Huawei GSM Handover Algorithm

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GSM Handover Algorithm


www.huawei.com

Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved.

Confidential Information ofHuawei. No Spreading Without Permission

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Foreword 

Handover is a key technology of mobile communication system and make continued conversation possible.



Handover algorithm in Huawei product is flexible and powerful.


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Objectives 

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

Outline the types of handover



Master handover judgment flow



Understand algorithm of different handovers



Explain HO data configuration


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Contents 1. Introduction of Han dover 2. HO Algorithm Process


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Contents 1. Introduction of Han dover 2. HO Algorithm Process


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Purposes of HO 

To keep a continuous communication with a moving MS



To improve network service performance 

To reduce the call drop rate



To reduce the congestion rate


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



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Classification by Reason

Classification by Reason

1

Emergency HO

2

Enhanced Dual Band HO

3

Load HO

4

Normal HO


No DL MR Emergency HO Timing Advance (TA) HO Interference HO Rx_Level_Drop HO Bad Quality (BQ) HO

EDGE HO PBGT HO Layer HO MS Fast Moving HO Concentric Cell HO AMR HO

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Classification by Synchronization

NSS Network

MSC

BSC

MSC

B SC

B SC

BTS CELL

BTS

Case 2 Case 3 Case 1

BTS

Case 4

BTS

BTS

Case 5

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


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Synchronous handover: source and target cell belong the same BTS

Asynchronous handover: source and target cell belong the different BTS



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Classification by Equipment and Channel Intra – Cell HO ( HR FR…) ↔ ↔

Inter – Cell HO

TCH → TCH

Intra – BSC HO

SDCCH → SDCCH

Intra – MSC HO

Inter – MSC HO


SDCCH → TCH (Direct Retry)

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Contents 1. Introduction of Handover 2. HO Algorithm Process


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Contents 2. HO Algorithm Process 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


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General HO Process MS Goes into Dedicated Mode

1

2

3

4

Measure and Measurement Result Report

Measurement Report Pr eprocessing

Handover Judgment

Handover Implementation

MS Goes into New Dedicated Mode


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1

2



3

Handover Judgment

4




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Measurement Report 

Uplink MR includes uplink receiving level and quality.



Downlink MR includes downlink receiving level, downlink receiving quality of the serving cell and other downlink receiving levels from the neighbor cells.

The downlink MR

The downlink measurement report of the neighbor cell (BCCH)

The uplink MR

Serving cell Neighbor cell


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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.



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Measurement Report


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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 DiscontinuousTransmission (DTX)function is activated.

RXQUAL level in MR 0 1 2 3 4 5 6 7

Huawei value 0 10 20 30 40 50 60 70

BER behind Less than 0.2% 0.2% ~ 0.4% 0.4% ~ 0.8% 0.8% ~ 1.6% 1.6% ~ 3.2% 3.2% ~ 6.4% 6.4% ~ 12.8% Greater than 12.8%



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Period of Measurement Report 

The downlink MR is sent to BTS in SACCH uplink 

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



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

4 TCH Multiframes

480ms

1 2T C H

1SACCH


1 Idle

12TCH

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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 26multiframes

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



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1

2

3

4



Handover Judgment




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MR Preprocessing

Interpolation





Recover the lost

Filtering





measurement report

Smooth the instantaneous fading point

MR Preprocessing


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MR preprocessing consists of two steps: interpolation and filtering.



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MR Interpolation o us t i nu Co n

MR

Fl ow MR

…

MR MR

No. n+4

MR MR …

No. n

Missing by some reasons


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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. 

Service cell: linear algorithm



Neighboring 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.



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MR Filtering

o tinu Co n

us M

R Fl

ow

…

MR

MR

MR

MR MR

MR …

Filter----Average several consecutive MRs


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Filtering – smooth the instantaneous fading point 

Calculate 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.



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Data Configuration of MR Preprocessing


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[MR Preprocessing]

•Value Range: Yes, No •Default Value: No •Description: This parameter indicates whether the BTS pre-processes the MR. 

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.



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



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]

•Value Range: Yes, No •Default Value: No •Description: This parameter indicates whether the srcinal MR is transferred to the BSC after the BTS pre-processes the MR. 

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

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



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[Transfer BS/MS Power Class]

•Value Range: Yes, No •Default Value: Yes •Description: This parameter indicates whether the srcinal 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.



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[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 MRsused for averaging the TCHsignal strength. 

This parameter helps to avoid sharp drop of signal levels caused correct handover decisions.

by Raileigh Fading and to ensure

•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 MRsused for averaging the TCHsignal quality.



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[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. 

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. 

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 indica tes the number of MRs used for TA averaging.



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Penalty Processing Ranking Processing

1


OM Forced HO Direct Retry

2

MR. Preprocessing

3

Handover Judgment

4



Emergency HO

Enhanced Dual Band HO Load HO Normal HO Edge HO

No DL MR HO

MS Fast Moving HO

TA HO

Layer HO

Interference HO

PBGT HO

Rx_Level_Drop HO

Concentric Cell HO

Bad Quality HO

AMR HO


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Penalty Processing Punish on the target cell

HO Fails

Emergency (TA&BQ)HO

Punish on the srcinal cell

AMR HO Fails

Penalty Intra-cell HO

Concentric Cell HO


MS Fast Moving HO Punish on other high priority layer cells

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There are several kinds of penalty process 

Penalty on target cell when a HO fails.



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



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



Penalty for concentric cell HO



Penalty for intra-cell HO



Penalty for AMR HO



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Penalty for Handover Failure 

Punish the target cell when a HO fails.



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

Cell A BTS

HO Fail BTS

BSC

Cell B


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



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Data Configuration of Penalty for Handover Failure


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[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: 

Cell congestion



A message indicating internal handover refusal is received.



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



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.



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Data Configuration of Penalty for Handover Failure


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[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.



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Penalty for Emergency Handover 

Punish the srcinal cell when an emergency HO ( due to BQ and TA) occurs.

Cell A

BQ&TA HO

BTS

BSC Cell B


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In case of BQ emergency handover, the srcinal serving cell will be penalized (called signal level penalty by BQ HO), during BQ HO penalty time, to avoid MS to behanded back to the srcinal serving cell again within certain time. It is the same for TA handover, i.e. the srcinal serving cell is penalized (signal le vel penalty by TA HO ) during TA HO penalty time.



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Data Configuration of Penalty for Emergency Handover


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[Penalty Level after BQ HO]

•Value Range: 0~63 •Unit: dB •Default Value: 63 This parameter indicates the penalty level given to the srcinal serving cell where emergency handover •isDescription: performed due to bad quality. After emergency handover is performed due to bad quality, the receive level of the srcinal serving cell is decreased by the penalty level. Thus, other cells are given higher priority and handover to the srcinal 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 srcinal serving cell where emergency handover is performed due to bad quality. During the penalty time, the receive level of the srcinal serving cell is decreased by the penalty level. Thus, other cells are given higher priority and handover to the srcinal serving cell is not allowed.



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Data Configuration of Penalty for Emergency Handover


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[Penalty Level after TA HO]

•Value Range: 0~63 •Unit: dB •Default Value: 63 •Description: This parameter indicates the penalty level given to the srcinal serving cell where emergency handover is performed due to TA. After emergency handover is performed due to TA, the receive level of the srcinal serving cell is decreased by the penalty level. Thus, other cells are given higher priority and handover to the srcinal 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 srcinal serving cell where emergency handover is performed due to TA. During the penalty time, the receive level of the srcinal serving cell is decreased by the penalty level. Thus, other cells are given higher priority and handover to the srcinal serving cell is not allowed.



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Penalty for MS Fast-moving Handover 

Giving penalty on the other three layers(Non-umbrella Layer ) after MS handovers to Umbrella cell by fast-moving-HO.



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

Back? No way!

Umbrella

Micro cell Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved.

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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 srcinal cell again. A possible example is that a fast moving car is running on a highway.



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Data Configuration of Penalty for MS Fast-moving Handover


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[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.



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Penalty for Concentric Cell 

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)!

Overlaid

Underlaid


Do not attempt again during penalty time after one failed HO(O->U)!

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



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Data Configuration of Penalty for Concentric Cell


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[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)]

•Value Range: 0~255 Unit: Seconds Default Value: 10 •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. Confidential Information ofHuawei. No Spreading Without Permission


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Penalty for Enhanced Concentric Cell 

A new UO HO is prohibited within a penalty time aft er a OU HO is performed successfully.

Overlaid Do not attempt back too fast!

Underlaid


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This penalty is valid only for Enhanced Concentric Cell.



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Data Configuration of Penalty for Enhanced Concentric Cell


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[Penalty Time of UtoO HO(s)]

•Value Range: 0~255 •Unit: Seconds •Default Value: 10 •Description: This parameter indicates the penalty time for forbidding pingpong 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.



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Penalty for Intra-cell HO A new intra-cell HO is prohibited if it occurs too frequently.



Intra-cell HO Time 4th. 3rd. 2nd. 1st.

Penalty time 0

3

7

12

32

( s)

T

Max. consecutive HO times: 3 Forbidden time after Max. times: 20s Interval for consecutive HO Jud: 6s


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Because of the co-channel interference and other interference, the voice quality of a MS on certain frequency may lower than the handover threshold, 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.



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Data Configuration of Penalty for Intra-cell HO


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[Max Consecutive HO Times]

•Value Range:1~20 •Default Value: 3 Description: This parameter indicates thecontinuous maximum intra-cell number of consecutive intra-cell •handovers allowed. If the interval of two 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 intracell handovers are consecutive.



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Data Configuration of Penalty for AMR FRHR Handover Failure


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[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.



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1



2

MR. Preprocessing

3

Handover Judgment

4



Emergency HO


No DL MR HO

MS Fast Moving HO

TA HO

Layer HO

Interference HO

PBGT HO

Rx_Level_Drop HO

Concentric Cell HO

Bad Quality HO

AMR HO


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Ranking Processing

Basic ranking





M rule

Network feature adjustment



16 bits ranking

K rule

The ranking result: target cell selection of handover


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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: 



Basic ranking 

M rule



K rule

Network feature adjustment 

16 bits ranking



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M Rule Begin Yes

Finish to all neighbor cells?

End

No No

Y es An BSC external neighboring cell& the current channel is SDCCH ?

Direct retry?

No

[Inter-BSC SDCCH HO Allowed] is Yes?

Yes

No

Delete the cell from the cell list?

Yes

Yes If the cell flow is overload ?

No RX_LEV_DL(n) < [Min DL Power on HO Candidate Cell](n)+ [Min Access Level Offset](s)?

No

Yes

Delete this cell from the cell list

For service cell: Min Access Level Offset=0

RX_LEV_UL(n) < [Min UP Power on HO Candidate Cell](s)+ [Min Access Level Offset](s)?

Yes

No


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

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

Under 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 

If the cell is overload



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



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

For service cell: Min Access Level Offset is 0.



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Data Configuration of M Rule


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[Inter-BSC SDCCH HO Allowed]

•Value Range: Yes, No •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.



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Data Configuration of M Rule


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[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 ofthe candidate cell for handover + the minimum access level offset).0-63 with 0 indicating -110 dBm and 63 indicating -47 dBm. [Min DL Level on Candidate Cell]

•Value Range: 0~63 (-110 dBm to -47 dBm) Default Value: 15 •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. Confidential Information ofHuawei. No Spreading Without Permission


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K Rule 

Flow of calculating K value.

Cell B Cell A

Begin

Finish to calculate value K to all cells? Yes

No Serving cell?

Cell C Serving Cell

Cell F

Yes

Cell D

Cell E

End

No E Receiving Level

K=0

K = RX_LEV (n) – RX_LEV (s)

A

Serving Cell F

C

D

B Cell

All the candidate cells are ranked in descending order according to the K value


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After the M rule , all the candidate cells are ranked in descending order according to the K value 

Service cell: K = 0



Neighboring cell: K = RX_LEV (n)– RX_LEV (s)



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Network Feature Adjustment 

After network feature adjustment, all the candidate cells have their own 16 bits value.



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.

hest Th e H i g Weight

10 12 11 14 13 16 15

9

8

7


6

5

4

3

2

1

The Low W eight

est

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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.

16

15

14

13

12

11

10

9

8


7

6

5

4

3

2

1

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The 4th bit: Inter-cell HO hy steresis bit. 

Note: In PBGT HO, whichever the greater of the inter-cell ( of the same layer ) hysteresis and PBGT threshold, that value will be us ed in the PBGT HO. Yes

No Is serving cell? RX_LEV_DL (n) >= RX_LEV_DL (s) + [Inter-cell HO hysteresis]

Always set to 0

Yes

Set to 0

No Set to1

16

15

14

13

12

11

10

9

8


7

6

5

4

3

2

1

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



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Data Configuration of Inter-cell HO Hysteresis


Page51

[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.



N-52



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.

16

15

14

13

12

11

10

9

8


7

6

5

4

3

2

1

Page52



N-53


Hierarchical Cell Structure Layer 4 （low）

GSM 900

Umbrella Cell

GSM 900

GSM 900 GSM900 Cell

GSM1800

GSM1800

GSM1800

GSM1800 Cell

Micro Cell

GSM900

GSM900

GSM900

GSM900

GSM1800

GSM1800

GSM1800

GSM1800


Layer 3

Layer 2

Layer 1 （high）

Page53

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.



N-54


Data Configuration of Cell Hierarchical Network Structure


Page54

[Cell Layer] er, the MACRO layer, and the •Value Range:1~4 (mapping to the PICO layer, the MICRO lay 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.



N-55



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

This bit is affected by 14th bit. Yes

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

11th bit is turned off

No Yes

No

No

Is serving cell?

cell load >=[ Load Rep.No on Candidate Cell](n)?

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

Yes set to 0

16

15

Yes

set 1 to

14

13

set 1 to

12

11

10

9

8


set to 0

7

6

5

4

3

2

1

Page55

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 thanSystem 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



N-56


Data Configuration of Cell-load-sharing


Page56

[Load HO Allowed]

•

Value Range: Yes, No

•

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. Loadsharing 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. 

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.



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.



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



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



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.



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



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



N-57


Data Configuration of Cell-load-sharing


Page57

[Load HO Threshold] 

Value Range: 0~100(%)



Default Value: 85



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.



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] 

Value Range: 0~100(%)



Default Value: 75



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.



Remarks: The same as that of Load HO Threshold



N-58



12th bit and 13th bit: Whether share the same BSC or MSC. Yes

No

Is serving cell? Yes

Both 12th and 13th set to 0 Yes

Co-MSC?

Different BSC: 12th set to 1 13th set to 0

The same BSC: 12th set to 0 13th set to 0

Turn off 12th &13th bit

No

Co-BSC? Yes

No

Is [Co-BSC/MSC Adj] yes?

No

Different MSC: 12th set to 0 13th set to 1

See 14th bit

16

15

14

13

12

11

10

9

8


7

6

5

4

3

2

1

Page58

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

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

Otherwise, set to 1 

Service cell: is always set to 0



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



N-59


Data Configuration of Co-BSC&MSC


Page59

[Co-BSC/MSC Adj]

•Value Range: Yes, No •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.



N-60


Network Feature Adjustment The 14th bit: Layer HO threshold adjustment bit.



Yes

Yes

RX_LEV_DL >= [Inter-layer HO Threshold] – [Inter-layer HO Hysteresis]?

No

No

RX_LEV_DL >= [Inter-layer HO Yes Threshold] + [Inter-layer HO Hysteresis]?

No

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

set to 0



Is serving cell?

set to 0

The 15th/16th bits are reserved 16

15

14

13

12

11

10

9

8

7


6

5

4

3

2

1

Page60

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

At the same time, bit 5th- 13th bits are turned off. The 15th/16th bits are reserved



N-61


Data Configuration of Layer HO Threshold Adjustment


Page61

[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 handed from 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



N-62




1



2

MR. Preprocessing

3

Handover Judgment

4



Emergency HO


No DL MR HO

MS Fast Moving HO

TA HO

Layer HO

Interference HO

PBGT HO

Rx_Level_Drop HO

Concentric Cell HO

Bad Quality HO

AMR HO


Page62



N-63


No DL MR HO 

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.

Bad uplink quality

S er v i n gC e l l


N ei g hb o r i ngC e l l

Page63

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.



N-64


Position of No DL MR HO MS Goes into Dedicated Mode


1

2


MR. Preprocessing

OM Forced HO Direct Retry Emergency HO

TA HO Handover Judgment

4



Load HO Normal HO Edge HO MS Fast Moving HO

No DL MR HO 3

Enhanced Dual Band HO

Layer HO

Interference HO

PBGT HO

Rx_Level_Drop HO

Concentric Cell HO

Bad Quality HO

AMR HO


Page64

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



N-65


No DL MR HO Begin

No

Is [No Dl Mr. HO Allowed] Yes ? Yes

Yes No

Report 1DL MR at l ease? Is serving cell?

Yes No

<=[Cons.No Dl Mr. Ho Allowed Limit]?

No

Select the candidate cell with the highest priority,

[Intrecell HOAllowed]?

exluding serving cell

Yes

>= signal quality filter length ?

No

Yes No

No

Yes

Yes No

UL_Qua. (after filering) >=[No Dl Mr.Ul Qual HO Limit]? Yes Only one No cadidate cell?

No Dl Mr. in current Mr.? Yes

End

>=[Forbidden time after MAX Times]? Yes Trigger No DL Mr. HO signal quality filter length : For TCH:[Filter Length for TCH Qual] For SDCCH:[Filter Length for SDCCH Qual]


Page65

Triggering condition 

No DL information in current MR



Stored UL Rx_Qual Value Number >= Rx_Qual Filter Length



UL Rx_Qual >= No DL MR HO UL Rx_Qual Threshold



Number of Lost DL MR
Object cell selection 

Prefer neighboring cell



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



N-66


Data Configuration of No DL MR HO


Page66

[No Dl Mr. HO Allowed]

•Value Range: Yes, No •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 upl ink receive qualitythreshold 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 this threshold, the handover is disabled and the timer is reset.



N-67


TA(Time Advance) HO Handover Triggering

TA(s)

TA(n) Handover Triggering Zone

TA Threshold(n)

TA Threshold(s) or

Time

Serving Cell


Neighboring Cell

Page67

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.



N-68


TA(Time Advance) HO Begin

No

End

No

Select the cell with the highest priority in the cadidate cell list

Is [TA HO Allowed] Yes ? Yes The actual TA >=

Yes

[TA Threshold]?

Is serving cell? No

Yes No

Any neighbour cell exist? Yes

TA(n is in the same BTS)Yes <=[TA Threshold](s)? No No

Suitable cell exist? Yes Trigger TA handover


Page68


The actual TA >= TA Threshold


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

Restriction 

The service cell cannot be the object cell.



HO is not allowed when TA Threshold of theneighboring cell withthe same BTS is equal or smaller than that of the service cell.



N-69


Data Configuration of TA HO


Page69

[TA HO Allowed]

•Value Range: Yes, No •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.



N-70


Interference Handover RX_Lev Handover Triggering Zone Lev_Thr

Qual_Thr

Rx_Qual

Interference Origin

Serving Cell


Neighboring Cell

Page70

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.



N-71


Interference HO Begin

No

Is [Interference HO Allowed] Yes ?

No

UL or DL receiving


Yes Yes End

Is serving cell?

No

Quality(s)>=A? Yes No

Any neighbour cell exist?

Yes

Yes None AMR FR: A = RXQUALn, 1<=n<=12 AMR FR: A = RXQUAL1, n=1; A = RXQUALn + RXLEVoff,

Rx_Level( n)>= [Inter-layer HO Threshold]( n) + No [Inter-layer HO Hysteresis]( n)?

No [IntracellHO Allowed] yes & cellnot punished?

No

Yes Any suitable cell exist? Yes Trigger interference handover

2<=n<=12


Page71


UL/DL receiving quality>=A



None AMR FR



AMR FR





A = RXQUALn, 1<=n<=12

A = RXQUAL1, n=1; A = RXQUALn + RXLEVoff, 2<=n<=12


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



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



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

Restriction

For none AMR FR, if one of the following conditions is met, the system will judge that interference occur: 1.

Rx_lev <= 30, and Rx_qual > RXQUAL 1

2.

Rx_lev = 31, and Rx_qual > RXQUAL 2

3.

Rx_lev is within [32,35], and Rx_qual > RXQUAL 3

4.


5.


6.


7.


8.


9.


10.

Rx_lev is wi thin [56,58], and Rx_qual > RXQUAL 10

11.

Rx_lev is wi thin [59,62], and Rx_qual > RXQUAL 11

12.

Rx_lev >= 63, a nd Rx_qual > RXQUAL 12



N-72


Data Configuration of Interference HO Default Value Receiving Level(-110dBm)

Receiving Quality

Parameter RXQUAL1

<=30

70

RXQUAL2

=31

60

RXQUAL3

32~35

59

RXQUAL4

36~38

58

RXQUAL5

39~41

57

RXQUAL6

42~45

40

RXQUAL7

46~48

55

RXQUAL8

49~52

54

RXQUAL9

53~55

53

RXQUAL10

56~58

52

RXQUAL11

59~62

51

RXQUAL12

>=63

50


Page72



N-73


Data Configuration of Interference HO


Page73

[Interference HO Allowed]

•Value Range: Yes, No •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 nonCAMRFR 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).



N-74


Rx_Level_Drop HO


Page74

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



N-75


Rx_Level_Drop HO Begin

No

[Rx_Level_Drop HO Allowed] Yes ?


Yes

End

No

Satisfy the Formula& The lastest RX_LEV_UL( s) < [Edge HO UL RX_LEV Threshold]?

Yes No

Yes

Is serving cell?

End

No

Priority is higher than serving cell? Yes


Trigger Rx_Level_Drop handover

Yes

Formula:

No

(A1 −)10(X1 +) A2( −10)X 2( + A)3 −10 X3 + A4 −10 X 4 + (A5 −)10(X5 +) A6( −10) X 6( + A)7 −10 X 7 + A8 −10 X8 < −B


Page75




The lastest RX_LEV_UL < Edge HO UL RX_LEV Threshold C1（nt）=(A1-10)X1＋(A2-10)X2+(A3-10)X3＋…＋(A8-10)X8<－B


The neighboring cell with the highest priority and whose priority is higher than that of the service cell in the

candidate cell group. Restriction 


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; C1（nt）=(A1-10)X1＋(A2-10)X2+(A3-10)X3＋…＋(A8-10)X8， 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 equal to 10, A1 to 20, and A2 to 0.



N-76


Data Configuration of Rx_Level_Drop HO


Page76

[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, srcinal MR is required for the BSC. [Filter Parameter A1~A8]

•Value Range: 0~20 Default Value: 10 •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]

•Value Range: 0~200 Default Value: 0 •Description: This is one of the parameters that determine whether a handover is required due to fast dropping levels.This parameter 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]

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

Default Value: 10

•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 handove r u plink/downlink receive level threshold < Uplink/downlink signal strength lower limit of HUAWEI II power control



N-77


BQ(Bad Quality) HO Begin

No

Is [BQ HO Allowed] Yes ?


Yes

End

No

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

Yes No


Yes

No

Is serving cell?

No

RX_LEV_DL n() > No RX_LEV_DL s() + Inter-cell HO hysteresis( s) -BQ HO Margin( s) ?

yes [IntracellHO Allowed] & cellnot punished?

Yes

Yes

Yes No

Suitable cell exist? Yes Trigger BQ handover


Page77

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

UL receiving quality >= UL Qual. Threshold



OR DL receiving quality >= DL Qual. Threshold



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


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

Restriction 

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



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.



N-78


Data Configuration of BQ HO


Page78

[BQ HO Allowed]

•Value Range: Yes, No •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.



N-79




Page79

[DL/UL QuaLimitAMRFR]

•Value Range: 0~70 •Default Value: 65 Description: Thisservice. parameter switchover control •for the AMR FR Theindicates values ofthe thisurgent parameter match downlink/uplink quality levels 0-7quality 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.



N-80




Page80

[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 Intercell HO Hysteresis > "Inter-cell HO Hysteresis-BQ HO Margin", the Intercell 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.



N-81




1



2

MR. Preprocessing

3

Handover Judgment

4



Emergency HO


No DL MR HO

MS Fast Moving HO

TA HO

Layer HO

Interference HO

PBGT HO

Rx_Level_Drop HO

Concentric Cell HO

Bad Quality HO

AMR HO


Page81



N-82


Enhanced Dual Band HO 

Enhanced dual band cell is two different band cells which locate a common site, and have the same azimuth.



Purpose 

During the procedure of channel assignment and handover, 900M cell and 1800M cell 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.


Page82



N-83


Channel Assignment of Enhanced Dual Band HO TCH assignment (SDCCH channel in UL)



Begin from UL No

[Assignment Optimization Yes of UL Subcell Allowed or not] ?

No

Cell load of UL > Yes [UL Subcell General Overload Threshold(%)]?

Yes No Assign TCH in UL or direct retry identification or queuing

A:

A No

Any idle TCH Available in OL?

Yes

Assign TCH in OL RX_LEV_OL>= [Incoming OL Subcell HO level Threshold(d and B)] RX_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 w hich has the same frequency band and l ayer with underlaid subcell, but locates in a different BTS. If there is no such a cell, this value is -110dBm If [ATCBHoSwitch] is [Close], the second condition is turn off.


Page83

TCH assignment (SDCCH channel in underlaid) 

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



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 Subcells－Distance 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



N-84


Data Configuration of Channel Assignment


Page84

[ATCBHoSwitch]

•Value Range: Close, Open •Default Value: Open Description: The switch of the ATCB handover algorithm. [Assignment Optimization of UL Subcell Allowered Or Not]

•Value Range: Yes, No •Default Value: Yes •Description: This parameter indicates whether the access request originated in the underlaid subcell 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 srcinated in the underlaid subcell are preferably assigned to the channel in overlaid subcell.



N-85




Page85

[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.



N-86


Channel Assignment of Enhanced Dual Band HO 

TCH assignment (SDCCH channel in OL) Begin from OL

No

[Assignment OptimizationYes of OL Subcell Allowed or not ] No ?

Yes Assign TCH in UL

Assign TCH in OL or direct retry identification or queuing

Cell load of UL< [UL Subce ll Lower Load Threshold]? Yes

No

Any idle TCH Available in OL?

No

Assign TCH in OL No

Any idle TCH Available in UL?

Yes

Assign TCH in UL


Page86

TCH assignment (SDCCH channel in overlaid) 

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



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



N-87




Page87

[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 subcell channel. [Assignment Optimization of OL Subcell Allowered Or Not]

•Value Range: Yes, No •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.



N-88


Enhanced Dual Band HO 

Classification of TCH HO in enhanced dual band HO

UL to OL for high load in UL

OL to UL for low load in UL


OL to UL for moving

Page88

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



N-89


Enhanced Dual Band HO(UO ) 

Triggering condition for TCH Load HO from UL to OL for high load in UL


Page89

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



N-90


Enhanced Dual Band HO(UO ) 

Triggering condition for TCH Load HO from UL to OL for high load in UL Begin

[Load HO From UL Subcell No to OL Subcell Allowed] Yes ?

End

Yes Refresh cell load per second

Y es

Cell load of UL>=[UL Subcell Serious Overload T hreshold(%)]?

B-C No

Cell load of UL>=[UL Subcell General Overload T hreshold(%)]?

Yes No

A:

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

No B

AdjustHO zonebasing on HO stepand HO period

Any MS in HO zone?

No

Yes B=[UL Subcell Load Hierarchical HO Period(s)] Trigger C=[Modified Step Length of UL Load HO P eriod(s)] UL to OL 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)] RX_LEV_OL >= [Incoming OL Subcell HO level Threshold(dB)] and RX_LEV_UL – RX_LEV (n) > [Distance Between Boundaries of UL and OL Subcells(dB)]


Page90

Triggering condition for TCH Load HO from underlaid to overlaid 

Load HO of UL Subcell to OL Subcell Enable is YES



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 Subcells(dB)



Satisfying P/N rule



HO zone is from Incoming OL Subcell HO level Threshold to -47dBm

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 -110dBm



N-91


Data Configuration of Enhanced Dual Band HO(UO )


Page91

[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 over laid subcell. Moreover, calls srcinated in the underl aid 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 v alue of Out Cell Load HO Modify Step eve ry second based on the value of Out Cell Load Classific ation HO Period. Thus the handove r from underlaid subcell to the overlaid subcell speeds up. [Load HO From UL Subcel l to OL Subcell Allowed]

•Value Range: Yes, No •Default Value: Yes •Description: When the ratio of underlaid subcell channel occupancy is high, whethe r some calls in the overlaid subcell are 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 indica tes 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.



N-92


Data Configuration of Enhanced Dual Band HO(UO )


Page92

[UL Subcell Load Hierarch ical HO Period(s)]

•

Value Range: 1~255 Unit: Seconds Default Value: 5

•

Description: This parameter indica tes the period of the hierarchical handove r from u nderlaid subcell to overlaid subcell. When the ratio of unde rlaid subcell cell channel occupancy is greater th an 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. the call may over drop the because thethe target is congested. Therefore algorithm of hierarchical handover isThus applied to hand calls in cell cell hierarchically to the overlaidthe subcell.This parameter 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 indica tes the level step of the hierarchical handover from underlaid subcell to overlaid subcell.

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

•


•

Description: If underla id subcell load is higher tha n the value of Out Cell Serious Ove rLoad Thred, the period of handover from underlaid subcell cell to overla id subcell cell is shorte ned 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 started. This parameter indicates the P in P/N criterion.

[Satisfy Condition Time]

•


•

Description: P/N criterion: In P measurement reports, N measurement results meet handover requirements. Handover is started. This parameter indicates the N in P/N criterion.



N-93


Enhanced Dual Band HO(OU ) 

Triggering condition for TCH HO from OL to UL for moving Begin Yes A

No

End

Yes Satisfy P/N?

No

Yes

Generally, Object cell maybe UL or other neighbor cell is

Select Neighbor cell with the highest priority Trigger OL to UL

A:

RX_LEV_OL <[Outgoing OL Subcell HO level Threshold(d or B)] RX_LEV_UL – RX_LEV (n) < [Distance Between Boundaries of UL and OL Subcells(dB)] – [Distance Hysteresis Between Boundaries of UL and OL Subcells(dB)]


Page93

Triggering condition for TCH Moving HO from overlaid to underlaid 

RX_LEV_OL < Outgoing OL Subcell HO level Threshold



OR RX_LEV_UL – RX_LEV (n) < Distance Between Boundaries of UL and OL Subcells(dB) - Distance Hysteresis Between Boundaries of UL and OL Subcells(dB)



Satisfying P/N rule


The cell with highest priority. It could be underlaid subcell or normal neighboring cell

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 -110dBm



N-94


Data Configuration of Enhanced Dual Band HO(OU )


Page94

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

•Value Range:0~63 Unit: dB Default Value: 10 •Description: This parameter indica tes the distance between the overlaid subce ll 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 betw een underlaid subcell and overlaid subc ell based on the comparati ve value of signal serving cell and cell. Suppose the signal strength of serving cell is SS(s), and neighboring cellstrength SS(n). of If SS(s) is equal to neighboring 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. [Distance Hysterisis Between Boundaries of UL And OL Subcell(dB)]

•Value Range: 0~63 Unit: dB Default Value: 2 •Description: To prevent ping-pong handover, the BSC determines whether the handover of the MS from overlaid subcell cell to underlaid subcell cell based on the value of this parameter . Suppose the signal strength of servin g cell is SS(s), and neighboring cell SS(n). If the value of SS(s) - SS(n) is smaller than the value of Distance Between Out And Inn Cell boundary - Distance Hyst Between Out And Inn Cell boundary, the MS handove r from overlaid subcell cell to underlaid subcell cell is allowed. [Outgoing OL Subcell HO level Threshold(dB )]

•Value Range: 0~63 Unit: dB Default Value: 25 •Description: This parameter indicates the lowest threshold of overlaid subcell level of the handover from overlaid subcell to underlaid subcell. When the MS receive level is lower than the value of this parame ter, the BSC allows the handover from overlaid subc ell cell to underl aid subcell. [Total Number of ]

•Value Range: 1~255 Unit: Seconds Default Value: 5 •Description: P/N criterion: In P measurement reports, N measurement results meet handover requirements. Handover is started. This parameter indicates the P in P/N criterion. [Satisfy Condition Time]

•Value Range: 1~255 Unit: Seconds Default Value: 4 •Description: P/N criterion: In P measurement reports, N measurement results meet handover requirements. Handover is started.Information This parameter indicates the N in P/N criterion. Confidential ofHuawei. No Spreading Without

Permission


N-95



Triggering condition for TCH Load HO from OL to UL for low load in UL


Page95

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



N-96



Triggering condition for TCH Load HO from OL to UL for low load in UL Begin End [Load HO of OL Subcell No to UL Subcell Enable] Yes ?

Confirm: HO zoneand HO step

Yes Refresh cell load per second No

Any MS inHO zone?

Cell load of UL <[UL Subcell Lower Load T hreshold(%)]?

Yes Satisfy P/N? Yes

No

Yes The object cell must be the underlaid subcell and satisfy condition A

Trigger OL to UL

No

HO zone: [Outgoing OL Subcell HO Level Threshold(dB)] ~ -47dBm HO step: [Step Length of OL Subcell Load HO(dB)] A: RX_LEV_UL >= Inter-layer HO Threshold + Inter-layer HO Hysteresis


Page96

Triggering condition for TCH Load HO from overlaid to underlaid 

Load HO of OL Subcell to UL Subcell Enable is YES



Cell load of underlaid < UL Subcell Lower Overload Threshold



Satisfying P/N rule



HO zone is from Outgoing OL Subcell HO level Threshold to -47dBm


The object cell must be the underlaid subcell



RX_LEV_UL >= Inter-layer HO Threshold + Inter-layer HO Hysteresis



N-97


Data Configuration of Enhanced Dual Band HO(OU )


Page97

[Out Cell Low Load Thred]

•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 subcell. [Load HO of OL Subcell to UL Subcell Enable]

•Value Range:Yes, No Default Value:No •Description: This parameter indicates whether theload handover fromoverlaid subcellto underlaid subcell is allowed. [OL Subcell Load Diversity HO Period(s)]

•Value Range: 1~255 Unit: Seconds Default Value:10 •Description: This parameter indicates the period of the hierarchical handover from underlaid subcell to overlaid subcell.When the ratio of overlaid 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 underlaid subcell.This parameter indicates the time duration of every hierarchical handover. [Step Length of OL Subcell Load HO(dB)]

•Value Range: 0~63 Unit: dB Default Value: 5 •Description: This parameter indicates the level step of the load handover from overlaid subcell to underlaid subcell.



N-98




1



2

MR. Preprocessing

3

Handover Judgment

4



Emergency HO


No DL MR HO

MS Fast Moving HO

TA HO

Layer HO

Interference HO

PBGT HO

Rx_Level_Drop HO

Concentric Cell HO

Bad Quality HO

AMR HO


Page98



N-99


Load HO Handover triggering zone Load of Serving Cell

Load of Neighboring Cell

Load HO Threshold Load Req. on Candidate Cell

Time

Normal Cell

Congested Cell

Congested Cell

Congested Cell Normal Cell

Normal Cell

Normal Cell


Page99



N-100


Load HO 

As load HO may trigger several HOs, we need to consider the CPU load (system flow level) before triggering it. In addition, load HO is executed step by step, that is, the edge HO thrsh. raises according to certain step and period and will stop when out of the Load HO Zone. Load HO zone

Cell A

Load HO bandwidth CONF_HO_RXLEV+CLS_Offset

Normal HO border

Cell B

Edge HO threshold CONF_HO_RXLEV CONF_HO_RXLEV+CLS_Ramp Load HO step level


Page100

A handover band is defined in load handover, in the range of edge handover threshold ~ edge handover threshold + load handover bandwidth. The handover band itself is divided into multiple equalized handover step sizes, MS (falling within edge handover threshold + N*handover step sizes) are handover to adjacent cells one by one from low to high. Once load of the serving cell decreases (as lower than the load handover start threshold) or load of the adjacent cell increases to a certain extent (as higher than the load handover received threshold), the handover stops. Load handover is an emergency measure, which mainly applicable to abnormal traffic peak in part of the radio network. It should not be used as the major means to solve the traffic congestion problem. If load handover always occurs to some area of a network, TRX reconfiguration and network topology re-design is the right way. Related parameters: Handover - [Load handover table] 

System flux Thrsh. for load HO



Load HO Thrsh.



Load HO Req. on candidate cell



Load handover bandwidth (dB)



Load HO step level (dB)



Load HO step period (second) Confidential Information ofHuawei. No Spreading Without Permission


N-101


Load HO Normal Cell

Congested Cell

Normal Cell Normal Cell


Page101

The handover bandwidth is gradually wider and wider.



N-102


Load HO Begin No

End No

Select the cell w ith the highest priority in the cadidate cell list

Is [Load HO Allowed] Yes ? Yes

No Yes

Yes No

Yes Load HO timer T begin? Yes Load HO timer T overflow?

No

No

CaculateA= T + 1) × Step ( Period No

C&D

End Yes

No

C

Yes No

Yes

Suitable cell exist?

Yes Trigger load handover

B: [Edge HO_DL_RX_LEV Threshod]
CaculateA= [Load HO Bandwidth]

B

No

BSC internal cell?

No

Load of service cell >= [Load HO Threshold]?

Star timer T

Yes

Is serving cell?

Current system flux<= [System Flux Threshold for Load HO]?

Yes Step

≤

C: RX_LEV (n)>= [Inter-layer HO Threshold] + [Inter-layer HO Hysteresis] D: load(n)< Load Req. on Candidate Cell Step: [Load HO Step Level] Period: [Load HO Step Period]

A ≤ [Load HO Bandwidth]


⇒

0≤T

≤

(

[Load HO Bandwidth]

Step

− 1) ×

Period

Page102


The CPU load of system <= SystemFlux Threshold for Load HO



The load of service cell >= Load HO Threshold



The DL receiving level is in the load HO zones


The service cell cannot be the object cell



If the service cell is a enhanced dual band cell, the other cell in this group cannot be the object cell



The load of object cell < Load Req. on Candidate Cell (Only valid for internal neighboring cell)



RX_LEV of object cell >= Inter-layer HO Threshold + Inter-layer HO Hysteresis

Restriction 

It is not available with SDCCH.



N-103


Data Configuration of Load HO


Page103

[Load HO Bandwidth]

•Value Range: 0~63 •Unit: dB •Default Value: 25 Description: Together with Edge HO DL RX_LEV Threshold, this parameter indicates whether a load handover is •allowed. Only when the receive level of the serving cell is within the range of (Edge HO RX_LEV Threshold, Edge HO RX_LEV Threshold + Load HO bandwidth), a load handover is allowed. [Load HO Step Period]

•Value Range:1~255 •Unit: Seconds •Default Value: 10 •Description: This parameter indicates the period required for each level of load handover. When the load of the cell is equal to or greater than the Load HO Thrsh, all connections in the cell may send handover requests simultaneously, thus leading to sudden increase of CPU load and possible call drops when the target cell is congested. Therefore, these requests are divided into steps based on the receive strength. [Load HO Step Level]

•Value Range: 1~63 •Unit: dB •Default Value: 5 •Description: This parameter indicates the bandwidth of each step during level-based load handover. In a layer load handover, starting from the Downlink Edge Handover Threshold, the upper limit of the load handover band of increases by a Layer Load Handover Step every one Layer Load Handover Period. Go on like this, all calls whose receive levels are between Edge HO RX_LEV Threshold and Edge HO RX_LEV Threshold + Load HO bandwidth in the current serving cell are switched out through level by level handover.

•Remarks: This parameter must be less than Load HO Bandwidth.



N-104




1



2

MR. Preprocessing

3

Handover Judgment

4



Emergency HO


No DL MR HO

MS Fast Moving HO

TA HO

Layer HO

Interference HO

PBGT HO

Rx_Level_Drop HO

Concentric Cell HO

Bad Quality HO

AMR HO


Page104



N-105


Edge Handover Handover Triggering

RX_Lev

RX_LEV Thr

Time

P /N P: Watch Time N: Valid Time

Serving Cell


Neighboring Cell

Page105

As a MS moves to the edge of a cell, when the receiving level of MS or BTS is lower than the edge handover threshold, handover is triggered in order to look for a better serving cell.



N-106


Edge HO Begin No

Is [Fringe HO Allowed] Yes ? Yes UL_Rx_Lev(s) < [Edge HO UL RX_LEV Threshod]?

No

Yes Refresh its timer

Select cell(n) whose 16 bit value is higher than serving cell and whose level satifys P/N rule( n) basing onA No

Yes

No

DL_Rx_Lev(s) < [Edge HO DL RX_LEV Threshod]?

End

No

Any neighbor cell? Yes Trigger Edge handover

Satisfy P/N rule( s)?

Yes Refresh its timer

No Satisfy P/N rule( s)?

Yes

A: DL_Rx_Lev(n)> DL_Rx_Lev(s)+[Inter-cell HO Hysteresis]


Page106


The DL receiving level < Edge HO DL RX_LEV Thrsh.



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



Satisfying P/N rule





The neighboring cell with the highest priority and whose priority is higher than that of the service cell



N-107


Data Configuration of Edge HO

[Edge HO UL/DL RX-LEV Threshold]<[UL/DL RX_LEV Lower Threshold] in HWII/III power control tabel

Should be lower than the[Outgoing OL Subcell HO Level Threshold(dB)] in enhance dual band data table


Page107

[Fringe HO Allowed]

•Value Range: Yes, No •Default Value: Yes •Description: The parameter indicates whether a fringe handover is allowed. A fringe handover is used to prevent call drops in cell edges and initiated when the downlink level in the serving cell is lower than Edge HO DL RX_LEV Threshold or the uplink level in the serving cell is lower than Edge HO UL RX_LEV Threshold.

•Remarks: To implement fringe handover, the comprehensive sequence of the target cell must be higher than that of the serving cell. [Edge HO UL RX_LEV Threshold]

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

25: urban areas without PBGT handover



20: suburbs with a single BTS



20: urban areas with PBGT handover




N-108

•Remarks: Edge handover uplink/downlink receive level threshold < Uplink/downlink signal strength lower limit of HW-II/III power control [Edge HO DL RX_LEV Threshold]

•Value Range: 0~63 (-110 dBm to -47 dBm) •Default Value: 20 •Description: The parameter indicates the downlink receive level threshold of an edge handover. An edge handover will be triggered if the downlink receive level is 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 manual overlapping coverage and channel interference. This parameter should be adjusted based on the performance statistics and actual networks to achieve uplink-downlink balance. 

30: Urban areas without PBGT handover



25: Suburbs with a single BTS



25: Urban areas with PBGT handover

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



N-109




Page109

[Edge HO Watch Time(s)]

•Value Range: 1~16 •Unit: Seconds •Default Value: 3 Description: This parameter indicates the period when uplink/downlink receive levels are measured to determine •whether an edge handover is triggered. [Edge HO Valid Time(s)]

•Value Range: 1~16 •Unit: Seconds •Default Value: 2 •Description: To trigger an edge handover, the receive level of the uplink or downlink should constantly remain lower than their corresponding edge handover thresholds within Edge HO Watch Time(s). This parameter indicates this duration. [Edge HO AdjCell Watch Time(s)]

•Value Range: 1~16 •Unit: Seconds •Default Value: 3 •Description: This parameter indicates the period when uplink/downlink receive levels are measured to determine whether an edge handover neighbor cell is triggered. [Edge HO AdjCell Valid Time(s)]

•Value Range: 1~16 •Unit: Seconds •Default Value: 2 •Description: During the edge handover continuance time, the UL/DL receive level should remain higher than the corresponding UL/DL edge handover threshold for a period. This parameter indicates the period.



N-110




Page110

[Inter-cell HO Hysteresis]

•Value Range: 0~63 •Unit: Levels •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 populous urban areas and 8 dB for suburbs.



N-111


MS Fast-Moving Handover Handover Triggering

Time

Time Threshold

1

123

Cells Number

P/N P: Watch Cells N: Valid Cells Umbrella Cell Micro Cell


Page111

The condition of MS Fast-Moving Handover is that a MS is moving fast (for example moving on a highway), and the area is covered by two layers, that is micro cell and macro cell. MS Fast-Moving Handover is mainly used to solve the handover of MS during fast-moving, that is to say, to avoid MS handover to the micro cell to increase handover time and signaling flow, thereby increase service quality

MS Fast-moving time Thrsh——If the time used by MS to pass this cell is less than this threshold, it means that MS passes the cell quickly. MS Fast-moving watch cells P —— The total number of cells for judging whether a MS is fast moving or not. MS Fast-moving valid cells N —— Total N of actual cells that MS fast passes. When N equal to or more than P cells that MS lately passes are fast passing ones, the fast moving handover algorithm will be started.



N-112


MS Fast-Moving Handover Begin No

Yes

Yes

Is [MS Fast Moving HO Allowed] Yes ? Yes Is the target cell the serving cell? No Is the serving cell on layer 4?

Refresh timer(s)

No

End Yes

No

No

Is the best neighbor cell is the last srcinal cell?

Satisfy P / N rule?

No

Yes Select the neighbor cell with the highest priority & on the 4th layer & satisfy RX_LEV(n)>= Inter-layer HO threshold(n) + I nter-layer HO hysterisis(n)

Any cell satisfy the condition above?

Yes

Trigger MS fastmoving handover


Page112

Triggering condition MS moves through P cells (watch cells), and the speed for Q cells (valid cells) among these p cells is fast 



The layer of service cell must be less than four





The neighboring cell with the highest priority



The layer of the object cell must be the 4th layer



RX_LEV of the object cell >= Inter-layer HO threshold + Inter-layer HO hysterisis



N-113


Data Configuration of MS Fast-moving Handover


Page113

•[MS Fast Moving HO Allowed] •Value Range: Yes, No •Default Value: No •Description: This parameter indicates whether a fast moving handover is allowed. The fast moving handover enables a fast moving MS to hand over rapidly to a macro cell, thus reducing handovers. It is recommended that this algorithm be applied only to special areas, such as highways, to reduce the CPU load. [MS Fast-moving Watch Cells]

•Value Range:1~10 •Default Value:3 •Description: During the moving, the MS passes P micro cells. According to the P/N rule, when the MS fast crosses N ones among the P micro cells, the BSC starts to trigger a fast-moving micro cell handover.

•Remarks: If this parameter is excessively high, it is difficult to reduce the system load effectively. If this parameter is excessively low, the judgment is inaccurate. [MS Fast-moving Valid Cells]




N-114

•Value Range: 1~10 •Default Value: 2 •Description: Suppose that the actual number of the micro cells that the MS fast crosses is N. According to the P/N rule, when the MS fast crosses N ones among the P micro cells, a fast moving handover is triggered by the BSC when this parameter satisfies the required conditions. [MS Fast-moving Time Threshold]

•Value Range: 0~255 •Unit: Seconds •Default Value: 15 •Description: This parameter indicates the threshold for judging whether an MS moves fast across a cell. The threshold is obtained based on the cell radius and specified velocity. If the time for crossing a cell is lower than this threshold, the MS is regarded as moving fast.

•Remarks: Conditions for triggering fast-moving handover are as follows: 

The serving cell does not belong to level-4.



The optimum target cell does belong to level-4.



A neighboring cell has a macro cell.



N-115


Layer HO

GSM900 Cell （Lay 3）

Serving Cell


GSM1800 Cell （Lay 2）

Neighboring Cell

Page115

The goal of layer handover is to control the destination cell of handover more flexibly, make a MS hand over to the most reasonable cell to reduce the occurrence of latter handover in order to save all kinds of system resources, and also effectively increase handover successful ratio, reduce call drop during handover, improve voice quality and service level.



N-116


Layer HO Begin Is [Level HO Allowed] Yes ?

No

Yes Any neighbor cell exit?

No

End

Yes No 16bit bitvalue( valu(ns)< 16 )l?

Identify the next cell

Yes A & ( layer(n)< layer(s) or level(n)
No

No

Yes Trigger layer handover

A: RX_LEV(n)>= Inter-layer HO threshold(n) + Inter-layer HO hysterisis(n)


Page116


The layer or level of object cell is lower than that of the service cell



RX_LEV_DL of the object cell >= Inter-layer HO threshold + Inter-layer HO hysteresis



Satisfying P/N rule





The neighboring cell with the highest priority and whose priority is higher than that of the

service cell



N-117


Data Configuration of Layer HO


Page117

[Level HO Allowed]

•Value Range: Yes, No •Default Value: Yes •Description: The parameter indicates whether the layer level handover is allowed.An Inter Layer HO is realized by setting different layers and levels for the cells. It is used to guide the traffic to the cell that has a high priority. When this parameter is set to Yes, traffic is routed to a cell with a higher priority.

•Remarks: The lower the layer is, the higher the priority is. The higher the level is, the lower the priority is. Layer level handover is not implemented when the comprehensive sequence (including basic sequence and network sequence) of the serving cell is the highest or when the level of the target cell is not greater than the Inter-layer HO Threshold. [Layer HO Watch Time(s)]

•Value Range: 1~16 Unit: Seconds Default Value: 3 •Description: Compare the candidate cells that are better than the current serving cell so as to decide whether to trigger a layer handover. This parameter indicates the duration to make the decision. [Layer HO Valid Time(s)]

•Value Range: 1~16 Unit: Seconds Default Value: 2 •Description: If a cell is ranked 1 of the candidate cells for a whole segment of measurement period, this cell is called the best cell.



N-118


Data Configuration of Layer HO


Page118

[Inter-layer HO Threshold]

•Value Range: 0~63 •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 handed from 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 •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 - Inter-layer HO hysteresis



Actual Inter-layer HO Threshold of a neighboring cell = Inter-layer HO Threshold + Interlayer HO hysteresis



N-119


PBGT HO

Handover Triggering

Path Loss (dB)

PBGT HO 5 Threshold

Time

P /N

P: Watch Time N: Valid Time

126-119=7dB>5dB

126dB

119dB

Serving Cell


Neighboring Cell

Page119

In areas with densely distributed cells, the actual radio coverage range has become far larger than the distance between BTS. If MS keeps the conversation within a cell, it will not be effectively handed over to a nearby cell with low transmission power and that will lead to over shooting, thus increasing the interference of radio environment and complicating network planning and optimization. To solve this problem, Huawei develops PBGT handover algorithm that is based on path loss. PBGT handover algorithm is intended for the handover based on path loss, in real time, it seeks a cell with lower path loss and meeting certain system requirements, and judges whether it’s necessary to perform handover.



N-120


PBGT HO Is [PBGT HO Allowed] Yes ?

Begin

No

Yes Is current channel signal channel? No

Yes

End

Search next neighborcell No No

No

layer(n)=layer(s)& level(n)=level(s)? Yes Path loss (s) – Path loss (n) >PBGT HO Threshold

Satisfy P / N rule?

Yes Trigger PBGT HO

Yes Refresh timer(s)


Page120


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



Path loss (service cell) – Path loss (neighbor cell) > PBGT HO Threshold



Satisfying P/N rule





The neighboring cell with the highest priority and whose priority is higher than that of the service cell.

Restriction 

It is not available with SDCCH.



N-121


Data Configuration of PBGT HO


Page121

[PBGT HO Allowed]

•Value Range: Yes, No •Default Value: Yes •Description: The parameter indicates whether a POWER BUDGET (PBGT) handover is allowed.Based on path loss, PBGT handover is used to search for a desired cell in real time and to judge whether handover is performed. The cell must provide less path loss and meet other requirements.To avoid ping-pong handovers, PBGT handover applies to only cells of the same level on the same layer and is triggered only over TCH. On a SDCCH, it is not allowed to trigger a PBGT handover.Proper use of PBGT handover helps to reduce over-cell coverage and co-channel interference. [PBGT Watch Time(s)]

•Value Range: 1~16 •Unit: Seconds •Default Value: 3 •Description: This parameter indicates the period when the path losses of neighboring cells are measured. Thus, operators can determine whether a PBGT handover is triggered. PBGT Valid Time(s)

•Value Range: 1~16 •Unit: Seconds •Default Value: 2 •Description: This parameter indicates the period that satisfies PBGT handover.



N-122


Data Configuration of PBGT HO


Page122

[PBGT HO Threshold]

•Value Range: 0~127 (-64 dB to +63 dB) •Default Value: 68 •Description: A threshold in PBGT handover algorithm used to judge whether to perform PBGT handover. When PBGT Handover Allowed is set to Yes and Inter-cell HO Hysteresis > PBGT HO Thresh., the Inter-cell HO Hysteresis will act instead of the PBGT HO Thresh. When this parameter is assigned with a value smaller than 64, MS can hand over to a lower level neighboring cell. 68 for popular urban areas, 72 for suburbs.

•Remarks: When PBGT handover is enabled, and Inter-cell HO Hysteresis > PBGT HO Thresh, the Inter-cell HO hysteresis instead of the PBGT HO Thresh works. PBGT HO Thresh must be adjusted as per handover performance statistic result and actual network.



N-123


Concentric Cell 



Purposes 

Maximize coverage area



Reduce interference and improve frequency reuse density

Construction methods 

Different combiner loss



Different propagation loss



Modify the transmission power of TRX, the down tilt of antennas, etc.



By HO parameters Overlaid Underlaid


Page123



N-124


Classification and HO Judgment of Concentric Cell

Normal con…centric cell

Enhance con…centric cell Receiving level



Receiving level





Time advance





Quality



Quality



ATCB



Cell load of underlaid


Time advance

Page124

There are two kinds of concentric cell handover:

•Normal concentric cell handover •Enhance concentric cell handover The difference of these two handovers is that enhance concentric cell handover takes into account the cell load of underlaid.



N-125


Data Configuration of Concentric Cell


Page125

[Concentric Circles HO Allowed]

•Value Range: Yes, No •Default Value: Yes •Description: The parameter indicates whether a concentric cell handover is allowed. A concentric cell handover is implemented to achieve mass coverage in the underlaid subcell and tight frequency reuse in the overlaid subcell, thus improving the system capability and service performance. A concentric cell handover consists of inward handover and outward handover. [Enhenced Concentric Allowed]

•Value Range: Yes, No •Default Value: No •Description: This parameter indicates whether a enhenced concentric circle handover is allowed. 

While the Enhanced Concentric Cell Allowed is set as "Yes", compare the receive level of the MS with O to U HO Receive Level Threshold and U to O HO Receive Level Threshold to decide whether to trigger an O to U HO or a U to O HO.



While the Enhanced Concentric Cell Allowed is set as "No", compare the receive level of the MS with RX_LEV Threshold so as to decide whether to trigger an enhanced concentric cell HO. It is required to consider the load of the UL when deciding whether to trigger a U to O HO.



N-126


Normal Concentric Cell HO 

Division of underlaid and overlaid is decided by MS downlink receive level ,TA value and quality.

underlaid Receiving Level Threshold Receiving Level Hysteresis Receiving Qaulityl Threshold

overlaid

TA Threshold TA Hysteresis


Page126

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



N-127


Normal Concentric Cell HO

U to O


O to U

Page127



N-128


Normal Concentric Cell HO(OU ) 

Flow for TCH HO from overlaid to underlaid No Begin

[OL to UL HO Allowed] Yes ?

Yes

[Penalty Time of OtoU HO Fail(s)] overflow ?

No

End

Yes

No

No

[RX_LEV for UO HO Allowed] Yes?

[RX_QUAL for UO HO Allowed] Yes?

[TA for UO HO Allowed] Yes?

Yes Rx_Dl_Level<=[RX_LEV thshold] -[RX_LEV Hysteresis]

No

No

Yes

Rx_Dl_Quality>= No Current TA>=[TA Threshold]+ [RX_QUAL Treshold]? [TA Hysteresis]?

Yes

Yes P/N rule?

No

Yes

End

Yes Trigger OL to UL


Page128

Criterion for TCH HO from overlaid to underlaid: 

TA value >= TA Threshold + TA Hysteresis



OR RX_LEV <= RX_LEV Threshold －RX_LEV Hysteresis



OR Quality >= RX_QUAL Threshold



Satisfying P/N rule



N-129


Normal Concentric Cell HO(UO ) 

Criterion for TCH HO from underlaid to overlaid [Penalty Time of UtoO HO Fail(s)] overflow ?

Begin

No

Yes [UL to OL HO Allowed] Yes ?

Yes

No Time of HO failure < [MaxR etry Time afte r UtoO Fail]?

No End

Yes [RX_LEV for UO HO Allowed] Yes? No [RX_QUAL for UO HO Allowed] Yes?

Yes

Yes

No [TA for UO HO Allowed] Yes?

Yes

End Rx_Dl_Level >= No [RX_LEV [RX_LEVThreshold] Hysteresis]+ Yes Rx_Dl_Qual<= No [RX_QUAL Treshold]? Yes Current TA<=[TA Threshold]-No [TA Hysteresis]?

No No

P/N rule? Yes

Trigger UL to OL


Page129

Criterion for TCH HO from underlaid to overlaid: 

TA value <= TA Threshold－ TA Hysteresis



AND RX_LEV >= RX_LEV Threshold + RX_LEV Hysteresis



AND Qua. <= RX_QUAL Threshold



Satisfying P/N rule



N-130


Data Configuration of Normal Concentric Cell HO


Page130

[UL to OL HO Allowed]

•Value Range: Yes, No Default Value: Yes •Description: This parameter indicates whether an underlay (UL) to overlay (OL) handover is allowed. [OL to UL HO Allowed]

•Value Range: Yes, No Default Value: Yes •Description: This parameter indicates whether an OL to UL handover is allowed. [RX_LEV for UO HO Allowed]

•Value Range: Yes, No Default Value: Yes •Description: This parameter indicates whether the downlink receive level is used to determine a Concentric Cell handover. [RX_QUAL for UO HO Allowed]

•Value Range: Yes, No Default Value: Thedefault value isgenerally set to Yes. When the cell is a dual-timeslot cell, the default value is set to No.

•Description: This parameter indicates whether the downlink receive quality is used to determine a Concentric Cell handover. [TA for UO HO Allowed] •Value Range: Yes, No Default Value: Yes

•Description: This parameter indicates whether the TA is used to determine a Concentric Cell handover.



N-131




Page131

[UO Signal Intensity Difference]

•Value Range: 0~63 •Default Value: 0 •Description: This parameter indicates the signal intensity compensation between the overlaid and underlaid subcells. It equals the sum of power difference between overlaid and underlaid power amplifiers, insertion loss difference between combiners, path loss difference caused by antennas, and path loss difference caused by frequencies.The parameter is invalid when Enhanced Concentric Cell is allowed. [RX_LEV Threshold]

•Value Range: 0~63 (-110 d Bm to -47 dBm) •Default Value: 35: This parameter is greater than the sum of fringe handover threshold and UO signal intensity difference. 0: The cell is a dual-timeslot extended cell. 40: The cell is a mixed cell. Description: This is one of the parameters that determine the regions of overlaid and underlaid subcells. It is invalid when Enhanced Concentric Cell is allowed.When Enhanced Concentric Cell is not allowed, the regions are co-determined by RX_LEV Threshold, RX_LEV Hysteresis, RX_QUAL Threshold, TA Threshold, and TA Hysteresis. [RX_LEV Hysteresis]

•Value Range: 0~63 (-110 d Bm to -47 dBm) •Default Value: 5 When the cell is a dual-timeslot cell, the default value is set to 0.DescriptionThis is one of the parameters that determine the regions of overlaid and underlaid subcells. It is invalid when Enhanced Concentric Cell is allowed.When Enhanced Concentric Cell is not allowed, the regions are co-determined by RX_LEV Threshold, RX_LEV Hysteresis, RX_QUAL Threshold, TA Threshold, and TA Hysteresis. [RX_QUAL Threshold]

•Value Range: 0~70 (RQ (0-7) 10) •Default Value: The default value is 60, but it is 70 when the cell is a dual-timeslot extended cell. •Description: This is one of the parameters that determine the regions of overlaid and underlaid subcells. When Enhanced Concentric Cell is not allowed, the regions are co-determined by RX_LEV Threshold, RX_LEV Hysteresis, RX_QUAL Threshold, TA Threshold, and TA Hysteresis. When Enhanced Concentric Cell is allowed, the regions are co-dete rmined by RX_QUAL Threshold, UtoO HO Receive Level Thresho ld, OtoU HO Receive Level Threshold, TA Threshold, and TA Hysteresis.



N-132




Page132

[TA Threshold]

•Value Range: 0~255 •Unit: Bit period (a bit period denotes 0.55 km) •Default Value: 63 Note: TA threshold is not used to distinguish the boundary between overlaid and underlaid subcells.

•Description: This is one of the parameters that determine the regions of overlaid and underlaid subcells. When Enhanced Concentric Cell is not allowed, the regions are codetermined by RX_LEV Threshold, RX_LEV Hysteresis, RX_QUAL Threshold, TA Threshold, and TA Hysteresis.When Enhanced Concentric Cell is allowed, the regions are co-determined by RX_QUAL Threshold, UtoO HO Receive Level Threshold, OtoU HO Receive Level Threshold, TA Threshold, and TA Hysteresis.

•Remarks: This parameter must be less than the TA threshold of an emergency handover. When set to 63, this parameter can be used to distinguishthe boundary of Underlaid subcell and OverLaid subcell of a dual-slot concentric cell instead of the boundary of a normal concentric cell. [TA Hysteresis]

•Value Range: 0~255 •Unit: Bit period (a bit period corresponds to 0.55 km) •Default Value: The default value is generally set to 0. When the cell is a dual-timeslot cell, the default value is set to 3.




N-133

•Description: This is one of the parameters that determine the regions of overlaid and underlaid subcells. When Concentric Circles HO Allowed is set to No, the regions are co-determined by RX_LEV Threshold, RX_LEV Hysteresis, RX_QUAL Threshold, TA Threshold, and TA Hysteresis. When Concentric Circles HO Allowed is set to Yes, the regions are co-determined by RX_QUAL Threshold, UtoO HO Receive Level Threshold, OtoU HO Receive Level Threshold, TA Threshold, and TA Hysteresis. [UO HO Watch Time]

•Value Range: 0~16 •Unit: Seconds •Default Value: 5 •Description: This parameter indicates the duration during which the BSC counts the duration when the conditions for an concentric cell handover are met to decide whether to trigger a concentric cell handover. [UO HO Valid Time]

•Value Range: 0~16 •Unit: Seconds •Default Value: 4 •Description: This parameter indicates the duration when the conditions for a concentric cell handover are met within UO HO Watch Time.



N-134


Enhance Concentric Cell HO 

Division of underlaid and overlaid is decided by MS downlink receive level, quality, TA value and cell load of underlaid.

underlaid U to O HO Receiving Level Threshold O to U HO Receiving Level Hysteresis Receiving Qaulityl Threshold

overlaid

TA Threshold TA Hysteresis


Page134



N-135


Enhance Concentric Cell HO 

Classification of TCH HO in enhance concentric cell HO

U to O for high load in U

O to U for moving


O to U for low load in U

Page135



N-136


Enhance Concentric Cell HO(UO ) 

Flow for TCH HO from underlaid to overlaid for high load in UL [Penalty Time of UtoO HO Fail(s)] overflow ?

Begin

No

Yes [UL to OL HO Allowed] Yes ?

Yes

No End

No Time of HO failure < [MaxR etry Time afte r UtoO Fail]?

End

Yes [RX_LEV for UO HO Allowed] Yes?

Yes

Rx_Dl_Level>[UtoO HO No Received Level Threshold] Yes

No [ATCBHoSwitch] Open?

Yes

A

No

Yes

No [RX_QUAL for UO HO Allowed] Yes? [TA for UO HO Allowed] Yes?

Rx_Dl_Qual< No [RX_QUAL Treshold]?

Yes

No Yes

Yes Current TA<[TA Threshold]- No [TA Hysteresis]?

No P/N rule?

Yes

Yes Go to the user selection flow in the next slide

A: RX_LEV_UL – RX_LEV (n) >[Distance Between Boundaries of UL and OL Subcells(dB)] RX_LEV (n): RX_LEV of the strongest neighboring cell w hich has the same frequency band and l ayer with underlaid subcell, but locates in a different BTS. If there is no such a cell, this value is -110dBm


Page136

Criterion for TCH HO from underlaid to overlaid 

RX_LEV > UtoO HO Received Level Threshold



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



And RX_QUAL < RX_QUAL Threshold



And TA < TA Threshold – TA Hysteresis



Satisfying P/N rule



N-137


Enhance Concentric Cell HO(UO ) 

User selection flow from UL to OL for high load in UL Begin

[UtoO Traffice HO Allowed] Yes ?

End

Yes Refresh cell load per second Y es No

Cell load of UL>=[En Iuo Out Cell General OverLoad Thred]?

Cell load of UL>=[En Iuo Out Cell Serious OverLoad Thred]?

B

(B-1)/second

Yes

B=[Underlay HO Step Period(s)] HO step: [Underlay HO Step Level] HO period: B-1or B HO zone: begin from -47dBm


No

Adjust HO zonebasing on HO stepand HO period

Any MS in HO zone?

No

Yes Trigger UL to OL

Page137



N-138


Enhance Concentric Cell HO(OU ) 

Flow for TCH HO from overlaid to underlaid for low load in underlaid Begin

[UtoO Traffice HO Allowed] Yes ?

Yes

No

End

[OL to UL HO Allowed] Yes ?

Yes Refresh cell load per second

No

AdjustHO zonebasing on HO stepand HO period

Cell load of UL<[En Iuo Out Cell Low Load Thred]?

Any MS in HO zone?

No

Yes Yes

Trigger UL to OL

HO period:[En Iuo Cell Load Classification HO Period] HO step: [En Iuo Cell Load Classification HO Step] HO zone: begin from[OtoU HO Received Level Threshold] to -47dBm


Page138

Criterion for TCH HO from overlaid to underlaid for underlaid low load 

Cell load of underlaid < En Iuo Out Cell Low Load Threshold



HO Zone is from OtoU HO Received Level Threshold~-47dBm


The object cell must be the underlaid subcell



N-139


Enhance Concentric Cell HO(OU ) 

Flow for TCH HO from overlaid to underlaid for moving No [OL to UL HO Allowed] Yes ?

Begin

Yes

[Penalty Time of OtoU HO Fail(s)] overflow ?

No

End

Yes

[RX_LEV for UO HO Allowed] Yes?

No

[ATCBHoSwitch]

No No

[RX_QUAL for UO HO Allowed] Yes?

Open? No Rx_Dl_Level>[OtoU HO Received Level Threshold] Yes

Yes

Yes No

A

[TA for UO HO No Allowed] Yes?

Rx_Dl_Qual> No Current TA>[TA Threshold]+ [RX_QUAL Treshold]? [TA Hysteresis]?

Yes

Yes P/N rule?

No

Yes

End

Yes Select the underlaid subcell or the neighbour cell with the highst priority in 16 bits list

Trigger OL to UL

A: RX_LEV_UL – RX_LEV (n) < [Distance Between Boundaries of UL and OL Subcells(dB)] － [Distance Hysteresis Between Boundaries of UL and OL Subcells(dB)] Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved.

Page139

Criterion for TCH HO from overlaid to underlaid for moving 

RX_LEV < OtoU HO Received Level Threshold



OR RX_QUAL > RX_QUAL Threshold



OR TA > TA Threshold + TA Hysteresis



OR RX_LEV_UL – RX_LEV (n) < Distance Between Boundaries of UL and OL Subcells(dB) – Distance Hysteresis Between Boundaries of UL and OL Subcells(dB)



Satisfying P/N rule


The cell with highest priority. It could be underlaid subcell or normal neighboring cell



N-140


Data Configuration of Enhance Concentric Cell HO


Page140

[ATCBHoSwitch]

•Value Range: Closed Open Unit: None Default Value: Open •Description: The switch of the ATCB handover algorithm. [UL to OL HO Allowed]

•Value Range: Yes, No Default Value: Yes •Description: This parameter indicates whether an U to O handover is allowed. [OL to UL HO Allowed]

•Value Range: Yes, No Default Value: Yes •DescriptionThis parameter indicates whether an OL to UL handover is allowed. [RX_LEV for UO HO Allowed]

•Value Range: Yes, No •Default Value: Yes •Description: This parameter indicates whether the downlink receive level is used to determine a Concentric Cell handover. [RX_QUAL for UO HO Allowed]

•Value Range: Yes, No •Default Value: The default value is generally set to Yes. When the cell is a dual-timeslot cell, the default value is set to No.

•Description: This parameter indicates whether the downlink receive quality is used to determine a Concentric Cell handover. [TA for UO HO Allowed]

•Value Range: Yes, No Default Value: Yes •Description: This parameter indicates whether the TA is used to determine a Concentric Cell handover.



N-141




Page141

[RX_QUAL Threshold]

•Value Range: 0~70 (RQ (0-7) 10) •Default Value: The default value is 60, but it is 70 when the cell is a dual-timeslot extended cell. •Description: This is one of the parameters that determine the regions of overlaid and underlaid subcells. When Enhanced Concentric Cell is not allowed, the regions are co-determined by RX_LEV Threshold, RX_LEV Hysteresis, RX_QUAL Threshold, TA Threshold, and TA Hysteresis. When Enhanced Concentric Cell is allowed, the regions are co-dete rmined by RX_QUAL Threshold, UtoO HO Receive Level Thresho ld, OtoU HO Receive Level Threshold, TA Threshold, and TA Hysteresis. [TA Threshold]

•Value Range: 0~255 Unit: Bit period (a bit period denotes 0.55 km) •Default Value: 63 Note: TA threshold is not used to distinguish the boundary between overlaid and underlaid subcells.

•Description: This is one of the parameters that determine the regions of overlaid and underlaid subcells. When Enhanced Concentric Cell is not allowed, the regions are co-determined by RX_LEV Threshold, RX_LEV Hysteresis, RX_QUAL Threshold, TA Threshold, and TA Hysteresis.When Enhanced Concentric Cell is allowed, the regions are co-dete rmined by RX_QUAL Threshold, UtoO HO Receive Level Thresho ld, OtoU HO Receive Level Threshold, TA Threshold, and TA Hysteresis.

•Remarks: This parameter must be less than the TA threshold of an emergency handover. When set to 63, this parameter can be used to disting uish the boundar y of Underlaid subcell and OverLaid subcell of a dual-slot concentric cell instead of the boundary of a normal concentric cell. [TA Hysteresis]

•Value Range: 0~255 Unit: Bit period (a bit period corresponds to 0.55 km) •Default Value: The default value is generally set to 0. When the cell is a dual-timeslot cell, the default value is set to 3.

•Description: This is one of the parameters that determine the regions of overlaid and underlaid subcells. When Concentric Circles HO Allowed is set to No, the regions are co-determined by RX_LEV Threshold, RX_LEV Hysteresis, RX_QUAL Threshold, TA Threshold, and TA Hysteresis. When Concentric Circles HO Allowed is set to Yes, the regions are co-dete rmined by RX_QUAL Threshold, UtoO HO Receive Level Threshold, OtoU HO Receive Level Threshold, TA Threshold, and TA Hysteresis.



N-142




Page142

[UO HO Watch Time]

•Value Range: 0~16 •Unit: Seconds •Default Value: 5 •Description: This parameter indicates the duration during which the BSC counts the duration when the conditions for an concentric cell handover are met to decide whether to trigger a concentric cell handover. [UO HO Valid Time]

•Value Range: 0~16 •Unit: Seconds •Default Value: 4 •Description: This parameter indicates the duration when the conditions for a concentric cell handover are met within UO HO Watch Time.



N-143




Page143

[OtoU HO Received Level Threshold]

•Value Range: 0~63 (-110 dBm to -47 dBm) Default Value: 25 •Description: This is one of the parameters that determine the regions of overlaid and underlaid subcells. When Enhanced Concentric Cell is allowed, the regions are codetermined by RX_QUAL Threshold, UtoO HO Receive Level Threshold, OtoU HO Receive Level Threshold, TA Threshold, and TA Hysteresis. [UtoO HO Received Level Threshold]

•Value Range: 0~63 (-110 dBm to -47 dBm) Default Value: 35 •Description: This is one of the parameters that determine the regions of overlaid and underlaid subcells.When Enhanced Concentric Cell is allowed, the regions are co-determined by RX_QUAL Threshold, UtoO HO Receive Level Threshold, OtoU HO Receive Level Threshold, TA Threshold, and TA Hysteresis. [UtoO Traffic HO Allowed]

•Value Range: Yes, No Default Value: No:dual-timeslot cells Yes:other cells •Description: This parameter indicates whether the traffic in the underlaid subcell determines the underlaid to overlaid (UL to OL) handover.When this parameter is set to Yes, the handover is allowed only when the traffic in the underlaid cell is equal to or greater than Traffic Threshold of Underlay.When this parameter is set to No, the traffic is n ot taken into consideration.

•Remarks: This parameter is valid only when Enhanced Concentric Cell is allowed. Confidential Information ofHuawei. No Spreading Without Permission


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[Underlay HO Step Period(s)]

•Value Range: 1~255 Unit: Seconds Default Value: 5 •Description: This parameter indicates the interval between two grades of level-based handovers. When multiple UL to OL handover requests are initiated simultaneously, it is possible that calls with low level are handed over. This does not conform to the principle that the call with the best quality should be handed over firstly. Thus, level gradebased handover is used to hand over high-level calls with higher priority. •Remarks: This parameter is valid only when Enhanced Concentric Cell is allowed. [Underlay HO Step Level]

•Value Range: 1~63 (-110 dBm to -47 dBm)

Default Value: 5

•Description: This parameter indicates the length of a grade in level grade-based UL to OL handover. Thus, highlevel calls are handed over with higher priority.After a step period of UL to OL handover, the handover band is decreased by the length of a grade.This parameter and Underlay HO Step Period control the level band of the stepby-step handover from under laid subcells to overlaid subce lls together. The time for the handove r band to step down for Underlay HO Step Level is Underlay HO Step Period.

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



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[En Iuo Out Cell Low Load Thre d]

•Value Range: 0~100 Unit: % Default Value: 20 •Description: If the ratio of the underlaid subcell channel occupancy is smaller than the value of this paramete r, some calls in the ove rlaid subcel l are handed ove r to the underlaid subcell. [En Iuo Out Cell General OverLoad Thred]

•Value Range: 0-100 Unit: % Default Value: 85 •Description: If the ratio of the underlaid subcell channel occupancy is greater than the value of this paramete r, some calls in the unde rlaid subcell are handed ove r to the overlaid subce ll. [En Iuo Out Cell Serious OverLoad Thred]

•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 hierarch ical handover from underlaid subcell to overlaid subce ll is shorten. That is, the value of Out Cell Load HO Modify Step is reduced 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.

•Remarks: The value of this par ameter must be greater than that of the En Iuo Out Cell General Over Load Thred. [En Iuo In Cell Load classific ation HO Period]

•Value Range: 1~255 Unit: Seconds Default Value: 5 •Description: When the ratio of overla id 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.This parameter indicates the time duration of every hierarchical handover. [En Iuo In Cell Load classific ation HO Step]

•Value Range: 0-63 Unit: Db Default Value: 5 •Description: This paramete r indicates the level step of the hierarc hical handover from underlaid subcell to overlaid subcell.



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[Distance Between Boundaries of UL And OL Subcell(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 Out And Inn Cell boundary, the cell is in the overlaid subcell. [Distance Hysterisis Between Boundaries of UL And OL Subcell]

•Value Range: 0~63 Unit: dB Default Value: 2 •Description:To prevent ping-pong handover, the BSC determines whether the handover of the MS from overlaid subcell cell to underlaid subcell cell based on the value of this parameter. Suppose the signal strength of serving cell is SS(s), and neighboring cell SS(n). If the value of SS(s) - SS(n) is larger than the value of Distance Between Out And Inn Cell boundary - Distance Hyst Between Out And Inn Cell boundary, the MS handover from overlaid subcell cell to underlaid subcell cell is allowed. Confidential Information ofHuawei. No Spreading Without Permission


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Channel Assignment strategies of Concentric HO Channel Assignment Strategies of Concentric HO

Immediate Assignment

Assignment

Intra-BSC Inter-cell Handover


Incoming Cell Handover

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Immediate Assignment 

The preferred SDCCH channel in two layers is controlled by parameter “TA pref. Of Imme-Assign Allowed ” 

If "No", system prefers the channel in Underlaid subcell



If “Yes", system prefers the channel according to in Channel Request message TA bigger


TA smaller

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When “TA pref. Of Imme-Assign Allowed” is set as “Yes”, if the TA is larger than the “TA Threshold of Imme-Assignment Pref.”, the underlay cell is assigned first. if the TA is smaller than the threshold, the overlay cell is assigned first.



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Data Configuration of Immediate Assignment


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[TA Pref of Imme-Assign Allowed]

•Value Range: Yes, No •Default Value: No •Description: This parameter indicates whether access_delay is used in the channel request message for immediate assignment. When this parameter is set to No, a channel in the underlaid subcell is assigned. When this parameter is set to Yes, a channel in the overlaid subcell is assigned if access_delay is less than TA Threshold of Imme-Assign Pref. If not, a channel in the underlaid subcell is assigned. [TA Threshold of Imme-Assign Pref]

•Value Range: 0~255 •Unit: Bit period (a bit period corresponds to 0.55 km) •Default Value: 63: Dual-timeslot extended cells 0: Other cells •Description: This parameter indicates the threshold of overlaid cell-based immediate assignment. If TA Pref of Imme-Assign Allowed is set toYes, the system prefers the channel in overlaid subcell while ACCESS_DELAY is smaller than TA Thrsh. of Imme- Assign pref. Otherwise, the system prefers the channel in Underlaid subcell.



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Assignment 

Preferred assignment in the overlay or underlay cell



Assign the channel of overlay or underlay cell according to the Rx_level and TA in the measurement report

TA smaller and Rx--level higher Rx higher


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The channel of overlay cell is assigned first only when the Rx level on the SDCCH is equal to or larger than the“Assign-optimum-level Threshold” and the TA is smaller than the “TA Threshold of Assignment Pref.”. Otherwise, the channel of underlay cell is assigned first to ensure the successful assignment.



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Data Configuration of Assignment


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[Assign Optimum Layer]

•Value Range: System Optimization, Overlaid Subcell, Underlaid Subcell, No Preference

•Default Value: 

Underlaid Subcell: The cell system is GSM900&DCS1800 and enhanced concentric cell.



System Optimization: The cell system is not GSM900&DCS1800.

•Description: This parameter indicates the method of TCH assignment a concentric cell. 

System Optimization: The system selects the optimum serving layer according to the MR provided through the SDCCH.



Underlaid Subcell: Channel assignment in the underlaid subcell has higher priority.



Overlaid Subcell: Channel assignment in the overlaid subcell has higher priority.



No Preference: No specific instruction is given.




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[Assign-optimum-level Threshold]

•Value Range: 0~63 (-110 dBm to -47 dBm) •Default Value: When the uplink and the downlink are not balanced, the default value = receive level + balance margin for uplink and downlink When the uplink and the downlink are balanced, the default value can be set to 35, which is the same as RX_LEV Threshold. When the cell is a dual-timeslot cell, the default value is set to 0. When the cell is a hybrid cell, the default value is set to 40.

•Description: When the optimal layer is selected through system optimization, the current SDCCH level can be estimated (inserted/filtered) based on the uplink measurement result in the previous SDCCH MR. Then, overlaid and underlaid subcells are allocated by comparing this parameter with the receive level of SDCCH, and by comparing TA with the TA threshold of optimum assignment. The MS is allocated with overlaid subcell only when the receive level is greater than level threshold and TA is smaller than the TA threshold. Otherwise, the MS is allocated with the underlaid cell. [TA Threshold of Assignment Pref.]

•Value Range: 0~255 •Unit: Bit period (a bit period corresponds to 0.55 km) •Default Value:63 •Description: When the optimal layer is selected through system optimization, the current SDCCH level can be estimated (inserted/filtered) based on the uplink measurement result in the previous SDCCH MR. Then, overlaid and underlaid subcells are allocated by comparing this parameter and the receive level of SDCCH, and by comparing TA and the TA threshold of optimum assignment. The MS is allocated with overlaid subcell only when the receive level is greater than level threshold and TA is smaller than the TA threshold. Otherwise, the MS is allocated with the underlaid cell.

•Remarks: When this parameter is set to 0, the MS is allocated with the underlaid cell.



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Intra-BSC Inter-Cell Handover 

In the case of intra-BSC inter-cell handover, the MS can be handed over to the underlay or overlay cell first.



If “System Optimization” is selected, the preferred assignment is conducted according to the level value in the measurement report.

According to the Rx-level

Overlaid overlaid

Underlaid


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the Rx level is higher than the“Rx level threshold”, the MS will be handed over to the overderlay cell. Otherwise, the MS will be handed over to the underlay cell If



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Data Configuration of Intra-BSC InterCell Handover


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[Pref. Subcell in HO of Intra-BSC]

•Value Range: System Optimization, Overlaid Subcell, Underlaid Subcell, No Preference

•Default Value: The default value is System Optimization. For a dual-timeslot extended cell or a hybrid cell, the default value is Underlaid Subcell.

•Description: This parameter indicates the method of channel assignment for intraBSC handover in a concentric cell. 

System Optimization: The BCCH of the target cell is specified in the handover request. Then, the target cell compares only the receive level with RX_LEV Threshold, thus selecting the layer with higher priority.



UnderLaid Subcell: Channel assignment in the underlaid subcell has higher priority.



OverLaid Subcell: Channel assignment in the overlaid subcell has higher priority.



No Preference: Channels are assigned based on routine algorithms.



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Inter-BSC Handover 

For the inter-BSC Handover, if the target cell is concentric cell , the channel of underlay cell should be assigned first. BSC2

BSC1

Overlaid overlaid

Assign underlaid first

Underlaid


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Data Configuration of Inter-BSC InterCell Handover


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[Incoming-to-BSC HO Optimum Layer]

•Value Range: Overlaid Subcell, Underlaid Subcell, No Preference •Default Value: 

Underlaid Subcell (common networks)



Overlaid Subcell (dual-frequency networks)



Underlaid Subcell (dual-frequency networks with decreasing success rate of handover)

•Description: This parameter indicates the method of selecting an optimum layer for an incoming handover.

•Remarks: The BCCH carrier must be configured in the underlaid subcell. The SDCCH must be configured in the underlaid subcell. Concentric Cell handover is forbidden if both RX-LEVThreshold and RX-LEV Hysteresis(or both TA Threshold and TA Hysteresis) are set to 63. The data configuration for a dualtimeslot extended cell adopts Concentric Cell techniques.



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AMR Handover Flow Begin Are [Intracell HO Allowed] & [Intracell F-H HO Allowed］ Yes ?

No

Yes End

No

Is current channel TCH & v ersion3? Yes

Yes

A: Cell load> [AMR TCH/H Prior

During [Penalty Time after AMR TCHF-H HO Fail(s)]?

Cell Load Threshold]

No Yes

No

current channel is FR

RQI/2 >[F2H HO th] &A

RQI/2 <[H2F HO th]

No

End

Yes

Yes No

No

Satisfy P/N rule?


Yes Trigger internal cell AMR handover

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Data Configuration of AMR HO


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[Intracell HO Allowed]

•Value Range: Yes, No

Default Value: No

•Description: This parameter indicates whether an intra-cell handover is allowed. After an intra-cell handover, the timeslot and TRX that the MS occupies change.

•Remarks: This parameter does not affect concentric cell handovers and forced handovers. During an AMR handover, an interference handover, and a bad quality handover, an intra-cell handover is unavailable if this parameter is set to No. [Intracell F-H HO Allowed ]

•Value Range: Yes, No

Default Value: Yes

•Description: This parameter indicates whether the handover between full-rate channels and half-rate channels in the cell is allowed. Only the value of the Intracell HO Allowed is set Yes, this parameter is valid. Only when this parameter is set to Yes, the BSC makes an AMR handover decision. Otherwise, the BSC makes no decision. [Intracell F-H HO State Time(s)]

•Value Range: 1~16

Unit: Seconds

Default Value:

5

•Description: This parameter indicates the time threshold that satisfies full rate to half rate handover. [Intracell F-H HO Last Time]


Unit:

Seconds

Default Value: 4

•Description: This parameter indicates the period that satisfies full rate to half rate handover. [F2H HO th]


Unit: dBm

Default Value: 25

•Description: This parameter indicates the threshold of a handover from full rate data TCH (TCHF) to half rate data TCH (TCHH). For AMR calls, intra-cell TCHF to TCHH handover is triggered when TCHF is in use and Radio Quality Indication (RQI) is constantly higher than this threshold. [H2F HO th]


Unit: dBm

Default Value: 10

•Description: This parameter indicates the threshold of TCHH to TCHF handover. For an AMR call, if the current channel is a HR channel and the RQI is constantly lower than H2F HO th within a period, a TCHH to TCHF handover is triggered.



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Data Configuration of AMR HO


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[AMR TCH/H Prior Allowed]

•Value Range: Yes, No •Default Value: Yes •Description: This parameter indicates whether the TCH/H prior function is allowed during the channel assignment. Yes—allowed; No—prohibited. 

The channel type to be assigned is decided according to the channel types that are allowed by the MSC and the percentage of seized TCHs in the cell.



During the channel assignment, the TCHF or TCCH, TCHH Prior channels are required when:





Half rate and full rate channels are allowed to be assigned by the MSC.



The AMR TCH/H Prior Allowed is set to Yes.



The percentage of seized TCHs in the cell is greater than the value of AMR TCH/H Prior Cell Load Threshold.

In other cases, the TCHF or TCCH, TCHF Prior channels are required.

[AMR TCH/H Prior Cell Load Threshold]

•Value Range: 0~99 •Default Value: 40 •Description: The channel type to be assigned is decided according to the channel types that are allowed by the MSC and the percentage of seized TCHs in the cell. 



During the channel assignment, the TCHF or TCCH, TCHH Prior channels are required when: 

Half rate and full rate channels are allowed to be assigned by the MSC.



The AMR TCH/H Prior Allowed is set to Yes.



The percentage of seized TCHs in the cell is greater than the value of AMR TCH/H Prior Cell Load Threshold.

In other cases, the TCHF or TCCH, TCHF Prior channels are required.



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1

2



3

Handover Judgment

4




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Handover Implementation Begin

No

BTS(s) keeps current power output

Is [Power boost befor HO enabled or not ］ Yes ?

For BTS

Yes

BTS(s) uses the max. power output

BSC send “HO Command” to MS

No power control during handover in order to make sure the handover i s successful

HO execute


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[Power boost befor HO enabled o r not］

•Value Range: StartUp,not StartUp,None •Default Value: not StartUp •Description: When the MS is in a corner, the receive level may decrease swiftly. Handover may be triggered. At this time, the BSC cannot adjust the power of the MS and BTS in time. The MS cannot receive the handover command. Thus call drop occurs.



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Data Configuration of Handover Implementation(BTS)


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N-163


Handover Implementation Begin

No

MS uses the highest power to access

Is [MS Power Prediction after HO］ Yes ?

For MS

Yes

BSC predict power

BSC send “HO Command” to MS

No power control during handover in order to m ake sure the handover i s successful

MS will use this predict power in new cell after finishing this handover

HO execute


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Data Configuration of Handover Implementation(MS)


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[MS Power Prediction after HO]

•Value Range: Yes, No •Default Value: No •Description: This parameter indicates whether the MS uses the optimum transmit power to access a new channel after the handover. Using the optimum transmit power helps to reduce interference and improve the service performance.



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Data Configuration of Handover Implementation(MS)


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UL Expected Level at HO Access

•Value Range: 0~63(-110 dBm ~ -47 dBm) •Unit: dB •Default Value: 30 •Description: This parameter indicates the expected uplink receive level on a new channel after an MS is handed over to a new cell.This parameter is consistent with UL RX_LEV Upper Threshold in G-II power control.



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Summary 

In this course, we have learned: 

Classification of HO



HO general procedure



HO judgment algorithm



HO implementation process



HO data configuration


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Thank you www.huawei.com



Huawei GSM Handover Algorithm

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