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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.

    16 9101112131415 12345678

    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.

    16 9101112131415 12345678

    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.

    16 9101112131415 12345678

    Basic Ranking and Secondary Ranking

    B i R ki d S d R ki

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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 )

    16 9101112131415 12345678

    Basic Ranking and Secondary Ranking

    B i R ki d S d R ki

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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.

    16 9101112131415 12345678

    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

    16 9101112131415 12345678

    Basic Ranking and Secondary Ranking

    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

    j g

    Major HO Parameters Configuration

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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

    j g

    Major HO Parameters Configuration

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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

    j g

    Major HO Parameters Configuration

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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

    j g

    Major HO Parameters Configuration

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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

    j g

    Major HO Parameters Configuration

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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)

    j g

    Major HO Parameters Configuration

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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

    j g

    Major HO Parameters Configuration

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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

    j g

    Major HO Parameters Configuration

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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

    j g

    Major HO Parameters Configuration

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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

    j g

    Major HO Parameters Configuration

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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

    Major HO Parameters Configuration

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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

    Major HO Parameters Configuration

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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

    Major HO Parameters Configuration

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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