OMF010002 Handover ISSUE2.0

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

OMF010002 Handover

ISSUE 2.0

2 Internal Use

Handover is key technology of Mobile communication system and make continued conversation possible

Handover algorithm in Huawei product

is flexible and powerful

Upon completion this course, you will be

able to:

 Understand the type of handover.

 Master handover judgment flow

 Configure handover data

 Master handover signaling flow

4 Internal Use

Chapter 1 Introduction of Handover Chapter 2 HO Algorithm process Chapter 3 HO Data Configuration Chapter 4 HO Signaling process

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

6 Internal Use

 Emergency HO

 Timing Advance (TA) Emergency HO

 Bad quality (BQ) Emergency HO

Chapter 2 HO Algorithm process

Section 1 General HO process Section 2 Measurement report preprocessing Section 3 Penalty processing

Section 4 Basic ranking and Secondary ranking

Basic ranking

Secondary ranking

Edge HO

Layer HO

PBGT HO

Processing program

OM forced HO Directed retry

Chapter 2 HO Algorithm process

Section 1 General HO process Section 2 Measurement report preprocessing Section 3 Penalty processing

Section 4 Basic ranking and Secondary ranking

12 Internal Use

Measurement Report

 Uplink MR includes uplink receiving level and quality

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

Serving cell Neighbour cell

The downlink measurement report

of the serving cell

The uplink measurement

report of MS The downlink measurement report of the neighbour cell (BCCH)

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.

Chapter 2 HO Algorithm process

Section 1 General HO process Section 2 Measurement report preprocessing Section 3 Penalty processing

Section 4 Basic ranking and Secondary ranking

19 Internal Use

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 ( b ase 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 an overlaid/underlaid HO fails.

HO failure

BSC

Cell A

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

Penalty on the Source Cell

Punish the original serving cell when an emergency HO ( due to BQ and TA) occurs

Back? No way!

Umbrella

penalty on Non-umbrella Layer

 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

attempt again after a failed HO!

Penalty on Overlaid/underlaid Cell

 A new Overlaid/underlaid HO is prohibited within a penalty time after an Ove rlaid/Underlaid HO failure.

Chapter 2 HO Algorithm process

Section 1 General HO process Section 2 Measurement report preprocessing Section 3 Penalty processing

Section 4 Basic ranking and Secondary ranking

25 Internal Use

Procedure of 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

 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))

27 Internal Use

 After the M rule , the serving cell and candidate neighbor cells are ranked

in descending order according to the receiving level only

 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.

K rule Criterion

16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1

 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.

The 4th bit: determined by HO hysteresis

16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1

29 Internal Use

The 5th—10th bit: determined by Layer

 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.

16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1

GSM900 GSM900

GSM1800 GSM1800

GSM900 GSM900 GSM1800 GSM1800

GSM1800

Cell

Hierarchical cell structure

31 Internal Use

 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 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1

The 12th/13th bit: determined by co-BSC/MSC

 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.

16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1

33 Internal Use

The 14th bit: determined by Layer HO

 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 10th—5th 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 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1

The 14th bit: determined by Layer HO

 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 10th—5th 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 valu

e of that individual cell’s value.

 Usual situation : When the neighbor cells are of the same layer, each of th

e neighbor cell’s layer HO threshold value will be the same Same conce

pt goes for the layer HO hysteresis This can maintain the entire hierarchi cal layers of the cell.

35 Internal Use

The 15th bit: determined by Cell Type

 The 15th bit: Bit value is decided by cell type

 Serving cell or Neighbor cells:

 When cell type is extension cell 1.

 When cell type is normal cell 0.

 The 16th bit: Reserved bit

16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1

Chapter 2 HO Algorithm process

Section 1 General HO process Section 2 Measurement report preprocessing Section 3 Penalty processing

Section 4 Basic ranking and Secondary ranking

39 Internal Use

Rx_Level_Drop HO

 Rx_Level_Drop HO

 Due to downlink signal level drop

 Triggered upon detecting rapid level drop during MS busy mod

e

 Requirements for the target cell:

 The target cell is the first cell in the neighbor cell list.

Interference 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

41 Internal Use

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

Edge HO

 Edge HO Criterion:

 In N seconds, when there are P seconds that neighbor cell’s D

L or MS’s UL signal level is lower than the Edge HO threshold Then the criterion is met and Edge HO occurs This method util izes the P/N rule

 Requirements for the target cell:

 The target cell should be ranked in front of the serving 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 cell’s.

PBGT HO

 PBGT HO Criterions :

 Target cell’s path loss is smaller than the serving cell’s 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 can occur in either inter-BSC or inter-MSC

45 Internal Use

Fast-Moving HO

 When the serving cell is micro cell :

 When the MS has traveled through P numbers of cell, and there are Q (=<P) numbers of cell that the MS has traveled in high speed, the criteria is satisfied MS will be handed over to umbrella cell.

 When the serving cell is umbrella cell :

 When the MS is traveling high speed in umbrella cell, a greater penalty can be given to the micro cell for a duration of time (penalty time) In this way, the MS will not use the micro cell Note :In this case, the micro cell is only used under urgency conditions( Poor TA and BQ ).

Overlaid/Underlaid Cell

Assume, 6TRX in one cell, one CDU and one SCU are adopted

Where can we configure BCCH CH? CDU or SCU?

SCU

Antenna Antenna

TRX TRX TRX TRX TRX TRX

47 Internal Use

Overlaid/Underlaid Cell

 Purpose

 Maximize coverage area

 Reduce interference and improve frequency reuse density

 Construct method

 Different combiner loss

 Decrease the power of TRX

 By HO parameter, it is called IUO

 Classify

 Normal Underlaid/Overlaid

 IUO: Enhance Underlaid/Overlaid

How to Allocate SDCCH/TCH?

 SDCCH

 SDCCH are always allocated in Underlaid

 Layer is allocated according the transmission delay of access burst

51 Internal Use

 Criterion for HO from overlaid to underlaid:

 TA value => TA threshold + TA hysteresis OR RX_LEV <= RX_LEV threshold － RX_LEV hysteresis OR Qua =>Qua threshold

 Satisfying P/N rule

 Criterion for HO from underlaid to overlaid:

 TA value =< TA threshold － TA hysteresis AND RX_LEV >=RX_LEV threshold + RX_LEV hysteresis AND Qua =<Qua threshold

 Satisfying P/N rule

Normal Overlaid/Underlaid HO

 Criterion for HO from overlaid to underlaid:

 TA value => TA threshold + TA hysteresis OR RX_LEV <= O to U level OR

Qua =>Qua threshold

 Satisfying P/N rule

 Criterion for HO from underlaid to overlaid:

 TA value =< TA threshold － TA hysteresis AND RX_LEV >= U to O level AND

Qua =<Qua Threshold

 If the box “U to O HO traffic threshold” is checked, just in the co ndition that underlaid load is more than this threshold, U to O ha ndover based on previous conditions can be triggered

Enhance Overlaid/Underlaid HO

53 Internal Use

Chapter 1 Introduction of Handover Chapter 2 HO Algorithm process Chapter 3 HO Data Configuration

Chapter 4 HO Signaling process

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

55 Internal Use

Parameter

Value range

Recommend value

Co BSC/MSC

Adj

It means whether the 12 and 13 bits acts in the 16bit order

“Yes” means handover in the same BSC/MSC is preferred

“No” means that the 12 and 13 bits are shielded and set to”0

or bad quality The penalty measures can apply to cells in or

out of the same BSC

on of the service in respective cells, and lower the cell congestion rate , and improve network performance It on ly applies

in the same BSC or cells at the same level

is not used To apply the handover algorithm, BSC must have original measurement report.

meanwhile it is only triggered on TCH

when intra BSC handover occurs

Handover Control Table

57 Internal Use

Parameter

Recommended value

MR

reprocessing

“Yes” means perform measurement reportpreprocessing on BTS “No” means preprocessing on BSC, then the two parameters of “Send original measurement 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 determines where to perform power control When it is set to

“Yes”, power control is performed at BTS side When

it is set to “No”, power control is performed at BSCside When setting this parameter, first be clearwhether BTS supports the power control algorithm to

set or not

Handover Control Table