09-WCDMA Handover Principle.ppt

Huawei Confidential. All Rights Reserved

WCDMA Handover Principle and Analysis

ISSUE 1.0

2Internal Use

Why mobile systems need handover?

It is decided by the characters of mobile system:

The mobility of UE The mobile system is composed by c

ells which the coverage ability is limited.

Providing the continuous service in mobile system is the basic element in QoS.

3Internal Use

ObjectObject

Upon completion this course, you will be able to:

The basic definitions of Handover The algorithms of handover

decision The handover flow The parameters of handover

4Internal Use

Chapter 1 Chapter 1 Introduction of HandoverIntroduction of Handover

Chapter 2 Measurement of Handover

Chapter 3 The Basic Handovers

Chapter 4 Blind Handover and

Direct Retry Algorithm

5Internal Use

The Purpose of HandoverThe Purpose of Handover

Providing the continuous service in mobile system is the basic element in QoS.

The load balance: sharing the resource

The hierarchy divided by speed and service: high efficiency of using resource

6Internal Use

The Basic Concepts of HandoverThe Basic Concepts of Handover

Active Set Monitored Set Detected set Event reporting

Event reporting to Periodic reporting Periodic reporting Radio Link (RL) Radio Link Set (RLS) Combination way:

maximum ratio combination selection combination

The soft handover gain CPICH Soft handover, softer handover, hard handover Blind handover

7Internal Use

The Categories of HandoverThe Categories of Handover According to the signaling characters:

Soft handover (softer handover) Hard handover

According to the properties of source cell and target cell Intra-frequency handover Inter-frequency handover Inter-mode handover (FDD <-> TDD) Inter-system handover (UMTS <-> GSM/CDMA2000)

According to the purpose of handover Based on Coverage Based on Load (Optional) Based on mobility of UE (Optional) Based on Service (Optional)

8Internal Use

The Characters of Different HandoversThe Characters of Different Handovers

Item Soft Handover Hard HandoverThe numbers of RL in active set after handover

Several One

Interruption during handover

No Yes

The frequencies of cells

Only happened in Intra-frequency cells

Can be happened in Intra-frequency cells or Inter-frequency cells

Comparison between soft handover and hard handover:

9Internal Use

The Characters of Different HandoversThe Characters of Different Handovers

During softer handover, the uplink signaling are combined in NodeB by maximum ratio combination, but during soft handover they are combined in RNC by selection combination.

Compare to later one, the maximum ration combination can get more gain. So the performance of maximum ration combination is better.

Since softer handover is completed in NodeB, it do not consume transport resource of Iub.

Comparison between soft handover and softer handover:

10Internal Use

RNC

NodeB 2NodeB 1

Soft HandoverSoft Handover

11Internal Use

RNC (WFMR)

NodeB

Softer HandoverSofter Handover

12Internal Use

Hard HandoverHard Handover

13Internal Use

Three Steps of HandoverThree Steps of Handover

Decision

Execute

Measurement

Measurement Measurement control Measurement execution and

the result processing The measurement report Mainly accomplished by UE

Decision Based on Measurement The application and

distribution of resource Mainly accomplished by

RRM in RNC Execution

The process of signaling Support the failure drawback Measurement control refresh

14Internal Use

QuestionsQuestions

The differences among Soft handover, softer handover and hard handover

Typical application scenarios

15Internal Use

SummarySummary

This chapter focus on the purpose of handovers and the categories of handover in WCDMA.

16Internal Use

Chapter 1 Introduction of Handover

Chapter 2Chapter 2 Measurement of HandoverMeasurement of Handover




17Internal Use

Chapter 2 Chapter 2 Measurement of HandoverMeasurement of Handover

Section 1 Measurement control and

measurement report

Section 2 The basic definitions of measurement

Section 3 Intra-frequency measurement event

Section 4 Inter-frequency and

inter-system measurement event

Section 5 UE internal measurement

18Internal Use

Measurement Control and Measurement Measurement Control and Measurement ReportReport

Measurement Control ：

UE UTRAN

MEASUREMENT CONTROL

Measurement Control, normal case

19Internal Use

Measurement Control and Measurement Measurement Control and Measurement ReportReport

Measurement report ：UE UTRAN

MEASUREMENT REPORT

Measurement report, normal case

20Internal Use



measurement report

Section 2 The basic concepts of measurement

Section 3 Intra-frequency measurement event


inter-system measurement event

Section 5 UE Internal Measurement

21Internal Use

The Basic Concepts of MeasurementThe Basic Concepts of Measurement

The measurement values of Handover Intra-frequency and inter-frequency: CPICH RSCP 、 CPICH Ec/

N0 、 Path loss Inter-frequency ： CPICH RSCP 、 CPICH Ec/N0 Inter-system ： GSM Carrier RSSI ， BSIC Identification ， BSI

C Reconfirmation The reporting methods of measurement

Periodic reporting Event reporting

The events of reporting Intra-frequency events ： 1A,1B,1C,1D,1E,1F Inter-frequency events ： 2D,2F,2B,2C Inter-system events ： 3A,3C Others ： 6G,6F

22Internal Use

Measurement ModelMeasurement Model

Layer 1filtering

Layer 3filtering Evaluation

of reportingcriteria

A DB C

C'

parameters parameters

23Internal Use

Reporting CriterionReporting Criterion

Reporting Criterion Decision formula: for example, 1A event : 1.Path Loss

2.Other measurement ：

Relative threshold, Absolute threshold, Hysteresis, Time to trigger

),2/(10)1(1010 11

aBest

N

iiNew HRLogMWMLogWLogM

A

),2/(10)1(1010 11

aBest

N

iiNew HRLogMWMLogWLogM

A

24Internal Use

Key ParametersKey Parameters

25Internal Use



measurement report


Section 3 Intra-frequency measurement events


inter-system measurement events


26Internal Use

Intra-frequency Measurement EventsIntra-frequency Measurement Events

All intra-frequency measurement report events are identified with 1X : 1A ， A primary pilot channel enters the reporting range. When th

e active set of UE is full, UE stops reporting 1A event; 1B ， A primary pilot channel leaves the reporting range; 1C ， The primary pilot channel in a non active set is better than t

he primary pilot channel in an active set; 1D ， The best cell changes; 1E ， The measurement value of a primary pilot channel exceeds

the absolute threshold 1F, The measurement value of a primary pilot channel is lower th

an the absolute threshold

27Internal Use



measurement report






28Internal Use

Inter-frequency Measurement EventsInter-frequency Measurement Events

Inter-frequency measurement events are identified with 2X 2A: The best frequency changes; 2B: The estimated quality value of the used frequency is lower than

a certain threshold, and that of the non-used frequency is higher than a certain threshold;

2C: The estimated quality value of the non-used frequency is higher than a certain threshold;

2DThe estimated quality value of the used frequency is lower than a certain threshold

2E:The estimated quality value of the non-used frequency is lower than a certain threshold

2F:The estimated quality value of the used frequency is higher than a certain threshold

29Internal Use

Inter-system Measurement EventsInter-system Measurement Events

Inter-system measurement events are identified with 3X 3A:The estimated quality value of the used UTRAN frequency

is lower than a certain threshold, and that of the other system is higher than a certain threshold;

3B: The estimated quality value of the other system is lower than a certain threshold ;

3C: The estimated quality value of the other system is higher than a certain threshold ;

3D: The best cell in the other system changes

30Internal Use



measurement report






31Internal Use

UE Internal MeasurementUE Internal Measurement

UE Internal measurement events are identified with 6X 6G: The time difference between downlink receiving and upli

nk transmission of the UE is shorter than an absolute threshold;

6F: The time difference between downlink receiving and uplink transmission of the UE is bigger than an absolute threshold;

32Internal Use

QuestionsQuestions

How many events are there in intra-frequency measurement? What are they?

How many events are there in UE internal measurement? How many events are there in inter-frequency measurement?

What are they?

33Internal Use

SummarySummary

This chapter covers intra-frequency measurement, inter-frequency measurement, inter-system measurement and UE internal measurement from their definitions and application scenarios.

SummarySummary

34Internal Use



Chapter 3Chapter 3 The Basic HandoversThe Basic Handovers



35Internal Use

Chapter 3 The Basic HandoversChapter 3 The Basic HandoversSection 1 Soft HandoverSection 2 Intra-frequency Hard HandoverSection 3 Inter-frequency Hard HandoverSection 4 Inter-system Hard HandoverSection 5 HSDPA HandoverSection 6 Compressed Mode

36Internal Use

Brief Introduction of Soft HandoverBrief Introduction of Soft Handover

Characters of Soft Handover During handover, UE has several RLs with different cells----activ

e set. The handover among different cells which are in same RLS can

be softer handover. Soft handover:

– Selection combination in uplink– Maximum combination in downlink

Softer handover– Maximum combination in uplink and downlink

37Internal Use

Brief Introduction of Soft HandoverBrief Introduction of Soft Handover Advantages

Soft handover gain: Multi-Cell gain: Multiple irrelated soft handover branches low the required

margin for fading Macro Diversity Combining gain: Gain for the link demodulation of the

soft handover: Load balance: Different cells receive the signals from UE in uplink, which

can decrease the transmission power of UE. And UE receive signal from different cells, which also can decrease the transmission power of base station.

Decrease the possibility of call drop caused by ping-pong handover. Disadvantages

More resource needed in downlink, especially for the code resource of BE service.

Usually, the gain of downlink power is negative. When the downlink power from different cells is not balanced, it will bring

side-effect.

38Internal Use

Measurement of Soft Handover Measurement of Soft Handover The measurement of soft handover/softer handover

Measurement value ： CPICH RSCP 、 CPICH Ec/No 、 Pathloss

Process of Measurement ： Layer 1 filter, Layer 2 filter Reporting way


– Event type ： 1A 、 1B 、 1C 、 1D 、 1F– UE measures the time difference between CFN and SFN– Reporting rules: trigger condition, Relative threshold, Abs

olute threshold, Hysteresis, Time to trigger– Event reporting to periodic reporting

39Internal Use

The Events of Soft Handover MeasurementThe Events of Soft Handover Measurement Soft/softer handover measurement events

Intra-frequency events reporting: 1A ， A primary pilot channel enters the reporting range. Whe

n the active set of UE is full, UE stops reporting 1A event; 1B ， A primary pilot channel leaves the reporting range; 1C ， The primary pilot channel in a non active set is better th

an the primary pilot channel in an active set; 1D ， The best cell changes; 1E ， The measurement value of a primary pilot channel exce

eds the absolute threshold 1F, The measurement value of a primary pilot channel is lowe

r than the absolute threshold

40Internal Use

The Decision Algorithm of Soft HandoverThe Decision Algorithm of Soft Handover

Soft/softer handover decision 1A ， add RL into active set ； 1B ， Delete RL from active set ； 1C ， replace cell ； 1D ， change best cell

41Internal Use

The Execution of Soft HandoverThe Execution of Soft Handover

Soft handover execution The update principal of measurement control

Configure the neighbor cells and the parameters according to best cell

RLC mode AM mode is used for measurement control UM mode is used for measurement reporting

The compensation and restriction of soft handover From event reporting to periodic reporting

– Parameters ： the time value for periodic reporting, the number for reporting times

42Internal Use

Soft Handover Flow (add RL)Soft Handover Flow (add RL)

The execution of soft handover (add RL)

43Internal Use

Soft Handover Flow (del RL)Soft Handover Flow (del RL)

The execution of soft handover (del RL)

44Internal Use


Relative threshold Set 1A, 1B value separately 1A < 1B ， which makes deleting RL is more difficult, and it can a

void ping-pong handover Usually 1A: 3dB; 1B: 6dB

Time to trigger Each event can be set separately Usually, 1B>1A ， which makes deleting RL is more difficult, and

it can avoid ping-pong handover Usually, 1A: 320ms, 1B: 640ms

Layer 3 filter coefficient Only one value for all intra-frequency measurement Sensitive to the delay of event trigger and ping-pong handover Usually ： 3

absolute threshold of soft handover

45Internal Use


46Internal Use

The Characters of Intra-frequency Hard HandoverThe Characters of Intra-frequency Hard Handover Characters

UE only has one RL with one cell in the process of handover Disconnect UE with the original cell, then hand it over to target ce

ll The working frequency of source cell and target cell are same

Advantages Enhance the using efficiency of the OVSF code and hardware re

source Disadvantages

High call drop possibility because of the intra-frequency interference

Application scenarios Without Iur interface between two RNCs or the Iur interface jam

(only happened in inter-RNC handover) The different strategies can be used for different conditions, such

as code resource condition, the QoS condition and so no.

47Internal Use

The Measurement, Decision and Execution of The Measurement, Decision and Execution of Intra-frequency Hard HandoverIntra-frequency Hard Handover

Measurement Similar to soft handover

Decision 1D event

Execution UE reports CFN-SFN information

Synchronization hard handover Use the original DOFF value Continuous CFN

UE does not report CFN-SFN information The hard handover based on timing Re-configure DOFF Calculate CFN according to DOFF

48Internal Use

Intra-frequency Hard Handover FlowIntra-frequency Hard Handover Flow

Intra-frequency hard handover flowUE

1.RADIO LINK SETUP REQUEST

Target NODEB

Source NODEB SRNC

2. RADIO LINK SETUP RESPONSE

3.ALCAP establish

4. PHYSICAL CHANNEL RECONFIGURATION

5. RADIO LINK FAILURE INDICATION

6. PHYSICAL CHANNEL RECONFIGURATION COMPLETE

7. RADIO LINK DELETION REQUEST

8. RADIO LINK DELETION RESPONSE

9.ALCAP release

49Internal Use


Handover decision threshold based on BE speed UE should do soft handover when the speed of BE service is less

than the threshold. UE should do intra-frequency hard handover when the speed of

BE service is greater than the threshold. The parameters about 1D event:

time to trigger ， hysteresis The parameters should be set accord with the Qos

50Internal Use


51Internal Use

The Brief Introduction of Inter-frequency The Brief Introduction of Inter-frequency Hard HandoverHard Handover

Characters The working frequency is different after handover The compressed mode needed if the UE only has one receiver Usually, the timing re-initiation hard handover is used for hard

handover Advantages

Compare to intra-frequency hard handover, the success possibility is higher

The load balance among cells with different frequencies Can realize the reasonable configuration for hierarchy cells

Disadvantages Compressed mode results in extra radio resource occupied The timing re-initiation hard handover increase the time of

handover and the risk of call drop Application scenarios

Disconnected coverage Handover based on load Hierarchy cells

52Internal Use

The Inter-frequency Hard Handover Measurement The Inter-frequency Hard Handover Measurement Values and EventsValues and Events

The Inter-frequency hard handover measurement values Measurement values:

CPICH RSCP 、 CPICH Ec/N0 Different handover purpose for different measurement type:

In the edge of carrier coverage: CPICH RSCP In the center of carrier coverage: CPICH Ec/No

53Internal Use

The Measurement Values and Events of Inter-The Measurement Values and Events of Inter-frequency Hard Handover frequency Hard Handover

Measurement reporting Periodic reporting Event reporting

2A: The best frequency changes;2B: The estimated quality value of the used frequency is lowe

r than a certain threshold, and that of the non-used frequency is higher than a certain threshold;

2C: The estimated quality value of the non-used frequency is higher than a certain threshold;

2DThe estimated quality value of the used frequency is lower than a certain threshold

2E:The estimated quality value of the non-used frequency is lower than a certain threshold

2F:The estimated quality value of the used frequency is higher than a certain threshold 。

54Internal Use

Compressed Mode ICompressed Mode Initiatnitiation in Inter-frequency ion in Inter-frequency Hard HandoverHard Handover

Conditions for measurement initiated 2D event ： can be used to enable the compressed mod

e to perform inter-frequency measurement. Enable inter-frequency measurement by moving speed e

stimation algorithm Conditions for Measurement stopping

2F event After the best cell is changed, the cell does not contain int

er-frequency neighbor cells. Inter-frequency measurement timer expired Because the moving speed of UE is changed, the inter-fre

quency handover measurement is stopped by cell hierarchy algorithm.

55Internal Use

Cells Hierarchy Algorithm Based on UE Cells Hierarchy Algorithm Based on UE Moving SpeedMoving Speed

When UE is in one of the hierarchy cells, the moving speed estimation algorithm is initiated Handover events in a while decides whether the speed of UE sati

sfies the current cell hierarchy condition UE is remained in the current cell if the speed is medium. If the speed is very high, it will be handed over to higher hiera

rchy cell. And if not, hand it over to lower hierarchy cell. UE’s moving speed decided the result.

If the hierarchy is configured by different frequencies, the inter-frequency blind handover or inter-frequency measurement handover can be initiated.

If the hierarchy is configured by one frequency, the intra-frequency handover can be initiated.

56Internal Use

Inter-frequency Hard Handover Decision Inter-frequency Hard Handover Decision AlgorithmAlgorithm

The inter-frequency hard handover decision The coverage triggers the handover

2B event ：– the quality in the used frequency is lower than absolute th

reshold, but the quality in another non-used frequency is higher than another absolute threshold.

The load triggers handover 2C event ：

– the quality in another frequency is higher than an absolute threshold

57Internal Use

The Execution of Inter-frequency Hard HandoverThe Execution of Inter-frequency Hard Handover The execution of Inter-frequency hard handover

UE report the timing information UE with two receivers does not need compressed mode. Synchronization hard handover Using the original DOFF Continued CFN

UE does not report timing information UE with a single receiver has to initiate compressed mode If the NodeB of target cell is not the same one which the cells

in active set belong to– the timing re-initiation hard handover– Re-configure DOFF– Calculate the CFN according to DOFF

If the NodeB of target cell is the same one which the cells in active set belong to

– Calculate the target cell timing relationship– Synchronization hard handover– Using the original DOFF– Continued CFN

58Internal Use

Inter-frequency Hard Handover FlowInter-frequency Hard Handover Flow

Signaling flow

UE

1.RADIO LINK SETUP REQUEST

Target NODEB

Source NODEB SRNC

2. RADIO LINK SETUP RESPONSE

3.ALCAP established

4. PHYSICAL CHANNEL RECONFIGURATION

5. RADIO LINK FAILURE INDICATION

6. PHYSICAL CHANNEL RECONFIGURATION COMPLETE

7. RADIO LINK DELETION REQUEST

8. RADIO LINK DELETION RESPONSE

9.ALCAP released

59Internal Use

Key Parameters (I)Key Parameters (I) Inter-frequency coverage handover parameters:

Inter-frequency measurement reporting: periodic reporting or event reporting

Inter-frequency measurement values: CPICH Ec/No or CPICH RSCP

Inter-frequency measurement layer 3 filter coefficient, delay trigger time and hysteresis

Inter-frequency initiated and stopped threshold: Considering the different demands of CPICH Ec/No and CPICH RSCP for PS domain and CS domain, the different 2D and 2F parameters are configured.

Inter-frequency handover based on coverage: the quality threshold of target cell

Using frequency quality threshold in inter-frequency hard handover

The minimum access threshold for inter-frequency handover

60Internal Use

Key Parameters (II)Key Parameters (II)

Inter-frequency handover parameters caused by non-coverage ability Inter-frequency measurement layer 3 filter coefficient, delay trigger

time and hysteresis Inter-frequency handover based on non-coverage ability

61Internal Use


62Internal Use

The Brief Introduction of Inter-system Hard The Brief Introduction of Inter-system Hard HandoverHandover

Application scenarios WCDMA FDD < － >GSM WCDMA FDD < － >WCDMA TDD WCDMA FDD < － >CDMA2000

Characters Different radio access technology is used after handover Usually, compressed mode should be used to help the mea

surement Advantages

For coverage, it can solve the problems from one system to another system

For capacity, it can enhance the utilizing efficiency of old equipments(2G->3G)

Disadvantages The flow is complicated, and it demands higher compatibilit

y for equipments Demands more complicated UE

63Internal Use

The Measurement for Inter-systemThe Measurement for Inter-system ：：Compressed Mode InitiatedCompressed Mode Initiated

The inter-system measurement (GSM measurement) Measurement type:

GSM Carrier RSSI BSIC Identification BSIC Reconfirmation

The process of measurement: layer 1 filter, layer 3 filter Measurement reporting

Event reporting– 2D Event: initiate GSM measurement– 2F Event: stop GSM measurement

64Internal Use

The Inter-system Hard Handover The Inter-system Hard Handover Decision AlgorithmDecision Algorithm

The inter-system hard handover decision Inter-system handover caused by coverage

Event reporting:– 3A event ： The estimated quality value of the used UTR

AN frequency is lower than a certain threshold, and that of the other system is higher than a certain threshold .

Periodic reporting:– Evaluation ： According to the periodic reported GSM R

SSI measurement value and the BSIC confirming state of target cell of GSM system, and meanwhile the UE evaluates the GSM RSSI of target cell is greater than the absolute threshold, then consider the cell confirmed by BSIC.

65Internal Use

The Inter-system Hard Handover The Inter-system Hard Handover Decision AlgorithmDecision Algorithm

The inter-system hard handover decision Inter-system handover caused by non-coverage

Event reporting– 3C event: The estimated quality value of the other system

is higher than a absolute threshold.

66Internal Use

Inter-system Handover FlowInter-system Handover Flow

The execution of inter-system handover

1. Relocation Required 2. Prepare

Handover 3. Handover Request

4. Handover Request Ack

12. Iu Release Command

13. Iu Release Complete 14. Send End

Signal Response

5. Prepare Handover Response

6. Relocation Command

7. DCCH : Handover from UTRAN Command

8. Handover Detect

9. Handover Complete

10. Handover Complete 11. Send

End Signal

Request

UE Node B SRNC CN MSC BSC

67Internal Use

Key Parameters (I)Key Parameters (I) Inter-system handover caused by coverage parameters

Inter-system measurement initiated and stopped threshold: Considering the different demands of CPICH Ec/No and CPICH RSCP for PS domain and CS domain, the different 2D and 2F parameters are configured

Inter-system measurement values (2D, 2F) CPICH Ec/No CPICH RSCP

BSIC confirmed (Optional) Inter-system handover caused by coverage parameters

configure the GSM RSSI threshold of CS domain and PS domain separately

Using inter-system frequency quality handover threshold Configure the delay trigger time, hysteresis for each event

68Internal Use

Key parameters (II)Key parameters (II)

Inter-system handover caused by non-coverage parameters The period of inter-system measurement report The decision threshold for inter-system handover: configure the

CS, PS, signaling separately Time delay trigger : configure BSIC with acknowledged and

unacknowledged mode Inter-frequency measurement layer 3 filter coefficient and

hysteresis Penalty time

69Internal Use


70Internal Use

The Brief Introduction HSDPA HandoverThe Brief Introduction HSDPA Handover

Application Scope Related to the handover between the HS-DSCH channel

of HSDPA The service cell update of HSDPA HSDPA< － >DCH

Purpose the service which data rate satisfied the threshold of HS

DPA should use the HSDPA resource. To realize the maximum traffic volume, the service cell with HS-DSCH should be the best cell in the active set.

71Internal Use

HSDPA MeasurementHSDPA Measurement

HSDPA handover measurement Measurement type: CPICH RSCP 、 CPICH Ec/N0 、 Pat

h loss The process of measurement: layer 1 filter coefficient and

layer 3 filter coefficient Measurement reporting


– Reporting type: 1A, 1B, 1C, 1D– The event reporting converted to periodic reportin

g

72Internal Use

Service Cell Change AlgorithmService Cell Change Algorithm

Change the service cell for HS-PDSCH in active set According to 1D event to decide the best cell, and hand it over

to the cell. After handover, initiate the timer to forbid the ping-pong

handover Change the service cell for HS-PDSCH after hard handover

Establish the HSDPA channel in target cell with hard handover Establish DCH channel if the target cell can not support HSDPA

Change the service cell for HS-PDSCH during soft handover The service should be handed over to the cell which support

HSDPA when the best cell does not support HSDPA and the original service cell for HSDPA already deleted from active set.

73Internal Use

Direct Retry for HSDPADirect Retry for HSDPA

Direct retry from R99 cell to R5 cell Conditions

UE in cell 1 requests to establish an BE/streaming RAB, or UE of Cell-FACH state has much BE/streaming data

volume to transfer (Switch channel type from FACH to HS-DSCH)

Existing cells: support HSDPA, with same coverage area Advantage: To make full use of HSDPA resource

Direct retry HSDPA resource

R5CELL ACarrier B

R99CELL2 R99 CELL 1Carrier A

74Internal Use

Service Cell Update FlowService Cell Update Flow

75Internal Use


HSDPA handover protecting timer Configure the T-HSDPA to avoid the influence for the data servic

e caused by the ping-pong handover. During this period, the service cell for HSDPA can not be changed.

The value scope ( 0… 1024) seconds

76Internal Use


77Internal Use

The Purpose of Compressed modeThe Purpose of Compressed mode

Purpose ： Measure the inter-frequency cell or inter-system cell under

FDD mode Cause:

Downlink compressed: Since one receiver only can work in one frequency, the U

E has to stop working if it is going to measure the signal from another frequency cell. To ensure the downlink service unaffected, the remained data should be sent in the limited time.

Uplink compressed UE should stop the uplink transmission when the uplink w

orking frequency is very close to the measured frequency, for example GSM 1800/1900 is very close to the UMTS FDD uplink working frequency.

78Internal Use

Compressed Mode Sketch MapCompressed Mode Sketch Map

Compressed mode sketch map

One frame(10 ms) Transmission gap available for

inter-frequency measurements

79Internal Use

The realization Methods of Compressed modeThe realization Methods of Compressed mode Realization Methods

SF/2 Should use the replace scrambling code Advantage: easy to handle for RNC Disadvantage: occupied the resource of NodeB, decrease the

utilizing efficiency of OVSF, influenced the coverage and increased interference caused by the replace scrambling code.

rate matching/puncturing Decrease the coding redundancy Advantage: easy to handle for RNC; the SF 4 can be used; no

influence to utilizing efficiency of OVSF Disadvantage: limited to the property of channel coding;

decreased the coding gain higher layer scheduling

MAC can restrict TFCS to change the downlink data rate. Advantage: the interference is lower Disadvantage: complicated for higher layer, only fit for non-

timing data service.

80Internal Use

QuestionsQuestions

What are the differences between soft handover and softer handover?

What is compressed mode? Draw out the hard handover signaling flow.

81Internal Use

SummarySummary

This chapter focus on the basic handovers in WCDMA: soft handover, softer handover, intra-frequency hard handover, inter-frequency hard handover and inter-system hard handover. It also introduced the application scenarios for these different handovers

Meanwhile, compressed mode is introduced in this chapter

82Internal Use




Chapter 4Chapter 4 Blind Handover andBlind Handover and

Direct Retry AlgorithmDirect Retry Algorithm

83Internal Use

Application scenarios and Trigger ConditionsApplication scenarios and Trigger Conditions RRC direct retry

During the initial signaling establishment, the RRC connection is refused.

RRC redirection The initial signaling is already established, but the requested cell

refused and RRC direct retry is failed. RAB direct retry

The signaling is established successfully, but the service establishment is failed.

Blind handover Load balanced between inter-frequency cells RRC direct retry RAB direct retry

84Internal Use

RRC Direct Retry (I)RRC Direct Retry (I)

Application scenarios (I) Same sector covered by different frequencies

cell1

cell21 2

3

The UE initial camping cell

Signaling process:1 RRC CONNECTION REQUEST2 RRC CONNECTION SETUP3 RRC CONNETION SETUP COMPLETE

85Internal Use

RRC Direct Retry (II)RRC Direct Retry (II)

Application scenarios (II) The soft handover area

cell1 cell2

1

23

UE camping cell1 first

Soft handover area

Signaling Process:1 RRC CONNECTION REQUEST2 RRC CONNECTION SETUP3 RRC CONNETION SETUP COMPLETE

86Internal Use

RRC Retry Key ParametersRRC Retry Key Parameters

DRMaxNumber The maximum allowed retry times for the direct retry module a

fter the initial failure CsThreshold.

When the signal quality of a cell is higher than this threshold, this cell will be included in the direct retry candidate set.

MinSignalRequired The basic access threshold described in Section 2.2.8, namel

y the minimum requirement of the UE form the receiving CPICH Ec/No density during normal demodulation.

MaxRelatingTime The maximum time that the RACH measurement report can c

ontinue to be used for the direct retry candidate set.

87Internal Use

RRC RedirectionRRC Redirection

Application scenarios The signaling connection is failed, and RRC retry is also failed.

Inter-freq cell

cell1

1

2

1’

UE camping cell1 first

GSM cell

1’’Signaling process:1 RRC CONNECTION REQUEST2 RRC CONNECTION REJECT1’ UE initial the access process after cell re-selection1’’ UE initial the access process in GSM cell after inter-system cell reselection

88Internal Use

RRC Direct Retry and Direction RRC Direct Retry and Direction

The trigger condition should be the signaling permitting failure if congestion happed, the RRC connection signaling is refused.

Advantages and disadvantages: RRC direct retry can ensure the time delay. RRC direction is more flexible, and can select to GSM cell. But

the time delay is longer.

89Internal Use

RAB Direct RetryRAB Direct Retry

Application scenarios

UTRAN CELL

GSM CELL

1 3

4

Signaling process：1 RAB Assignment (from CN)2 SRNS relocation (to CN)3 Handover from UTRAN ( Inform UE access to GSM system)4 Handover Complete (GSM message)

2

CN

90Internal Use

QuestionsQuestions

What is the difference of RRC direct retry and RRC redirection?

What are the trigger conditions for RRC direct retry and RRC direction?

91Internal Use

SummarySummary

This chapter focus on RRC direct retry, RRC redirection, the application scenarios of RAB direct retry and blind handover.

Huawei Confidential. All Rights Reserved

Documents

09-WCDMA Handover Principle.ppt