Omf010002 Handover Issue1.4
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Transcript of Omf010002 Handover Issue1.4
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OMF010002 Handover
ISSUE1.4
Wireless Training Department
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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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General process of HO Algorithm
M.R.
preprocessing
Penaltyprocessing
Basic ranking
Secondaryranking
HO judgement
TA emergency HO
BQ emergency HO
RSD emergencyHO
Interf. emergency HO
Load Sharing HO
Edge HO
Layer HO
PBGT HO
Processingprogram
OM forced HO
Directed retry
Overlaid/underlaid HO
Fast moving MS
HO
1
1
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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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Measurement Report 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 of
MS
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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 emergency HO( 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 time after anoverlaid/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. This is 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 cell list 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
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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
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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 912345 1
Basic Ranking and Secondary Ranking
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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
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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 are set 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 and each layer can
be further divided into 16 different priorities. So there are 64
different priorities in Huawei hierarchical cell structure.
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Basic ranking and Secondary ranking
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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
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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 11this 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
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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 parameter Co-BSC/MSC Adj.in the HO control table is set
to No,then this function is turned off and the value is 0.
13th bit : Bit value is decided by Co-MSC parameter, having the
same concept as the 12th bit.
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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, bit 13th, 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
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 to 1.
Example : 20+5 = 25 ( -85 dBm )
note :
The layer HO threshold and hierarchical hysteresis correspond to the
value of that individual cellsvalue.
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 the entire
hierarchical layers of the cell.
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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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General HO process
Measurement report preprocessing
Penalty processing
Basic ranking and secondary ranking
HO judgment
HO Algorithm process
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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
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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
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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.
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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.
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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.
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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
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Normal HO
Edge HO Criterion:
In N seconds, when there are P seconds that neighbor cellsDL
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.
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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.
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PBGT HO Criterions :
Target cellspath loss is smaller than the serving cellspath loss
by the PBGT threshold value.
Satisfying the P/N rule.
Target cell should be ranked in front of the serving cell.
Note :
PBGT HO can only occur between same-priority cell. If the
system permits PBGT HO for the cell, PBGT HO can occur ineither inter-BSC or inter-MSC.
PBGT 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 downlink
receive level and TA value.
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?
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Summary of Handover (HO)
HO Algorithm process
HO Data Configuration
HO Signaling process
Course Contents
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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
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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
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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
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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
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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
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Major HO Parameters Configuration
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 whenMeasurement 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
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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
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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
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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
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Major HO Parameters Configuration
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
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Major HO Parameters Configuration
[Penalty Table] -1
Parametername
Meaning Value range Recommendedvalue
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
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Major HO Parameters Configuration
[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
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Major HO Parameters Configuration
[Emergency Handover Table] -1
Parameter
name
Meaning Value range Recommended
value
TA Thrsh. When TAthis value, emergency handover is
triggered
0~63 bit
period
63
DL QUAL.
Thrsh
The downlink receiving quality threshold for BQ
emergency handover. When frequency hopping orDTX is enabled, RQ becomes worse (normal
phenomenon), 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,
corresponding to BQ levels
of 0~7
60
UL QUAL.
Thrsh.
The uplink receiving quality threshold for BQ
emergency HO.
correspondin
g to BQ levels
of 0~7
60
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Major HO Parameters Configuration
[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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Major HO Parameters Configuration
[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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Major HO Parameters Configuration
[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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Major HO Parameters Configuration
[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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Major HO Parameters Configuration
[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
j O C fi i
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Major HO Parameters Configuration
[Normal Handover Table] -1
Parametername
Meaning 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)
M j HO P C fi i
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Major HO Parameters Configuration
[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
M j HO P C fi i
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Major HO Parameters Configuration
[Normal Handover Table] -3
Parametername
Meaning Value range Recommendedvalue
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
M j HO P t C fi ti
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Major HO Parameters Configuration
[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
M j HO P t C fi ti
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Major HO Parameters Configuration
[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
M j HO P t C fi ti
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Major HO Parameters Configuration
[Concentric Cell Handover Table] -1
Parameter
name
Meaning Value range Recommended value
UO signal
intensity
difference
BTS transmitting Power difference between
underlaid and overlaid may cause MS receiving
signal intensity difference in underlaid and overlaid .
The parameter uaually indicates the antenna EIRPdifference 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 to
actual conditions
M j HO P t C fi ti
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Major HO Parameters Configuration
[Concentric Cell Handover Table] -2Parameter
name
Meaning Value range Recommended
value
RX_LEV
Thrsh
Rx level hysteresis, TA threshold and TA hysteresis
jointly define underlaid area and overlaid area. It
must be bigger than edge handover threshold, and
the recommended value is: edge handover
threshold + signal intensity difference betweenunderlaid and overlaid .
0~63 25
RX_LEV
hysteresis
Works with Rx threshold. 0~63 5
TA Thrsh. It must be bigger than TA emergency handover
threshold.
0~63 bit period,
with 1 bit period
corresponding to
0.55km
TA hysteresis Works with TA threshold. 0~63 bit period
Major HO Parameters Configuration
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Major HO Parameters Configuration
[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
M j HO P t C fi ti
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Major HO Parameters Configuration
[Concentric Cell Handover Table] -4Parameter
name
Meaning Value range Recommended
value
Assign
optimum
layer
In 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 first for TCHassignment. (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
Major HO Parameters Configuration
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Major HO Parameters Configuration
[Concentric Cell Handover Table] -5
Parameter
name
Meaning Value
range
Recommended
value
Pref. subcell
in HO of
intra-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
layer
If there is a incoming BSC HO, and the target cell is a
Overlaid/Underlaid, then, this parameter will show which
layer is preferred to provide service for the MS.
overlaid ,
underlaid ,
none
None
HO Parameters Configuration
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HO Parameters Configuration
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, cell number
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 to CGI, 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.
Summary of BSC HO
Course Contents
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Summary of Handover (HO)
HO Algorithm process
HO Data Configuration
HO Signaling process
Course Contents
HO Signaling process
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HO Signaling process
Intra BSC Handover
Intra MSC Handover
Inter MSC Handover
Intra-BSC Handover Signaling process
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Intra BSC Handover Signaling process
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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Intra BSC Handover Signaling process
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 and HO 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 handover
Successful outgoing internal inter cell handovers
(Original) (Target)
Intra BSC Handover Signaling process
Measurement Points of Intra BSC Handover
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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 internal inter 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
HO Signaling process
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HO Signaling process
Intra BSC Handover
Intra MSC Handover
Inter MSC Handover
Intra-MSC HO Signaling process
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MS BTS BTSBSC1 BSC2MSC(original) (Target)
Measurement Report
Measurement ReportHandover Required
Handover Request
Channel_Active
Channel_Active_ACK
Handover_Request_ACKHandover Command
Handover Access
Handover Detect
Handover Complete
Handover Complete
Clear Command (HO Successful)
RF Channel Release
Clear Complete
Attempted outgoing interBSC inter cell handovers
Attempted incoming interBSC inter cell handovers
Successful incoming inter BSC handovers
Successful outgoing interBSC inter cell handovers
Signaling intra MSC
Intra MSC HO Signaling process
HO Signaling process
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O S g g p ocess
Intra BSC Handover
Intra MSC Handover
Inter MSC Handover
Measurement Points of Inter-BSC Handover
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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
Measurement Points of Inter-BSC Handover
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Signalingprocess 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-Complete
MAP_Send_End_SignalClear-Command
Clear-Complete
MAP_Send_End_Signal_ACK
Some intermediate steps are omitted
IAI
ACM
Inter-MSC HO Signaling process
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g g p
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
q p
Inter MSC HOSubsequent HO process
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Highway
MSC-AMSC-C
MSC-B MSC-C
q p
Subsequent HO
Inter MSC HO Signaling process
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g g p
Statistics countersame as
Intra MSC HO, Statistics is
handled by BSC
HO formula-- same as Intra
MSC HO
Basic process of HO Signaling process
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p g g p
1. There is no HOrequestinformation for intra-BSC HO, and all of the HO are analyzedand processed in BSC. Once the target cell as required is found in the BSC, Channel
activationinformation 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-Requestto 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-HOmessage 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 HO
number, 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-REQmessage 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 will the system
send this message to MS?
Why Internal inter cell radio handover success rate >=
Internal inter cell handover success rate?
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