WCDMA Handover Algorithm and Parameters-libre

8/9/2019 WCDMA Handover Algorithm and Parameters-libre

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WCDMA Handover Principle

and Relevant Parameters


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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 coverage ability islimited.

Providing the continuous service in mobile system is the basic elementin 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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The Purpose of Handover

Providing the continuous service in mobile system is thebasic 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)

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maximum ratio combination

selection combination

The soft handover gain

CPICH


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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 in

active 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

Comparison between soft handover and softer 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


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Soft Handover

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RNC

NodeB 2NodeB 1

Cell A Cell B


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Softer Handover

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RNC

NodeB

Cell BCell A


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Hard Handover

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RNC

NodeB 2NodeB 1

Cell A Cell B


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Three Steps of Handover

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Decision

Execution

Measurement

The following figure shows handoverprocedure (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 andits neighboring cells as well as the relative timedifference between the cells


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Contents

1. Introduction of Handover



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Contents


2.1 Measurement Control and Measurement Report

2.2 Measurement Phase

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Measurement Control

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Measurement Control, normal case

UE UTRAN

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

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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Layer 1filtering

Layer 3filtering

Evaluationof reporting

criteria

A DB C

C'

parameters parameters


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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 Intra-freq meas L3 filter coeff)

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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

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Periodic Report

Event Trigger Report

Event to Periodic Report


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Contents

1. Introduction of Handover2. Measurement of Handover


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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 Handover3.5 Blind Handover

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Contents


3.1 Soft Handover



3.4 Inter-RAT Hard Handover3.5 Blind Handover

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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 Description

1A The PCPICH quality of the cells in the monitored set enters the reporting 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 reporting 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 worst

cell in the active set ; thus achieving a higher combined gain

1D Event of the change of the best cell

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The Trigger Algorithm of 1A Event

),2/(10)1(1010 111

aaBest

N

i

iNewNew HRLogMWMLogWCIOLogMA

+

+

=

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


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The Trigger Algorithm of 1B Event

),2/(10)1(1010 111bbBest

N

iiOldOld HRLogMWMLogWCIOLogM

A

++

+

=

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


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Example of 1B Event

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

B: signal curve of a cell in the monitoring setC: The 1B curve


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Key parameters of 1B EventINTRARELTHDFOR1BCS

Parameter name: CS service 1B event relative threshold

The default value of this parameter is 12 ( 6dB )

INTRARELTHDFOR1BPS

Parameter name: PS service 1B event relative threshold


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Key parameters of 1B EventHYSTFOR1B

Parameter name: 1B event hysteresis

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

TRIGTIME1B

Parameter name: 1B event trigger delay time

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

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The Trigger Algorithm of 1C Event

,2/10101cInASInASNewNew

HCIOLogMCIOLogM +++

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


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Example of 1C Event

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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 EventHYSTFOR1C

Parameter name: 1C event hysteresis


TRIGTIME1C

Parameter name: 1C event trigger delay time


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The Trigger Algorithm of 1D Event

,2/10101cInASNew

HLogMLogM +

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


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Example of 1D Event

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

C: Th1D curve


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Key parameters of 1D EventHYSTFOR1D

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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Contents


3.1 Soft Handover



3.4 Inter-RAT Hard Handover

3.5 Blind Handover

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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 targetcell

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-frequency interference

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Contents


3.1 Soft Handover




3.5 Blind Handover

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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 Description

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 handover

based on coverage

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

preset threshold

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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 EventHYSTFOR2D

Parameter name: 2D event hysteresis


TRIGTIME2D



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The Trigger Algorithm of 2F Event

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

2/22 ffUsedUsed HTQ +

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Key parameters of 2F EventInterFreqCSThd2FEcN0

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

InterFreqCSThd2FRSCP

Parameter name: Inter-freq CS measure stop RSCP THD


InterFreqPSThd2FRSCP

Parameter name: Inter-freq PS measure stop RSCP 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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The Trigger Algorithm of 2B Event

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

2/22 bbusedNonusedNon HTQ + 2/22 bbUsedUsed HTQ , and

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Key parameters of 2B Event

InterFreqCovHOCSThdEcN0

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


InterFreqCovHOPSThdEcN0

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


g

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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


g

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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


g

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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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Key parameters of 2B EventHYSTFOR2B

Parameter name: 2B event hysteresis


TRIGTIME2B

Parameter name: 2B event trigger delay time



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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


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

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Contents


3.1 Soft Handover




3.5 Blind Handover

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Brief Introduction of Inter-RAT Handover

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

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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 Description

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-RAT

measurement.

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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2/H-TQ 2dUsed2dUsed

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

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Key Parameters of 2D Event

INTERRATCSTHD2DECNO

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

The default value of this parameter is -14 ( -14 dB )

INTERRATPSTHD2DECNO

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


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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 )

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HYSTFOR2D

Parameter name: 2D hysteresis

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

TRIGTIME2D


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


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2/HTQ 2fUsed2fUsed +

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

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Key Parameters of 2F Event

INTERRATCSTHD2FECNO

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


INTERRATPSTHD2FECNO

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


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Key Parameters of 2F Event

INTERRATCSTHD2FRSCP

Parameter name: Inter-RAT CS measure stop RSCP THD


INTERRATPSTHD2FRSCP

Parameter name: Inter-RAT PS measure stop RSCP THD



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The Trigger Algorithm of 3A Event

2/HTQ3aUsed3aUsed

+

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

2/HTM3aOtherRatOtherRatOtherRat ++CIO

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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


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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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INTERRATCOVHOCSTHD Parameter name: Inter-RAT CS handover decision THD

The default value of this parameter is 16 ( -95 dBm )

INTERRATCOVHOPSTHD

Parameter name: Inter-RAT PS handover decision 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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2/HTM 3cOtherRatOtherRatOtherRat ++CIO

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

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Key Parameters of 3C Event

INTERRATNCOVHOCSTHD Parameter name: Inter-RAT CS handover decision THD


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


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


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

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

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Contents

3. The Basic Handovers3.1 Soft Handover




3.5 Blind Handover

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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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AbsoluteThreshold T1f

Reportingevent 1F

MeasurementQuantity

Time

Cell 1

HysteresisH1f /2

1F Trigger

Delay Time

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Key Parameters of Event 1F

INTRAABLTHDFOR1FECNO Parameter name: 1F event absolute EcNo threshold

The recommended value is -24 dB

INTRAABLTHDFOR1FRSCP

Parameter name: 1F event absolute RSCP threshold The recommended value is -115 dBm

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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

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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 forthe cell.

If multiple blind handover neighbors are configured, theRNC would perform blind handover to the target cell

with the highest priority

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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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