Post on 08-Aug-2015
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Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved.
GSM Handover Algorithm
Page2Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved.
Foreword
Handover is a key technology of mobile communication system and make continued conversation possible.
Handover algorithm in Huawei product is flexible and powerful.
Page3Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved.
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 Handover
2. HO Algorithm Process
Page5Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved.
Contents
1. Introduction of Handover
2. HO Algorithm Process
Page6Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved.
Purposes of HO
To keep a continuous communication with a moving MS
To improve network service performance
To reduce the call drop rate
To reduce the congestion rate
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Classification by Reason
No DL MR Emergency HOTiming Advance (TA) HOInterference HORx_Level_Drop HOBad Quality (BQ) HO
Emergency HO
Enhanced Dual Band HO
Load HO
Normal HO
1
2
3
4
Classification by
ReasonEDGE HO PBGT HOLayer HO MS Fast Moving HOConcentric Cell HOAMR HO
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Classification by Synchronization
CELL
Case 1
Synchronous Handover: the target BTS shall not send PHY INFO message
Case 2
Asynchronous Handover: the target BTS shall send PHY INFO message
Case 3 Case 4Case 5
MSC
BSC
BTS
BSC BSC
MSC
BTS BTSBTS
BTS
NSS Network
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Classification by Equipment and Channel
SDCCH → TCHSDCCH → TCH(Direct Retry)(Direct Retry)
SDCCH → SDCCHSDCCH → SDCCH
Intra – Cell HOIntra – Cell HO (( HRHR↔FR↔FR……))
Inter – Cell HOInter – Cell HO
Intra – BSC HOIntra – BSC HO
Intra – MSC HOIntra – MSC HO
Inter – MSC HOInter – MSC HO
TCH TCH → TCH→ TCH
Page10Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved.
Contents
1. Introduction of Handover
2. HO Algorithm Process
Page11Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved.
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
Page12Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved.
General HO Process
MS Goes into New Dedicated
Mode
MS Goes into Dedicated
Mode
Measure and Measurement Result Report1
Measurement Report Preprocessing2
Handover Judgment3
Handover
Implementation4
Page13Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved.
General HO Process
MS Goes into New Dedicated
Mode
MS Goes into Dedicated
Mode
Measure and Measurement Result Report1
Measurement Report Preprocessing2
Handover Judgment3
Handover
Implementation4
Page14Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved.
The downlink measurement reportof the neighbor cell (BCCH)
Measurement Report
Uplink MR includes uplink receiving level and quality.
Downlink MR includes downlink receiving level, downlink
receiving quality of the serving cell and other downlink
receiving levels from the neighbor cells.
Serving cell
Neighbor cell
The uplink MR
The downlink MR
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Measurement Report
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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
12TCH 12TCH1SACCH 1 Idle
480ms 4 TCH Multi-frames
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General HO Process
MS Goes into New Dedicated
Mode
MS Goes into Dedicated
Mode
Measurement Report Preprocessing
Handover Judgment3
Handover
Implementation4
Measure and Measurement Result Report1
2
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MR Preprocessing
MR Preprocessing
Interpolation Recover the lost measur
ement report
Filtering Smooth the instantaneo
us fading point
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MR Interpolation
MR
MR
No. n
No. n+4
Continuous MR Flow
MRMR
MR
Missing by some reasons
…
…
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MR Filtering
MR
MRContinuous MR Flow
MRMR
MR
…
…Filter----Average several consecutive MRs
MR
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Data Configuration of MR Preprocessing
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Data Configuration of MR Preprocessing
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Data Configuration of MR Preprocessing
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Data Configuration of MR Preprocessing
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General HO Process
MS Goes into New Dedicated Mode
MS Goes intoDedicated Mode
Measure and Measurement Result Report1
MR. Preprocessing2
Handover Judgment3
Handover Implementation4
TA HO
Interference HO
Rx_Level_Drop HO
Bad Quality HO
Load HO
Edge HO
Layer HO
PBGT HO
AMR HO
No DL MR HO
Concentric Cell HO
MS Fast Moving HO
Enhanced Dual Band HO
Penalty Processing
Ranking Processing
OM Forced HO
Direct Retry
Emergency HO
Normal HO
Page26Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved.
Penalty Processing
Intra-cell HO
HO FailsEmergency (TA&BQ)HO
MS Fast Moving
HO
Concentric Cell HO
Penalty
Punish on the target
cell
Punish on the original cell
Punish on other high priority layer
cells
AMR HOFails
Page27Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved.
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
BSC
Cell B
BTS
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Data Configuration of Penalty for Handover Failure
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Data Configuration of Penalty for Handover Failure
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Cell A
Cell B
BTSBQ&TA HO
BSC
Penalty for Emergency Handover Punish the original cell when an emergency HO ( due to
BQ and TA) occurs.
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Data Configuration of Penalty for Emergency Handover
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Data Configuration of Penalty for Emergency Handover
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Back? No way!Back? No way!
Umbrella
Micro cell
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 H
O.
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Data Configuration of Penalty for MS Fast-moving Handover
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Underlaid
Overlaid Do not attempt again during penalty time
after one failed HO(O->U)!
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)!
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Data Configuration of Penalty for Concentric Cell
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Underlaid
OverlaidDo not
attempt back too fast!
Penalty for Enhanced Concentric Cell A new UO HO is prohibited within a penalty time
after a OU HO is performed successfully.
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Data Configuration of Penalty for Enhanced Concentric Cell
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Penalty for Intra-cell HO A new intra-cell HO is prohibited if it occurs too frequently.
3 7 12 32 T (s)0
Penalty time
Intra-cell HO Time
2nd.3rd.
4th.
Max. consecutive HO times: 3
Forbidden time after Max. times: 20s
Interval for consecutive HO Jud: 6s
1st.
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Data Configuration of Penalty for Intra-cell HO
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Data Configuration of Penalty for AMR FRHR Handover Failure
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General HO Process
MS Goes into New Dedicated Mode
MS Goes intoDedicated Mode
Measure and Measurement Result Report1
MR. Preprocessing2
Handover Judgment3
Handover Implementation4
TA HO
Interference HO
Rx_Level_Drop HO
Bad Quality HO
Load HO
Edge HO
Layer HO
PBGT HO
AMR HO
No DL MR HO
Concentric Cell HO
MS Fast Moving HO
Enhanced Dual Band HO
Penalty Processing
Ranking Processing
OM Forced HO
Direct Retry
Emergency HO
Normal HO
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Ranking Processing
M ruleK rule
Basic ranking
16 bits ranking
Network feature adjustment
The ranking result: target cell selection of handover
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M Rule Begin
Finish to all neighbor cells?
An BSC external neighboring cell& the current channel is
SDCCH ?
No
Yes
Direct retry? [Inter-BSC SDCCH HO Allowed] is Yes?
Delete the cell from the cell list?
If the cell flow is overload ?
Yes No
Yes
No
RX_LEV_DL(n) < [Min DL Power on HO Candidate Cell](n)+
[Min Access Level Offset](s)?
RX_LEV_UL(n) < [Min UP Power on HO Candidate Cell](s)+
[Min Access Level Offset](s)?
Delete this cell from the cell list
Yes
No
No
No
No
Yes
End
For service cell: Min Access Level Offset=0 M rule will remove the
neighbor cells from the candidate
cell listaccording to the flow.
Yes
Yes
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Data Configuration of M Rule
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Data Configuration of M Rule
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K Rule Flow of calculating K value.
Begin
Finish to calculate value K to all cells?
Serving cell?
K=0
No
K = RX_LEV (n) – RX_LEV (s)
Yes
End
No
Yes
All the candidate cells are ranked in descending order according to the K value
A
F
E
D BC
Serving Cell
Receiving Level
Cell
Serving Cell
Cell ACell B
Cell C
Cell D
Cell E
Cell F
Page48Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved.
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.
The Lowest
Weight
The Highest
Weight16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1
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Network Feature Adjustment 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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Network Feature Adjustment The 4th bit: Inter-cell HO hysteresis bit.
Note: In PBGT HO, whichever the greater of the inter-cell ( of the same layer ) hysteresis and PBGT threshold, that value will be used in the PBGT HO.
16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1
Is serving cell?
Always set to 0
No
RX_LEV_DL (n) >= RX_LEV_DL (s) +
[Inter-cell HO hysteresis]
Yes
Set to 0Yes
Set to1
No
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Data Configuration of Inter-cell HO Hysteresis
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Network Feature Adjustment
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
Page53Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved.
Hierarchical Cell Structure
GSM900 Cell
Micro Cell
Umbrella Cell GSM 900
GSM1800 GSM1800GSM1800
GSM 900
GSM900GSM900
GSM1800GSM1800
GSM1800 Cell
GSM 900
GSM900GSM900
GSM1800GSM1800
Layer 4( low )
Layer 3
Layer 2
Layer 1( high )
Page54Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved.
Data Configuration of Cell Hierarchical Network Structure
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Network Feature Adjustment The 11th bit: The bit value is decided by cell-load-sharing
criterion.
This bit is affected by 14th bit.
16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1
System load>=[System Flux Threshold for Load HO] or [Load HO Allowed ] =No ?
Yes 11th bit is turned off
Is serving cell?
set to 0
NoYes
Cell load >= [Load HO Threshold](s)?
set to 1 set to 1
cell load >=[ Load Rep. on Candidate Cell](n)?
set to 0
Yes
No
Yes
No
No
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Data Configuration of Cell-load-sharing
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Data Configuration of Cell-load-sharing
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Network Feature Adjustment 12th bit and 13th bit: Whether share the same BSC or MSC.
16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1
Is serving cell? NoYes
Both 12th and 13th set to 0
Different BSC: 12th set to 113th set to 0
Is [Co-BSC/MSC Adj] yes?
See 14th bit
Yes
No
Co-BSC?
Co-MSC?
No
Yes
Different MSC: 12th set to 013th set to 1
No
Yes
Turn off 12th &13th bit
The same BSC: 12th set to 013th set to 0
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Data Configuration of Co-BSC&MSC
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The 14th bit: Layer HO threshold adjustment bit.
Network Feature Adjustment
16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1
The 15th/16th bits are reserved
Is serving cell?
set to 0
NoYes
Bit 14th set to 1, and bit 5th ~13th are turned off set to 0
Yes Yes RX_LEV_DL >= [Inter-layer HO Threshold] – [Inter-layer HO Hysteresis]?
RX_LEV_DL >= [Inter-layer HO Threshold] + [Inter-layer HO Hysteresis]?
No No
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Data Configuration of Layer HO Threshold Adjustment
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General HO Process
MS Goes into New Dedicated Mode
MS Goes intoDedicated Mode
Measure and Measurement Result Report1
MR. Preprocessing2
Handover Judgment3
Handover Implementation4
TA HO
Interference HO
Rx_Level_Drop HO
Bad Quality HO
Load HO
Edge HO
Layer HO
PBGT HO
AMR HO
No DL MR HO
Concentric Cell HO
MS Fast Moving HO
Enhanced Dual Band HO
Penalty Processing
Ranking Processing
OM Forced HO
Direct Retry
Emergency HO
Normal HO
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No DL MR HO
Serving Cell Neighboring Cell
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
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Position of No DL MR HO
MS Goes into New Dedicated Mode
MS Goes intoDedicated Mode
Measure and Measurement Result Report1
MR. Preprocessing2
Handover Judgment3
Handover Implementation4
TA HO
Interference HO
Rx_Level_Drop HO
Bad Quality HO
Load HO
Edge HO
Layer HO
PBGT HO
AMR HO
Concentric Cell HO
MS Fast Moving HO
Enhanced Dual Band HO
Penalty Processing
Ranking Processing
OM Forced HO
Direct Retry
Emergency HO
Normal HO
No DL MR HO
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No DL MR HO Begin
Report 1 DL MR at lease?
Is [No Dl Mr. HO Allowed] Yes ?
<=[Cons.No Dl Mr.
Ho Allowed Limit]?
Is serving cell? Select the candidate cell
with the highest priority,
exluding serving cell
Trigger No DL Mr. HO
Yes
No
End
No
No
Yes
Yes
>= signal quality filter length?
Yes
signal quality filter length:For TCH:[Filter Length for TCH
Qual]For SDCCH:[Filter Length for
SDCCH Qual]
No Dl Mr. in current Mr.?
Yes
UL_Qua. (after filering)
>=[No Dl Mr.Ul Qual
HO Limit]?Yes
Only one cadidate cell?
>=[Forbidden time
after MAX Times]?
Yes
No
No
No
Yes
Yes
No
No
[Intrecell HOAllowed]?
Yes
No
Page66Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved.
Data Configuration of No DL MR HO
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TA(Time Advance) HO
Serving Cell Neighboring Cell
TA Threshold(s)
Time
TA(s)
HandoverTriggering
TA Threshold(n)
or
Handover Triggering ZoneTA(n)
Page68Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved.
TA(Time Advance) HO
Trigger TA handover
Begin
The actual TA >= [TA Threshold]?
Is [TA HO Allowed] Yes ?
Any neighbour cell
exist?
Is serving cell?
Select the cell with the highest priority in the
cadidate cell list
TA(n is in the same BTS)<=[TA Threshold](s)?
Suitable cell exist?
Yes
No
End
No
No
YesYes
No
No
Yes
Yes
Yes
No
Page69Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved.
Data Configuration of TA HO
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Interference Handover
Lev_Thr
Rx_Qual
RX_Lev
Qual_Thr
InterferenceOrigin
Serving Cell Neighboring Cell
Handover Triggering Zone
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Interference HOBegin
UL or DL receiving Quality(s)>=A?
Is [Interference HO
Allowed] Yes ?
Any neighbour cell
exist?
Is serving cell?
Select the cell with the
highest priority in the cadidate cell list
Rx_Level(n)>= [Inter-layer HO Threshold](n) +[Inter-layer HO Hysteresis](n)?
Yes
No
End
No
No
Yes No
NoYes
None AMR FR: A = RXQUALn, 1<=n<=12 AMR FR:A = RXQUAL1, n=1; A = RXQUALn + RXLEVoff, 2<=n<=12
[Intracell HO Allowed] yes & cell not punished?
Any suitable cell exist?
Trigger interference handover
No
Yes
Yes
Yes
Yes
No
Page72Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved.
Data Configuration of Interference HO
Parameter Receiving Level(-110dBm) Receiving Quality
RXQUAL1 <=30 70
RXQUAL2 =31 60
RXQUAL3 32~35 59
RXQUAL4 36~38 58
RXQUAL5 39~41 57
RXQUAL6 42~45 56
RXQUAL7 46~48 55
RXQUAL8 49~52 54
RXQUAL9 53~55 53
RXQUAL10 56~58 52
RXQUAL11 59~62 51
RXQUAL12 >=63 50
Default Value
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Data Configuration of Interference HO
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Rx_Level_Drop HO
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Rx_Level_Drop HOBegin
Satisfy the Formula& The lastest RX_LEV_UL(s) <
[Edge HO UL RX_LEV Threshold]?
[Rx_Level_Drop HO
Allowed] Yes ?
Any neighbour cell
exist?
Is serving cell?
Select the cell with the
highest priority in the cadidate cell list
Yes
No
End
No
No
Yes
NoYes
Formula:
Priority is higher than
serving cell?
Trigger Rx_Level_Drop handover
Yes
Yes
BXAXAXAXA
XAXAXAXA
88776655
44332211
10101010
10101010
End No
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Data Configuration of Rx_Level_Drop HO
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BQ(Bad Quality) HO Begin
Is [BQ HO Allowed] Yes ?
Any neighbour cell
exist?
Is serving cell?
Select the cell with the
highest priority in the
cadidate cell list
Yes
No
End
No
No
Yes
NoYes
Yes
UL_Rx_Q(s)>=[UL Qual. Threshold] or DL_Rx_Q(s) >=[DL Qual. Threshold]?
RX_LEV_DL (n) > RX_LEV_DL (s)
+ Inter-cell HO hysteresis(s)
-BQ HO Margin(s) ?
[Intracell HO Allowed] yes & cell not punished?
Suitable cell exist?
Trigger BQ
handover
Yes
Yes
Yes
No
No No
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Data Configuration of BQ HO
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Data Configuration of BQ HO
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Data Configuration of BQ HO
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General HO Process
MS Goes into New Dedicated Mode
MS Goes intoDedicated Mode
Measure and Measurement Result Report1
MR. Preprocessing2
Handover Judgment3
Handover Implementation4
TA HO
Interference HO
Rx_Level_Drop HO
Bad Quality HO
Load HO
Edge HO
Layer HO
PBGT HO
AMR HO
No DL MR HO
Concentric Cell HO
MS Fast Moving HO
Enhanced Dual Band HO
Penalty Processing
Ranking Processing
OM Forced HO
Direct Retry
Emergency HO
Normal HO
Page82Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved.
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.
Page83Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved.
Channel Assignment of Enhanced Dual Band HO
RX_LEV_OL>= [Incoming OL Subcell HO level Threshold(dB)] andRX_LEV_UL – RX_LEV (n) >[Distance Between Boundaries of UL and OL Subcells(dB)] Attention:RX_LEV (n): RX_LEV of the strongest neighboring cell which has the same frequency band and layer with underlaid subcell, but locates in a different BTS. If there is no such a cell, this value is -110dB
mIf [ATCBHoSwitch] is [Close], the second condition is turn off.
A:
Begin from UL
[Assignment Optimization of UL Subcell Allowed
or not] ? Cell load of UL >
[UL Subcell General Overload Threshold(%)]?
Yes
A
Yes
No
Any idle TCH Available in OL?
Assign TCH in OL
YesNo
Yes
Assign TCH in ULor direct retry
identificationor queuing
No
No
TCH assignment (SDCCH channel in UL)
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Data Configuration of Channel Assignment
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Data Configuration of Channel Assignment
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Begin from OL
[Assignment Optimization of OL Subcell Allowed or
not ] No ? Cell load of UL<
[UL Subcell Lower Load Threshold]?
Yes
Yes
No
Assign TCH in UL
Any idle TCH Available in UL?
Assign TCH in UL
Any idle TCH Available in OL?
Assign TCH in OL
Yes No
YesAssign TCH in OLor direct retry
identificationor queuing
No
No
TCH assignment (SDCCH channel in OL)
Channel Assignment of Enhanced Dual Band HO
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Data Configuration of Channel Assignment
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Enhanced Dual Band HO
Classification of TCH HO in enhanced dual band HO
OL to UL for low load in UL
UL to OL for high load in
UL
OL to UL for moving
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Enhanced Dual Band HO(UO ) Triggering condition for TCH Load HO from UL to OL for high load in UL
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Enhanced Dual Band HO(UO ) Triggering condition for TCH Load HO from UL to OL for high load in UL
Cell load of UL>=[UL Subcell Serious Overload Threshold(%)]?
Begin [Load HO From UL Subcell to OL Subcell Allowed] Yes ?
Cell load of UL>=[UL Subcell General Overload Threshold(%)]?
No
A & Satisfy P/N ¬ within penalty
time?
Trigger UL to OL
Yes No
Adjust HO zone basing on HO step and HO perio
d
Refresh cell load
per secondBB-C
YesB=[UL Subcell Load Hierarchical HO Period(s)]C=[Modified Step Length of UL Load HO
Period(s)]
Any MS in HO zone?
Yes
No
No
Yes
Yes
HO step: [Step Length of UL Subcell Load HO(dB)]HO zone: [Incoming OL Subcell HO level Threshold(dB)]~-47dBmHO Period: [UL Subcell Load Hierarchical HO Period(s)]RX_LEV_OL >= [Incoming OL Subcell HO level Threshold(dB)] andRX_LEV_UL – RX_LEV (n) > [Distance Between Boundaries of UL and OL Subcells(dB)]A:
No
End
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Data Configuration of Enhanced Dual Band HO(UO )
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Data Configuration of Enhanced Dual Band HO(UO )
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Enhanced Dual Band HO(OU ) Triggering condition for TCH HO from OL to UL for moving
RX_LEV_OL <[Outgoing OL Subcell HO level Threshold(dB)] orRX_LEV_UL – RX_LEV (n) < [Distance Between Boundaries of UL and OL Subcells(dB)] – [Distance Hysteresis Between Boundaries of UL and OL Subcells(dB)]
A:
Satisfy P/N?
Begin
A
Yes
End
Trigger OL to UL
Yes
Select Neighbor cellwith the highest priority
No
Ye
s
Generally, Object cell maybe UL or other neighbor
cell is
No
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Data Configuration of Enhanced Dual Band HO(OU )
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Enhanced Dual Band HO(OU ) Triggering condition for TCH Load HO from OL to UL for low load in UL
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Enhanced Dual Band HO(OU ) Triggering condition for TCH Load HO from OL to UL for low load
in UL Begin
[Load HO of OL Subcell to UL Subcell Enable] Yes ?
Cell load of UL <[UL Subcell Lower Load Threshold(%)]?
Yes
No
End
Satisfy P/N?
HO zone: [Outgoing OL Subcell HO Level Threshold(dB)] ~ -47dBmHO step: [Step Length of OL Subcell Load HO(dB)]A: RX_LEV_UL >= Inter-layer HO Threshold + Inter-layer HO Hysteresis
Yes
No
Confirm:HO zone and HO step
Refresh cell load
per second
The object cell must be the underlaid subcell
and satisfy condition A
Any MS in HO zone?
Yes
Trigger OL to ULNo
Yes
No
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Data Configuration of Enhanced Dual Band HO(OU )
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General HO Process
MS Goes into New Dedicated Mode
MS Goes intoDedicated Mode
Measure and Measurement Result Report1
MR. Preprocessing2
Handover Judgment3
Handover Implementation4
TA HO
Interference HO
Rx_Level_Drop HO
Bad Quality HO
Load HO
Edge HO
Layer HO
PBGT HO
AMR HO
No DL MR HO
Concentric Cell HO
MS Fast Moving HO
Enhanced Dual Band HO
Penalty Processing
Ranking Processing
OM Forced HO
Direct Retry
Emergency HO
Normal HO
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Load HOHandover triggering zone
Load HO Threshold
Time
Load of Serving Cell
Load Req. on Candidate Cell
Load of Neighboring Cell
Congested CellCongested Cell
Congested CellNormal Cell
Normal CellNormal Cell
Normal Cell
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Cell A Cell B
Normal HO border
CONF_HO_RXLEV
CONF_HO_RXLEV+CLS_Ramp
CONF_HO_RXLEV+CLS_Offset
Load HO zone
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 bandwidth Edge HO threshold
Load HO step level
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Load HO
Congested Cell
Normal Cell
Normal Cell
Normal Cell
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Load HO Begin
Is [Load HO Allowed] Yes ?
BSC internal cell?
Select the cell with the highest
priority in the cadidate cell list
End
No
No
Yes
NoYes
Yes
Current system flux<=[System Flux Threshold
for Load HO]?
C & D
Suitable cell exist?
Trigger load handover
Yes
Yes
Yes
End No
Load of service cell >= [Load HO Threshold]?
Yes
No
Yes
Load HO timer T overflow?
Yes
Caculate
StepPeriod
T )1(
Caculate A=[Load HO Bandwidth]
B
Yes
Is serving cell?
No
No
B: [Edge HO_DL_RX_LEV Threshod]<DL_RX_Lev(s) < [Edge HO_DL_RX_LEV Threshod]+AC: 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]
CNo
A=
No
Yes
Load HO timer T begin?
No
No
Star timer T
PeriodStep
TAStep )1Bandwidth] HO [Load
(0 Bandwidth] HO [LoadA T
Yes
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Data Configuration of Load HO
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General HO Process
MS Goes into New Dedicated Mode
MS Goes intoDedicated Mode
Measure and Measurement Result Report1
MR. Preprocessing2
Handover Judgment3
Handover Implementation4
TA HO
Interference HO
Rx_Level_Drop HO
Bad Quality HO
Load HO
Edge HO
Layer HO
PBGT HO
AMR HO
No DL MR HO
Concentric Cell HO
MS Fast Moving HO
Enhanced Dual Band HO
Penalty Processing
Ranking Processing
OM Forced HO
Direct Retry
Emergency HO
Normal HO
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Edge HandoverHandoverTriggering
P/N
Serving Cell Neighboring Cell
P: Watch Time N: Valid Time
RX_LEV Thr
Time
RX_Lev
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Edge HOBegin
Is [Fringe HO Allowed] Yes ?
End
No
Yes
Yes
UL_Rx_Lev(s) < [Edge HO UL RX_LEV Threshod]?
Yes
Any neighbor cell?No
Refreshits timer
Yes
Satisfy P/N rule(s)?
DL_Rx_Lev(s) < [Edge HO DL RX_LEV Threshod]?
N
o
Refreshits timer
Yes
Satisfy P/N rule(s)?
No
Select cell(n) whose 16 bit value is
higher than serving cell andwhose level satifys P/N rule(n)
basing on A
Trigger Edge handover
No
No
Yes
A: DL_Rx_Lev(n)> DL_Rx_Lev(s)+[Inter-cell HO
Hysteresis]
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Data Configuration of Edge HO
Should be lower than the[Outgoing OL Subcell HO Level Threshold(dB)] in enhanc
e dual band data table
[Edge HO UL/DL RX-LEV Threshold]<[UL/DL RX_LEV Lower Threshold] in HWII/III p
ower control tabel
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Data Configuration of Edge HO
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Data Configuration of Edge HO
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MS Fast-Moving HandoverHandover Triggering
Time Threshold
Umbrella Cell
Time
P/NP: Watch CellsN: Valid Cells
1 1 2 3
Micro Cell
Cells Number
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MS Fast-Moving HandoverBegin
Is [MS Fast Moving HO
Allowed] Yes ?
End
No
Yes
Yes
Is the target cell the serving cell?
Is the serving cell on layer 4?
Is the best neighbor cell is the last original cell?
Satisfy P / N rule?No
Select the neighbor cell with the highest priority &
on the 4th layer & satisfy RX_LEV(n)>= Inter-layer
HO threshold(n) + Inter-layer HO hysterisis(n)
Any cell satisfy the condition above?
Trigger MS fast-moving handover
No
Yes
Yes
No
Yes Refresh timer(s)
No
No
Yes
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Data Configuration of MS Fast-moving Handover
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Layer HO
Neighboring CellServing Cell
GSM900 Cell( Lay 3 )
GSM1800 Cell( Lay 2 )
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Begin
Is [Level HO Allowed] Yes ?
End
No
Yes
Yes
Any neighbor cell exit?
16 bit valu(n)<16 bit value(s)l?
A & ( layer(n)< layer(s) or level(n)<level(s) )?
Satisfy P/N rule(n)?No
Trigger layer handover
Yes
No
Yes
No
A: RX_LEV(n)>= Inter-layer HO threshold(n) + Inter-layer HO hysterisis(n)
Yes
Identify the next cell
No
Layer HO
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Data Configuration of Layer HO
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Data Configuration of Layer HO
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PBGT HO
Serving Cell Neighboring Cell
PBGT HO Threshold
Time
Path Loss (dB)
126dB 119dB
5
126-119=7dB>5dB
HandoverTriggering
P/NP: Watch Time N: Valid Time
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Begin Is [PBGT HO
Allowed] Yes ?
End
No
YesIs current channel
signal channel?
Satisfy P / N rule?
No
Yes
Search next
neighborcell
layer(n)=layer(s)&level(n)=level(s)?
Path loss (s) – Path loss (n) >PBGT HO Threshold
Refresh timer(s)
Trigger PBGT HO
Yes
No
Yes
No
Yes
No
PBGT HO
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Data Configuration of PBGT HO
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Data Configuration of PBGT HO
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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 parametersOverlaid
Underlaid
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Classification and HO Judgment of Concentric Cell
Receiving levelTime advanceQuality
…
Receiving levelTime advanceQualityATCBCell load of underlaid
…Normal concentric cell Enhance concentric cell
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Data Configuration of Concentric Cell
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Normal Concentric Cell HO
Division of underlaid and overlaid is decided by MS
downlink receive level ,TA value and quality.
underlaid
overlaid
Receiving Level Threshold
Receiving Level Hysteresis
Receiving Qaulityl Threshold
TA Threshold
TA Hysteresis
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Normal Concentric Cell HO
U to O O to U
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Normal Concentric Cell HO(OU ) Flow for TCH HO from overlaid to underlaid
Begin [Penalty Time of OtoU HO Fail(s)] overflow ? End
No
Ye
s
[RX_LEV for UO HO Allowed] Yes?
Yes
[OL to UL HO Allowed] Yes ?
NoYes
[RX_QUAL for UO HO Allowed] Yes?
Yes
Rx_Dl_Quality>=[RX_QUAL Treshold]? Current TA>=[TA Threshold]+
[TA Hysteresis]?
[TA for UO HO Allowed] Yes?
Trigger OL to UL
P/N rule?
Yes Yes
Yes
Yes
No
No No
No No No
End
Rx_Dl_Level<=[RX_LEV thshold]
-[RX_LEV Hysteresis]
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Normal Concentric Cell HO(UO ) Criterion for TCH HO from underlaid to overlaid
Begin [Penalty Time of UtoO HO Fail(s)] overflow ?
End
No
Yes
Time of HO failure< [MaxRetry Time after UtoO Fail]?
Current TA<=[TA Threshold]-[TA Hysteresis]?
No
Yes
[RX_QUAL for UO HO Allowed] Yes?
Yes
Yes
No
No[RX_LEV for UO HO Allowed] Yes?
Rx_Dl_Level >=[RX_LEV Threshold] +
[RX_LEV Hysteresis]No
[TA for UO HO Allowed] Yes?
Rx_Dl_Qual<=[RX_QUAL Treshold]?
Yes
P/N rule?
Yes
No
No
No
Yes
Yes
No
[UL to OL HO Allowed] Yes ?
End
Yes
No
Trigger UL to OL
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Data Configuration of Normal Concentric Cell HO
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Data Configuration of Normal Concentric Cell HO
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Data Configuration of Normal Concentric Cell HO
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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
overlaid
U to O HO Receiving Level Threshold
O to U HO Receiving Level Hysteresis
Receiving Qaulityl Threshold
TA Threshold
TA Hysteresis
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Enhance Concentric Cell HO
Classification of TCH HO in enhance concentric cell HO
O to U for low load in U
U to O for high load in
U
O to U for moving
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Enhance Concentric Cell HO(UO )
Begin [Penalty Time of UtoO HO Fail(s)] overflow ?
End
No
Yes
Time of HO failure< [MaxRetry Time after UtoO Fail]?
Current TA<[TA Threshold]-[TA Hysteresis]?
No
Yes
[ATCBHoSwitch] Open?
[RX_QUAL for UO HO Allowed] Yes?
Go to the user selection
flow in the next slide
Yes
Yes
No
No[RX_LEV for UO HO Allowed] Yes?
Rx_Dl_Level>[UtoO HO
Received Level Threshold]
No
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 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 -110dB
m
AYes
No
[TA for UO HO Allowed] Yes?
Rx_Dl_Qual<[RX_QUAL Treshold]?
Yes
P/N rule?
YesNo
Flow for TCH HO from underlaid to overlaid for high load in UL
No
No
No
Yes
Yes
Yes
Yes
[UL to OL HO Allowed] Yes ?
End
Yes
No
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Enhance Concentric Cell HO(UO )
Cell load of UL>=[En Iuo Out Cell Serious OverLoad Thred]?
Begin [UtoO Traffice
HO Allowed] Yes ?
Cell load of UL>=[En Iuo Out Cell General OverLoad Thred]?
Trigger UL to OL
Yes No
Adjust HO zone basing on HO step and HO perio
d
Refresh cell load
per second
B(B-1)/second
Yes
B=[Underlay HO Step Period(s)]HO step: [Underlay HO Step Level]HO period: B-1 or BHO zone: begin from -47dBm
Any MS in HO zone?
Yes
No
Yes
No
End
User selection flow from UL to OL for high load in UL
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Enhance Concentric Cell HO(OU ) Flow for TCH HO from overlaid to underlaid for low load in underlaid
Begin [UtoO Traffice
HO Allowed] Yes ?
Cell load of UL<[En Iuo Out Cell Low Load Thred]?
No
Trigger UL to OL
Adjust HO zone basing on HO step and HO perio
dRefresh cell
load per second
Yes
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
Any MS in HO zone?
Yes
No
Yes
No
End [OL to UL HO
Allowed] Yes ?
Yes
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Enhance Concentric Cell HO(OU ) Flow for TCH HO from overlaid to underlaid for moving
Begin [Penalty Time of OtoU HO Fail(s)] overflow ? End
No
Ye
s
[ATCBHoSwitch]
Open?
No[RX_LEV for UO HO Allowed] Yes?
Rx_Dl_Level>[OtoU HO
Received Level Threshold]
A
Yes
[OL to UL HO Allowed] Yes ?
NoYes
[RX_QUAL for UO HO Allowed] Yes?
Yes
Rx_Dl_Qual>[RX_QUAL Treshold]? Current TA>[TA Threshold]+
[TA Hysteresis]?
[TA for UO HO Allowed] Yes?
Trigger OL to UL
P/N rule?
Select the underlaid subcell or
the neighbour cell with the
highst priority in 16 bits list
Yes Yes Yes
Yes
No
Yes
No No No
No No
No End
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)]
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Data Configuration of Enhance Concentric Cell HO
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Data Configuration of Enhance Concentric Cell HO
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Data Configuration of Enhance Concentric Cell HO
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Data Configuration of Enhance Concentric Cell HO
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Data Configuration of Enhance Concentric Cell HO
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Data Configuration of Enhance Concentric Cell HO
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Data Configuration of Enhance Concentric Cell HO
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Channel Assignment strategies of Concentric HO
Channel Assignment Strategies of Concentric HO
Immediate Assignment
AssignmentIntra-BSC Inter-cell
Handover
Incoming Cell
Handover
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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 smallerTA bigger
Immediate Assignment
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Data Configuration of Immediate Assignment
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Preferred assignment in the overlay or underlay cell Assign the channel of overlay or underlay cell accordin
g to the Rx_level and TA in the measurement report
TA smaller and Rx-level higher
Assignment
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Data Configuration of Assignment
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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.
overlaid
Underlaid
OverlaidAccording to the Rx-level
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Data Configuration of Intra-BSC Inter-Cell Handover
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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.
overlaid
Underlaid
Overlaid
BSC1 BSC2
Assign underlaid first
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Data Configuration of Inter-BSC Inter-Cell Handover
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AMR Handover FlowBegin
Are [Intracell HO Allowed] & [Intracell F-H
HO Allowed ] Yes ?
Yes
Is current channel TCH & version3?
No
A: Cell load > [AMR TCH/H Prior Cell Load Threshold]
During [Penalty Time after AMR TCHF-H HO
Fail(s)]?
Yes
Yes
current channel is FR
Satisfy P/N rule?Trigger internal
cellAMR handover
Yes
NoEnd
RQI/2 >[F2H HO th] & A RQI/2 <[H2F HO th] End
Yes Yes
NoNo
No
No
No
Yes
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Data Configuration of AMR HO
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Data Configuration of AMR HO
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General HO Process
MS Goes into New Dedicated
Mode
MS Goes into Dedicated
Mode
Measure and Measurement Result Report1
Measurement Report Preprocessing2
Handover Judgment3
Handover
Implementation4
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Handover Implementation
No power control during handover in order to
make sure the handover is
successful
Begin
Is [Power boost befor HO
enabled or not ] Yes ?
BTS(s) uses the max.
power output
Yes No
BSC send “HO Command” to
MS
HO execute
BTS(s) keeps current
power output
BTS(s) keeps current
power output For BTS
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Data Configuration of Handover Implementation(BTS)
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Handover Implementation
No power control during handover in order to
make sure the handover is
successful
Begin
Is [MS Power Prediction after HO ] Yes ?
BSC predict power
Yes No
BSC send “HO Command” to
MS
HO execute
MS uses the highest power
to access For MS
MS will use this predict power in new cell after finishing this handover
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Data Configuration of Handover Implementation(MS)
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Data Configuration of Handover Implementation(MS)
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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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