Huawei - Handover

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Handover

Huawei Wireless Training Department

Contents

Summary

of Handover(HO) Flow

HO Algorithm

HOHO

Data ConfigurationSignaling Flow

Summary of HOPurpose

of HO of HO

Classification

Summary of HOPurpose of HO

Purpose of HOTo To

keep moving MS continuous communication improve network service performance

To reduce the call drop rate To reduce the congestion rate

Summary of HOClassification of HOClassification of HO: according to different HO triggering conditions1.Emergency HO TA Emergency HO Bad quality(BQ) Emergency HO Rapid signal drop(RSD) Emergency HO Interference Emergency HO

2.Load HO 3.Normal HO

Margin HO Hierarchical HO PBGT HO 4.Speed-sensitive HO (Fast moving HO) 5.Over-layer/under-layer HO

HO Algorithm Flow

HO Algorithm Flow

General HO flowMeasurement Penalty Basic HO

report preprocessing

processing

sequencing of cells and adjustment of network characteristics judgement

General Flow of HO AlgorithmM .. R p os r re e s p cOr d M H fc O o e MH a O r g i n

pl ey n a t p sg re os ci n

Drr i ct rt y e e Hc l O ir h H e ia ac r T en O Ar c e gy m H e

Bs e g a en s qc i c ui nB en O Qr c e gy m H e

PH B O G T Fm H ao O s v t ig n

Ate f dm js n u t o no er t k w ca its hts a ec r ri c

Rm c S en Dr y eg e H O I e m cO n. en tf re gy r eH

O y n- e vaur y e e da r r e r - / l l H O Cn a tl lcr lo o pr r a om g

Hgn Oe t jd e um

LH o O a d

HO Algorithm Flow

HO algorithm flowGeneral

HO flow

Measurement report preprocessingPenalty Basic HO

processing

sequencing of cells and adjustment of network characteristics judgment

Measurement Report Preprocessing

Serving cellThe downlink measurement report of the serving cell The uplink measurement report of MS

Neighbour cell

The downlink measurement report of the neighbour cell (BCCH)

M oc p i a e e Rn a n en a e- io pe t s p l t tu r p u r -n t k n r e t I gh s o m eM n )ur le r d t ( Rw - ds mr : e u a m t t ne t h er e ae d sp o ur we l i n n k t m r o m Us p e pa e i l ee o i mr n n r od k e ta :e r b t u i h n t m t s fT il i ek iee r o cltica x oe l n p g ( v m g un g R B n c l el U S ed r s L fr , tvde i n L h as e s nh v v ) e un l i l e an i u a ne n r s y f, T denL S w tica Ra r helt x e i gU un l p g ( lM . l v a ) k i qQ B i o S rd _ p o D e r o MB e omr ira o c wu ta S Td na e n n Ss l ee b i n r p e d ,n k e i : s od it a t h n t o s n m t s m f s e d n i t l u t n g ( e ov u h en xe en e ca L ws y del D delt ove v n g ws Lh ca l ii v ) i n gR k r i nl l e a l ii a ni dk g t n r i nl q i ( a rl ove nl De , ws f e l L st n gsg Re e ent h x Qn l ca h c lh h el o o ) f v d i i v iu oc i r i t g n gr b e k l r i nl e e l e r s ( x Se e A N d a en C Ml T (c e l vpl l) _ R o aa ) L e , a esde nr w iv t , s m . w t h c a e T ,

Measurement Report Preprocessing

Measurement Report PreprocessingPeriod of measurement reportThe measurement report is sent to BTS in SACCH uplink 1.The interval is 470ms/per time when MS is on SDCCH 2.The interval is 480ms/time when MS is on TCH

480ms

4 TCH multi-frames

12TCH

1SACCH

12TCH

1 idle

Measurement Report Preprocessing

Missing MR processingEvery time BSC receives a measurement report, there will be an update to the basic sequencing of cells. As BTS may fail to receive the measurement report from MS, so before the sequencing updating, BSC needs to recover the missing measurement report according to Filter Data Table. If the missing MR amount is within the

allowed range, then recover the missing MRs accordingto the algorithm.

Measurement Report Preprocessing

How to recover a MR?

Co ou ns t i nM uR f l o w

M R

M R

M R

M RM R

Me em a n s t u r e r ro e . p n o t N

M eo e mr a n t s tp u r r e e N o .4 n +

Measurement Report Preprocessing

How to filter the measurement report?

Continuous MR flow

MR

MR

MR

MR

MR

MR

Filter----Average several continuous MR.

Flow of HO Algorithm

General HO flow Measurement report preprocessing

Penalty processing

Basic sequencing of cells and

adjustment of network characteristics

HO judgment

Penalty Processing

There are altogether four types of penalty processing1. Penalty on the target cell when a HO fails. 2. Penalty on the original serving cell when an emergency HO is performed. 3. Penalty on the other non-layer4 cells after a fast moving HO is performed 4. A second HO is prohibited within the penalty time after a overlayer/under-layer HO fails.

Penalty Processing1. Penalty on the target cell:Punish the target cell where a HO fails to avoid MS to select this cell again in another HO judgment and fail again.

Cell A

BTS

HO failure BSC

Cell D BSC gives corresponding signal level penalty on cell D

Penalty Processing2. Penalty on the serving cell:Punish the original serving cell after TA\BQ\interf. HO, to avoid it to be handed over to the original cell again and cause ping-pang HO.

Cell A

BTS

BQ HO BSC

Cell DIn cases of HO from cell A to cell D due to poor quality, punishing the original serving cell (cell A)

Penalty Processing3. Give penalty to all non-layer4 neighbor cells after MS is handed over to a layer4 cell(Umbrella cell) by fast moving HO, to keep MS staying in the umbrella cell and avoid frequent HO.

Back? No way!

Umbrella

Macro cell

Micro cell

Penalty Processing4. A second over-layer/under-layer HO is prohibited within the penalty time after an over-layer/under-layer HO fails

Under-layer Over-layer

No second attempt after a failed HO!

HO Algorithm FlowGeneral

HO flowreport preprocessing

Measurement Penalty

processing

Basic sequencing of cells and adjustmentof network characteristicsHO

judgment

Basic Sequencing of Cells and Adjustment of Network CharacteristicsBasic sequencing of cells and adjustment of network characteristics are major parts of the HO judgment. Sequencing is made by 16bits

algorithm. The serving cell and the candidate neighbor cells will belisted in a cell list according to their 16bits value. The sequencing process includes:

M ruleK rule 16bits sequencing

Basic Sequencing of Cells and Adjustment of Network CharacteristicsI. M judgment:According to the min downlink receiving level and the min receiving level offset of the reported neighbor cell, judge whether the cell is qualified as a candidate neighbor cell to be put into the cell list for handover.

M rule: only the cells with receiving signal level satisfy the following conditions can be put into the candidate cell list. For serving cell: RXLEV (o) >MSRXMIN(o) + MAX(0,Pa(o)) For neighbour cell: RXLEV(n) > MSRXMIN(n)+ MAX(0,Pa(n)) + OFFSET

Basic Sequencing of Cells and Adjustment of Network Characteristics

II. K rule:The cells surviving from M rule, including the serving cells and candidate neighbor cells, are sequenced according to their receiving signal level which is actually a part of 16bits

rule.

Basic Sequencing of Cells and Adjustment of Network CharacteristicsIII. 16bits rule Both the serving cell and the neighbor cell have their own 16bits value. The smaller the value is, the higher the priority and the position is in

the cell list.

16 15 14 13 12 11 10 9 8

7 6 5 4 3 2 1

The 1st-3rd bits: bit value is decided according to the cell signal level. The value result of 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.

Basic Sequencing of Cells and Adjustment of Network Characteristics

16 15 14 13 12 11 10 9 8

7 6 5 4 3 2 1

The 4th bit: bit value is decided by inter-cell HO hysteresis. The 4th bit of the serving cell is always 0, The receiving level of the neighbor cell > The receiving level of the serving cell + Inter-cell HO hysteresis, set to 0. The receiving level of the neighbor cell < The receiving level of the serving cell + Inter-cell HO hysteresis, set to 1. Note: In PBGT HO, if inter-cell hysteresis is larger than PBGT threshold, then inter-cell hysteresis will replace PBGT threshold.

Basic Sequencing of Cells and Adjustment of Network Characteristics

16 15 14 13 12 11 10 9 8

7 6 5 4 3 2 1

The 5th-10th bits: bit value is decided according to their position in Huawei hierarchical network structure. When the signal level of the neighbor cell or the serving cell is lower than the hierarchical HO threshold(hysteresis), shield it and set all bits to 0). Huawei network 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 network.

Basic Sequencing of Cells and Adjustment of Network CharacteristicsHierarchical network structureUmbrella Cell GSM900 Cell GSM 900

GSM 900

GSM 900

GSM 900

GSM1800 Cell

GSM1800

GSM1800

GSM1800

Micro Cell

GSM900 GSM1800

GSM900 GSM1800

GSM900 GSM1800

GSM900 GSM1800

Basic Sequencing of Cells and Adjustment of Network Characteristics

16 15 14 13 12 11 10 9 8

7 6 5 4 3 2 1

The 11th bit: bit value is decided by cell load Serving cell: if Load>= Start thr