Wcdma Handover Algorithm and Parameters(FILEminimizer) (1)

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Leong kwong Onn

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2011-08 Update

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WCDMA Handover Algorithm and Parameters



Foreword

Why mobile system need handover?

The mobility of UE

Load Balance

Any others?





References

3GPP TS 23.122: Non Access Stratum functions related to Mobile

Station (MS) in idle mode

3GPP TS 24.008: Mobile radio interface layer 3 specification; Core

Network Protocols - Stage 3

3GPP TS 25.304: UE Procedures in Idle Mode and Procedures for Cell

Reselection in Connected Mode

3GPP TS 25.331: RRC Protocol Specification

3GPP TS 23.060: General Packet Radio Service (GPRS); Service

description

3GPP TS 25.931: UTRAN Functions, Examples on Signalling

Procedures



Objectives

Upon completion of this course, you will be able to:

Explain the features of each handover

Describe the procedures of each handover

Perform the parameters setting of each handover



The Basic Concepts of Handover

Active set

Monitored set

Detected set

Radio link (RL)

Radio link set (RLS)

Maximum ratio

combination

Selective combination

Soft handover gain

PCPICH



Contents

1. Intra-Frequency Handover

2. Inter-Frequency Handover

3. Inter-RAT Handover



Contents


1. Intra-Frequency Handover Overview

2. Intra-Frequency Handover Measurement

3. Intra-Frequency Handover Decision and Execution

4. Signaling Procedures for Intra-Frequency Handover



Intra-Frequency Handover Types

The carrier frequencies of the current cell and target cell are

the same:

Intra-frequency soft handover

Intra-frequency hard handover



Intra-Frequency Handover Types (Cont.)

Item Soft Handover Hard Handover

The number of RLs in

active set during

handover

Several One

Interruption during

handoverNo Yes

The frequencies of cells

Only happened

between Intra-

frequency cells

Can be happened in Intra-

frequency cells or Inter-

frequency cells

Comparison between soft handover and hard handover:



Intra-Frequency Soft Handover

The types of intra-frequency soft handover are as follows:

Intra-NodeB soft handover (also known as softer handover)

Intra-RNC inter-NodeB soft handover

Inter-RNC soft handover



Intra-Frequency Soft Handover (cont.)

Item Softer Handover Soft Handover

Scenario

When the UE is in the overlapped

coverage area of two

neighboring cells of a NodeB

with combined RLs

When the UE is in the

overlapped coverage area of

two neighboring cells of

different NodeBs

Uplink signal Using maximum-ratio

combination Using selection combination

Downlink

signal

Using maximum-ratio

combination

Using maximum-ratio

combination

Resource use Occupying less Iub bandwidth Occupying more Iub bandwidth

Comparison between soft handover and softer handover:



Intra-Frequency Hard Handover

Intra-frequency hard handover:

No Iur interface

Iur interface is congested

Soft handover fails



Contents








Intra-Frequency Handover Procedure

Decision

Execution

Measurement



Contents




1. Intra-Frequency Handover Measurement Quantities

2. Intra-Frequency Handover Measurement Events

3. Intra-Frequency Handover Neighboring Cell Combination

Algorithm





Intra-Frequency Handover Measurement Measurement control:

UE UTRAN

MEASUREMENT CONTROL



Intra-Frequency Handover Measurement (Cont.) Measurement report:

UE UTRAN

MEASUREMENT REPORT



Intra-Frequency Handover Measurement Quantities

nnn MFF 1)1(

Measurement model in the WCDMA system:

L3 filtering formula:



Parameters of Intra-Frequency Measurement IntraFreqMeasQuantity

Parameter name: Intra-freq Measure Quantity

Recommended value: CPICH_EC/NO

FilterCoef

Parameter name: Intra-freq meas L3 filter coeff

Recommended value: D3, namely K=3



Contents







Algorithm





Intra-Frequency Handover Measurement Events

Event Description

1AA primary CPICH enters the reporting range. This indicates that the quality of a cell is close to the quality of the best cell in the active set. A relatively high combined gain can be achieved when the cell is added to the active set.

1BA primary CPICH leaves the reporting range. This indicates that a cell has a lower quality than the best cell in the active set. The cell has to be deleted from the active set.

1C

A non-active primary CPICH becomes better than an active primary CPICH. This indicates that the quality of a cell is better than the quality of the worst cell in the active set. The RNC replaces a cell in the active set with a cell in the monitored set.

1D The best cell changes.



Intra-Frequency Handover Measurement Events (Cont.)

)2/()1()( 111

aaBest

N

iiNewNew HRMWMWCIOM

A

1A event

Event 1A is triggered on the basis of the following formula:




A: signal quality curve of the best cell in the active set

B: signal quality curve of a cell in the monitored set

C: curve of Th1A



Parameters of Intra-Frequency Handover (Cont.) CIO

Parameter name: Cell oriented Cell Individual Offset

Recommended value: 0, namely 0dB

CIOOffset

Parameter name: Neighboring cell oriented CIO




Parameters of Intra-Frequency Handover (Cont.) IntraRelThdFor1ACSNVP

Parameter name: CS non VP service 1A event relative THD


IntraRelThdFor1ACSVP

Parameter name: VP service 1A event relative THD


IntraRelThdFor1APS

Parameter name: PS service 1A event relative threshold




Parameters of Intra-Frequency Handover (Cont.) Hystfor1A

Parameter name: 1A hysteresis


TrigTime1A

Parameter name: 1A event trigger delay time

Recommended value: D320, namely 320ms

Weight

Parameter name: Weighted factor

Recommended value: 0



Intra-Frequency Handover Measurement Events (Cont.) 1A event report mode:

Event trigger report

Event to periodical report



Parameters of Intra-Frequency Handover (Cont.) ReportIntervalfor1A

Parameter name: 1A event to periodical rpt period


PeriodMRReportNumfor1A

Parameter name: 1A event to periodical rpt number

Recommended value: D16




)2/()1()( 111

bbBest

N

iiOldOld HRMWMWCIOM

A

1B event

Event 1B is triggered on the basis of the following formula:





B: signal quality curve of the worst cell in the active set

C: curve of Th1B



Parameters of Intra-Frequency Handover (Cont.) IntraRelThdFor1BCSNVP

Parameter name: CS non VP service 1B event relative THD


IntraRelThdFor1BCSVP

Parameter name: VP service 1B event relative THD


IntraRelThdFor1BPS

Parameter name: PS service 1B event relative threshold




Parameters of Intra-Frequency Handover (Cont.) Hystfor1B

Parameter name: 1B hysteresis


TrigTime1B

Parameter name: 1B event trigger delay time





2/1cInASInASNewNew HCIOMCIOM

1C event

Event 1C is triggered on the basis of the following formula:





B: signal quality curve of a cell in the active set

C: signal quality curve of the worst cell in the active set

D: signal quality curve of a cell in the monitored set

E: curve of Th1C



Parameters of Intra-Frequency Handover (Cont.) Hystfor1C

Parameter name: 1C hysteresis


TrigTime1C

Parameter name: 1C event trigger delay time




Intra-Frequency Handover Measurement Events (Cont.) 1C event report mode:

Event trigger report

Event to periodical report



Parameters of Intra-Frequency Handover (Cont.) ReportIntervalfor1C

Parameter name: 1C event to periodical rpt period


PeriodMRReportNumfor1C

Parameter name: 1C event to periodical rpt number





2/1dBestBestNotBestNotBest HCIOMCIOM

1D event

Event 1D is triggered on the basis of the following formula:





B: signal quality curve of a cell in the active set or the monitored set

C: curve of Th1D



Parameters of Intra-Frequency Handover (Cont.) Hystfor1D

Parameter name: 1D hysteresis


TrigTime1D

Parameter name: 1D event trigger delay time




Contents







Algorithm





Neighboring Cell Combination Algorithm

Cell A Cell B Cell C

Cell A Cell B Cell C A B C

Firstly, the cells inthe active set areadded.

Secondly, theneighboring cellsof cell A areadded.

After that, theneighboring cellsof cell B areadded.

Finally, theneighboring cellsof cell C areadded.

Cell A, Cell B and Cell Care in active set. Cell A isthe best cell. Cell BEc/No is greater thanCell C.





Parameters of Neighboring Cell Combination Algorithm HO_MC_NCELL_COMBINE_SWITCH

Parameter name: Neighboring Cell Combination Switch

Recommended value: ON

NprioFlag

Parameter name: The flag of the priority

Recommended value: FALSE

Nprio

Parameter name: the priority of the neighboring cell

Recommended value: None



Contents








Intra-Frequency Handover Decision and Execution The intra-frequency handover decision and execution

procedure depends on the different measurement events

that the RNC receives:

1A Event

1B Event

1C Event

1D Event





Parameters of Intra-Frequency Handover (Cont.) MaxCellInActiveSet

Parameter name: Max number of cell in active set


SHOQualmin

Parameter name: Min quality THD for SHO

Recommended value: -24, namely -24dB



Rate Reduction After an SHO Failure

If the radio link addition for a soft handover fails, the rate

reduction is triggered for R99 NRT (Non Real Time) services to

increase the probability of a successful soft handover

1A,1C,1D is received by RNC

Execute admission control in target cell

Admission succeed?

Execute Handover

Rate Reduction

Estimation

Execution

Yes

No



Estimation Procedure for Rate Reduction





Parameters of Intra-Frequency Handover (Cont.) RelThdForDwnGrd

Parameter name: Relative threshold of SHO failure


ShoFailPeriod

Parameter name: Max evaluation period of SHO failure

Recommended value: 60, namely 60s

ShoFailNumForDwnGrd

Parameter name: Threshold number of SHO failure




Procedure of Rate Reduction Execution



Parameters of Intra-Frequency Handover (Cont.) DcccShoPenaltyTime

Parameter name: Period of penalty timer for SHO failure

after down rate




Contents








Typical Soft Handover Flow (L3 Signaling)

Soft handover is triggered by 1A/1B/1C or 1D event



Intra-Frequency Hard Handover

Intra-Frequency hard handover is triggered by 1D event



Contents






Contents


1. Inter-Frequency Handover Overview

2. Inter-Frequency Handover Measurement

3. Inter-Frequency Handover Decision and Execution

4. Signaling Procedures for Inter-Frequency Handover



Inter-Frequency Handover Types

The carrier frequency of the current cell and target cell

are different

Based on the triggering causes of handover, inter-

frequency handover can be categorized into four types:

Coverage-based inter-frequency handover

QoS-based inter-frequency handover

Load-based inter-frequency handover



Contents




1. Inter-Frequency Handover Measurement Switches

2. Inter-Frequency Handover Measurement Report Modes

3. Inter-Frequency Handover Measurement Events

4. Inter-Frequency Handover Measurement Quantity

5. Inter-Frequency Handover Compressed Mode





Inter-Frequency Handover Measurement In the measurement phase of inter-frequency handover,

the UE takes measurement according to the

MEASUREMENT CONTROL message received from the

RNC. When the measurement report conditions are met,

the UE sends measurement reports to the RNC according

to the rules defined in the MEASUREMENT CONTROL

message.



Inter-Frequency Handover Measurement Switches Switches related to inter-frequency handover:

HO_MC_SIGNAL_SWITCH: The switch decides when the RNC

performs the active set signal quality measurement.

HO_INTER_FREQ_HARD_HO_SWITCH: The switch decides

whether to enable the inter-frequency handover

measurement



Contents













Inter-Frequency Handover Measurement Report Modes Event-triggered measurement report mode

UE test the Inter-frequency neighbor RSCP and Ec/No

Periodical measurement report mode

UE test the Inter-frequency neighbor RSCP and Ec/No, and

current cell Ec/No or RSCP

InterFreqReportMode

Parameter name: Inter-frequency measure report mode

Recommended value: Periodical reporting



Inter-Frequency Handover Measurement Report Modes PrdReportInterval

Parameter name: Inter-frequency measure periodical rpt

period


InterFreqMeasTime

Parameter name: Inter-freq measure timer length




Contents













Inter-Frequency Handover Measurement Events Measurement events involved in inter-frequency

handover Event Description

2D The estimated quality of the currently used frequency is below a certain threshold.

2F The estimated quality of the currently used frequency is above a certain threshold.

2B The estimated quality of the currently used frequency is below a certain threshold and the estimated quality of a non-used frequency is above a certain threshold.



Inter-Frequency Handover Measurement Events - 2D 2D event:

The estimated quality of the currently used frequency is

below a certain threshold.


QUsed ≤ TUsed2d - H2d/2



Parameters of Inter-Frequency Handover -2D

Parameter Recommended Value

InterFreqCSThd2DEcN0 -14, namely -14dB

InterFreqR99PsThd2DEc

N0

-14, namely -14dB

InterFreqHThd2DEcN0 -14, namely -14dB

InterFreqCSThd2DRSCP -95, namely -95dBm

InterFreqR99PsThd2DRS

CP

-95, namely -95dBm

InterFreqHThd2DRSCP -95, namely -95dBm

Recommended values of TUsed2d :



Parameters of Inter-Frequency Handover -2D


InterFreqCSThd2DEcN0 -14, namely -14dB

InterFreqR99PsThd2DEc

N0

-14, namely -14dB

InterFreqHThd2DEcN0 -14, namely -14dB

InterFreqCSThd2DRSCP -95, namely -95dBm

InterFreqR99PsThd2DRS

CP

-95, namely -95dBm

InterFreqHThd2DRSCP -95, namely -95dBm




Parameters of Inter-Frequency Handover - 2D (Cont.) HystFor2D

Parameter name: 2D hysteresis


TimeToTrig2D

Parameter name: 2D event trigger delay time




Inter-Frequency Handover Measurement Events - 2F 2F event


above a certain threshold.

Event 2F is triggered on the basis of the following formula:

QUsed ≥ TUsed2f + H2f/2



Parameters of Inter-Frequency Handover -2F


InterFreqCSThd2FEcN0 -12, namely -12dB

InterFreqR99PsThd2FEcN

0

-12, namely -12dB

InterFreqHThd2FEcN0 -12, namely -12dB

InterFreqCSThd2FRSCP -92, namely -92dBm

InterFreqR99PsThd2FRSC

P

-92, namely -92dBm

InterFreqHThd2FRSCP -92, namely -92dBm

Recommended values of TUsed2f :



Parameters of Inter-Frequency Handover -2F


InterFreqCSThd2FEcN0 -12, namely -12dB

InterFreqR99PsThd2FEcN

0

-12, namely -12dB

InterFreqHThd2FEcN0 -12, namely -12dB

InterFreqCSThd2FRSCP -92, namely -92dBm

InterFreqR99PsThd2FRSC

P

-92, namely -92dBm

InterFreqHThd2FRSCP -92, namely -92dBm

Recommended values of TUsed2f :



Parameters of Inter-Frequency Handover - 2F (Cont.) HystFor2F

Parameter name: 2F hysteresis


TimeToTrig2F

Parameter name: 2F event trigger delay time




Inter-Frequency Handover Measurement Events - 2B 2B event:


below a certain threshold and the estimated quality of a

non-used frequency is above a certain threshold


QNoused ≥ TNoused2b + H2b/2

QUsed ≤ TUsed2b - H2b/2



Inter-Frequency Handover Measurement Events - 2B 2B event:


below a certain threshold and the estimated quality of a

non-used frequency is above a certain threshold


QNoused ≥ TNoused2b + H2b/2

QUsed ≤ TUsed2b - H2b/2



Parameters of Inter-Frequency Handover - 2B Recommended values of TNoused2b :


TargetFreqCsThdEcN0 -12, namely -12dB

TargetFreqR99PsThdEcN

0

-12, namely -12dB

TargetFreqHThdEcN0 -12, namely -12dB

TargetFreqCsThdRscp -92, namely -92dBm

TargetFreqR99PsThdRscp -92, namely -92dBm

TargetFreqHThdRscp -92, namely -92dBm



Parameters of Inter-Frequency Handover - 2B Recommended values of TNoused2b :


TargetFreqCsThdEcN0 -12, namely -12dB

TargetFreqR99PsThdEcN

0

-12, namely -12dB

TargetFreqHThdEcN0 -12, namely -12dB

TargetFreqCsThdRscp -92, namely -92dBm

TargetFreqR99PsThdRscp -92, namely -92dBm

TargetFreqHThdRscp -92, namely -92dBm



Parameters of Inter-Frequency Handover - 2B (conj.) Recommended values of TUsed2b :


UsedFreqCSThdEcN0 -12, namely -12dB

UsedFreqR99PsThdEcN0 -12, namely -12dB

UsedFreqHThdEcN0 -12, namely -12dB

UsedFreqCSThdRSCP -92, namely -92dBm

UsedFreqR99PsThdRSCP -92, namely -92dBm

UsedFreqHThdRSCP -92, namely -92dBm



Parameters of Inter-Frequency Handover - 2B (conj.) Recommended values of TUsed2b :










Parameters of Inter-Frequency Handover -2B (Cont.) HystFor2B

Parameter name: 2B hysteresis


TimeToTrig2B

Parameter name: 2B event trigger delay time




Parameters of Inter-Frequency Handover - Common CIO



CIOOffset





Parameters of Inter-Frequency Handover - Common (Cont.) HystForPrdInterFreq

Parameter name: HHO hysteresis


TimeToTrigForPrdInterFreq

Parameter name: HHO period trigger delay time

Recommended value: 0, namely 0ms



Contents













Inter-Frequency Handover Measurement Quantity

Measurement quantities vary according to the types of inter-frequency

handover

In inter-frequency handover based on coverage, event (2B/2D/2F) or

periodical measurement takes both CPICH Ec/No and RSCP as measurement

quantities

In inter-frequency handover based on QoS, event (2B) or periodical

measurement takes both CPICH Ec/No and RSCP as measurement quantities.

In load-based inter-frequency blind handover, CPICH RSCP of the used

frequency is measured.

In load- and measure-based inter-frequency handover, both CPICH_RSCP and

CPICH_Ec/No of the target frequency are measured



Contents













Inter-Frequency Handover Compressed Mode Compressed Mode control is a mechanism whereby

certain idle periods are created in radio frames during

which the UE can perform measurements on other

frequencies.

If the UE needs to measure the pilot signal strength of an

inter-frequency 3G or 2G cell and has a single-frequency

receiver only, the UE must use the compressed mode.



Inter-Frequency Handover Compressed Mode The parameter DlSFLimitCMInd decides whether to start the DL

compressed mode according to the parameter LimitCMDlSFThd

If DlSFLimitCMInd = True

When the downlink spreading factor is smaller than or equal to the

parameter LimitCMDlSFThd, the compressed mode is disabled

When the downlink spreading factor is greater than the parameter

LimitCMDlSFThd, the compressed mode is enabled

If DlSFLimitCMInd = False and the compressed mode is not limited



Inter-Frequency Handover Compressed Mode DlSFLimitCMInd

Parameter name: Dl SF limit CM ind

Recommended value: FALSE

LimitCMDlSFThd

Parameter name: Dl SF threshold to limit CM

Recommended value: D8 , namely SF8



Inter-Frequency Handover Compressed Mode Categories

Downlink compressed mode

Uplink compressed mode

Realization Methods

Spreading factor reduction (SF/2)

Higher layer scheduling



Inter-Frequency Handover Compressed Mode DlSFTurnPoint

Parameter name: Dl SF threshold


UlSFTurnPoint

Parameter name: Ul SF threshold




Contents





1. Coverage- and QoS-based Inter-Frequency Handover Decision and

Execution

2. Load-based Inter-Frequency Handover Decision and Execution




Coverage- and QoS-based Inter-

Frequency Handover Procedure



Reporting Mode

The coverage- and QoS-based inter-frequency handovers

are categorized into two types according to the following

two measurement report modes:


Event-triggered measurement report mode.

Each mode corresponds to a different decision and

execution procedure.



Periodical Measurement Report Mode

After receiving the periodical measurement report of the

inter-frequency cell, the RNC starts the following

decision procedures:

Decide whether both the CPICH Ec/No value and CPICH RSCP

value of the pilot signal of the target cell meet the requirement of

inter-frequency handover. The evaluation formula is : Mother_Freq +

CIOother_Freq ≥ Tother_Freq + H/2

Start the hard handover time-to-trigger timer, which is configured

through the parameter TimeToTrigForPrdInterFreq

If Mother_Freq + CIOother_Freq < Tother_Freq - H/2, stop the

timer

Select the cells in sequence, that is, from high quality cells to low

quality ones, to initiate inter-frequency handover




Periodical measurement report mode:



Event-Triggered Measurement Report Mode After receiving the event 2B measurement reports of

CPICH RSCP and CPICH Ec/No of the inter-frequency cell,

the RNC starts the following procedure:

Add all the pilot cells that trigger event 2B to a cell set and

arrange the cells according to the measurement quality of

CPICH_Ec/No in descending order

Select the cells in turn from the cell set to perform inter-

frequency handover



Contents





1. Coverage- and QoS-based Inter-Frequency Handover Decision and

Execution

2. Load-based Inter-Frequency Handover Decision and Execution




Load-based Inter-Frequency Handover

The LDR algorithm may trigger an inter-frequency

handover.

The inter-frequency LDR handover can be performed

based on blind handover or measurement that can be

decided by the parameter

InterFreqLDHOMethodSelection

InterFreqLDHOMethodSelection

Parameter name: InterFreq Load Handover Method

Selection

Recommended value: BLINDHOPage102



Load-based Inter-Frequency Blind Handover



Load-based Inter-Frequency Blind Handover Decision The LDR algorithm learns that a cell is in basic congestion

and provides target cells and the UE with low priority for

handover.

The RNC determines to trigger an inter-frequency blind

handover.



Load-based Inter-Frequency Blind Handover Decision If the UE is not in soft handover state, the RNC directly

performs load-based inter-frequency blind handover.

If the UE is in soft handover state, the RNC operates based on

the following conditions:

If the HO_ALGO_LDR_ALLOW_SHO_SWITCH is set to ON, the RNC

determines whether the cell that triggers LDR is the best cell:

If this cell is the best cell, the RNC initiates an intra-frequency

measurement for load-based inter-frequency blind handover. If this cell is

not the best cell, the RNC does not initiate a load-based inter-frequency

blind handover.

If the HO_ALGO_LDR_ALLOW_SHO_SWITCH is set to OFF, the RNC

does not initiate a load-based inter-frequency blind handover.



Load-based Inter-Frequency Blind Handover Execution 1. The RNC initializes the timer of intra-frequency measurement for

blind handover.

2. The RNC initiates a periodical intra-frequency measurement.

3. After receiving from the UE the intra-frequency measurement

reports for conditional blind handover, the RNC checks whether the

following condition is met:

CPICH RSCP of the cell in the measurement report >=

BlindHOQualityCondition

If the condition is met, the RNC increments the counter of the number of

intra-frequency measurement reports for blind handover by 1.

If the condition is not met, the RNC does not perform a blind handover to

the cell that triggers LDR and stops intra-frequency measurement for blind

handover.



Load-based Inter-Frequency Blind Handover Execution 4. When the counter reaches the value of

BlindHOIntrafreqMRAmount, the RNC initiates a blind

handover to the target cell.

5. If the timer of intra-frequency measurement for blind

handover expires, the RNC does not perform a blind

handover to the target cell and stops intra-frequency

handover measurement for blind handover.



Parameters of Load-based Inter-Frequency Blind Handover BlindHOFlag

Parameter name: Blind handover flag

Recommended value: False

HO_ALGO_LDR_ALLOW_SHO_SWITCH

Parameter name: HandOver switch




Parameters of Load-based Inter-Frequency Blind Handover (Cont.) BlindHOIntrafreqMRInterval

Parameter name: Intrafrequency measurement report

interval of blind HO


BlindHOQualityCondition

Parameter name: Blind handover condition

Recommended value: -92, namely -92dBm



Parameters of Load-based Inter-Frequency Blind Handover (Cont.) BlindHOIntrafreqMRAmount

Parameter name: Intrafrequency measurement report

amount of blind handover

Recommended value: D2, namely 2 times



Load-based Inter-Frequency Measure-based Handover

Page111



Load-based Inter-Frequency Measure-based Handover Decision and Execution The LDR algorithm learns that a cell is in basic congestion

and provides target cells and the UE with low priority for

handover.

The RNC selects the target cell based on the

measurement results. The report period is specified by

the parameter PrdReportInterval.



Load-based Inter-Frequency Measure-based Handover Decision and Execution The target cell must meet the following conditions:

The CPICH RSCP value of the target cell is larger than

TargetFreqThdRscp.

The CPICH Ec/No value of the target cell is larger than

TargetFreqThdEcN0

The target cell is not in the basic congestion state.

The RNC performs an inter-frequency hard handover to

the target cell directly.

Page113



Parameters of Load-based Inter-Frequency Measure-based Handover DrdOrLdrFlag

Parameter name: DrdOrLdrFlag

Recommended value: FALSE(Do not send)

PRDREPORTINTERVAL

Parameter name: Inter-freq Measure Periodical Report Period


TARGETFREQTHDRSCP

Parameter name: Inter-freq Target Frequency Trigger RSCP THD

Recommended value: -92, namely -92dBm

TARGETFREQTHDECN0

Parameter name: Inter-freq Target Frequency Trigger Ec/No THD

Recommended value: -12, namely -12dB



Contents








Inter-frequency Handover



Contents






Contents


1. Inter-RAT Handover Overview

2. 3G-to-2G Handover Measurement

3. 3G-to-2G Handover Decision and Execution

4. Signaling Procedures for Inter-RAT Handover



Inter-RAT Handover Scenarios



Inter-RAT Handover Types

Based on the triggering causes of handover, inter-

frequency handover can be categorized into five types:

Coverage-based 3G to 2G handover

QoS-based 3G to 2G handover

Load-based 3G to 2G handover

Service-based 3G to 2G handover



3G-to-2G Handover Preconditions

Before handover, the RNC checks whether all the preconditions

for the 3G-to-2G handover are met:

Service handover indicators

Service requirements

Handover rules

Before deciding the 3G-to-2G handover, the RNC checks

whether all the preconditions are met :

2G cell capability

Service capability

UE capability



Service Handover Indicator

The IE Service Handover Indicator indicates the CN policy

for the service handover to the 2G network. It is

indicated in the RAB assignment signaling assigned by

the CN, or provided by the RNC

The algorithm switch HoSwitch:

HO_INTER_RAT_RNC_SERVICE_HO_SWITCH decides

whether the service attribute of inter-RAT handover is

based on the RNC or the CN




Through the SHIND parameter, the service handover indicators

are set in RNC as follows:

HO_TO_GSM_SHOULD_BE_PERFORM: means that the handover to

the 2G network is performed when 2G signals are available.

HO_TO_GSM_SHOULD_NOT_BE_PERFORM: means that the

handover to the 2G network is performed when 3G signals are

weak but 2G signals are strong.

HO_TO_GSM_SHALL_NOT_BE_PERFORM: means that the handover

to the 2G network is not performed even when 3G signals are

weak but 2G signals are strong.



Rules for Enabling 3G-to-2G Handover

Rules for enabling Coverage- and QoS-based 3G-to-2G

handover:

Service Handover Indicator:

HO_TO_GSM_SHOULD_BE_PERFORM

HO_TO_GSM_SHOULD_NOT_BE_PERFORM

Impacts of different types of capability on handover

decision:

Refer to the following table




Rules for enabling Load-based 3G-to-2G handover: :



HO_TO_GSM_SHOULD_NOT_BE_PERFORM


decision:





Rules for enabling Service-based 3G-to-2G handover: :




decision:


Switches for Service-based 3G-to-2G Handover



2G Cell Capability

2G cell capability is configured through the parameter

RATCELLTYPE. This parameter indicates whether the cell

supports the GSM, GPRS, or EDGE.

RATCELLTYPE

Parameter name: Inter-RAT cell type




Service Capability

The Required 2G Capability (Req2GCap) specifies the

capability of 2G cells required by inter-RAT handover.

This indicates whether the service is supported by the

GSM, GPRS, or EDGE

Req2GCap

Parameter name: Required 2G Capability




UE Capability

Upon the reception of the UE capability information

message, the RNC decides whether to start the inter-RAT

measurement. The information indicates whether the UE

supports the GSM, GPRS, or EDGE.



Inter-RAT Handover Rules (Cont.)

Rules for service-based 3G to 2G Handover



Three types of capability:

Refer to the table of load-based handover

Service switch



Contents




1. 3G-to-2G Handover Measurement Switches

2. 3G-to-2G Handover Measurement Report Modes

3. 3G-to-2G Handover Measurement Events

4. 3G-to-2G Handover Measurement Quantity

5. 3G-to-2G Handover Compressed Mode





3G-to-2G Handover Measurement Switches The 3G-to-2G handover measurement switches are specified by

the sub-parameters of HoSwitch:

HO_MC_SIGNAL_SWITCH: The switch decides whether the quality

measurement on the active set is delivered after signaling setup

but before service setup.

HO_INTER_RAT_PS_OUT_SWITCH: The switch decides whether the

RNC will initiate inter-RAT measurement to trigger inter-RAT

handover of the PS domain from the UTRAN.

HO_INTER_RAT_CS_OUT_SWITCH: The switch decides whether the

RNC will initiate inter-RAT measurement to trigger inter-RAT

handover of the CS domain from the UTRAN.



Contents













3G-to-2G Handover Measurement Report Modes Event-triggered measurement report mode

UE test the 2G neighbor RSSI


UE test the 2G neighbor RSSI, and current cell Ec/No or

RSCP

InterRatReportMode

Parameter name: Inter-RAT report mode

Recommended value: PERIODICAL_REPORTING



3G-to-2G Handover Measurement Report Modes InterRATPeriodReportInterval

Parameter name: Inter-RAT period report interval [ms]

Recommended value: D1000 , namely 1000ms

InterRATMeasTime

Parameter name: Inter-RAT measure timer length [s]




Contents













3G-to-2G Handover Measurement Events Measurement events involved in 3G-to-2G Handover

Event Description

Event 2D The estimated quality of the currently used frequency is below a certain threshold.

Event 2F The estimated quality of the currently used frequency is above a certain threshold.

Event 3A The estimated quality of the currently used UTRAN frequency is below a certain threshold and the estimated quality of the other system is above a certain threshold.

Event 3C The estimated quality of other system is above a certain threshold.



3G-to-2G Handover Measurement Events - 2D 2D event:


below a certain threshold.


QUsed ≤ TUsed2d - H2d/2



Parameters of 3G-to-2G Handover - 2D



InterRATCSThd2DEcN0 -14, namely -14dB

InterRATR99PsThd2DEcN0 -15, namely -15dB

InterRATHThd2DEcN0 -15, namely-15dB

InterRATCSThd2DRSCP -100, namely -100dBm

InterRATR99PsThd2DRSCP -110, namely -110dBm

InterRATHThd2DRSCP -110, namely -110dBm

HystFor2D 4, namely 2dB

TimeToTrig2D D320, namely 320ms



3G-to-2G Handover Measurement Events – 2F 2F event:

Event 2F is triggered on the basis of the following formula:

QUsed ≥ TUsed2f + H2f/2



Parameters of 3G-to-2G Handover - 2F


InterRATCSThd2FEcN0 -12, namely -12dB

InterRATR99PsThd2FEcN0 -13, namely -13dB

InterRATHThd2FEcN0 -13, namely-13dB

InterRATCSThd2FRSCP -97, namely -97dBm

InterRATR99PsThd2FRSCP -107, namely -107dBm

InterRATHThd2FRSCP -107, namely -107dBm

HystFor2F 4, namely 2dB

TimeToTrig2F D1280, namely 1280ms

Recommended values of 2F event:



3G-to-2G Handover Measurement Events - 3A 3A event:

The estimated quality of the currently used UTRAN

frequency is below a certain threshold and the estimated

quality of the other system is above a certain threshold

Event 3A is triggered on the basis of the following formula:

QOtherRAT + CIOOtherRAT ≥ TOtherRAT + H3a/2

QUsed ≤ TUsed - H3a/2



Parameters of Inter-Frequency Handover -3A








Recommended values of TUsed :



Parameters of Inter-Frequency Handover -3A (Cont.)


TargetRatCsThd 16, namely -95dBm

TargetRatR99PsThd 16, namely -95dBm

TargetRatHThd 16, namely -95dBm

Recommended values of TOtherRAT:



Parameters of Inter-Frequency Handover -3A (Cont.) Hystfor3A

Parameter name: 3A hysteresis


TrigTime3A

Parameter name: 3A event trigger delay time




3G-to-2G Handover Measurement Events – 3C 3C event:

The estimated quality of other system is above a certain

threshold

Event 3C is triggered on the basis of the following formula:

MOtherRAT + CIOOtherRAT ≥ TOtherRAT + H3c/2



Parameters of Inter-Frequency Handover -3C


InterRATNCovHOCSThd 21, namely -90dBm

InterRATNCovHOPSThd 21, namely -90dBm

Hystfor3C 0, namely 0dB

TrigTime3C D640, namely 640ms

Recommended values of 3C :



Parameters of Inter-Frequency Handover - Common CIO



CIOOffset





Contents













3G-to-2G Handover Measurement Quantity In coverage-based UMTS-to-GSM handover,

Event 2D/2F or periodical measurement takes both CPICH Ec/No and

RSCP as measurement quantities

In coverage-based inter-RAT handover, the system delivers both

CPICH Ec/N0 and CPICH RSCP for 2D/2F measurement

The event 3A measurement quantity is set through the parameter

MeasQuantityOf3A

In QoS-based 3G-to-2G handover, the event 3A measurement

quantity is set through the parameter

UsedFreqMeasQuantityForQos3A



3G-to-2G Handover Measurement Quantity MeasQuantityOf3A

Parameter name: 3A Measure Quantity

Recommended value: Auto, namely based on the 2D

UsedFreqMeasQuantityForQos3A

Parameter name: 3A Used-Freq Measure Quantity for Qos

Recommended value: CPICH_RSCP



Contents













3G-to-2G Handover Compressed Mode

The 3G-to-2G handover compressed mode is the same

with inter-frequency handover compressed mode.



Interoperability between Inter-RAT and Inter-Frequency Handover

Inter-frequency measurement:

2D, 2F event

Inter-frequency neighboring cell

Inter-RAT measurement:

2D, 2F event

Inter-RAT neighboring cell

Measure inter-RAT neighbor?

Measureinter-frequency

neighbor?



Parameters of Inter-RAT Handover

InterFreqRATSwitch

Parameter name: Inter-freq and Inter-RAT coexist switch

Recommended value: SIMINTERFREQRAT

CoexistMeasThdChoice

Parameter name: InterFreq and InterRat coexist measure

threshold choice

Recommended value:

COEXIST_MEAS_THD_CHOICE_INTERFREQ



Contents





1. Coverage and QoS-based UMTS-to-GSM Handover Decision and

Execution

2. Load- and Service-based 3G-to-2G Handover Decision and Execution




Coverage and QoS-based UMTS-to-GSM Handover Procedure



Reporting Mode

The coverage-based and QoS-based 3G-to-2G handover is

categorized into two types according to the following

two measurement report modes:


Event-triggered measurement report mode

Each mode corresponds to a different decision and

execution procedure.




After receiving the periodical measurement report of GSM

cells, the RNC performs the following decision and execution

procedures:

Decide whether the quality of 2G cells meets the conditions of

inter-RAT handover. The evaluation formula is:

Mother_RAT + CIOother_RAT ≥ Tother_RAT + H/2

Start the evaluation of the cells that meet the quality requirement

and start the time-to-trigger timer. If the measurement report

meet the following formula and time-to-trigger timer does not

expire, stop the time-to-trigger timer

Mother_RAT + CIOother_RAT < Tother_RAT - H/2

Select the cells in sequence, that is, from high quality cells to low

quality ones, to initiate 3G-to-2G handover



Parameters of Inter-RAT Handover (Cont.) HystforInterRAT

Parameter name: Inter-RAT hysteresis


TimeToTrigForVerify

Parameter name: Time to trigger for verified GSM cell


TimeToTrigForNonVerify

Parameter name: Time to trigger for non-verified GSM cell




Event-Triggered Measurement Report Mode After receiving the event 3A measurement report of 2G

cells, the RNC performs the following decision and

execution procedures:

Put all the 2G cells that trigger event 3A into a cell set and

arrange the cells according to the measurement quality in

descending order

Select the cells in sequence from the cell set to perform

inter-RAT handover



Contents





1. Coverage and QoS-based UMTS-to-GSM Handover Decision and

Execution

2. Load- and Service-based 3G-to-2G Handover Decision and Execution




Load-based Inter-RAT Handover



Service-based Inter-RAT Handover



Load- and Service-based 3G-to-2G Handover The load status between the source cell and the target

cell can be acquired by interchanging load information

between a 3G cell and a 2G cell during the load-based

and service-based 3G-to-2G handover.

Thus, whether to further conduct the handover can be

determined to avoid the 2G cell overload and possible

handover to the congested cell.



Decision and Execution Procedure

After receiving the event 3C measurement report of 2G

cells, the RNC performs the following handover decision

and execution procedure:

Put all the 2G cells that trigger event 3C into a cell set and

arrange the cells according to the measurement quality in

descending order

Select the cells in sequence from the cell set

InterRATHOAttempts

Parameter name: Inter-RAT handover max attempt times




Interchanging Load Information Procedure 1. When the RNC sends a RELOCATION REQUIRED

message to the 3G CN,

If the switch SndLdInfo2GsmInd is set to ON, the

RELOCATION REQUIRED message includes the Old BSS To

New BSS Information IE that includes the load information

of the 3G source cell.

If the switch SndLdInfo2GsmInd is set to OFF, then the

RELOCATION REQUIRED message does not include the Old

BSS To New BSS Information IE.



Interchanging Load Information Procedure 2. When the RNC receives the RELOCATION COMMAND message from

the 2G CN:

If the switch NcovHoOn2GldInd is set to ON, the RNC obtains the load

information of the 2G target cell:

If the 2G load is lower than CSHOOut2GloadThd or PSHOOut2GloadThd, the RNC

continues the inter-RAT handover procedure; otherwise, the RNC returns the

Relocation Cancel message to the CN to cancel this inter-RAT handover and makes

another handover attempt to the next candidate cell generated in the cell list based on

inter-RAT measurement.

If the Inter-System Information Transparent Container IE, is not included in the

RELOCATION COMMAND message, the load information of the 2G target cell is not

considered and this inter-RAT handover is continued

If the switch NcovHoOn2GldInd is set to OFF, the RNC continues the inter-

RAT handover procedure without considering the thresholds



Parameters of Interchanging Load Information SndLdInfo2GsmInd

Parameter name: Send Load Info to GSM Ind


NcovHoOn2GldInd

Parameter name: NCOV Reloc Ind based on GSM cell load




Parameters of Interchanging Load Information CSHOOut2GloadThd

Parameter name: CS domain Reloc GSM load THD

Recommended value: 80, namely 80%

PSHOOut2GloadThd

Parameter name: PS domain Reloc GSM load THD

Recommended value: 60, namely 60%



Parameters of Service-based Inter-RAT Handover

CSServiceHOSwitch

Parameter name: Inter-RAT CS handover switch

Recommended value: OFF

PSServiceHOSwitch

Parameter name: Inter-RAT PS handover switch

Recommended value: OFF



Contents








CS Domain Inter-RAT Handover Flow (UMTS->GSM)



CS Domain Inter-RAT Handover Flow (UMTS->GSM)



PS Domain Inter-RAT Handover Flow (UMTS->GSM & UE in CELL_DCH)


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