handover training
TRANSCRIPT
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Huawei Confidential
OMF010002 Handover
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Summary of Handover
HO Algorithm process
HO Data Configuration
HO Signaling process
Course Contents
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Summary of HOPurposes of HO
Purposes of HO
To keep a continuous communication with a moving MS
To improve network service performance
To reduce the call drop rate To reduce the congestion rate
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Classification of HO:
Emergency HO
Timing Advance (TA) Emergency HO
Bad quality (BQ) Emergency HO
Rx_Level_Drop Emergency HO Interference Emergency HO
load HO
Normal HO
Edge HO
Layer HO
Power Budget (PBGT) HO
Speed-sensitive HO (Fast moving MS HO)
Concentric Cell HO
Summary of HOClassification of HO
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Summary of Handover (HO)
HO Algorithm process
HO Data Configuration
HO Signaling process
Course Contents
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General HO process
Measurement report preprocessing
Penalty processing
Basic ranking and Secondary ranking
HO judgment
HO Algorithm process
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HO Algorithm process
General HO process
Measurement report preprocessing
Penalty processing
Basic ranking and secondary ranking
HO judgment
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Preprocessing Measurement Report (MR):
Uplink MR includes uplink receiving level and quality.
Downlink MR includes downlink receiving level,
downlink receiving quality of the serving cell and other
downlink receiving levels from the neighbor cells.
Serving cell Neighbour cell
The downlinkmeasurement report of theneighbour cell (BCCH)
The downlinkmeasurement report
of the serving cell
The uplinkmeasurement report ofMS
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Measurement Report Preprocess
MR interpolation
Every time BSC receives a measurement report, there
will be an update to the basic rank of the cells.
BTS may fail to receive the measurement report from
MS. Before the rank-update, BSC needs to recover the
lost measurement reports according to Filter Table. If
the lost MR amount is within the allowed range, then
recovers the lost MR according to the algorithm.
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How to interpolate MR?
MRMR
MR MRMR
Measurementreport No. n
Measurement rNo. n+4
ContinuousMR
flow
Measurement Report Preprocess
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General HO process
Measurement report preprocessing
Penalty processing
Basic ranking and secondary ranking
HO judgment
HO Algorithm process
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Penalty Processing
There are altogether four types of penalty
process (second step of HO algorithm process )
Penalty on the target cell when a HO fails.
Penalty on the original serving cell when an emergencyHO ( base on BQ and TA ) is performed.
Penalty on other high priority layer cells after a fast
moving HO is performed.
A new HO attempt is prohibited within the penalty timeafter an overlaid/underlaid HO fails.
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BTS
HO failure
BSC
Cell A
Cell B
Penalty Processing
Penalty on the target cell:
Punish the target cell when a HO fails. This is to avoid the MS
to select this cell again in next HO judgment.
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BTS
BQ& TA HO
BSC
Cell A
Cell B
Penalty Processing
Penalty on the serving cell:
Punish the original serving cell when an emergency HO ( due to
BQ and TA) occurs.
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Back? No way!
Umbrella
Micro cell
Penalty Processing
Giving penalty on the other three layers after MS
handovers to Umbrella cell by fast-moving-HO. Thisis to keep MS staying in the umbrella cell and avoid
frequent HO.
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Underlaid
Overlaid Do not
attemptagain after a
failed HO!
Penalty Processing
A new Overlaid/underlaid HO is prohibited within a
penalty time after an Overlaid/Underlaid HO failure.
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HO Algorithm process
General HO process
Measurement report preprocessing
Penalty processing
Basic ranking and secondary ranking
HO judgment
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Basic Ranking and Secondary Ranking
Basic ranking and secondary ranking of cells
are major parts of the HO judgment. Ranking is
made through 16bits-algorithm. The serving
cell and the neighbor cells will be listed in a celllist according to their 16bits value. The ranking
processes include:
M rule
K rule
16bits ranking
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M rule:
Only the cells with received signal level satisfy the following conditions can be put into the
candidate cell list.
For serving cell: RX_LEV (o) >MSRXMIN(o) + MAX(0,Pa(o))
i.e : RX_LEV(o) MSRXMIN(o)-MAX(0,Pa(o))> 0 .. ( 1 )
For Neighbor cell: RX_LEV (n) > MSRXMIN(n)+ MAX(0,Pa(n))+ OFFSET
i.e : Having the same formula as above
Pa(0) : MS_TXPWR_MAX(0) P
Pa(n) : MS_TXPWR_MAX(n) P
MS_TXPWR_MAX( ) : The appointed MS transmitting power by the BSS.
P : Max_Power_of_MS
Max_Power_of_MS : MS maximum transmitting power
Basic ranking and Secondary ranking
S
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K rule Criterion:
After the M rule , the serving cell and candidate neighbor
cells are ranked in descending order according to the
receiving level only.
Basic Ranking and Secondary Ranking
B i R ki d S d R ki
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The 16bits rule
Both the serving cell and the neighbor cells have their
own 16bits value. The smaller the value is, the higher
the priority and position the cell is in the cell list.
The 1st-3rd bits: bit value is decided according to the
cell signal level and the penalty process taking place
beforehand. The values come from max. 6 candidate cells and 1
serving cell according to the level ranges from
000~110. The value for the cell with the strongest
signal level is 000.
16 9012345 1
Basic Ranking and Secondary Ranking
B i ki d S d ki
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The 4th bit: bit value is determined by inter-cell HO ( of
the same layer ) hysteresis.
The 4th bit of the serving cell is always 0,
The receiving signal level of the neighbor cell >= The
receiving level of the serving cell + Inter-cell HO ( of
the same layer ) hysteresis, bit 4th is set to 0.
The receiving level of the neighbor cell < The
receiving level of the serving cell + Inter-cell HO ( of
the same layer ) hysteresis, bit 4th is set to 1.
Note: In PBGT HO, whichever the greater of the inter-
cell ( of the same layer ) hysteresis and PBGT
threshold, that value will be used in the PBGT HO.
16 9101112131415 12345678
Basic ranking and Secondary ranking
B i ki d S d ki
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The 5th-10th bits: bit value is decided according to their
position in Huawei hierarchical network structure.
When the signal level of the neighbor cells or the
serving cell is lower than the layer HO threshold and
hysteresis, this function is turned off and all bits areset to 0.
That is to say only when the above criterions are met,
then this function take effect.
Huawei cell layers can be divided into 4 layers andeach layer can be further divided into 16 different
priorities. So there are 64 different priorities in
Huawei hierarchical cell structure.
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Basic ranking and Secondary ranking
B i ki d S d ki
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GSM900
Cell
Micro Cell
Umbrella
CellGSM 900
GSM1800 GSM1800GSM1800
GSM 900 GSM 900 GSM 900
GSM900GSM900
GSM1800GSM1800
GSM900 GSM900
GSM1800 GSM1800
GSM1800
Cell
Hierarchical cell structure
Basic ranking and Secondary ranking
B i R ki d S d R ki
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The 11th bit: bit value is decided by cell-load-sharing
criterion.
Serving cell: if Cell Load>= Start threshold of load
HO, bit 11th is set to 1, otherwise is set to 0. Neighbor cell: if Cell Load>=Receive threshold of
load HO, bit 11th is set to 1, otherwise is set to 0.
Refer to Load HO Table for the load HO threshold
and load req. on candidate cell. Clue : When the cell load is higher than the threshold,
then the bit 11th is set to 1.This is done in order to put
the cell in a lower part of the cell list.
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Basic Ranking and Secondary Ranking
B i R ki d S d R ki
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12th bit: bit value is decided by co-BSC criterion.
Serving cell: is always set to 0.
Neighbor cell: if co-BSC with the serving cell, 12th bit
is set to 0, otherwise is set to 1.
When the signal level from the neighbor cell or the
serving cell is lower than layer HO threshold and
hysteresis. This function is turned off and the value
is set to 0.
If the parameterCo-BSC/MSC Adj. in the HO
control table is set to No, then this function is turned
off and the value is 0.
13th bit : Bit value is decided by Co-MSC parameter,
having the same concept as the 12th bit.
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Basic Ranking and Secondary Ranking
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The 14th bit: Layer HO threshold adjustment bit
Serving cell criterion:
Receive level >= layer HO threshold layer HO
hysteresis, bit 14th is set to 0. At the same time, bit13th, 12th and 10th5th bits are set to 0.
If the above criterion is not met, then bit 14th is set to
1.
Example : 20-5 = 15 ( -95 dBm )
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Basic Ranking and Secondary Ranking
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Basic Ranking and Secondary Ranking
Neighbor cell criterion:
Receive level >=layer HO threshold + layer HO
hysteresis, bit 14th is set to 0. At the same time, bit
13th, 12th and 10th5th bits are set to 0
If the above criterion is not met, then bit 14th is set to1.
Example : 20+5 = 25 ( -85 dBm )
note :
The layer HO threshold and hierarchical hysteresis
correspond to the value of that individual cells value.
Usual situation : When the neighbor cells are of the
same layer, each of the neighbor cells layer HO
threshold value will be the same. Same concept goes
for the layer HO hysteresis. This can maintain theentire hierarchical la ers of the cell.
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B i R ki d S d R ki
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The 15th bit: Bit value is decided by cell type
Serving cell or Neighbor cells:
When cell type is extension cell1.
When cell type is normal cell0. The 16th bit: Reserved bit
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HO Algorithm process
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General HO process
Measurement report preprocessing
Penalty processing
Basic ranking and secondary ranking
HO judgment
HO Algorithm process
HO Algorithm
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HO Algorithm
Initializing
M rule
K rule
16bits rule
Emergency HO judgment
Load-HO judgment
Normal HO judgment
Fast moving HO judgment
Layer HO judgment
PBGT HO judgment
Send HO command
Send HO command
Send HO command
Overlaid/underlaid HO
judgment
Edge HO judgment
Forced HO Direct re-tryO&M reason
Types of HO
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Types of HO
Types of HO :
Emergency HO
TA & BQ HO, interference HO, Rx_Level_Drop HO
Load HO
Normal HO
Edge HO, layer cell HO and PBGT HO
Fast moving HO
Overlaid/underlaid HO
Emergency HO
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Emergency HO
TA HO criterion :
TA of the serving cell > TA Thrsh.
BQ HO criterion :
The average value of the uplink quality of the serving cell>
UL Qual. Thrsh.
The average value of the downlink quality of the serving
cell > DL Qual. Thrsh. Requirements on the target cell (same as the
above two types of HO):
Select the first cell in the neighbor cell list i.e. lowest
16bits value.
Emergency HO
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Emergency HO
Rx_Level_Drop HO:
Due to downlink signal level drop
Triggered upon detecting rapid level drop during MS
busy mode.
Requirements for the target cell:
The target cell is the first cell in the neighbor cell list.
Emergency HO
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Emergency HO
Interference HO (DL&UL) :
When the receiving level > receiving threshold level. But
Receiving quality < threshold of quality interference.
Requirements for the target cell:
The target cell is in the cell list.
Cell Load HO
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Cell Load HO
Cell Load HO Criterions :
System load of BSC < Permissible load of HO threshold
Load of serving cell > Load HO threshold
Requirements for the target cell
Load of target cell < Load HO threshold
BTS
BSC
Normal HO
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Normal HO
Edge HO Criterion:
In N seconds, when there are P seconds that neighbor
cells DL or MSs UL signal level is lower than the Edge
HO threshold. Then the criterion is met and Edge HO
occurs. This method utilizes the P/N rule.
Requirements for the target cell:
The target cell should be ranked in front of the serving
cell.
Normal HO
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Normal HO
Layer HO criterions:
Serving cell :
No requirement.
Target cell :
Layer of the target cell is lower than the serving cell.
Receive level of the target cell > layer cell threshold
+ layer cell hysteresis.
Target cell should be ranked in front of the serving
cell. The priority of target cell should be higher than
the serving cells.
PBGT HO
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PBGT HO Criterions :
Target cells path loss is smaller than the serving cells
path loss by the PBGT threshold value.
Satisfying the P/N rule.
Target cell should be ranked in front of the serving cell.
Note :
PBGT HO can only occur between same-priority cell. If
the system permits PBGT HO for the cell, PBGT HO canoccur in either inter-BSC or inter-MSC.
PBGT HO
Fast Moving HO
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Fast-Moving HO
When the serving cell is micro cell : When the MS has traveled through P numbers of cell,
and there are Q (=
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underlaid
overlaid
Overlaid/underlaid :
Division of underlaid and overlaid is decided by MS downlinkreceive level and TA value.
Overlaid/Underlaid HO
Overlaid/Underlaid HO
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Criterion for HO from overlaid to underlaid:
TA value => TA threshold + TA hysteresis Or
RX_LEV
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Question
Can you list the function of each bit in 16bit
ranking?
What is the period of measurement report?
Course Contents
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Summary of Handover (HO)
HO Algorithm process
HO Data Configuration
HO Signaling process
Course Contents
Major HO Parameters Configuration
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Major HO Parameters Configuration
Major HO parameter configuration 1.[Handover Control Table]
2.[Cell Description Table]
3.[Adjacent Cell Relation Table]
4.[Penalty Table]
5.[Emergency Handover Table]
6.[Load Handover Table]
7.[Normal Handover Table]
8.[Fast-Moving Handover Table]
9.[Concentric Cell Handover Table]
HO data lookup process
Major HO Parameters Configuration
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Major HO Parameters Configuration
[Handover Control Table] -1Parameter
nameMeaning Value range Recommen
ded value
Co-BSC/MSCAdj.
It means whether the 12th
and 13th
bits acts in the 16bit order.Yes means handover in the same BSC/MSC is preferred.No means that the 12
thand 13
thbits are shielded and set to
0.
Yes, No Yes
Penaltyallowed
It determines whether to punish the target cell of handoverfailure, or the original served cell of handover upon too big TA
or bad quality. The penalty measures can apply to cells in orout of the same BSC.
Yes, No No
Load HOallowed
It determines whether to perform the handover to share trafficload. Load sharing can lower the channel assignment failureratio caused by cell congestion, so as to make evenerallocation of the service in respective cells, and lower the cellcongestion rate , and improve network performance. It on lyapplies in the same BSC or cells at the same level.
Yes, No No
MS Fastmoving HO
allowed
It determines whether to handle the fast moving MS with thealgorithm. It is only recommended in special a reas (such as a
highway), to lower CPU load. This algorithm should only beused in suitable conditions, and usually it is not applied.
Yes, No No
Major HO Parameters Configuration
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Major HO Parameters Configuration
[Handover Control Table] -2
Parameter name Meaning Value range Recommendedvalue
RX_Level_DropHO allowed
It means whether RX_Level_Drop emergencyhandover algorithm is allowed, handover the MSwhich receiving signal level is dropping quickly inadvance to avoid potential call drop. This algorithmshould be applied in suitable conditions, and usually itis not used. To apply the handover algorithm, BSC
must have original measurement report.
Yes, No No
PBGT HOallowed
It means whether PBGT handover algorithm isallowed. PBGT handover algorithm currently isprocessed on LAPD board. To avoid Ping -panghandover, PBGT handover is only performed betweencells at the same layer and with the same priority, andmeanwhile it is only triggered on TCH.
Yes, No Yes
MS powerprediction afterHO
It means after a handover whether MS is to useproper predicted transmitting power to access thenew channel. This can reduce system interferenceand improve service qualit y (this parameter actswhen intra BSC handover occurs).
Yes, No Yes
Major HO Parameters Configuration
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Major HO Parameters Configuration
Parametername
Meaning Value range Recommendedvalue
MR.Preprocessing
Yes means perform measureme nt reportpreprocessing on BTS; No means preprocessing onBSC, then the two parameters of Send originalmeasurement report and Send BS/MS power level do not act. Yes means decreasing of Abis interfacesignaling and BSC load, and improving of network
response time performance. The switch determineswhere to perform power control. When it is set toYes, power control is performed at BTS side. Whenit is set to No, power control is performed at BSCside. When setting this parameter, first be clearwhether BTS supports the power control algorithm toset or not.
Yes, No Yes
[Handover control table] -3
Major HO Parameters Configuration
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Major HO Parameters Configuration
Parametername
Meaning Value range Recommendedvalue
Transferoriginal MR.
It means whether to send the original measurementreport to BSC after measurement report preprocessingon BTS. When it is set to Yes, BTS sends not onlyprocessed measurement rep ort but also originalmeasurement report to BSC.
Yes, No No
TransferBS/MS powerclass
It means whether to send BS/MS power level from BTSto BSC. This function is used to view the effect of powercontrol on BTS. Meanwhile, when preprocessing isavailable, if BS/MS power level is not reported, the uplinkand downlink balance measurements will be affected,and handover types such as PBGT handover andoverlaid/underlaid handover needing powercompensation will be abnormal.
Yes, No Yes
[Handover control table] -4
Major HO Parameters Configuration
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Parametername
Meaning Value range Recommendedvalue
Sent Freq. ofpreprocessedMR.
It indicates the time interval at which a measurement reportis preprocessed at B TS side and sent to BSC thePreprocessed measurement report. This parameter actsonly when Measurement report pre-processing is enabled .For 15:1 link configuration, the report frequency should be
as low as once per second due to limited link resource. Atthis time, for handover nee ding P/N judgment such as edgehandover, layer handove r, PBGT handover andoverlaid/underlaid handover,
Twice persecond, Onceper second
According toconcreteconditions
[Handover control table] -5
Major HO Parameters Configuration
Major HO Parameters Configuration
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Parametername
Meaning Valuerange
Recommendedvalue
Layer of thecell
Huwei hierarchical network structure is divided into 4 layers. 16priorities can be set for each layer, which provides enough roomof network planning for the operator to adapt to various complexnetwork environment. Normally, Macro layer is the major 900layer, Micro layer is the major 1800 layer, Pico is the 900 and1800 micro cell layer. The smaller layer value, the higherpriority.
The1st~4thlayers
M900: the 3 rd
layer
M1800: the 2 ndlayer
Cell priority Each layer may have 16 priorities, used to control the handoverpriority between cells at the same layer. Usually priorities ofcells at the same layer are set the same. For cells at the samelayer, the smaller the priority value, the higher the priority.
1~16priorities
1
Layer HOThrsh.
It affects the value of the 14th bit in the 16bit ranking, and it isalso the level requirement on the target cell for int erferencehandover, layer handover and load handover. Then su ch levelshould be higher than layer h andover threshold + layer
handover hysteresis. The layer handover threshold should beset >= Edge handover threshold + Inter -cell handoverhysteresis.
0~63 25
Layer HOhysteresis
Works together with the Layer handover threshold. 0~63dB 3
Major HO Parameters Configuration
[Cell Description Table] -1
Major HO Parameters Configuration
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Parametername
Meaning Value range Recommendedvalue
Penalty onMS Fastingmoving HO
It is valid when the fast m oving handover algorithm isenabled. It is the signal level penalty value on the otherneighbor cells when MS moves fast and is handed over
to umbrella cell. The paramete r is only valid within thepenalty time.
0~63dB 30
PenaltyTime on MSFastingmoving HO
It means that within this tim e, the penalty on the otherneighbor cells will be exerted a fter MS is handed overto umbrella cell by fast moving HO.
0~255seconds
40
Min DL level
0ncandidatecell
This is the min signal level requirement for the cell itself
to be a candidate cell . Too low configuration may easilycause call drops, while too high a configuration mightturn handover too hard to occur.
0~63 15
Major HO Parameters Configuration
[Cell Description Table] -2
Major HO Parameters Configuration
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Parametername
Meaning Value range Recommendedvalue
Ncell ID Neighbor cell ID index. 0~255 forinternal cell;0~799 forexternal cell
Min accesslevel offset
This offset is based on Min downlink level of handovercandidate cell. Different offsets can be defined for differentadjacent cells, and to enter the can didate cell list, thecorresponding adjacent cell rec eiving signal level must behigher tha n the sum of Mi n downlink level of handover
candidate cell and Min. Access level offset.
0~63 0
Major HO Parameters Configuration
[Adjacent Cell Relation Table] -1
Major HO Parameters Configuration
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Parametername
Meaning Value range Recommendedvalue
PBGT HOThrsh.
It means that PBGT handover is performed when thedifference between the target cell downlink path loss and theserving cell downlink path loss is bigger than PBGT handoverthreshold. Whe n PBGT handover is enabled , and Inter -cellhandover hysteresis > PBGT handover threshold
(corresponding dB value), Inter -cell handover hysteresistakes place of PBGT handover threshold to act. . PBGThandover threshold also needs to be adjusted acc ording tohandover performance statistics result.
0~127,corresponding to--64~63dB
It is around 68 in thedensely populateddowntown, andaround 72 on theoutskirts.
Inter-cell HOhysteresis
Handover hysteresis between an adjacent cell and the servingcell. It is set to reduce Ping -pang HO. The hysteresis valuealso needs to be adjusted according to the handoverperformance statistics result and live network. Flexible
configuration of the value can effectively lead handover andtraffic between two adjacent cells.
0~63db It is around 4 in thedensely populateddowntown, andaround 8 on the
outskirts.
[Adjacent Cell Relation Table] -2
Major HO Parameters Configuration
Major HO Parameters Configuration
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[Penalty Table] -1Parameter
nameMeaning Value range Recommended
value
Penalty levelafter HO fail
The signal level value in dB, to punish the target cellwhich has caused a HO failure due to problems suchas congestion , to prevent MS from a handover
re-attempt to that ce ll again. This value is only validwithin the penalty time for handover failure.
0~63dB 30
Penalty timeafter HO fail
Penalty time on the corresponding target cell afterhandover failure
0~60 seconds 10
Penalty levelafter BQ HO
fail
The signal level pen alty value for the original servingcell, to avoid Ping -pang handover after emergency
handover upon bad quality. It is only valid within thepenalty time for BQ HO.
0~63dB 63
Penalty timeafter BQ HOfail
Penalty time for the original serving cell after BQ HO. 0~60 seconds 10
Major HO Parameters Configuration
Major HO Parameters Configuration
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[Penalty Table] -2
Parametername
Meaning Value range Recommendedvalue
Penaltylevel afterTA HO fail
The signal strength penalty value for the original serving cell,to avoid Ping -pang handover after TA emergencyhandover. It is only valid within the penalty time for tahandover.
0~63dB 63
Penalty timeafter TA HOfail
Penalty time for the original serving cell after TA emergencyhandover.
0~60Seconds 10
Penalty time
after IUOHO fail
After an overlaid/underlaid handover failure (big circle hands
over to small circle o r vice versa), within certain time (thisparameter configuration value) overlaid/und erlaid handoveris forbidden for the same call.
0~16Seconds 10
Major HO Parameters Configuration
Major HO Parameters Configuration
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[Emergency Handover Table] -1
Parameter
name Meaning Value range RecommendedvalueTA Thrsh. When TAthis value, emergency handover is
triggered 0~63 bitperiod 63DL QUAL.
Thrsh The downlink receiving quality threshold for BQemergency handover. When frequency hoppingor DTX is enabled, RQ becomes worse (normalphenomenon), this value should be set to 70.
The adjustment should also base on the current
network quality and handover statistics. When
triggering emergency handover, the first to
select is the inter-cell handover, the intra-cell
handover is only triggered when there is no
candidate cell and the intra-cell handover is
allowed in the serving cell.
0~70,
correspondi
ng to BQlevels of 0~7
60
UL QUAL.
Thrsh. The uplink receiving quality threshold for BQemergency HO. corresponding to BQlevels of 0~7
60
Major HO Parameters Configuration
Major HO Parameters Configuration
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[Emergency Handover Table] -2
Parametername
Meaning Value range Recommendedvalue
ULQual.Thrsh.for interf.HO
Uplink receiving quality threshold in the serving cell forinterference handover. When frequency hopping or DTX isenbaled, RQ becomes worse (normal phenomenon), thisvalue should be set to 60. The adjustment should also baseon the current network quality and handover statistics. Whentriggering interference handover. If the serving cell is in thefirst position and intra-cell handover is permitted, performintra-cell handover. Otherwise select the second candidatecell to perform inter-cell handover.
correspondingto BQ levels of0~7
50, interferencequality thresholdmust be better thanthe emergencyquality threshold
DL Qual.Thrsh. Forinterf HO.
Downlink receiving quality threshold in the serving cell forinterference handover.
0~70,correspondingto BQ levels of0~7
50
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[Emergency Handover Table] -3
Paramete
r name
Meaning Value range Recommended
value
UL
RX_LEV
Thrsh. for
interf.HO
Min uplink receiving power threshold from the serving cell
required for interf. HO, when interference handover is
triggered if the uplink quality is worse than quality thr eshold
and at this time the uplink signal level is higher than the signalthreshold. When triggering interference handover, If the
serving cell is in the first posi tion in the cell list, and intra-cell
handover permitted, then start intra -cell HO. Otherwise select
the second cell to perform inter-cell HO.
0~63 25
DL
RX_LEV
Thrsh. for
interf HO.
Min downlink receiving power threshold from the serving cell
required for interf. HO.
0~63 30
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[Emergency Handover Table] -4
Parametername
Meaning Value range Recommendedvalue
Filterparameters
A1~A8
Used for configuration of filter for rapid signaldrop judgment, and together with filter parameterB, they are 9 parameters for a filter. Thecorresponding formula is (in the program, A1~A8
is configuration value minus 10 and B is thenegative configuration value):
C1(nt)=A1C(nt)+A2C(nt-t)+A3C(nt 2t)+
+A8C(nt-7t)Where, C (nt) is the receiving signal level in theuplink measurement report of the serving cellsent at the time of nt. If C1 (nt) < B, and C (nt) isbelow the edge handover threshold, then the
signal level is considered to be of rapid drop.
0~20 10
Filterparameter B
Used for configuration of filter for rapid signaldrop judgment. Please refer to the explanationfor A1~A8 of filter.
0~255 0
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[Load Handover Table] -1
Parametername
Meaning Value range Recommendedvalue
System fluxThrsh. for
load HO
The pre-condition for load HO is that the system flow (signalingflow) is lower the threshold. This value can not be set too high
because load handover upon max threshold may cause seriouseffect to the system.
0, 8~11 systemflow levels,
correspondingto 0, 70, 80, 90and 95.
10
Load HOThrsh
Load handover is triggered when the serving cell load is higherthan the threshold, TCH seized in the cell has reaching thecorresponding percentage.
0~7 cell loadlevels,correspondingto 0, 50, 60, 70,75, 80, 85, 90
5
Load Req. oncandidate cell
The Load threshold for the ta rget cells that can accept MS fromserving cell in load HO, i.e. when the TCH under Idle mode inthe neigh bor cell is lower than the corresponding percentage ,the cell refuses to accept MS from serving cell handed over dueto the load reason.
0~7,correspondingto 0, 50, 60, 70,75, 80, 85, 90
2
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[Load Handover Table] -2
Parametername
Meaning Value range Recommendedvalue
Load HObandwidth
This config uration is related to the edge handoverthreshold. Load handover is only allowed when the MSreceiving level from the serving cell is within the range of
margin handover threshold, margin handover threshold +load handover bandwidth.
0~63db 25
Load HO stepperiod
When a cell is up to conditions for load handover, all callswithin the serving cell will send handover request at thesame time, this will cause abrupt increase on processorload, and under certain conditions this will cause the
target cell congestion and result in call drops. Thereby,step by step load handover algorithm is used to controlhandover. The cycle is the time needed for handovers ofeach step.
1~60 seconds 10
Load HO steplevel
The whole load HO bandwidth will be divided into severalsub-bands by this parameter.
1~63db 5
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[Normal Handover Table] -1Parameter
nameMeaning Value range Recommended value
Edge HO UL
RX_LEV
Thrsh.
During the statistics time, if the time in which the uplinkreceiving level is lower than the value is longer thancertain time called continuous time, edge handoverwill be performed. If PBGT handover is enabled,Corresponding edge handover threshold will be set lower.
0~63 25 (without PBGThandover, downtown),15 (single station onoutskirts), 15 (withPBGT handover,downtown)
Edge HO DL
RX_LEV
Thrsh.
Downlink consideration for edge HO. 63 30 (without PBGThandover, downtown),20 (single station onoutskirts), 20 (withPBGT handover,downtown)
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[Normal Handover Table] -2
Parametername
Meaning Value range Recommendedvalue
Edge HOwatch time
It means that within the time statistics, if thetime in which the signal level is lower thanthreshold is higher than the continuous time,then margin HO is to be triggered.
1~16 seconds 5
Edge valid
time
See the above. 1~16 seconds 4
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[Normal Handover Table] -3Parameter
nameMeaning Value range Recommended
value
PBGT watch
time
Statistics time for PBGT HO signal level judgment. 1~16 seconds 5
PBGT validtime
Continuous time for PBGT HO signal level judgment. 1~16 seconds 4
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[Normal Handover Table] -4Parameter
nameMeaning Value range Recommended
value
Layer HOwatch time
Statistics time for Layer HO judgment 1~16 seconds 5
Layer HOvalid time Continuous time for Layer HO judgment. 1~16 seconds 4
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[Fast-Moving Handover Table]Parameter
nameMeaning Value range Recommended
value
MSFast-movingwatch cells
The cell sum P for judge whether MS is fast moving.The value, if too large, may cause abrupt increase ofsystem flow, while too small value may causeinaccurate judgment for fast moving MS.
1~10 3
MSFast-movingvalid cells
The cell sum N by which MS actually quickly passes. Ifwithin P cells that MS continuously past, the number ofcells by which the MS is judged to pass quickly is equalto or more than N, then the MS will b e judged as a fastmoving MS.
1~10 2
MSFast-movingtime Thrsh.
The time threshold (2r/v) determined by the cell radius(r) and moving speed (v). If the time in which MSpasses the cell is smaller than the threshold, then MSis judged to quickly pass the cell.
0~255seconds
15
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[Concentric Cell Handover Table] -1
Parameter
name Meaning Value range RecommendedvalueUO signal
intensity
differenceBTS transmitting Power difference
between underlaid and overlaid may
cause MS receiving signal intensitydifference in underlaid and overlaid . The
parameter uaually indicates the antenna
EIRP difference in dB between underlaid
cell and overlaid cell. According to field
measurement, multi-point measurement
is necessary if the underlaid and
overlaid use different antenna.
0~63db Set according toactual conditions
Major HO Parameters Configuration
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[Concentric Cell Handover Table] -2Parameter
name Meaning Value range RecommendedvalueRX_LEV
Thrsh Rx level hysteresis, TA threshold and TAhysteresis jointly define underlaid areaand overlaid area. It must be bigger than
edge handover threshold, and therecommended value is: edge handover
threshold + signal intensity difference
between underlaid and overlaid .
0~63 25
RX_LEV
hysteresis Works with Rx threshold. 0~63 5
TA Thrsh. It must be bigger than TA emergencyhandover threshold. 0~63 bitperiod, with 1
bit period
correspondin
g to 0.55km
TA
hysteresis Works with TA threshold. 0~63 bitperiod
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[Concentric Cell Handover Table] -3Parameter name Meaning Value
rangeRecommended
value
UO HO watch time P/N judgment statistics time for U/O HO judgment. 0~16seconds
5
UO HO valid time P/N judgment continuous time for U/O HO judgment. 0~16seconds
4
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[Concentric Cell Handover Table] -4Parameter
name Meaning Value range RecommendedvalueAssign
optimum
layerIn Overlaid/Underlaid, the following selection are
available for TCH assignment: (1) The system judges
according to the measurement report on SDCCH and
assign to the best sub-cell. (2) Select the overlaid
first for TCH assignment. (3) Select the underlaid firstfor TCH assignment. (4) Do not give extra priority.
System
optimization,
overlaid ,
underlaid , no
preferential
System
optimization
Assign-
optimum
level Thrsh.If system optimization is selected, estimate
(interpolate, filter) current SDCCH level value through
uplink measurement value in the former SDCCH
measurement report, and compare with Assign-
optimum Level threshold, so as to assign overlaid or
underlaid channel.If SDCCH is in the overlaid : edge handover threshold+ signal intensity difference between underlaid and
overlaid + uplink and downlink balance allowance +
SDCCH and TCH difference allowance. If SDCCH is in
the underlaid : edge handover threshold + uplink and
downlink balance allowance + SDCCH and TCH
difference allowance.
0~63
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[Concentric Cell Handover Table] -5
Parameter
name Meaning Valuerange RecommendedvaluePref.
subcell in
HO ofintra-BSC
When the cell is configured into a
Overlaid/Underlaid, there are two processing
methods for incoming handover request in BSC:(1) No special processing for channel
assignment. (2) Add BCCH signal level value of
the target cell in inter-cell handover request
message to BSC to make BSC allocate
optimum channel for MS from underlaid or
overlaid .
Yes, No Yes
Incoming-to-BSC HO
optimum
layerIf there is a incoming BSC HO, and the targetcell is a Overlaid/Underlaid, then, this
parameter will show which layer is preferred to
provide service for the MS.overlaid ,underlaid ,
noneNone
HO Parameters Configuration
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HO data lookup process
BA2 table defines BCCH frequencies of all neighbor
cells. It is sent to MS by system message 5, system
message 5-bis and system message 5ter on SACCH
channel.
MS reports the serving cell and BCCH, BSIC and signal
levels of 6 strongest neighbor cells to BSS. This is done
through SACCH.
MR pre-process is done in BTS. Module number, cellnumber and CGI of all neighbor cells are derived from
Adjacent cell Relation Table, and Cell Description Table
(or External Cell Description Table) through BCCH and
BSIC in the MR.
Summary of BSC HO
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HO data lookup process
BSC performs HO judgment process, such as basic rank
of cells (completed in LAPD board). When BSC finds
suitable target, It sends HO request messages
containing the target CGI to MPU of BSC. According toCGI, MPU derive the module number of the cell from
Cell Module Information Table.
MPU sends a HO command message to the target
module and step up the inter-cell/ intra-cell HO requestcounter by one.
Course Contents
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Summary of Handover (HO)
HO Algorithm process
HO Data Configuration
HO Signaling process
HO Signaling process
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Intra BSC Handover
Intra MSC Handover
Inter MSC Handover
Intra-BSC Handover Signaling process
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MS MSBTS1 BTS2BSC MSC
Measurement Report from MS
Channel_Active
Channel_Active ACK
HANDOVER COMMAND
Handover AccessHandover_Detect
PHY INFO
First SABM
Establish_IND
PHY INFO
Handover Complete
Handover_Performed
Intra-BSC Handover Signaling process
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Attention
In asynchronous HO, if MS could not reach the new TCH
channel after the target cell has sent PHY INFO up to
max times, the target cell reports CONN FAIL IND to
BSC with the reason: HO access failure.
After the above message is received, BSC release the
assigned TCH channel in the target cell .
Max resend times of physical information*Radio link
connection timer > Time interval between EST IND andHO DETECT (120~180ms). This is to make sure that the
physical information reach MS.
Intra-BSC Handover Signaling process
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MS BTS BTSBSC MSC
Measurement ReportMeasurement Report
Channel_Activate
Channel_Activate ACK
Handover Command (Old FACCH)
Handover Access (New FACCH)
Handover Complete (New FACCH)
RF Channel ReleaseHandover Performed
T09++
T12++
T10++
T13++
Attempted outgoing internal inter cell handovers
Attempted incoming internal inter cell handovers
Successful incoming internal inter cell handovers
Successful outgoing internal inter cell handovers
(Original) (Target)
Measurement Points of Intra BSCH d
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Handover formula definition
Internal inter cell radio handover success rate
=(Successful incoming internal inter cell handovers +
Successful outgoing internal inter cell handovers) /
(Incoming internal inter cell handovers + Outgoing internalinter cell handovers )
Internal inter cell handover success rate
=(Successful incoming internal inter cell handovers +
Successful outgoing internal inter cell handovers) / (Attempted
incoming internal inter cell handovers + Attempted outgoing
internal inter cell handovers)
Internal inter cell radio handover success rate
>= Internal inter cell handover success rate
Handover
HO Signaling process
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Intra BSC Handover
Intra MSC Handover
Inter MSC Handover
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HO Signaling process
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Intra BSC Handover
Intra MSC Handover Inter MSC Handover
Measurement Points of Inter-BSCH d
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Signaling process between MSC
MSC-BMSC-A VLR-BBSC-A BSC-B
HO-REQUIREDMAP_Prepare_HO
MAP_Prepare_HO_ACK
MAP_Allocate_HO_NUM
MAP_Send_HO_Report
MAP_Send_HO_Report_ACK
MS
HO-REQUEST
HO-REQUEST-ACK
HO-Command
MS
HO-AccessMAP_Process_Access_Signalling
HO-CompleteMAP_Send_End_Signal
Clear-CommandClear-Complete
MAP_Send_End_Signal_ACK
Some intermediate steps are omitted
IAI
ACM
Handover
Measurement Points of Inter-BSCH d
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Signaling process betweenMSC
MSC-BMSC-A VLR-BBSC-A BSC-B
HO-REQUIREDMAP_Prepare_HO
MAP_Prepare_HO_ACK
MAP_Allocate_HO_NUM
MAP_Send_HO_Report
MAP_Send_HO_Report_ACK
MS
HO-REQUEST
HO-REQUEST-ACK
HO-Command
MS
HO-AccessMAP_Process_Access_Signalling
HO-Complete
MAP_Send_End_SignalClear-Command
Clear-Complete
MAP_Send_End_Signal_ACK
Some intermediate steps are omitted
IAI
ACM
Handover
Inter-MSC HO Signaling process
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Signaling process Abnormal conditions The following conditions will cause HO failure
MSC-B fails to identify the target cell.
MSC-B does not allow HO to the indicated target cell.
The target cell has no channel available.
VLR-B has no HO number available.
HO error or unsuitable data.
Inter MSC HOSubsequent HO process
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Roaming
E
MS
MSCa MSCbMSCb'
VLRbVLRb'
BSS2
BSS2'
Radio transmission signal measurementHO REQUIRED (target cell table)
Perform subsequent HO(MAP) (target cell ID, serving cell ID, MSC number)
Perform HO
(target cell ID, serving cell ID, channel type)HO REQUEST (PCM&Channel type)
HO REQUEST ACKNOWLmargin (including New TCH number and HO number)
Allocate HO number
Send HO report(HON)Radio channel ack. (MAP) (includes New TCH number and HON)
IAI
ACM
Subsequent HO ack.
HO COMMAND HO DETECT
HO COMPLETESend end signal (MAP)
ANS
End signal (MAP)Release HO report Release HON
CLEAR COMMAND
CLEAR COMPLETERelease (TUP)
Cut physical connection between MSCa and MSCb
End signal (MAP)
Release (TUP/ISUP)
Release HO report Release HON
Cut physical connection between MSCAa and MSCb'
~~~~
MS
Inter MSC HOSubsequent HO process
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Highway
MSC-AMSC-C
MSC-B MSC-C
Subsequent HO
Inter MSC HO Signaling process
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Statistics countersameas Intra MSC HO,
Statistics is handled by
BSC
HO formula-- same asIntra MSC HO
Basic process of HO Signaling process
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1. There is no HO request information for intra-BSC HO, and all of the
HO are analyzed and processed in BSC. Once the target cell as
required is found in the BSC, Channel activation information is sent
to it directly.
2. When the target cell is not in the same BSC, BSC reports CGI numbers
of the serving cell and target cell, and HO cause to MSC through Ho-
Required. When MSC finds the LAC of the target cell is in the MSC, it
sends Ho-Request to the BSC of the target cell, and the target BSC
activates the target cell channel to complete the following procedure.
3. When MSC finds that the target cell LAC does not belong to the MSC,
it will query its LAI and GCI Table (including LAC and router
address of the adjacent MSC), and send Prepare-HO message to the
target MSC-B according to the router address. The message includes
CGI of the target cell and indication whether or not to allocate HOnumber, etc. According to the message, the target MSC-B sends HO-
Request message to the target BSC-B after demanding HO number
(unless it is not required in the indication) from VLR-B, and sends
Prepare-HO acknowledgement to serving MSC after received HO-
Request acknowledgement, to execute the next procedure.
Intra-BSC HO and Inter-BSC HO
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Major differences: Inter BSC HO transfers HO-REQ message through
MSC, with CGI of the serving cell and target cell carried
in the message.
Intra BSC HO does not have any CGI in any messages,
it is handled inside BSC.
Intra BSC HO only sends HO-Performed to MSC upon
completion of HO, and MSC is not involved before that
time. In inter BSC HO, MSC is involved since the HO request .
Question
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What is the content of PHY INFO? When willthe system send this message to MS?
Why Internal inter cell radio handover
success rate >= Internal inter cell handover
success rate?
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Thank You