibited within a penalty time after a OU HO is performed successfully.

This penalty is valid only for Enhanced Concentric Cell.




Data Configuration of Penalty for Enhanced Concentric Cell

[Penalty Time of UtoO HO(s)]

Value Range: 0~255

Unit: Seconds

Default Value: 10

Description: This parameter indicates the penalty time for forbidding ping-pong handovers. After an OL to UL handover is performed, UL to OL handover is not allowed before the penalty time expires. If this parameter is set to 0, a UL to OL handover is allowed when required.

Remarks: This parameter is valid only when Enhanced Concentric Cell is allowed.




Penalty for Intra-cell HO

z A new intra-cell HO is prohibited if it occurs too frequently.

3 7 12 32 T (s)0

Penalty time

Intra-cell HO Time

2nd.3rd.

4th.

Max. consecutive HO times: 3

Forbidden time after Max. times: 20s

Interval for consecutive HO Jud: 6s

1st.

Because of the co-channel interference and other interference, the voice quality of a MS on certain frequency may lower than the handoverthreshold, now, the voice quality can be satisfied if the MS hands over to another frequency in the same cell. On the other side, the signaling flow of this kind of intra-cell handover is less and handover successful ratio is higher.

But under some specific condition (for example: several frequency are all interfered in a cell), then continual intra-cell handover may occurred. So it is necessary to control the frequency of intra-cell handover.




Data Configuration of Penalty for Intra-cell HO

[Max Consecutive HO Times]

Value Range:1~20

Default Value: 3

Description: This parameter indicates the maximum number of consecutive intra-cell handovers allowed. If the interval of two continuous intra-cell handovers is less than a specified threshold, the two handovers are regarded as consecutive handovers.Intra-cell handover is forbidden if the number of consecutive handovers exceeds this threshold.

[Forbidden Time after Max Times]

Value Range: 1~200

Unit: Seconds

Default Value: 20

Description: This parameter indicates the timer that starts when the threshold of maximum consecutive intra-cell handovers is reached. Intra-cell handovers is allowed only when the timer expires.

[Interval for Consecutive HO Jud.]

Value Range: 1~200

Unit: Seconds

Default Value: 6

Description: This parameter indicates the period for judging whether two continuous intra-cell handovers are consecutive.




Data Configuration of Penalty for AMR FRHR Handover Failure

[Penalty Time after AMR TCHF-H HO Fails(s)]

Value Range: 0~255

Unit: Seconds

Default Value: 30

Description: This parameter indicates the penalty time for AMR full rate to half rate (FR-to-HR) handovers. Before the timer expires, no AMR FR-to-HR handover request is allowed if the previous full-half handover fails due to channel unavailability or channel mismatch.




General HO Process




MR. Preprocessing2

Handover Judgment3


TA HO

Interference HO

Rx_Level_Drop HO

Bad Quality HO

Load HO

Edge HO

Layer HO

PBGT HO

AMR HO

No DL MR HO

Concentric Cell HO

MS Fast Moving HO


Penalty Processing

Ranking Processing

OM Forced HO

Direct Retry

Emergency HO

Normal HO




Ranking Processing

M rule

K rule

Basic ranking

16 bits ranking

Network feature adjustment

The ranking result: target cell selection of handover

Ranking processing of cells are major parts of the HO judgment.

The ranking result is used for target cell selection of handover.

The ranking processing includes:

zBasic ranking

M rule

K rule (Integrated with 16bits ranking, will be discussed together with 16bits ranking)

zNetwork feature adjustment

16 bits ranking




M Rule Begin

Finish to all neighbor cells?

An BSC external neighboring cell& the current channel is

SDCCH ?

No

Yes

Direct retry? [Inter-BSC SDCCH HO Allowed] (S) is Yes?

Delete the cell from the cell list?

the cell overload ?

Yes No

Yes

No

RX_LEV_DL(n) < [Min DL Poweron HO Candidate Cell](n)+

[Min Access Level Offset](s->n)?

RX_LEV_UL(n) < [Min UP Power on HO Candidate Cell](n)+

[Min Access Level Offset](s->n)?

Delete this cell from the cell list

Yes

No

No

No

No

Yes

End

For service cell: Min Access Level Offset=0

M rule will remove the neighbor cells from the candidate cell listaccording to the flow.

Yes

Yes

M rule will remove the cells from the candidate cell list according to the following conditions:

zUnder the condition of non-direct retry, if Inter-BSC SDCCH HO Allowed is No, and this is an external neighboring cell, and the current channel is SDCCH

zIf the cell is overload

zRX_LEV_DL < Min DL Power on HO Candidate Cell + Min Access Level Offset

zRX_LEV_UL < Min UL Power on HO Candidate Cell + Min Access Level Offset

For service cell: Min Access Level Offset is 0.




Data Configuration of M Rule

[Inter-BSC SDCCH HO Allowed]


Default Value: No

Description: This parameter indicates whether an inter-BSC SDCCH handover is allowed. An inter-BSC SDCCH handover is triggered when an MS succeeds in requesting SDCCH but fails to request TCH in a BSC.




Data Configuration of M Rule

[Min UP Power on HO Candidate Cell]

Value Range: 0~63 (-110 dBm to -47 dBm) Default Value: 10

Description: The M criterion supports the minimum value constraint of uplink received level of the neighbor cell. Expected uplink level of the neighbor cell >= (the minimum uplink power of the candidate cell for handover + the minimum access level offset)The M criterion is satisfied only when the expected downlink level of the neighbor cell >= (the minimum downlink power of the candidate cell for handover + the minimum access level offset).0-63 with 0 indicating -110 dBmand 63 indicating -47 dBm.

[Min DL Level on Candidate Cell]


Description: This parameter indicates the lower threshold of downlink receive level when a cell becomes a candidate cell.

Remarks: This parameter must be appropriately specified. If it is too high, some desired cells may be excluded from the candidate cells. If it is too low, an unwanted cell may become the target cell, thus leading to handover failures or call drops. A cell can become a candidate cell only when the receive level minus this parameter is greater than the minimum access level offset.

[Min Access Level Offset]

Value Range: 0~63 Unit: dB Default Value: 0

Description: This offset is based on the Min DL level on Candidate Cell. For different adjacent cells, different offsets can be defined. Only when the receiving level of an adjacent cell > Min DL Level on Candidate Cell + Min Access Level Offset, then this cell become a candidate cell.




Network Feature Adjustment

z After network feature adjustment, all the candidate cells have their own

16 bits value.

z The smaller the value is, the higher the handover priority and position of

the cell are in the candidate cell list, then it is possible to be the

candidate cell.

The Lowest

Weight

The Highest

Weight 16 15 1413 12 1

1 10 98 7 6

5 4 32 1





z The 1st~3rd bits

The bit value indicates the priority of downlink receiving level 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, for the cell with second strongest signal

level is 001 and so on.

Actually that is the core of K rule.

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z The 4th bit: [Inter-cell HO hysteresis] bit.

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serving cell?

Always set to 0

No

RX_LEV_DL (n) >=RX_LEV_DL (s) +

[Inter-cell HO hysteresis] (s->n) ?

Yes

Set to 0Yes

Set to1

No

Service cell: always 0

Neighboring cell: when RX_LEV_DL (n) >= RX_LEV_DL (s) + Inter-cell HO hysteresis, bit 4th is set to 0. Otherwise, set to 1




Data Configuration of Inter-cell HO Hysteresis

[Inter-cell HO Hysteresis]

Value Range: 0~63

Unit: dB

Default Value: 5

Description: This parameter indicates the handover hysteresis between adjacent cells of the same layer. The purpose of setting this parameter is to reduce the "Ping-Pong" handovers. The value of this parameter is invalid if cells are not on the same layer. 4 dB for populous urban areas and 8 dB for suburbs.





z The 5th~10th bits

The bit value is decided according to their position in Huawei hierarchical

network structure.

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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Hierarchical Cell Structure

GSM900 Cell

Micro Cell

Umbrella Cell GSM 900

GSM1800 GSM1800GSM1800

GSM 900

GSM900GSM900

GSM1800GSM1800

GSM1800 Cell

GSM 900

GSM900GSM900

GSM1800GSM1800

Layer 4low

Layer 3

Layer 2

Layer 1high

The handover algorithm of Huawei divides the whole network into four layers, each of which further divided into 16 levels. The lower the layer is, the higher the handover priority level will be. The Micro Cell layer has the highest priority level.




Data Configuration of Cell Hierarchical Network Structure

[Cell Layer]

Value Range:1~4 (mapping to the PICO layer, the MICRO layer, the MACRO layer, and the UMBRELLA layer)

Unit: Layer

Default Value: 3

Description: The framework of Huawei network is divided into four layers: Umbrella layer, Macro layer, Micro layer, and Pico layer. Each layer is designed with 16 priorities. The Umbrella layer refers to the GSM900 layer with a large coverage area. It implements the high-layer coverage and the connection of MSs moving at a high speed. The Macro layer carries most traffic on the GSM900 band. The Micro layer carries most traffic on the DCS1800 band. It solves the problem of insufficient resources. The Micro layer is a main cell layer for dual-band MSs in the future. The Pico layer is a microcell layer on the GSM900 and DCS1800 bands. It meets the requirements for the provisioning of traffic at hot spots and dead zones.

Remarks: You can set multiple priorities (a maximum of 16 priorities) for each layer. From the aspect of traffic priority, if the layer and level of a cell is low, the priority is high.

[Cell Priority]

Value Range:1~16

Unit: Level

Default Value:1

Description: This parameter controls handover between cells at the same layer. Generally, the cells at the same layer have the same priority. If the cells at the same layer have different priorities, the cell with a smaller value has a higher priority.





z The 11th bit: The bit value is decided by cell-load-sharing criterion.

This bit is affected by 14th bit.

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System load>=[System Flux Threshold for Load HO](s) or [Load HO Allowed](s) =No ?

Yes 11th bit is turned off

serving cell?

set to 0

NoYes

Cell load >= [Load HO Threshold](s)?

set to 1 set to 1

cell load >=[ Load Req. on Candidate Cell](n)?

set to 0

Yes

No

Yes

No

No

The 11th bit: bit value is decided by cell-load-sharing criterion. And this bit will be turned off when the system load is higher than System Flux Threshold for Load HO or Load HO Allowed is set to NO

Service cell: if cell load >= Load HO Threshold, bit 11th is set to 1. Otherwise, set to 0

Neighboring cell: if cell load >= Load Rep. on Candidate Cell, bit 11th is set to 1. Otherwise, set to 0




Data Configuration of Cell-load-sharing

[Load HO Allowed]


Default Value: No

Description: This parameter indicates whether a traffic load-sharing handover is allowed. Load-sharing helps to reduce cell congestion, improve the success rate of assignment, and balance the traffic load among cells. Load-sharing functions only within the same BSC or in cells of the same layer. It applies to only TCH. If load handover is frequently required, TRX configuration and network planning should be properly adjusted.

Remarks: In areas with tight frequency reuse, extra interference may occur if Load HO Allowed is set to Yes.

[System Flux Threshold for Load HO]

Value Range: 0~11

Default Value: 10

Description: System Flux Threshold for Load HO is obtained based on message load, CPU load, and so on. The system flow level is the current flow control level of the system.

z 0~11:It is the system flux control level when the alarm module send out alarms information. Level 11 is the highest and level 0 is the lowest.

z A load handover is allowed only when the system flow is lower than this threshold. Otherwise, unexpected situations may occur. Therefore, this parameter must be set properly.

z Flow control threshold for the CPU to start to discard the channel access messages and paging messages: 80%

z Flow control threshold for the CPU to discard all the channel access messages and paging messages: 100%

z CPU usage smaller than 80% corresponds to level 0. CPU usage equal to or greater than CPU flow control threshold 80% corresponds to level 2.

z An increase of 5% means an increase of 2 levels.

z Level 10 is the highest. The level value can be 0, 2, 4, 6, 8, and 10.




Data Configuration of Cell-load-sharing

[Load HO Threshold]

z Value Range: 0~100(%)

z Default Value: 85

z Description: When the load handover is switched on, it is recommended that the Load HO Threshold is set to 85.The cell load refers to TCH usage. When the cell load exceeds the value of Load HO Threshold, the BSC starts the load handover. That is, the BSC starts the load handover after the TCH in the cell are proportionally occupied.

z Remarks: Even if the Load HO Allowed is set to Yes, the Load HO Threshold and Load Req. on Candidate Cell affect the queuing of the candidate cell handover. Therefore, when the cell is overloaded, the handovers such as PBGT cannot be performed if this parameter is not properly set.

[Load Req. on Candidate Cell]

z Value Range: 0~100(%)

z Default Value: 75

z Description: If the cell load is lower than the value of this parameter, the cell accepts users that are handed over to the cell due to their cell load. If the cell load is not lower than the value of this parameter, the cell refuses the users.

z Remarks: The same as that of Load HO Threshold




Network Feature Adjustmentz 12th bit and 13th bit: Whether share the same BSC or MSC.

141516 12345678910111213

serving cell?NoYes

Both 12th and 13th set to 0

12th set to 113th set to 0

Is [Co-BSC/MSC Adj] (s)yes?

Yes

No

Co-BSC?

Co-MSC?

No

Yes


No

Yes

Turn off 12th &13th bit


12th bit: if neighbor cell is co-BSC with the serving cell, 12th bit is set to 0. Otherwise, set to 1

13th bit: if neighbor cell is co-MSC with the serving cell, 13th bit is set to 0. Otherwise, set to 1

z Service cell: is always set to 0

z These two bits will be turned off when Co-BSC/MSC Adj. is set to NO




Data Configuration of Co-BSC&MSC

[Co-BSC/MSC Adj]


Default Value: Yes

Description: This parameter indicates whether the sequence of candidate cells is adjusted. After the sequence is adjusted, the handover within the same BSC/MSC takes priority.




z The 14th bit: [Inter-layer HO Threshold/Hysteresis] adjustment bit.


141516 12345678910111213

z The 15th/16th bits are reserved

Yes

serving cell?

set to 0

NoYes

Bit 14th set to 1, and bit 5th ~13th are turned off

set to 0

Yes

RX_LEV_DL >= [Inter-layer HO Threshold](s) [Inter-layer HO Hysteresis](s)?

RX_LEV_DL >= [Inter-layer HO Threshold](n) + [Inter-layer HO Hysteresis](s->n)?

No No

The 14th bit: Layer HO threshold adjustment bit

Serving cell: RX_LEV_DL >= Inter-layer HO Threshold Inter-layer HO Hysteresis, bit 14th is set to 0

Neighboring cell: RX_LEV_DL >= Inter-layer HO Threshold + Inter-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 5th- 13th bits are turned off.

The 15th/16th bits are reserved




Data Configuration of Layer HO Threshold Adjustment

[Inter-layer HO Threshold]

Value Range: 0~63(-110 dBm to -47 dBm)

Default Value: 25

Description: In BSC handover algorithm, the M criterion is used to rank the handover candidate cells. The M criterion includes 16 bits. This parameter is one bit of the 16 bits and it affects the rank of a candidate cell. When the downlink level of a cell is lower than this threshold, the cell takes low priority as far as comprehensive sequence is concerned.

Remarks: Make sure that the receive level of the destination cell is higher than this threshold in inter-layer handover or load handover. Otherwise, the MS may be handedfrom a cell with heavy load and high level (high priority cell) to a cell with light load and low level (low priority cell), thus leading to call drops.

[Inter-layer HO Hysteresis]

Value Range: 0~63

Unit: dB

Default Value: 3

Description: This parameter indicates the hysteresis of an inter-layer or inter-priority handover. It is used to avoid inter-layer ping-pong handovers. Actual Inter-layer HO Threshold of a serving cell = Inter-layer HO Threshold C Inter-layer HO hysteresis Actual Inter-layer HO Threshold of a neighboring cell = Inter-layer HO Threshold + Inter-layer HO hysteresis




General HO Process




MR. Preprocessing2

Handover Judgment3


TA HO

Interference HO

Rx_Level_Drop HO

Bad Quality HO

Load HO

Edge HO

Layer HO

PBGT HO

AMR HO

No DL MR HO

Concentric Cell HO

MS Fast Moving HO


Penalty Processing

Ranking Processing

OM Forced HO

Direct Retry

Emergency HO

Normal HO




No DL MR HO

Serving Cell Neighboring Cell

z When the quality of Um interface become worse and worse, it is for

the worse uplink quality that MS can not deliver downlink MR, while

the downlink quality is not bad enough for MS to receive the

downlink message normally.

Baduplink quality

When the quality of Um interface become worse and worse, it is for the worse uplink quality that MS can not deliver downlink MR, while the downlink quality is not bad enough for MS to receive the downlink message normally. Under this kind of urgency condition, in order to save this call, the network send handover command to MS.




Position of No DL MR HO



Measure and Measurement Result Report

1

MR. Preprocessing2

Handover Judgment3


TA HO

Interference HO

Rx_Level_Drop HO

Bad Quality HO

Load HO

Edge HO

Layer HO

PBGT HO

AMR HO

Concentric Cell HO

MS Fast Moving HO


Penalty Processing

Ranking Processing

OM Forced HO

Direct Retry

Emergency HO

Normal HO

No DL MR HO

Attention: After MR. Preprocessing, the No DL MR handover is triggered if trigger condition is satisfied.




No DL MR HO

Begin

Report 1 DL MR at least?

[No Dl Mr. HO Allowed](s) Yes ?

=[No Dl Mr.Ul Qual

HO Limit](s)?

Yes

Only one cadidate cell?

Within Penalty Time

Yes

No

No

Yes

Yes

Yes

No

[Intracell HO Allowed](s)?

Yes

No

No

Triggering condition

z No DL information in current MR

z Stored UL Rx_Qual Value Number >= Filter Length for TCH/SDCCH Qual

z UL Rx_Qual >= No DL MR HO UL Rx_Qual Threshold

z Number of Lost DL MR < Cons. No DL MR HO Allowed Limit

Object cell selection

z Prefer neighboring cell

z If choose the service cell, it cannot in the penalty time for intra-cell handover.




Data Configuration of No DL MR HO

[No Dl Mr. HO Allowed]


Default Value: No

Description: This parameter is used to control the handover algorithm without downlink measurement report. If this parameter is set to 0, the no handover algorithm without downlink measurement report is disabled. Therefore, handover decision without downlink measurement report is not allowed in this cell. If this parameter is set to 1, the no downlink measurement report handover algorithm is enabled. Therefore, handover decision without downlink measurement report is allowed in this cell.

[No Dl Mr. Ul Qual HO Limit]

Value Range: 0~70 (mapping to RQ (0~7)10)Default Value: 60

Description: This parameter indicates the uplink receive quality threshold of triggering an emergency handover when no measurement result on downlink channels is contained in the MR. The emergency handover is allowed only when the filtered uplink receive quality crossed this threshold. When an emergency handover is triggered, inter-cell handover takes priority. Intra-cell handover, however, is triggered if no candidate cell is available and intra-cell handovers are allowed.

[Cons. No Dl Mr. HO Allowed Limit]

Value Range: 0~64

Default Value: 8

Description: This parameter indicates the upper threshold of consecutive MRs containing no downlink measurement result for a call. Each call is configured with a global timer, which counts the number of consecutive MRs containing no downlink measurement. When the timer exceeds thisthreshold, the handover is disabled and the timer is reset.




TA(Time Advance) HO


[TA Threshold](s)

Time

TA(s)

HandoverTriggering

[TA Threshold](n)

or

Handover Triggering ZoneTA(n)

Because a MS is far away from its serving BTS, the practice TA value is more than TA threshold configured in data configuration, TA handover is triggered.




TA(Time Advance) HO

TriggerTA handover

Begin

The actual TA >=[TA Threshold](s)?

[TA HO Allowed] Yes ?

Any neighbour cell exist?

serving cell?

Select the cell with the highest priority in the

cadidate cell list

Suitable cell exist?

Yes

No

End

No

No

YesYes

No

No

Yes

Yes

Yes

No

[TA Threshold](n,in the same BTS) = TA Threshold


z The cell must be of the highest priority in the candidate cell sequence and meet the following restrictions.

Restriction

z The service cell cannot be the object cell.

z HO is not allowed when TA Threshold of the neighboring cell with the same BTS is equal or smaller than that of the service cell.




Data Configuration of TA HO

[TA HO Allowed]


Default Value: Yes

Description: The parameter indicates whether a Timing Advance (TA) handover is allowed. A TA handover is triggered when the TA is higher than the triggering threshold. TA is calculated based on the distance between the MS and the BTS. The longer the distance is, the greater the TA is.

[TA Threshold]

Value Range: 0~255

Unit: Bit period (A bit period corresponds to 0.55 km.)

Default Value: 255

Description: This parameter indicates the TA threshold of triggering emergency handover. Emergency handover is triggered when TA is equal to or greater than this threshold.




Interference Handover

Lev_Thr

Rx_Qual

RX_Lev

Qual_Thr

InterferenceOrigin


Handover Triggering Zone

For a MS or a BTS, when the receiving quality is lower than the interference quality threshold and receiving level is higher than the interference level threshold, it is considered that interference exists in serving cell, so interference handover is triggered.




Interference HOBegin

UL or DL receiving

Quality(s)>=A?

[Interference HO Allowed] Yes ?


serving cell?


cadidate cell list

Rx_Level(n)>= [Inter-layer HO Threshold](n) +

[Inter-layer HO Hysteresis](s->n)?

Yes

No

End

No

No

Yes No

NoYes

None AMR FR: A = RXQUALn, 1 RXQUAL8

9. Rx_lev is within [53,55], and Rx_qual > RXQUAL9



12. Rx_lev >= 63, and Rx_qual > RXQUAL12




Data Configuration of Interference HO

50>=63RXQUAL12

5159~62RXQUAL11

5256~58RXQUAL10

5353~55RXQUAL9

5449~52RXQUAL8

5546~48RXQUAL7

5642~45RXQUAL6

5739~41RXQUAL5

5836~38RXQUAL4

5932~35RXQUAL3

60=31RXQUAL2

70




Data Configuration of Interference HO

[Interference HO Allowed]


Default Value: Yes

Description: The parameter indicates whether an interference handover is allowed. An interference handover is triggered when the receive level is higher than the receive threshold, but the transmission quality is lower than the handover triggering threshold.

Remarks: Both downlink and uplink interference is judged, and inter-cell handover takes priority. If no target cell is available, intra-cell interference handover can be implemented in the serving cell if intra-cell handovers are allowed.

[RXQUAL1] ~ [RXQUAL12]

Value Range: 0~70

Description: Quality threshold 1~12 for the interference handover of nonCAMR FR voice services. The value corresponds to (quality level 0~7) x 10.See the next slide

[RXLEVOff]

Value Range: 0~70

Default Value: 5

Description: The quality level offset of the interface handover of the AMR FR service relative to non-AMR services or the AMR HR service (x 10).




Rx_Level_Drop HO

Rx_Level_Drop HO will be triggered when receiving level drops fast because of barrier such as high building.




Rx_Level_Drop HOBegin

Satisfy the Formula& The latest RX_LEV_UL(s) <

[Edge HO UL RX_LEV Threshold](s)?

[Rx_Level_Drop HO Allowed] Yes ?


serving cell?


cadidate cell list

Yes

No

End

No

No

Yes

NoYes

Formula:

Is priority higher than serving cell?

Trigger Rx_Level_Drop handover

Yes

Yes

( ) ( ) ( ) ( )( ) ( ) ( ) ( ) BXAXAXAXA

XAXAXAXA




Data Configuration of Rx_Level_Drop HO

[Rx_Level_Drop HO Allowed]

Value Range: Yes, No Default Value: No

Description: The parameter indicates whether the emergency handover algorithm is allowed. The emergency handover algorithm is used to prevent call drops when the receive level of the MS drops rapidly. Generally this algorithm is not enabled until the conditions are met. To enable this algorithm, original MR is required for the BSC.

[Filter Parameter A1~A8]


Description: Filter Parameter A1~A8 and Filter Parameter B work together to decide whether the rapid drop of the receive level must be reflected in one or multiple MRs. The conditions to trigger a rapid level dropping handover are as follows; In the algorithm above, X1, X2, X3, X4, X5, X6, X7, and X8 indicate the uplink receive levels of the last eight MRs in the queue. Filter Parameter A1~A8 must meet the following conditions: A1+A2+A3+A4+A5+A6+A7+A8=80. For example, if you want to reflect the rapid drop of the cell level in a MR, you can set A3-A8 to greater than 10, A1 to 0, and A2 to 20.

[Filter Parameter B]


Description: This is one of the parameters that determine whether a handover is required due to fast dropping levels.Thisparameter indicates the drop trend of the receive level within a period. The greater the parameter B is, a more rapid level drop is required for triggering a rapid level dropping handover.See Filter Parameter A1-A8.

[Edge HO UL RX_LEV Threshold]


Description: The parameter indicates the uplink receive level threshold of an edge handover. An edge handover will be triggered if the uplink receive level is constantly lower than "Edge HO UL RX_LEV Thrsh." for a period longer than Edge HO Valid Time(s) within Edge HO Watch Time(s). If PBGT handover is enabled, the corresponding edge handover threshold can be lowered. If PBGT handover is disabled, this parameter must be properly specified to avoid overlapping coverage and channel interference. This parameter should be adjusted based on the performance statistics and actual networks to achieve uplink-downlink balance.

Remarks: Edge handover uplink/downlink receive level threshold < Uplink/downlink signal strength lower limit of HUAWEI II power control




BQ(Bad Quality) HO

Begin

Is [BQ HO Allowed] Yes ?


serving cell?


cadidate cell list

Yes

No

End

No

No

Yes

NoYes

Yes

UL_Rx_Q(s)>=[UL Qual. Threshold](s) or DL_Rx_Q(s)>=[DL Qual. Threshold](s)?

RX_LEV_DL (n) > RX_LEV_DL (s) + Inter-cell HO hysteresis(s->n)

-BQ HO Margin(s->n) ?

[Intracell HO Allowed](s) yes& cell not punished?

Suitable cell exist?

Trigger BQ handover

Yes

Yes

Yes

No

No

No

When the receiving level of a MS or a BTS is lower than the quality threshold, bad quality handover will be triggered.

Triggering condition

z UL receiving quality >= UL Qual. Threshold

z OR DL receiving quality >= DL Qual. Threshold

z For AMR call, the quality threshold is DL/UL Qual. Limit AMR FR/HR


z The cells must be of the highest priority in the candidate cell sequence and meet the following restrictions.

Restriction

z Prefer neighboring cell. If the number of neighboring cell is more than one, it is required that RX_LEV_DL (n) > RX_LEV_DL (s) + Inter-cell HO hysteresis - BQ HO Zone

z If there is no neighboring cell, handover can occur to the service cell, and the channel at different frequency band, different MA, different TRX or different channel (from left to right) is preference.




Data Configuration of BQ HO

[BQ HO Allowed]


Default Value: Yes

Description: The parameter indicates whether a Bad Quality (BQ) handover is allowed. BQ handover is triggered when Bit Error Ratio (BER) over uplink/downlink channels is higher than the triggering threshold. If BER rises, or signal strength drops, suspect that the signal power is low or channel interference increases.

Remarks: Inter-cell BQ handover is preferentially performed. If no target cell is available, intra-cell BQ handover can be implemented in the serving cell if intra-cell handovers are allowed.

[DL Qual. Threshold]

Value Range: 0~70 (RQ (0~7) 10)

Default Value: 60

Description: This parameter indicates the downlink receive quality threshold of triggering an emergency handover. When the receive quality of the downlink is greater than DL Qual Threshold, an emergency handover is triggered. When frequency hopping or DTX of the cell is enabled, it is recommended that you set this parameter to 70. When an emergency handover is triggered, inter-cell handover takes priority. An intra-cell handover, however, is triggered if no candidate cell is available and intra-cell handovers are allowed.

[UL Qual. Threshold]

Value Range: 0~70 (RQ (0~7)10)

Default Value: 60

Description: This parameter indicates the uplink receive quality threshold of triggering an emergency handover. When the receive quality of the uplink is greater than UL Qual Threshold, an emergency handover is triggered due to bad quality. When frequency hopping or DTX of the cell is enabled, it is recommended that you set this parameter to 70.When an emergency handover is triggered, inter-cell handover takes priority. An intra-cell handover, however, is triggered if no candidate cell is available and intra-cell handovers are allowed.





[DL/UL QuaLimitAMRFR]

Value Range: 0~70

Default Value: 65

Description: This parameter indicates the urgent switchover downlink/uplink quality control for the AMR FR service. The values of this parameter match quality levels 0-7 multiplying 10. The urgent switchover is triggered only when the downlink/uplink receiving quality of the MS is greater than the switchover threshold, that is, the receiving quality is poor.

[DL/UL QuaLimitAMRHR]

Value Range: 0~70

Default Value: 60

Description: This parameter indicates the urgent switchover downlink quality control for the AMR HR service. The values of this parameter match quality levels 0-7 multiplying 10. The urgent switchover is triggered only when the downlink receiving quality of the MS is greater than the switchover threshold, that is, the receiving quality is poor.





[BQ HO Margin]

Value Range: 0~127 (-64 dB to +63 dB)

Default Value: 69

Description: A Margin in BQ handover algorithm used to judge whether to perform BQ handover. When BQ Handover Allowed is set to Yes and Inter-cell HO Hysteresis > "Inter-cell HO Hysteresis-BQ HO Margin", the Inter-cell HO Hysteresis will act instead of the BQ HO Margin. When "Inter-cell HO Hysteresis-BQ HO Margin" is assigned with a value smaller than 64, MS can hand over to a lower level neighboring cell. 69 for popular urban areas, 72 for suburbs.

Remarks: If the data is updated from M900/M1800 BSC to HUAWEI BSC6000,the default value of this parameter is 5.Then it's necessary to modify the value of this parameter to 69,otherwise the BQ HO algorithm will be invalid.




General HO Process




MR. Preprocessing2

Handover Judgment3


TA HO

Interference HO

Rx_Level_Drop HO

Bad Quality HO

Load HO

Edge HO

Layer HO

PBGT HO

AMR HO

No DL MR HO

Concentric Cell HO

MS Fast Moving HO


Penalty Processing

Ranking Processing

OM Forced HO

Direct Retry

Emergency HO

Normal HO





z Two single band cells which are configured as bi-directional neighbor

cell relationship can be configured as enhanced dual band cell to each

other.

z Purpose

During the procedure of channel assignment and handover, the

two single band cells can share their resource.

Assign the channel with low load in UL to MS preferentially.

Make MS handover from the high load cell to the low load cell.




Channel Assignment of Enhanced Dual Band

RX_LEV_OL>= [Incoming OL Subcell HO level Threshold(dB)](o) andRX_LEV_UL RX_LEV (n) >[Distance Between Boundaries of UL and OL Subcells(dB)] Attention:RX_LEV (n): RX_LEV of the strongest neighboring cell which has the same frequency band and layer with underlaid subcell, but locates in a different BTS. If there is no such a cell, this value is -110dBmIf [ATCBHoSwitch] is [Close], the second condition is turn off.

A:

z TCH assignment (SDCCH channel in UL)Begin

from UL

[Assignment Optimization of UL Subcell Allowed

or not] (u) ?

Cell load of UL >[UL Subcell General

Overload Threshold(%)](u)?

Yes

AYes

No

Any idle TCH Available in OL?

Assign TCHin OL

Yes

No

Yes

Assign TCH in ULor direct retry identification

or queuing

No

No

TCH assignment (SDCCH channel in underlaid)

z If Assignment Optimization of UL Subcell Allowed or not is set to NO, assign TCH in underlaid as the normal assignment procedure

z If Assignment Optimization of UL Subcell Allowed or not is set to YES, assign TCH in overlaid when the following conditions are met

Cell load of underlaid > UL Subcell General Overload Threshold

RX_LEV_OL >= Incoming OL Subcell HO level Threshold

RX_LEV_UL RX_LEV (n) > Distance Between Boundaries of UL and OL SubcellsDistance Hysteresis Between Boundaries of UL and OL Subcell(dB)

RX_LEV (n): RX_LEV of the strongest neighboring cell which has the same frequency band and layer with underlaid subcell, but locates in a different BTS. If there is no such a cell, this value is -110dBm




Data Configuration of Channel Assignment

[ATCBHoSwitch]

Value Range: Close, Open

Default Value: Open

Description: The switch of the ATCB handover algorithm.

[Assignment Optimization of UL Subcell Allowered Or Not]


Default Value: Yes

Description: This parameter indicates whether the access request originated in the underlaidsubcell is preferably assigned between overlaid subcell cell and underlaid subcell cell according to the Out Cell Low Load Thred.

[UL Subcell General OverLoad Threshold(%)]

Value Range: 0~100

Unit: %

Default Value: 80

Description: If the ratio of underlaid subcell channel occupancy is greater than the value of this parameter, some calls in the underlaid subcell are handed over to the overlaid subcell. Moreover, calls originated in the underlaid subcell are preferably assigned to the channel in overlaid subcell.





[Distance Between boundaries of UL And OL Subcells(dB)]

Value Range:0~63

Unit: dB

Default Value: 10

Description: This parameter indicates the distance between the overlaid subcell and underlaid subcell. The value of this parameter is comparative. The greater the value is, the longer the distance is. The enhanced dual-band network handover algorithm refers to the boundary between underlaid subcell and overlaid subcell based on the comparative value of signal strength of serving cell and neighboring cell. Suppose the signal strength of serving cell is SS(s), and neighboring cell SS(n). If SS(s) is equal to SS(n), the cell is in the underlaid subcell boundary. If the value of SS(s) - SS(n) is larger than the value of Distance Between boundaries of UL And OL Subcells(dB), the cell is in the overlaid subcell.

[Incming OL Subcell HO Level Threshold(dB)]

Value Range: 0~63

Unit: dB

Default Value: 30

Description: This parameter indicates the lowest threshold of overlaid subcell level of the handover from underlaid subcell to overlaid subcell. When the MS receive level is higher than the value of this parameter, the BSC allows the handover of overlaid subcell cell.




Begin from OL

[Assignment Optimization of OL Subcell Allowed or

not ](o) No ?

Cell load of UL< [UL Subcell LowerLoad Threshold](u)?

Yes

Yes

No

Assign TCHin UL

Any idle TCH Available in UL?

Assign TCHin UL

Any idle TCH Available in OL?

Assign TCHin OL

Yes No

Yes

Assign TCH in OLor direct retry identification

or queuing

No

No

z TCH assignment (SDCCH channel in OL)

Channel Assignment of Enhanced Dual Band

TCH assignment (SDCCH channel in overlaid)

z If Assignment Optimization of OL Subcell Allowed or not is set to NO, assign TCH in overlaid as the normal assignment procedure

z If Assignment Optimization of OL Subcell Allowed or not is set to YES

Assign TCH in underlaid, if cell load of underlaid < UL Subcell Lower Load Threshold

Assign TCH in overlaid, if cell load of underlaid >= UL Subcell Lower Load Threshold





[UL Subcell Lower Load Threshold(%)]

Value Range: 0~100

Unit: %

Default Value: 50

Description: If the underlaid subcell channel occupancy ratio is smaller than the value of this parameter, some calls of the overlaid subcell is handed over to the underlaid subcell. Moreover, the MS that requests for the overlaid subcell channel is preferably assigned to the underlaid subcellchannel.

[Assignment Optimization of OL Subcell Allowered Or Not]


Default Value: No

Description: This parameter indicates whether the channel request in the overlaid subcell is preferably assigned between overlaid subcell and underlaid subcell according to the Out Cell Low Load Thred.





z Classification of TCH HO in enhanced dual band HO

OL to UL for low load in UL

UL to OL for high load in UL

OL to UL for moving

There are three kinds of handover for enhanced dual band network:

UL to OL for high load in UL

OL to UL for moving

OL to UL for low load in UL




Enhanced Dual Band HO(UO )z Triggering condition for TCH Load HO from UL to OL for high load in UL

The order of handover is from the MS who is near the OL to the MS who is far away from OL.




Enhanced Dual Band HO(UO )z Triggering condition for TCH Load HO from UL to OL for high load in UL

RX_LEV_OL >= [Incoming OL Subcell HO level Threshold(dB)] (o)andRX_LEV_UL RX_LEV (n) > [Distance Between Boundaries of UL and OL Subcells(dB)]A:

Cell load of UL>=[UL SubcellSerious Overload Threshold(%)](u)?

Begin [Load HO From UL Subcell

to OL Subcell Allowed](u) Yes ?

Cell load of UL>=[UL SubcellGeneral Overload Threshold(%)](u)?

No

A & Satisfy P/N &not within penalty time?

Trigger UL to OL

Yes No

Adjust HO zone basing on HO step and HO period

Refresh cell load per second

BB-C

Yes

Any MS in HO zone?

Yes

No

No

Yes

Yes No

End

Cell load of OL>=[Inner Cell Serious Overload

Threshold(%)](o)?Yes

No

B=[UL Subcell Load Hierarchical HO Period(s)]

C=[Modified Step Length of UL Load HO Period(s)]

HO step: [Step Length of UL Subcell Load HO(dB)]

HO zone: [Incoming OL Subcell HO level Threshold(dB)]~-47dBm

HO Period: [UL Subcell Load Hierarchical HO Period(s)]

Triggering condition for TCH Load HO from underlaid to overlaid

z Load HO of UL Subcell to OL Subcell Enable is YES

z Cell load of underlaid > UL Subcell General Overload Threshold

z RX_LEV_OL >= Incoming OL Subcell HO level Threshold

z RX_LEV_UL RX_LEV (n) > Distance Between Boundaries of UL and OL Subcells(dB)

z Satisfying P/N rule

z HO zone is from Incoming OL Subcell HO level Threshold to -47dBmAttention:

RX_LEV (n): RX_LEV of the strongest neighboring cell which has the same frequency band and layer with underlaidsubcell, but locates in a different BTS. If there is no such a cell, this value is -110dBm




Data Configuration of Enhanced Dual Band HO(UO )

[UL Subcell General OverLoad Threshold(%)]

Value Range: 0~100

Unit: %

Default Value: 80

Description: If the ratio of underlaid subcell channel occupancy is greater than the value of this parameter, some calls in the underlaid subcell are handed over to the overlaid subcell. Moreover, calls originated in the underlaid subcell are preferably assigned to the channel in overlaid subcell.

[UL Subcell Serious OverLoad Threshold(%)]

Value Range: 0~100

Unit: %

Default Value: 90

Description: If the ratio of the underlaid cell channel occupancy is greater than the value of this parameter, the period of handover from underlaid subcell to overlaid subcell is reduced by the value of Out Cell Load HO Modify Step every second based on the value of Out Cell Load Classification HO Period. Thus the handover from underlaid subcell to the overlaid subcell speeds up.

[Load HO From UL Subcell to OL Subcell Allowed]


Default Value: Yes

Description: When the ratio of underlaid subcell channel occupancy is high, whether some calls in the overlaid subcellare allowed to be handed over to the overlaid subcell.

[Incming OL Subcell HO Level Threshold(dB)]

Value Range: 0~63

Unit: dB

Default Value: 30

Description: This parameter indicates the lowest threshold of overlaid subcell level of the handover from underlaidsubcell to overlaid subcell. When the MS receive level is higher than the value of this parameter, the BSC allows the handover of overlaid subcell cell.




Data Configuration of Enhanced Dual Band HO(UO )

[UL Subcell Load Hierarchical HO Period(s)]


Description: This parameter indicates the period of the hierarchical handover from underlaid subcell to overlaid subcell. When the ratio of underlaid subcell cell channel occupancy is greater than the value of En Iuo Out Cell General OverLoad Thred, all the calls in the cell request for handover at the same time. The BSC load is sharply increased. Thus the call may drop because the target cell is congested. Therefore the algorithm of hierarchical handover is applied to hand over the calls in the cell hierarchically to the overlaid subcell.Thisparameter indicates the time duration of every hierarchical handover.

[Step Length of UL Subcell Load HO(dB)]

Value Range: 0~63 Unit: dB Default Value: 5

Description: This parameter indicates the level step of the hierarchical handover from underlaid subcell to overlaid subcell.

[Modified Step Lenghth of UL Load HO Period(s)]


Description: If underlaid subcell load is higher than the value of Out Cell Serious OverLoad Thred, the period of handover from underlaid subcell cell to overlaid subcell cell is shortened by the value of Out Cell Serious OverLoad Thred every second based on the value of the Out Cell Load classification HO Period.

[Total Number of ]


Description: P/N criterion: In P measurement reports, N measurement results meet handover requirements. Handover is start

Documents

OMF810002 GSM Handover Algorithm ISSUE2.01