08- OWJ200102 WCDMA Handover Algorithm and Parameters

8/12/2019 08- OWJ200102 WCDMA Handover Algorithm and Parameters

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Copyright 2006 Huawei Technologies Co., Ltd. All rights reserved. Page1

Foreword

Why mobile systems need handover?

It is decided by the characters of mobile system:

The mobility of UE

The mobile system is composed by cells which the coverageability is limited.

Providing the continuous service in mobile system is the basic

element in QoS.


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Objectives

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

Know the basic definitions of Handover

The algorithms of handover decision

The handover flow

The parameters of handover


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Contents

1. Introduction of Handover

2. Measurement of Handover

3. The Basic Handovers


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Contents





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The 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


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The Basic Concepts of Handover

Active Set

Monitored Set

Detected set

Radio Link (RL)

Radio Link Set

(RLS)

maximum ratio combination

selection combination

The soft handover gain

CPICH


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The 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-RAT handover (UMTS GSM/GPRS)

According to the purpose of handover:

Based on Coverage

Based on Noncoverage


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The Characters of Different Handover

Comparison between soft handover and hard handover:

Item Soft Handover Hard Handover

The number of RLs inactive set after handover

Several One

Interruption during

handover

No Yes

The frequencies of cells Only happened

between Intra-

frequency cells

Can be happened in Intra-

frequency cells or Inter-frequency

cells


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The Characters of Different Handover

Item Soft Handover Softer Handover

UL combination Signal combined in

RNC by selective

combination

Signal combined in NodeB by


DL combination Signal combined in

UE by maximum ratio

combination

Signal combined in UE by


Comparison between soft handover and softer handover :


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Soft Handover

RNC

NodeB 2NodeB 1

Cell A Cell B


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Softer Handover

RNC

NodeB

Cell BCell A


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Hard Handover

RNC

NodeB 2NodeB 1

Cell A Cell B


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Three Steps of Handover

Decision

Execution

Measurement

The following figure shows handover

procedure (measurement quality set toPCPICH Ec/No)

Decision phase

Execution phase

Measurement phase

Yes

NoAre handover criteria satisfied?

Perform a handover and update relative parameters

Measure the CPICH Ec/N0 of the serving cell and

its neighboring cells as well as the relative time

difference between the cells


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Contents


2.1 Measurement Control and Measurement Report

2.2 Measurement Phase


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Measurement Control, normal case

UE UTRAN

MEASUREMENT CONTROL

Measurement Control


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Measurement Control, normal case

UE UTRAN

MEASUREMENT REPORT

Measurement Report


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Contents


2.1 Measurement Control and Measurement Report

2.2 Measurement Phase


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Measurement Model

Layer 1

filteringLayer 3

filteringEvaluation

of reporting

criteria

A DB C

C'

parameters parameters

A is measurement value at the physical layer

B is the measurement value after layer 1 filtering at physical layer.

The value goes from the physical layer to high layer

C is measurement after processing in the layer3 filter C is another measurement value

D is measurement report information sent on the radio interface or

Iub interface


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Measurement Quantity

Ec/No

CPICH signal quality

RSCP

CPICH signal level

RSSI

GSM cell signal level


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Measurement Quantity Configuration

IntraFreqMeasQuantity

Parameter name: Intra-frequency measure quantity

The default value of this parameter is Ec/No

InterFreqMeasQuantity

Parameter name: Inter-frequency measure quantity

The default value of this parameter is Both

MeasQuantityOf3A

Parameter name: 3A Measure Quantity

The default value of this parameter is RSCP


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Layer 3 filtering

Fn is the new measurement value after filtering.

Fn-1 is the last measurement value after filtering.

Mn is the latest measurement value from the physical layer.

a= 1/2(k/2) (k is set to Intr a-freq meas L3 fi l ter coeff)

nnn MaFaF 1)1(

Where:


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Layer 3 filtering coefficient

FilterCoef

Parameter name: Intra-frequency measurement filter coefficient

The default value of this parameter is D3

InterFreqFilterCoef

Parameter name: Inter-frequency measure filter coefficient


InterRATFilterCoef

Parameter name: Inter-RAT filter coefficient



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Measurement Report Mode

Periodic Report

Event Trigger Report

Event to Periodic Report


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Contents





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Contents


3.1 Soft Handover

3.2 Intra-frequency Hard Handover

3.3 Inter-frequency Hard Handover

3.4 Inter-RAT Hard Handover

3.5 Blind Handover


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Brief Introduction of Soft Handover

Characters of Soft Handover

During handover, UE has several RLs with different cells

The handover among different cells which are in same RLS can be

softer handover

Signals from each RL will be combined in UL and DL.


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Brief Introduction of Soft Handover

Advantages

Soft handover gain

Decrease the possibility of call drop

Disadvantages More resource needed in downlink

it way cause side-effect


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Measurement of Soft Handover

Measurement quantity

CPICH RSCP

CPICH Ec/No

Reporting mode Periodic reporting

Event trigger reporting

Event trigger reporting to Periodic reporting

Event type

1A,1B,1C,1D,1F


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Soft Handover Measurement EventsEvent Descr ip t ion

1A The PCPICH quality of the cells in the monitored set enters the repor t ing range.

This indicates that the quality of a cell is close to the quality of the best cell . A

relative high combined gain can be achieved when the cell is added to the active

set

1B The PCPICH quality of the cells in the active set leaves the repor t ing range. This

indicates that quality of a cell is much worse than the quality of the best cell. The

cell should not stay in the active set

1C A non-active PCPICH becomes better than an active PCPICH. This indicates that

the quality of a cell is close to the quality of the best cell. In addition ,the number of

cells in the active set has reached the maximum value. The cell replaces the worstcell in the active set ; thus achieving a higher combined gain

1D Event of the change of the best cell


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Example of 1A Event

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

B: signal curve of a cell in the monitoring set

C: The 1A curve


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Key parameters of 1A Event

INTRARELTHDFOR1ACS

Parameter name: CS service 1A event relative threshold

The default value of this parameter is 6 ( 3dB )

INTRARELTHDFOR1APS

Parameter name: PS service 1A event relative threshold



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Key parameters of 1A Event

HYSTFOR1A

Parameter name: 1A event hysteresis

The default value of this parameter is 0( 0dB )

TRIGTIME1A

Parameter name: 1A event trigger delay time

The default value of this parameter is D320 ( 320ms )


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The Trigger Algorithm of 1B Event

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

),2/(10)1(1010 111

bbBest

N

i

iOldOld HRLogMWMLogWCIOLogMA


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Example of 1B Event


B: signal curve of a cell in the monitoring set

C: The 1B curve


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Key parameters of 1B Event

INTRARELTHDFOR1BCS

Parameter name: CS service 1B event relative threshold


INTRARELTHDFOR1BPS

Parameter name: PS service 1B event relative threshold



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HYSTFOR1B

Parameter name: 1B event hysteresis


TRIGTIME1B

Parameter name: 1B event trigger delay time



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The Trigger Algorithm of 1C Event

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

,2/1010 1cInASInASNewNew HCIOLogMCIOLogM


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Example of 1C Event


B: signal curve of a cell in the active set

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

D: signal curve of a cell in the monitoring set

E: The 1C curve


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Key parameters of 1C Event

HYSTFOR1C

Parameter name: 1C event hysteresis


TRIGTIME1C

Parameter name: 1C event trigger delay time



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The Trigger Algorithm of 1D Event

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

,2/1010 1cInASNew HLogMLogM


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Key parameters of 1D Event

HYSTFOR1D

Parameter name: 1D event hysteresis


TRIGTIME1D

Parameter name: 1D event trigger delay time



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Other key parameters for SHO

Weight

Parameter name: Weighted factor

The default value of this parameter is 0

SHOQualmin

Parameter name: Min quality THD for SHO

The default value of this parameter is -24(-24 dB)

CELLINDIVIDALOFFSET

Parameter name: Cell offset



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Brief Introduction of Intra-Frequency Handover

Characters of Intra-Frequency Handover

During handover, UE has only one RL with one cell

Switch off the RL with the original cell, then setup the RL with target

cell

The frequency of source cell and target cell are same


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Brief Introduction of Intra-Frequency Handover

Advantages

Enhance the usage efficiency of the OVSF code and hardware

Disadvantages

High call drop possibility because of the intra-frequencyinterference


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Key parameters of Intra-frequency Hard handover

BEBITRATETHD

Parameter name: BE service handover rate threshold

The default value of this parameter is 384k

The Parameters about 1D Event

Time to trigger

Hysteresis


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Brief Introduction of Inter-Frequency Handover

Characters of Soft Handover

The frequency of original cell and source cell are different

There is only one RL for the UE

The compressed mode is needed


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Compressed Mode

Purpose

Measure the inter-frequency cell or Inter-RAT cell under FDD mode

Categories

Downlink compressed mode

Uplink compressed mode

Realization Methods

SF/2

Higher layer scheduling


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Measurement of Inter-frequency Handover

Measurement quantity

CPICH RSCP

CPICH Ec/No

Reporting mode Periodic reporting

Event trigger reporting

Event trigger reporting to Periodic reporting

Event type

2B,2C,2D,2F


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Inter-frequency Handover Measurement Events

Event Descr ipt ion

2D When the current signal quality is lower than the preset threshold , the

UTRAN enables the compressed mode and starts inter-frequency

measurement

2F When the current signal quality is higher than the preset threshold, the

UTRAN disables the compressed mode and stops inter-frequency

measurement

2B When the current signal frequency is lower than the preset threshold and

the signal quality of an inter-frequency neighbouring cell is higher than

the preset threshold , the UTRAN trigger an inter-frequency handoverbased on coverage

2C The estimated quality of a inter-frequency neighbor cell is higher than the

preset threshold


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The Trigger Algorithm of 2D Event

Event 2D is triggered on the basis of the following formula

2/22 ddUsedUsed HTQ


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Key parameters of of 2D Event

InterFreqCSThd2DEcN0

Parameter name: Inter-freq CS measure start Ec/No THD

The default value of this parameter is -14 dB

InterFreqPSThd2DEcN0

Parameter name: Inter-freq PS measure start Ec/No THD



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Key parameters of of 2D Event

InterFreqCSThd2DRSCP

Parameter name: Inter-freq CS measure start RSCP THD

The default value of this parameter is -95 dBm

InterFreqPSThd2DRSCP

Parameter name: Inter-freq PS measure start RSCP THD



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Key parameters of 2D Event

HYSTFOR2D

Parameter name: 2D event hysteresis


TRIGTIME2D

Parameter name: 2D event trigger delay time



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The Trigger Algorithm of 2F Event

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

2/22 ffUsedUsed HTQ


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Key parameters of 2F Event

InterFreqCSThd2FEcN0

Parameter name: Inter-freq CS measure stop Ec/No THD


InterFreqPSThd2FEcN0

Parameter name: Inter-freq PS measure stop Ec/No THD



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Key parameters of 2F Event

HYSTFOR2F

Parameter name: 2F event hysteresis


TRIGTIME2F

Parameter name: 2F event trigger delay time



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InterFreqCovHOCSThdEcN0

Parameter name: Inter-freq CS target frequency trigger Ec/No THD


InterFreqCovHOPSThdEcN0

Parameter name: Inter-freq PS target frequency trigger Ec/No THD



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InterFreqCovHOCSThdRSCP

Parameter name: Inter-freq CS target frequency trigger RSCP THD


InterFreqCovHOPSThdRSCP

Parameter name: Inter-freq PS target frequency trigger RSCP THD



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IFHOUsedFreqCSThdEcN0

Parameter name: Inter-freq CS Used frequency trigger Ec/No THD

The default value of this parameter is -12dB

IFHOUsedFreqPSThdEcN0

Parameter name: Inter-freq PS Used frequency trigger Ec/No THD



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IFHOUsedFreqCSThdRSCP

Parameter name: Inter-freq CS Used frequency trigger RSCP THD

The default value of this parameter is -92dBm

IFHOUsedFreqPSThdRSCP

Parameter name: Inter-freq PS Used frequency trigger RSCP THD



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HYSTFOR2B

Parameter name: 2B event hysteresis


TRIGTIME2B

Parameter name: 2B event trigger delay time



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The Trigger Algorithm of 2C Event

Event 2C is triggered on the basis of the following formula

2/22 ccusedNonusedNon

HTQ


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Key parameters of 2C Event

InterFreqNCovHOThdEcN0

Parameter name: Inter-freq CS target frequency trigger Ec/No THD


Hystfor2C

Parameter name: 2C hysteresis

The default value of this parameter is 6 (3dB)

TrigTime2C

Parameter name: 2C event trigger delay time

The default value of this parameter is D640 (640ms)


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Characters of Inter-RAT Handover

Based on handover directions, inter-RAT handover is of two

types:

UMTS->GSM handover

UMTS->GSM coverage-based handover

UMTS->GSM load-based handover

UMTS->GSM service-based handover

GSM->UMTS handover

Brief Introduction of Inter-RAT Handover


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Brief Introduction of Inter-RAT Handover

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 compatibility for

equipments Demands more complicated UE


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Inter-RAT Handover Measurement Events

Event Descr ip t ion

2D When the signal quality of the currently used frequency is lower than the preset

threshold, the RNC enables the compressed mode and starts inter-RAT

measurement.

2F When the signal quality of the currently used frequency is higher than the preset

threshold, the RNC disables the compressed mode and stops inter-RATmeasurement.

3A When the signal quality of the currently used UMTS frequency is lower than the

preset threshold while the signal quality of any other system is higher than the

preset threshold, the RNC triggers UMTS->GSM handover based on coverage.

3C When the signal quality of any other system is higher than the preset threshold,

the RNC triggers UMTS->GSM handover based on load or service.


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K P t f 2D E t


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Key Parameters of 2D Event

INTERRATCSTHD2DRSCP

Parameter name: Inter-RAT CS measure start RSCP THD

The default value of this parameter is -100 ( -100 dBm )

INTERRATPSTHD2DRSCP

Parameter name: Inter-RAT PS measure start RSCP THD

The default value of this parameter is -110 (-110 dBm )

K P t f 2D E t


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Key Parameters of 2D Event

HYSTFOR2D Parameter name: 2D hysteresis

The default value of this parameter is 4 ( 2 dB )

TRIGTIME2D Parameter name: 2D event trigger delay time

The default value of this parameter is D320 (320 ms )

Th T i Al ith f 2F E t


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2/HTQ 2fUsed2fUsed

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

K P t f 2F E t


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Key Parameters of 2F Event

INTERRATCSTHD2FECNO Parameter name: Inter-RAT CS measure stop Ec/No THD

The default value of this parameter is -12 ( -12 dB )

INTERRATPSTHD2FECNO Parameter name: Inter-RAT PS measure stop Ec/No THD


K P t f 2F E t


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INTERRATCSTHD2FRSCP Parameter name: Inter-RAT CS measure stop RSCP THD


INTERRATPSTHD2FRSCP Parameter name: Inter-RAT PS measure stop RSCP THD


K P t f 2F E t


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HYSTFOR2F Parameter name: 2F hysteresis


TRIGTIME2F Parameter name: 2F event trigger delay time

The default value of this parameter is D1280 (1280 ms )

Th T i Al ith f 3A E t


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The Trigger Algorithm of 3A Event

2/HTQ 3aUsed3aUsed

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

2/HTM 3aOtherRatOtherRatOtherRat CIO

K P t f 3A E t


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Key Parameters of 3A Event

IRHOUSEDFREQCSTHDECNO Parameter name: Inter-RAT CS Used frequency trigger Ec/No

THD


IRHOUSEDFREQPSTHDECNO

Parameter name: Inter-RAT PS Used frequency trigger Ec/No

THD


K P t f 3A E t


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IRHOUSEDFREQCSTHDRSCP Parameter name: Inter-RAT CS Used frequency trigger RSCP

THD


IRHOUSEDFREQCSTHDRSCP

Parameter name: Inter-RAT PS Used frequency trigger RSCP

THD



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HYSTFOR3A Parameter name: 3A hysteresis


TRIGTIME3A Parameter name: 3A event trigger delay time

The default value of this parameter is D0 ( 0 ms )



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CELLINDIVIDALOFFSET Parameter name: Cell individual offset



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Key Parameters of 3C Event


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INTERRATNCOVHOCSTHD Parameter name: Inter-RAT CS handover decision THD

The default value of this parameter is 21 ( -90 dBm )

INTERRATNCOVHOPSTHD Parameter name: Inter-RAT PS handover decision THD

The default value of this parameter is 21 (-90 dBm )



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HYSTFOR3C Parameter name: 3C hysteresis


TRIGTIME3C Parameter name: 3C event trigger delay time

The default value of this parameter is D640 ( 650 ms )



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PENALTYTIMEFORINTERRATHO Parameter name: Inter-RAT handover failure penalty timer

length

The default value of this parameter is 30 ( 30 s )

INTERRATHOATTEMPTS

Parameter name: Inter-RAT handover max attempt times

The default value of this parameter is 16



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

The default value of this parameter is 60 ( 60 s )

Contents


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Contents

3. The Basic Handovers3.1 Soft Handover

3.2 Intra-frequency Hard Handover

3.3 Inter-frequency Hard Handover

3.4 Inter-RAT Hard Handover

3.5 Blind Handover

Blind Handover Measurement


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Blind Handover Measurement

Blind handover means UE can directly handover to theneighboring cell without measuring it.



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Where:

MOld is the measurement value of the cell signal that becomesworse

T1f is the absolute threshold of event 1F.

H1f is the hysteresis value of event 1F.

2/HTLogM10 f1f1Old



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Absolute

Threshold T1f

Reporting

event 1F

Measurement

Quantity

Time

Cell 1

Hysteresis

H1f/2

1F TriggerDelay Time


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Key Parameters of Event 1F


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Key Parameters of Event 1F

HYSTFOR1F

Parameter name: 1F hysteresis

The recommended value is 8, namely 4 dB

TRIGTIME1F

Parameter name: 1F event trigger delay time

The recommended value is D640, namely 640 ms

Blind Handover Decision


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Blind Handover Decision

After receiving event 1F of best cell from UE, the RNCwould check if blind handover neighbor is configured for the

cell.

If multiple blind handover neighbors are configured, the

RNC would perform blind handover to the target cell with

the highest priority

Key Parameters of Blind Handover


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Key Parameters of Blind Handover

BLINDHOFLAG

Parameter name: Blind handover flag

The default value is FALSE

BLINDHOPRIO

Parameter name: Blind handover Priority

The value is set according to actual situation.


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Thank youwww.huawei.com

08- OWJ200102 WCDMA Handover Algorithm and Parameters

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Transcript of 08- OWJ200102 WCDMA Handover Algorithm and Parameters