2G 3G Handover Algorithms

RAN

Handover Feature Parameter Description

Issue Draft

Date 2009-12-05

Copyright © Huawei Technologies Co., Ltd. 2009. All rights reserved.

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Contents

iii

Contents

1 Introduction ...........................................................................................................................1-1

1.1 Scope ..................................................................................................................................................... 1-1

1.2 Intended Audience .................................................................................................................................. 1-1

2 Overview of Handover .........................................................................................................2-1

2.1 Handover Types...................................................................................................................................... 2-1

2.2 Intra-Frequency Handover ...................................................................................................................... 2-2

2.3 Inter-Frequency Handover ...................................................................................................................... 2-4

2.4 Inter-RAT Handover (3G to 2G).............................................................................................................. 2-5

2.4.1 Inter-RAT Handover Introduction................................................................................................... 2-5

2.4.2 Rules for Enabling 3G-to-2G Handover ......................................................................................... 2-6

3 Intra-Frequency Handover...................................................................................................3-1

3.1 Intra-Frequency Handover Procedure ...................................................................................................... 3-1

3.2 Intra-Frequency Handover Measurement................................................................................................. 3-2

3.2.1 Intra-Frequency Handover Measurement Quantities ....................................................................... 3-2

3.2.2 Intra-Frequency Handover Measurement Events............................................................................. 3-3

3.2.3 Intra-Frequency Handover Neighboring Cell Combination Algorithm........................................... 3-10

3.3 Intra-Frequency Handover Decision and Execution ................................................................................3-11

3.3.1 Decision and Execution ................................................................................................................3-11

3.3.2 Rate Reduction After an SHO Failure........................................................................................... 3-12

3.4 Signaling Procedures for Intra-Frequency Handover.............................................................................. 3-15

3.4.1 Intra-NodeB Intra-Frequency Soft Handover Signaling Procedure ................................................ 3-15

3.4.2 Intra-RNC Inter-NodeB Intra-Frequency Soft Handover Signaling Procedure ............................... 3-16

3.4.3 Inter-RNC Intra-Frequency Soft Handover Signaling Procedure ................................................... 3-18

3.4.4 Intra-RNC Inter-NodeB Intra-Frequency Hard Handover Signaling Procedure.............................. 3-19

3.4.5 Inter-RNC Intra-Frequency Hard Handover Signaling Procedure .................................................. 3-21

4 Inter-Frequency Handover...................................................................................................4-1

4.1 Inter-Frequency Handover Procedure ...................................................................................................... 4-1

4.1.1 Coverage- or QoS-based Inter-Frequency and Inter-RAT Handover Procedure ................................ 4-1

4.1.2 Load-based Inter-Frequency Handover Procedure........................................................................... 4-3

4.1.3 Speed-based Inter-Frequency Handover Procedure ......................................................................... 4-3

4.2 Inter-Frequency Handover Measurement................................................................................................. 4-5

4.2.1 Inter-Frequency Handover Measurement Switches ......................................................................... 4-5

4.2.2 Inter-Frequency Handover Measurement Report Modes ................................................................. 4-6

4.2.3 Inter-Frequency Handover Measurement Quantity.......................................................................... 4-6

Contents

iv

4.2.4 Inter-Frequency Handover Measurement Events............................................................................. 4-7

4.2.5 Inter-Frequency Handover Neighboring Cell Combination Algorithm........................................... 4-10

4.2.6 Inter-Frequency Handover Compressed Mode .............................................................................. 4-10

4.3 Inter-Frequency Handover Decision and Execution ............................................................................... 4-12

4.3.1 Coverage- and QoS-based Inter-Frequency Handover Decision and Execution.............................. 4-12

4.3.2 Load-based Inter-Frequency Handover Decision and Execution.................................................... 4-14

4.3.3 Speed-based Inter-Frequency Handover Decision and Execution .................................................. 4-16

4.3.4 Blind Handover Decision and Execution Based on Event 1F......................................................... 4-16

4.3.5 Inter-Frequency Anti-Ping-Pong Algorithm .................................................................................. 4-17

4.3.6 Inter-Frequency Handover Retry .................................................................................................. 4-17

4.4 Signaling Procedures for Inter-Frequency Handover.............................................................................. 4-17

4.4.1 Inter-Frequency Handover Within One RNC................................................................................ 4-17

4.4.2 Inter-Frequency Handover Between RNCs ................................................................................... 4-19

5 Inter-RAT Handover.............................................................................................................5-1

5.1 3G-to-2G Handover Procedure................................................................................................................ 5-1

5.1.1 Coverage-based 3G-to-2G Handover Procedure ............................................................................. 5-1

5.1.2 Load-based 3G-to-2G Handover Procedure .................................................................................... 5-1

5.1.3 Service-based 3G-to-2G Handover Procedure................................................................................. 5-2

5.1.4 Speed-based 3G-to-2G Handover Procedure................................................................................... 5-2

5.2 3G-to-2G Handover Measurement .......................................................................................................... 5-3

5.2.1 3G-to-2G Handover Measurement Switches................................................................................... 5-3

5.2.2 3G-to-2G Handover Measurement Report Modes ........................................................................... 5-3

5.2.3 3G-to-2G Handover Measurement Quantity ................................................................................... 5-3

5.2.4 3G-to-2G Handover Measurement Events ...................................................................................... 5-4

5.2.5 3G-to-2G Handover Neighboring Cell Combination Algorithms ..................................................... 5-7

5.2.6 3G-to-2G Handover Compressed Mode.......................................................................................... 5-7

5.2.7 BSIC Verification Requirements for 2G Cells................................................................................. 5-7

5.3 3G-to-2G Handover Decision and Execution........................................................................................... 5-7

5.3.1 Coverage and QoS-based UMTS-to-GSM Handover Decision and Execution ................................. 5-7

5.3.2 Load- and Service-based 3G-to-2G Handover Decision and Execution ........................................... 5-8

5.3.3 3G-to-2G Handover Retry.............................................................................................................. 5-9

5.3.4 3G-to-2G Multimedia Fallback .................................................................................................... 5-10

5.3.5 3G-to-2G Handover in the PS Domain with NACC...................................................................... 5-12

5.3.6 3G<->2G Handover in the PS Domain with PS Handover............................................................. 5-12

5.4 2G-to-3G Handover .............................................................................................................................. 5-12

5.5 Interoperability Between Inter-RAT Handover and Inter-Frequency Handover....................................... 5-13

5.6 Signaling Procedures for Inter-RAT Handover....................................................................................... 5-14

5.6.1 3G-to-2G Handover in CS Domain .............................................................................................. 5-14

5.6.2 3G-to-2G Handover in PS Domain............................................................................................... 5-15

5.6.3 3G-to-2G Handover in Both CS Domain and PS Domain ............................................................. 5-16

5.6.4 2G-to-3G Handover in CS Domain .............................................................................................. 5-18

Contents

v

5.6.5 2G-to-3G Handover in PS Domain............................................................................................... 5-19

6 Glossary..................................................................................................................................6-1

7 Reference Documents.............................................................................................................. 2

1 Introduction

1-1

1 Introduction 1.1 Scope

The document describes the handover functional area. It provides an overview of the main

functions and goes into details regarding handover.

1.2 Intended Audience This document is intended for:

� Personnel who are familiar with WCDMA basics

� Personnel who need to understand handover

� Personnel who work with Huawei products

2 Overview of Handover

2-1

2 Overview of Handover Handover is a basic function of the cellular mobile network. The purpose of handover is to

ensure that a UE in CELL_DCH state is served continuously when it moves.

2.1 Handover Types Figure 2-1 shows the handovers supported by the Universal Mobile Telecommunications

System (UMTS), which include intra-frequency handover, inter-frequency handover, and

inter-RAT handover.


2-2

Figure 2-1 Handovers supported by the UMTS

2.2 Intra-Frequency Handover Intra-frequency handover is of the following two types:

� Intra-frequency soft handover: means that multiple radio links are connected to the UE at the same time.

� Intra-frequency hard handover: means that only one radio link is connected to the UE at

the same time.

Intra-Frequency Soft Handover

Intra-frequency soft handover is more commonly used than intra-frequency hard 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 is characterized by the function that the UE can be connected to

multiple Universal Terrestrial Radio Access Network (UTRAN) access points at the same


2-3

time. Addition and/or release of radio links are controlled by the ACTIVE SET UPDATE

procedure.

Table 2-1 Differences between soft handover and softer handover

Item Softer Handover Soft Handover

Scenario When the UE is in the

overlapped coverage area of

multiple neighboring cells of a NodeB with combined RLs

When the UE communicates

with multiple cells by setting

up multiple channels over the Uu interface

When the UE is in the overlapped

coverage area of two neighboring cells of different NodeBs

When the UE communicates with

different cells by setting up multiple

channels over the Uu interface

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

The HO_INTRA_FREQ_SOFT_HO_SWITCH parameter is used to determine whether to

enable both soft handover and softer handover. By default, this switch is set to ON, indicating

that both soft handover and softer handover are enabled. After the RNC receives the event 1A,

1B, 1C, or 1D report, it initiates the corresponding soft handover procedure for the UE. For

example, the RNC can add or delete links.

The DivCtrlField parameter indicates whether maximum-ratio combination is enabled in the

uplink during softer handover. When NodeB determines not to perform maximum-ratio

combination (softer combine), RNC must perform selection combination.

Intra-Frequency Hard Handover

Intra-frequency hard handover refers to a handover where all the old radio links are released

before the new radio links are established. Compared with soft handover, intra-frequency hard

handover uses fewer resources.

The scenarios of intra-frequency hard handover are as follows:

� No Iur interface is present between RNCs. In this scenario, intra-frequency hard

handover instead of soft handover can be performed between two RNCs.

� The Iur interface is congested between RNCs. In this scenario, also intra-frequency hard handover instead of soft handover can be performed between two RNCs.

� There is a high-speed Best Effort (BE) service.

Compared with soft handover, intra-frequency hard handover is used to save downlink bandwidth for a high-speed BE service.

� The intra-frequency soft handover fails and intra-frequency hard handover is allowed.

When intra-frequency soft handover fails because of a congestion problem of the target cell, the RNC tries an intra-frequency hard handover with a lower service bit rate.


2-4

The HO_INTRA_FREQ_HARD_HO_SWITCH parameter is used to determine whether to

enable intra-frequency hard handover. By default, this switch is set to ON.

2.3 Inter-Frequency Handover Inter-frequency handover provides supplementary coverage for inter-frequency cells to share

load with each other and to ensure service continuity.

From the UE point of view, inter-frequency handover is the same as intra-frequency hard

handover, because for both cases, the old connection is released before a new connection is

set up.

The types of inter-frequency handover are as follows:

Table 2-2 Types of inter-frequency handover

Type Description

Coverage-based

inter-frequency handover

If a moving UE leaves the coverage of the current frequency, the RNC needs to

trigger the coverage-based inter-frequency handover to avoid call drops.

QoS-based inter-frequency

handover

According to the Link Stability Control Algorithm, the RNC needs to trigger the

QoS-based inter-frequency handover to avoid call drops.

Load-based inter-frequency

blind handover

To balance the load between inter-frequency con-coverage cells, the RNC

chooses some UEs and performs the inter-frequency handover according to user

priorities and service priorities.

Speed-based

inter-frequency handover

When the Hierarchical Cell Structure (HCS) applies, the cells are divided into

different layers according to coverage. The macro cell has a larger coverage and a

lower priority, whereas the micro cell has a smaller coverage and a higher priority.

Inter-frequency handover can be triggered by the UE speed estimation algorithm

of the HCS. To reduce frequent handovers, the UE at a higher speed is handed

over to a cell under a larger coverage, whereas the UE at a lower speed is handed

over to a cell under a smaller coverage. For detailed information, see Error! Reference source not found.Error! Reference source not found..

The coverage-based inter-frequency measurement and the QoS-based inter-frequency

measurement can coexist.

The HO_INTER_FREQ_HARD_HO_SWITCH subparameter of HoSwitch parameter is

used to determine whether to allow load-based inter-frequency handover.

For detailed description of QoS-based inter-frequency blind handover switches, see the Rate

Control Feature Parameter Description.


2-5

2.4 Inter-RAT Handover (3G to 2G)

2.4.1 Inter-RAT Handover Introduction

Inter-RAT handover refers to the handover performed between 3G network and 2G network.

The handover causes can be coverage limitation, link stability, or load limitation of the UMTS

network. This document mainly describes the 3G-to-2G handover.

Inter-RAT handover provides continuous coverage, load sharing, and HCS services, which

fully utilizes the existing 2G network resources and thus reduces operator's cost.

Based on the handover triggering causes, the 3G-to-2G handover can be categorized as five

types, as described in Table 2-3.

Table 2-3 3G-to-2G handover types

Type Description

Coverage-based

3G-to-2G handover

The coverage of the 3G network is incontinuous at the initial stage.

On the border of the coverage, the poor signal quality of the 3G

network triggers the 3G-to-2G measurement. If the signal quality of

the 2G network is good enough and all the services of the UE are

supported by the 2G network, the coverage-based 3G-to-2G handover is triggered.

QoS-based

3G-to-2G handover

According to the Link Stability Control Algorithm, the RNC needs to

trigger the QoS-based 3G-to-2G handover to avoid call drops.

Load-based

3G-to-2G

handover

If the load of the 3G network is heavy and all the RABs of the UE are

supported by the 2G network, the load-based 3G-to-2G handover is

triggered.

Service-based

3G-to-2G handover

Based on layered services, the traffic of different classes is handed

over to different systems. For example, when an Adaptive Multi Rate

(AMR) speech service is requested, this service can be handed over to the 2G network.

Speed-based

3G-to-2G handover

When the Hierarchical Cell Structure (HCS) applies, the cells are

divided into different layers according to coverage. The macro cell

has a larger coverage and a lower priority, whereas the micro cell has a smaller coverage and a higher priority.

The 3G-to-2G handover can be triggered by the UE speed estimation

algorithm of the HCS. To reduce the frequencies of handover, the UE

at a higher speed is handed over to a cell under a larger coverage,

whereas the UE at a lower speed is handed over to a cell under a

smaller coverage. For detailed information, see Error! Reference

source not found.Error! Reference source not found..

Note:

The principles of the 3G-to-2G handover based on HCS speed estimation are similar to those of inter-frequency handover.


2-6

2.4.2 Rules for Enabling 3G-to-2G Handover

Before handover, the RNC checks whether all the preconditions for the 3G-to-2G handover

are met. The preconditions include service handover indicators, service requirements, and

handover rules.

Before deciding the 3G-to-2G handover, the RNC considers 2G cell capability, service

capability and UE capability.

� 2G cell capability

2G cell capability is configured through the parameter RATCELLTYPE. This

parameter indicates whether the cell supports the GSM, GPRS, or EDGE.

� 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. For the default value provided by the RNC, see Table 2-6.

� 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.

The rules for enabling the 3G-to-2G handover are based on the Service Handover

Indicator and the three types of capability. The rules vary according to the types of inter-RAT handover.

Rules for Enabling Coverage- and QoS-based 3G-to-2G Handover

The RNC initiates the coverage- or QoS-based UMTS-to-GSM handover only when Service

Handover Indicator is set as follows:

� HO_TO_GSM_SHOULD_BE_PERFORM

� HO_TO_GSM_SHOULD_NOT_BE_PERFORM

The following tables describe the impacts of different types of capability on handover

decision. If the capability of all 2G neighboring cells does not meet the requirement, the

inter-RAT measurement will not be triggered.

Table 2-4 Impacts of different types of capability on handover decision

Service Capability (Required by 2G) Cell Capability

UE Capability

EDGE GPRS GSM

EDGE Allowed Allowed Allowed

GPRS Allowed Allowed Allowed

GSM Not allowed Not allowed Allowed

EDGE

Not supported by 2G Not allowed Not allowed Not allowed


GPRS Allowed Allowed Allowed

GPRS



2-7


UE Capability

EDGE GPRS GSM


EDGE Not allowed Not allowed Allowed

GPRS Not allowed Not allowed Allowed


GSM


Rules for Enabling Load- and Service-based 3G-to-2G Handover

The RNC initiates the load-based 3G-to-2G handover only when Service Handover Indicator

is set as follows:

� HO_TO_GSM_SHOULD_BE_PERFORM

� HO_TO_GSM_SHOULD_NOT_BE_PERFORM

The RNC initiates the service-based 3G-to-2G handover only when the Service Handover

Indicator is set to HO_TO_GSM_SHOULD_BE_PERFORM.

The following three tables describe the impacts of different types of capability on handover

decision.

Table 2-5 Impacts of different types of capability on handover decision


UE Capability

EDGE GPRS GSM


GPRS Not allowed Allowed Allowed


EDGE


EDGE Not allowed Allowed Allowed

GPRS Not allowed Allowed Allowed


GPRS


EDGE Not allowed Not allowed Allowed

GPRS Not allowed Not allowed Allowed


GSM



2-8

If the capability of all neighboring 2G cells does not meet the requirement, the inter-RAT

measurement will not be triggered.

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

To perform the service-based 3G-to-2G handover, the RNC must turn on the related switches

for services in the CS and PS domains.

� When a single CS service is initially set up by the UE, the RNC allows the 3G-to-2G service-based handover if CSServiceHOSwitch is set to ON.

� When a single PS service is initially set up by the UE, the RNC allows the service-based

3G-to-2G handover if PSServiceHOSwitch is set to ON.

� For the combined services, no service-based handover is triggered.

Service Handover Indicator

The IE Service Handover Indicator indicates the CN policy for the service handover to the 2G

network. This IE is indicated in the Radio Access Bearer (RAB) assignment signaling

assigned by the CN, or in Table 2-6 provided by the RNC side.

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.

� If the switch is set to ON, the service attribute of inter-RAT handover is based on the

parameter configured on the RNC side.

� If the switch is set to OFF, the service attribute of inter-RAT handover is first based on

the CN when the indicator is contained in the RAB assignment signaling assigned by the

CN. If the CN does not allocate a service indicator, the service attribute of inter-RAT

handover is based on the RNC side.

Through the SHIND parameter, the service handover indicators are set 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.

Figure 2-2 shows an example of rules for the indicator of the 3G-to-2G handover based on

load and service.


2-9

Figure 2-2 Example of rules for indicator of 3G-to-2G handover based on load and service

By default, the RNC does as follows:

� For a UE with a single signaling RAB, the RNC supports the handover to the GSM. But

it is not recommended.

� For the UE accessing combined services (with CS services), the RNC sets the service

handover indicator of the UE to that of the CS service, because the CS service has the highest QoS priority.

� For the UE accessing combined services (with only PS services), the RNC sets the

service handover indicator of the UE to that of the PS service, because the PS service has the highest QoS priority

If the service handover indicators are not configured by the CN, each indictor can be set to the

service parameter index of a service on the RNC. Each service parameter index is the index of

one typical service RAB, which involves a set of service type, source description, CN domain

ID, and maximum rate (bit/s).

Table 2-6 describes the service handover indicators recommended by Huawei.

Table 2-6 Service handover indicators (default values)

RAB Index

Traffic Direction

CN Domain ID

Traffic Class

Max Rate (bit/s)

Source Description


Required 2G Capability

0 Uplink and

downlink

CS_DOM

AIN

CONVER

SATIONAL

12200 SPEECH HO_TO_GSM_SHOUL

D_NOT_BE_PERFORM GSM


2-10

RAB Index

Traffic Direction

CN Domain ID

Traffic Class

Max Rate (bit/s)

Source Description



1 Uplink and downlink

CS_DOMAIN

CONVER

SATION

AL

23850 SPEECH HO_TO_GSM_SHOULD_NOT_BE_PERFORM

GSM

2 Uplink and

downlink

CS_DOM

AIN

CONVER

SATIONAL

28800 UNKNO

WN

HO_TO_GSM_SHALL_

NOT_BE_PERFORM GSM

3

Uplink and

downlink CS_DOM

AIN

CONVER

SATIONAL

32000 UNKNO

WN

HO_TO_GSM_SHALL_

NOT_BE_PERFORM GSM

4

Uplink and

downlink CS_DOM

AIN

CONVER

SATIONAL

56000 UNKNO

WN

HO_TO_GSM_SHALL_

NOT_BE_PERFORM GSM

5

Uplink and

downlink CS_DOM

AIN

CONVER

SATIONAL

64000 UNKNO

WN

HO_TO_GSM_SHALL_

NOT_BE_PERFORM GSM

6 Uplink and

downlink

CS_DOM

AIN

STREAM

ING 57600

UNKNO

WN

HO_TO_GSM_SHALL_

NOT_BE_PERFORM GSM

11

Uplink and

downlink PS_DOM

AIN

CONVER

SATION

AL

8000 UNKNO

WN

HO_TO_GSM_SHALL_

NOT_BE_PERFORM GSM

12

Uplink and

downlink PS_DOM

AIN

CONVER

SATIONAL

16000 UNKNO

WN

HO_TO_GSM_SHALL_

NOT_BE_PERFORM EDGE

13

Uplink and

downlink PS_DOM

AIN

CONVER

SATIONAL

32000 UNKNO

WN

HO_TO_GSM_SHALL_

NOT_BE_PERFORM EDGE

15

Uplink and

downlink PS_DOM

AIN

CONVER

SATION

AL

64000 UNKNO

WN

HO_TO_GSM_SHALL_

NOT_BE_PERFORM EDGE

16

Uplink and

downlink PS_DOM

AIN

CONVER

SATIONAL

38800 UNKNO

WN

HO_TO_GSM_SHALL_

NOT_BE_PERFORM EDGE

17

Uplink and

downlink PS_DOM

AIN

CONVER

SATIONAL

39200 UNKNO

WN

HO_TO_GSM_SHALL_

NOT_BE_PERFORM EDGE

18

Uplink and

downlink PS_DOM

AIN

CONVER

SATION

AL

40000 UNKNO

WN

HO_TO_GSM_SHALL_

NOT_BE_PERFORM EDGE

19 Uplink and PS_DOM

CONVER

SATION42800 UNKNO HO_TO_GSM_SHALL_ EDGE


2-11

RAB Index

Traffic Direction

CN Domain ID

Traffic Class

Max Rate (bit/s)

Source Description



downlink AIN AL WN NOT_BE_PERFORM

21 Uplink and

downlink

PS_DOM

AIN

STREAM

ING 8000

UNKNO

WN

HO_TO_GSM_SHALL_

NOT_BE_PERFORM EDGE

22 Uplink and

downlink

PS_DOM

AIN

STREAM

ING 16000

UNKNO

WN

HO_TO_GSM_SHALL_

NOT_BE_PERFORM EDGE

23 Uplink and

downlink

PS_DOM

AIN

STREAM

ING 32000

UNKNO

WN

HO_TO_GSM_SHALL_

NOT_BE_PERFORM EDGE

24 Uplink and

downlink

PS_DOM

AIN

STREAM

ING 64000

UNKNO

WN

HO_TO_GSM_SHALL_

NOT_BE_PERFORM EDGE

25 Uplink and

downlink

PS_DOM

AIN

STREAM

ING 128000

UNKNO

WN

HO_TO_GSM_SHALL_

NOT_BE_PERFORM EDGE

26 Uplink and

downlink

PS_DOM

AIN

STREAM

ING 144000

UNKNO

WN

HO_TO_GSM_SHALL_

NOT_BE_PERFORM EDGE

27 Uplink and

downlink

PS_DOM

AIN

STREAM

ING 256000

UNKNO

WN

HO_TO_GSM_SHALL_

NOT_BE_PERFORM EDGE

28 Uplink and

downlink

PS_DOM

AIN

STREAM

ING 384000

UNKNO

WN

HO_TO_GSM_SHALL_

NOT_BE_PERFORM EDGE

40 Uplink and

downlink

PS_DOM

AIN

INTERAC

TIVE 0

UNKNO

WN

HO_TO_GSM_SHOUL

D_NOT_BE_PERFORM GPRS

41 Uplink and

downlink

PS_DOM

AIN

INTERAC

TIVE 8000

UNKNO

WN

HO_TO_GSM_SHOUL


42 Uplink and

downlink

PS_DOM

AIN

INTERAC

TIVE 16000

UNKNO

WN

HO_TO_GSM_SHOUL


43 Uplink and

downlink

PS_DOM

AIN

INTERAC

TIVE 32000

UNKNO

WN

HO_TO_GSM_SHOUL


44 Uplink and

downlink

PS_DOM

AIN

INTERAC

TIVE 64000

UNKNO

WN

HO_TO_GSM_SHOUL


45 Uplink and

downlink

PS_DOM

AIN

INTERAC

TIVE 128000

UNKNO

WN

HO_TO_GSM_SHOUL

D_NOT_BE_PERFORM EDGE

46 Uplink and

downlink

PS_DOM

AIN

INTERAC

TIVE 144000

UNKNO

WN

HO_TO_GSM_SHOUL


47 Uplink and

downlink

PS_DOM

AIN

INTERAC

TIVE 256000

UNKNO

WN

HO_TO_GSM_SHOUL


48 Uplink and

downlink

PS_DOM

AIN

INTERAC

TIVE 384000

UNKNO

WN

HO_TO_GSM_SHOUL


49 Uplink PS_DOM INTERAC 608000 UNKNO HO_TO_GSM_SHALL_ EDGE


2-12

RAB Index

Traffic Direction

CN Domain ID

Traffic Class

Max Rate (bit/s)

Source Description



AIN TIVE WN NOT_BE_PERFORM

50 Downlink PS_DOM

AIN

INTERAC

TIVE 768000

UNKNO

WN

HO_TO_GSM_SHALL_

NOT_BE_PERFORM EDGE

51 Downlink PS_DOM

AIN

INTERAC

TIVE 1024000

UNKNO

WN

HO_TO_GSM_SHALL_

NOT_BE_PERFORM EDGE

52 Uplink PS_DOM

AIN

INTERAC

TIVE 1440000

UNKNO

WN

HO_TO_GSM_SHALL_

NOT_BE_PERFORM EDGE

53 Downlink PS_DOM

AIN

INTERAC

TIVE 1536000

UNKNO

WN

HO_TO_GSM_SHALL_

NOT_BE_PERFORM EDGE

54 Downlink PS_DOM

AIN

INTERAC

TIVE 1800000

UNKNO

WN

HO_TO_GSM_SHALL_

NOT_BE_PERFORM EDGE

55 Uplink and

downlink

PS_DOM

AIN

INTERAC

TIVE 2048000

UNKNO

WN

HO_TO_GSM_SHALL_

NOT_BE_PERFORM EDGE

56 Uplink PS_DOM

AIN

INTERAC

TIVE 2880000

UNKNO

WN

HO_TO_GSM_SHALL_

NOT_BE_PERFORM EDGE

57 Downlink PS_DOM

AIN

INTERAC

TIVE 3600000

UNKNO

WN

HO_TO_GSM_SHALL_

NOT_BE_PERFORM EDGE

58 Uplink PS_DOM

AIN

INTERAC

TIVE 5740000

UNKNO

WN

HO_TO_GSM_SHALL_

NOT_BE_PERFORM EDGE

59 Downlink PS_DOM

AIN

INTERAC

TIVE 7200000

UNKNO

WN

HO_TO_GSM_SHALL_

NOT_BE_PERFORM EDGE

60 Downlink PS_DOM

AIN

INTERAC

TIVE 10100000

UNKNO

WN

HO_TO_GSM_SHALL_

NOT_BE_PERFORM EDGE

61 Downlink PS_DOM

AIN

INTERAC

TIVE 13900000

UNKNO

WN

HO_TO_GSM_SHALL_

NOT_BE_PERFORM EDGE

62 Downlink PS_DOM

AIN

INTERAC

TIVE 21000000

UNKNO

WN

HO_TO_GSM_SHALL_

NOT_BE_PERFORM EDGE

63 Downlink PS_DOM

AIN

INTERAC

TIVE 27900000

UNKNO

WN

HO_TO_GSM_SHALL_

NOT_BE_PERFORM EDGE

70 Uplink and

downlink

PS_DOM

AIN

BACKGR

OUND 0

UNKNO

WN

HO_TO_GSM_SHOUL


71 Uplink and

downlink

PS_DOM

AIN

BACKGR

OUND 8000

UNKNO

WN

HO_TO_GSM_SHOUL


72 Uplink and

downlink

PS_DOM

AIN

BACKGR

OUND 16000

UNKNO

WN

HO_TO_GSM_SHOUL


73 Uplink and PS_DOM BACKGR 32000 UNKNO HO_TO_GSM_SHOUL GPRS


2-13

RAB Index

Traffic Direction

CN Domain ID

Traffic Class

Max Rate (bit/s)

Source Description



downlink AIN OUND WN D_NOT_BE_PERFORM

74 Uplink and

downlink

PS_DOM

AIN

BACKGR

OUND 64000

UNKNO

WN

HO_TO_GSM_SHOUL


75 Uplink and

downlink

PS_DOM

AIN

BACKGR

OUND 128000

UNKNO

WN

HO_TO_GSM_SHOUL


76 Uplink and

downlink

PS_DOM

AIN

BACKGR

OUND 144000

UNKNO

WN

HO_TO_GSM_SHOUL


77 Uplink and

downlink

PS_DOM

AIN

BACKGR

OUND 256000

UNKNO

WN

HO_TO_GSM_SHOUL


78 Uplink and

downlink

PS_DOM

AIN

BACKGR

OUND 384000

UNKNO

WN

HO_TO_GSM_SHOUL


79 Uplink PS_DOM

AIN

BACKGR

OUND 608000

UNKNO

WN

HO_TO_GSM_SHALL_

NOT_BE_PERFORM EDGE

80 Downlink PS_DOM

AIN

BACKGR

OUND 768000

UNKNO

WN

HO_TO_GSM_SHALL_

NOT_BE_PERFORM EDGE

81 Downlink PS_DOM

AIN

BACKGR

OUND 1024000

UNKNO

WN

HO_TO_GSM_SHALL_

NOT_BE_PERFORM EDGE

82 Uplink PS_DOM

AIN

BACKGR

OUND 1440000

UNKNO

WN

HO_TO_GSM_SHALL_

NOT_BE_PERFORM EDGE

83 Downlink PS_DOM

AIN

BACKGR

OUND 1536000

UNKNO

WN

HO_TO_GSM_SHALL_

NOT_BE_PERFORM EDGE

84 Downlink PS_DOM

AIN

BACKGR

OUND 1800000

UNKNO

WN

HO_TO_GSM_SHALL_

NOT_BE_PERFORM EDGE

85 Uplink and

downlink

PS_DOM

AIN

BACKGR

OUND 2048000

UNKNO

WN

HO_TO_GSM_SHALL_

NOT_BE_PERFORM EDGE

86 Uplink PS_DOM

AIN

BACKGR

OUND 2880000

UNKNO

WN

HO_TO_GSM_SHALL_

NOT_BE_PERFORM EDGE

87 Downlink PS_DOM

AIN

BACKGR

OUND 3600000

UNKNO

WN

HO_TO_GSM_SHALL_

NOT_BE_PERFORM EDGE

88 Uplink PS_DOM

AIN

BACKGR

OUND 5740000

UNKNO

WN

HO_TO_GSM_SHALL_

NOT_BE_PERFORM EDGE

89 Downlink PS_DOM

AIN

BACKGR

OUND 7200000

UNKNO

WN

HO_TO_GSM_SHALL_

NOT_BE_PERFORM EDGE

90 Downlink PS_DOM

AIN

BACKGR

OUND 10100000

UNKNO

WN

HO_TO_GSM_SHALL_

NOT_BE_PERFORM EDGE

91 Downlink PS_DOM BACKGR 13900000 UNKNO HO_TO_GSM_SHALL_ EDGE


2-14

RAB Index

Traffic Direction

CN Domain ID

Traffic Class

Max Rate (bit/s)

Source Description



AIN OUND WN NOT_BE_PERFORM

92 Downlink PS_DOM

AIN

BACKGR

OUND 21000000

UNKNO

WN

HO_TO_GSM_SHALL_

NOT_BE_PERFORM EDGE

93 Downlink PS_DOM

AIN

BACKGR

OUND 27900000

UNKNO

WN

HO_TO_GSM_SHALL_

NOT_BE_PERFORM EDGE

Note:

Rows without RAB index are all NA.

3 Intra-Frequency Handover

3-1

3 Intra-Frequency Handover 3.1 Intra-Frequency Handover Procedure

The intra-frequency handover procedure is divided into three phases: handover measurement,

handover decision, and handover execution.

After the UE transits to the CELL_DCH state in connected mode during a call, the RNC

sends a MEASUREMENT CONTROL message to instruct the UE to take measurements and

report the measurement event results.

The MEASUREMENT CONTROL message carries the following information:

� Event trigger threshold

� Hysteresis value

� Event trigger delay time

� Neighboring cell list

Upon the reception of an event report from the UE, the RNC makes a handover decision and

performs the corresponding handover, as shown in Figure 3-1.

Figure 3-1 Intra-frequency handover procedure


3-2

3.2 Intra-Frequency Handover Measurement In the measurement phase, the UE takes measurements according to the MEASUREMENT

CONTROL message received from the RNC. When the event triggering conditions are met,

the UE sends measurement reports to the RNC according to the rules defined in the

MEASUREMENT CONTROL message.

3.2.1 Intra-Frequency Handover Measurement Quantities

Intra-frequency handover uses Ec/No or RSCP of the CPICH as the measurement value.

Intra-frequency handover measurement quantity can be configured through the parameter

IntraFreqMeasQuantity.

The UE performs layer 3 filtering on measurement values before it decides measurement

events and sends measurement reports. The measurement model, as shown in Figure 3-2, is

defined in 3GPP25.302. Figure 3-2 shows the position of layer 3 filtering in the measurement

procedure.

Figure 3-2 Measurement model in the WCDMA system

Figure 3-2 also shows the measurement points of the model, where

� A: measurement value of the physical layer

� B: measurement value obtained after layer-1 filtering. The value is weighted by the layer 3 filtering coefficient.

� C: measurement value obtained after layer 3 filtering. This value is controlled by the higher layer. Filtering coefficient C is applicable to event reports and periodic reports.

� C': another measurement value. C' and C are measured in the same way.

� D: measurement report information (message) of Uu or Iub transmission.

� Parameters (a) include the layer 3 filtering system and Parameters (b) include the

measurement report configuration.

The calculation is based on the following formula:

Fn = (1 - α) x Fn-1 + α x Mn

� Fn: measurement value obtained after the nth filtering

� Fn-1: measurement value obtained after the (n-1)th filtering

� Mn: measurement value of the nth physical layer

� α = 1/2(k/2)

: k is determined by the parameter which is the layer 3 filtering coefficient of

intra-frequency handover measurement.

When α is set to 1, k = 0 and layer 3 filtering is not performed.


3-3

3.2.2 Intra-Frequency Handover Measurement Events

In intra-frequency handover, the UE reports measurement results to the RNC through event

reporting.

Event Description

1A A 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.

1B A 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.

1J RAN10.0 provides the solution to the issue of how to add an HSUPA cell in a

DCH active set to an E-DCH active set. Event 1J is added to the 3GPP protocol.

This event is triggered when a non-active E-DCH but active DCH primary CPICH becomes better than an active E-DCH primary CPICH.

Triggering of Event 1A

Event 1A is triggered under the following condition:

10 x Log(MNew) + CIONew ≥ W x 10 x Log(∑=

AN

i

iM1

) + (1 - W) x 10 x Log(MBest) - (R1a -

H1a/2)

� MNew is the measurement value of the cell in the reporting range.

� CIONew is equal to the sum of CIO and CIOOffset, which adjusts the cell boundary in

the handover algorithms. This parameter is determined by network planning according to

actual environment configuration. To facilitate handover in neighboring cell

configuration, the parameter is set as a positive value; otherwise, the parameter is set as a negative value.

� W represents Weighted factor, which is determined by the parameter Weight. The total

quality of the best cell and the active set is specified by W.

� Mi is the measurement value of a cell in the active set.

� NA is the number of cells not forbidden to affect the reporting range in the active set. The

parameter CellsForbidden1A indicates whether adding the cell to the active set affects the relative threshold of event 1A.

� MBest is the measurement value of the best cell in the active set.

� R1a is the reporting range or the relative threshold of soft handover. The threshold parameters of the CS non-VP service, VP service, and PS service are as follows:

− IntraRelThdFor1ACSVP


3-4

− IntraRelThdFor1ACSNVP

− IntraRelThdFor1APS

� For the PS and CS combined services, the threshold for CS services is used.

� For the single signaling connection of the UE, the threshold for CS services is used.

� H1a represents 1A hysteresis, the hysteresis value of event 1A

Figure 3-3 shows the triggering of event 1A. In this procedure, the default parameter values

are used.

If the signal quality of a cell that is not in the active set is higher than Th1A for a period of

time specified by TrigTime1A (that is, Time to trigger in Figure 3-3), the UE reports event

1A.

Th1A = (CPICH Ec/No of the best cell in the active set) - (reporting range for event 1A)

� If Weighted factor > 0, then Th1A = (general signal quality of all the cells in the active set) - (reporting range for event 1A).

� Reporting range for event 1A is equal to the value of IntraRelThdFor1ACSVP, IntraRelThdFor1ACSNVP, or IntraRelThdFor1APS.

Figure 3-3 Triggering of event 1A

� 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

Triggering of Event 1B

Event 1B is triggered under the following condition:

10 x Log(Mold) + CIOold ≤ W x 10 x Log(∑=

BN

i

iM1

) + (1-W) x 10 x Log(MBest) - (R1b+H1b/2)

� MOld is the measurement value of the cell that becomes worse.


3-5

� CIOOld is equal to the sum of CIO and CIOOffset, which is the offset between the cell in

the reporting range and the best cell in the active set.

� W represents Weighted factor, used to weight the quality of the active set. The total quality of the best cell and the active set is specified by the parameter Weight.

� Mi is the measurement value of a cell in the active set.

� NB is the number of cells not forbidden to affect the reporting range in the active set. The

parameter CellsForbidden1B indicates whether adding the cell to the active set affects

the relative threshold of event 1B.


� R1b is the reporting range or the relative threshold of soft handover. The threshold

parameters of the CS non-VP service, VP service, and PS services are as follows:

− IntraRelThdFor1BCSVP

− IntraRelThdFor1BCSNVP

− IntraRelThdFor1BPS

� For the PS and CS combined services, the threshold for CS services is used.

� If the UE currently has only signaling connections, the threshold for CS services is used.

� H1b is the hysteresis value of event 1B, which is determined by the parameter

Hystfor1B.

Configuration rule and restriction

� The value of IntraRelThdFor1BCSNVP has to be larger than that of

IntraRelThdFor1ACSNVP.

� The value of IntraRelThdFor1BCSVP has to be larger than that of

IntraRelThdFor1ACSVP.

� The value of IntraRelThdFor1BPS has to be larger than that of IntraRelThdFor1APS.

Figure 3-4 shows the triggering of event 1B. In this procedure, the default parameter values

are used.


3-6

Figure 3-4 Triggering of event 1B


� B: signal quality curve of the best cell in the monitored set

� C: curve of Th1B

Th1B = (CPICH Ec/No of the best cell in the active set) - (reporting range for event 1B)

where

� Reporting range for event 1B is equal to the value of IntraRelThdFor1BCSVP, IntraRelThdFor1BCSNVP, or IntraRelThdFor1BPS.

� If Weight > 0, then Th1B = (general signal quality of all the cells in the active set) - (reporting range for event 1B).

If the signal quality of a cell in the active set is lower than Th1B for a period of time specified

by TrigTime1B (Time to trigger in the figure), the UE reports event 1B.

Triggering of Event 1C

Event 1C is triggered under the following condition:

10 x Log(MNew) + CIONew ≥ 10 x Log(MInAS) + CIOInAS + H1c/2

� MNew is the measurement value of the cell in the reporting range.

� CIONew is the cell individual offset value of the cell in the reporting range. It is equal to

the sum of CIO and CIOOffset, which is the offset between the cell in the reporting range and the best cell in the active set.

� MInAS is the measurement value of the worst cell in the active set.

� H1c is the hysteresis value of event 1C, which is determined by the parameter Hystfor1C.

Figure 3-5 shows the triggering of event 1C. In this procedure, the default parameter values

are used.


3-7

Figure 3-5 Triggering of event 1C


� 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

Th1C = (CPICH Ec/No of the worst cell in the active set) + (hysteresis/2)

where

� Hysteresis is equal to the value of Hystfor1C.

If the signal quality of a cell not in the active set is higher than Th1C for a period of time

specified by TrigTime1C (Time to trigger in the figure), the UE reports event 1C, as shown

in the figure.

The UE reports event 1C for qualified cells after the number of cells in the active set reaches

the maximum value. The maximum number of cells in the active set can be set by the

MaxCellInActiveSet parameter.

Triggering of Event 1D

Event 1D is triggered under the following condition:

10 x Log(MNotBest) + CIONotBest ≥ 10 x Log(MBest) + CIOBest + H1d/2

� MNotBest is the measurement value of a cell that is not the best cell.

� CIONotBest is equal to the sum of CIO and CIOOffset, which is the offset between the cell in the reporting range and the best cell in the active set.


� CIOBest is the cell individual offset value of the best cell. This parameter is not used for event 1D.

� H1d is the hysteresis value of event 1D, which is determined by the parameter

Hystfor1D.


3-8

Figure 3-6 shows the triggering of event 1D. In this procedure, the default parameter values

are used.

Figure 3-6 Triggering of event 1D


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

� C: curve of Th1D

� Hysteresis is equal to the value of Hystfor1D.

If the signal quality of a cell not in the active set is higher than Th1D for a period of time

specified by TrigTime1D (Time to trigger in the figure), the UE reports event 1D.

Triggering of Event 1J

Event 1J is triggered under the following condition:

10 x Log(MNew) + CIONew ≥ 10 x Log(MInAS) + CIOInAS + H1j/2

� MNew is the measurement result of the cell not in the E-DCH active set but in the DCH active set.

� CIONew and CIOInAS refer to the offset of each cell.

� MInAS is the measurement result of the cell in the E-DCH active set with the lowest

measurement result.

� H1J is the hysteresis parameter for event 1J and is determined by Hystfor1J.

� If the measurement result is CPICH-Ec/No, MNew and MInAS are expressed as ratios.

� If the measurement result is CPICH-RSCP, MNew and MInAS are expressed in mW.


3-9

Figure 3-7 Triggering of event 1J

� A: signal quality curve of a cell in the E-DCH active set

� B: signal quality curve of the worst cell in the E-DCH active set

� C: signal quality curve of a cell not in the E-DCH active set but included in DCH active set

� D: signal quality curve of a cell not in the E-DCH active set but included in DCH active

set

In Figure 3-7, the hysteresis and the cell individual offsets for all cells equal 0.

The first measurement report is sent when primary CPICH D becomes better than primary

CPICH B. The "cell measurement event result" of the measurement report contains the

information of primary CPICH D and CPICH B.

On the assumption that the E-DCH active set has been updated after the first measurement

report (E-DCH active set is now primary CPICH A and primary CPICH D), the second report

is sent when primary CPICH C becomes better than primary CPICH A. The "cell

measurement event result" of the second measurement report shows that primary CPICH C is

better than primary CPICH A in quality.

The following parameters need to be set on the RNC LMT:

� Hystfor1J: hysteresis of event 1F

� TrigTime1J: time to trigger event 1J

� PeriodMRReportNumfor1J: number of periodic reports for event 1J

� ReportIntervalfor1J: report interval for event 1J after change to the periodic report

� HO_INTRA_FREQ_RPRT_1J_SWITCH: measurement control switch for event 1J.

When the switch is ON, the UE version is R6 and event 1J is included in the intra-frequency measurement control message.

After receiving the intra-frequency measurement report from the UE, the RNC decides

whether to go to the execution phase, depending on the information in the report.


3-10

3.2.3 Intra-Frequency Handover Neighboring Cell Combination Algorithm

After the active set is updated, the RNC updates the neighboring cell list by using the

neighboring cell combination algorithm according to the status of the active set. This list

includes the new intra-frequency, inter-frequency, and inter-RAT neighboring cells. The

combination methods of intra-frequency handover, inter-frequency handover, and inter-RAT

handover are the same.

If the radio link of the Drift RNC (DRNC) is added to the active set, the Source RNC (SRNC)

buffers the intra-frequency, inter-frequency, and inter-RAT neighboring cell lists of the DRNC

until the radio link of the DRNC is released.

The neighboring cell combination result is contained in the MEASUREMENT CONTROL

message and sent to the UE, which instructs the UE to perform intra-frequency,

inter-frequency, and inter-RAT measurement and handover procedures.

The maximum number of neighboring cells of a cell that can be configured is as follows:

� The maximum number of intra-frequency neighboring cells is 32, which includes the cell

itself.

� The maximum number of inter-frequency neighboring cells of single carrier is 32.

� The maximum number of inter-frequency neighboring cells of 2 carriers is 64. No more

than 2 carriers of inter-frequency cells can be configured.

� The maximum number of inter-RAT neighboring cells of multi-carrier is 32

Neighboring Cell Combination Switch

HO_MC_NCELL_COMBINE_SWITCH is the neighboring cell combination switch.

� If the switch is set to ON, measurement objects are chosen from the neighboring cells of all the cells in the active set.

� If the switch is set to OFF, measurement objects are chosen from the neighboring cells

of the best cell.

HO_MC_NCELL_COMBINE_SWITCH is set to ON by default.

Description of the Neighboring Cell Combination Algorithm

After obtaining the intra-frequency neighboring cells of each cell in the active set, the RNC

calculates the union neighboring cell set of the intra-frequency cells, which is referred as Sall,

by using the following method. This method can also be used to generate the Sall of

inter-frequency or inter-RAT cells.

� The intra-frequency, inter-frequency, and inter-RAT neighboring cells of each cell in the

current active set are obtained.

� The RNC sequences the cells in the active set in descending order of CPICH Ec/No

according to the latest measurement report (event 1A, 1B, 1C, or 1D) from the UE. The

best cell is based on event 1D, whereas other cells are based on the latest measurement

report.

� The cells in the active set are added to Sall.

� The neighboring cells of the best cell in the active set are added to Sall. NprioFlag (the

flag of the priority) and Nprio (the priority of the neighboring cell), which are set for


3-11

each neighboring cell, are used to change the order of adding the neighboring cells to

Sall.

− When NprioFlag is switched to FALSE, NPrio is cleared.

− When NprioFlag is switched to TRUE, NPrio is set simultaneously.

� The neighboring cells of other cells in the active set are added to Sall in descending order

by CPICH Ec/No values of these cells in the active set. The neighboring cells of the

same cell in the active set are added according to Nprio and the number of repeated

neighboring cell is recorded.

If there are more than 32 intra-frequency neighboring cells in Sall, delete the repeated

neighboring cells whose number in Sall is less. The top 32 neighboring cells are grouped into

the final Sall. The limit of 32 neighboring cells is the same for the inter-frequency neighboring

cells.

3.3 Intra-Frequency Handover Decision and Execution The intra-frequency handover decision and execution procedure depends on the different

measurement events that the RNC receives.

3.3.1 Decision and Execution

Table 3-1 lists different types of intra-frequency handover decision and execution based on

different events.

Table 3-1 Intra-frequency handover decision and execution

Event Decision and Execution

1A When receiving an event 1A report, the RNC decides whether to add a cell.

For event 1A, the UE can report more than one cell in the event list in one

measurement report. These cells are in the list of the MEASUREMENT

CONTROL message, and they are sequenced in descending order of measurement quantity.

For the cells in the list, the RNC adds the radio link to the active set only if the

number of cells in the active set does not reach the maximum value. This

operation is not required if the number of cells in the active set reaches a specified value.

1B When receiving an event 1B report, the RNC decides whether to delete a cell.

For event 1B, if there is more than one radio link in the active set, the RNC

decides whether to delete a radio link. This operation is not required if there is only one radio link in the active set.

1C When receiving an event 1C report, the RNC decides whether to change the worst

cell.

For event 1C, the UE reports a list that contains good cells and the cells to be

replaced, and sequences the cells in descending order by measurement quantity.

After receiving the list from the UE, the RNC replaces the bad cells in the active set with the good cells in the list.


3-12

Event Decision and Execution

1D As stipulated in related protocols, an event 1D report includes information about

only one cell. This cell can be listed in an active set or a monitored set. The RNC

learns that the quality of this cell is better than that of the serving cell and takes one of the following actions:

If the reported cell is in the active set, the RNC decides whether to change the best cell or reconfigure measurement control.

If the reported cell is in the monitored set, then:

� If the number of cells in the active set has not reached the maximum value, the

RNC adds the cell to the active set.

� If the number of cells in the active set has reached the maximum value, the RNC replaces the worst cell in the active set with the reported cell.

� The best cell is changed to the reported cell.

The RNC determines whether the intra-frequency hard handover scenarios are

applicable. For detailed information, see 2.1 Handover Types. If any scenario is

applicable, the RNC performs an intra-frequency hard handover.

1J When receiving an event 1J report with information about the good cells and the

cells to be replaced, the RNC proceeds as follows:

If the current number of cells in the E-DCH active set is smaller than the value of

MaxEdchCellInActiveSet, the uplink of the cell where event 1J is triggered is reconfigured to E-DCH.

If the current number of cells in the E-DCH active set is equal to the value of

MaxEdchCellInActiveSet, the RNC searches the measurement report for the

non-serving E-DCH with the lowest measured quality in the E-DCH active set.

Then, the uplink of the cell where event 1J is triggered is reconfigured from DCH to E-DCH.

Minimum Quality Threshold for Soft Handover

When receiving an event 1A, 1C, or 1D report, the RNC adds a target cell to the active set

only when the CPICH Ec/No of the target cell is higher than the absolute threshold

SHOQualmin.

SHO: soft handover

Switch for Cross-Iur Intra-Frequency Handover

If the RRC connection has been set up but the Radio Bearers (RBs) have not, whether a

cross-Iur soft handover can be executed is determined by

HO_MC_SIGNAL_IUR_INTRA_SWITCH of the SET UCORRMALGOSWITCH

parameter. Only if the switch is set to ON, can the cross-Iur soft handover be executed.

3.3.2 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.


3-13

Estimation Procedure for Rate Reduction

If the RNC receives a 1A, 1C, or 1D measurement report, the RNC tries to add the

corresponding cell to the active set. If the addition fails, the RNC performs the estimation

procedure for rate reduction.

Figure 3-8 Estimation procedure for rate reduction

1. The RNC evaluates whether the measurement quantity of the cell failing to be admitted meets the condition of rate reduction.

− If the condition is met, the RNC performs a rate reduction process for the access

service immediately, as described in the next section Procedure of Rate Reduction Execution.

− If the condition is not met, the RNC performs the next step (Step 2).

The condition of rate reduction is as follows: Mnew > Mbest_cell - RelThdForDwnGrd

− Mnew is the CPICH Ec/No measurement value of the cell failing to be admitted.

− Mbest_cell is the CPICH Ec/No measurement value of the best cell in the active set.

− RelThdForDwnGrd is configured through the parameter Relative threshold of SHO failure.

2. The RNC evaluates whether the number of SHO failures in the cell exceeds the

Threshold number of SHO failure.

� If the number of SHO failures in the cell is smaller than the ShoFailNumForDwnGrd:

− If the timer has not been started, the RNC starts it.

− If the timer has been started, the RNC increments the SHO failure counter by one.

The timer length is set through the parameter ShoFailPeriod.


3-14

The SHO failure counter of a cell is used to record the number of SHO failures in this

cell. For each UE, the RNC records the number of SHO failures in three cells at most. For SHO failures in any other cells, the RNC does not record the number.

Before the SHO failure evaluation timer expires, no action is taken and the RNC waits for the next measurement report period.

When the SHO failure evaluation timer expires, the RNC sets the SHO failure counter of

the corresponding cell to 0 and ends the evaluation.

� If the number of SHO failures in the cell is larger than or equal to the parameter

ShoFailNumForDwnGrd, the RNC performs a rate reduction process for the access service,

Procedure of Rate Reduction Execution

Figure 3-9 Procedure of rate reduction execution

1. The RNC performs a rate reduction process for the access service. The method of

determining the access rate after the rate reduction is the same as that described in Rate Negotiation of Load Control Feature Parameter Description.

2. After the rate reduction succeeds, the RNC immediately attempts to add this cell to the active set without measurement:

� If the cell succeeds in admitting the UE, the RNC adds the radio link and sets the SHO

failure counter of the cell to 0 and ends the execution.

� If the cell fails to admit the UE, the RNC starts the Period of penalty timer for SHO

failure after down rate to avoid an increase in the rate triggered by DCCC within the

period. Also in this period, the RNC sets the SHO failure counter of the cell to 0 and

ends the execution.


3-15

If the RNC fails to perform a soft handover again, it performs the estimation procedure and

the execution procedure, as previously described.

3.4 Signaling Procedures for Intra-Frequency Handover

3.4.1 Intra-NodeB Intra-Frequency Soft Handover Signaling Procedure

This section describes the signaling procedure for intra-frequency soft handover within a

NodeB.

Figure 3-10 shows the procedure for intra-frequency soft handover when the UE moves from

one cell to another cell within the same NodeB.

Figure 3-10 Procedure for intra-NodeB intra-frequency soft handover

The connections involved in the intra-NodeB intra-frequency softer handover change are as

follows:

� Before the softer handover, only cell 1 is connected to the UE.

� During the softer handover, both cell 1 and cell 2 are connected to the UE.

� After the softer handover, only cell 2 is connected to the UE. Cell 1 is removed from the

active set.


3-16

Figure 3-11 Signaling procedure for intra-NodeB intra-frequency soft handover

3.4.2 Intra-RNC Inter-NodeB Intra-Frequency Soft Handover Signaling Procedure

Figure 3-12 Procedure for intra-RNC inter-NodeB intra-frequency soft handover

� Before the soft handover, only NodeB 1 is connected to the UE.

� During the soft handover, both NodeBs are connected to the UE.


3-17

� After the soft handover, only NodeB 2 is connected to the UE. The active set of NodeB 1

is removed.

Figure 3-13 Signaling procedure for intra-RNC inter-NodeB intra-frequency soft handover


3-18

3.4.3 Inter-RNC Intra-Frequency Soft Handover Signaling Procedure

Figure 3-14 Procedure for inter-RNC intra-frequency soft handover

� Before the soft handover, the UE is connected to NodeB 1 and NodeB 2.

� After the SRNC makes a soft handover decision, it sets up a connection between NodeB

3 under another RNC and the UE, and releases the connection between NodeB 1 and the UE.


3-19

Figure 3-15 Signaling procedure for inter-RNC intra-frequency soft handover

3.4.4 Intra-RNC Inter-NodeB Intra-Frequency Hard Handover Signaling Procedure

The signaling procedure of intra-NodeB Intra-Frequency Hard Handover is similar to that of

Intra-RNC inter-NodeB Intra-Frequency Hard Handover. Only the latter are described here.


3-20

Figure 3-16 Procedure for intra-RNC inter-NodeB intra-frequency hard handover

Figure 3-17 Signaling procedure for intra-RNC inter-NodeB intra-frequency hard handover

In Figure 3-17, NodeB 1 is the source NodeB, and NodeB 2 is the target NodeB.


3-21

3.4.5 Inter-RNC Intra-Frequency Hard Handover Signaling Procedure

Figure 3-18 shows the procedure for intra-frequency hard handover when a UE moves from

one NodeB in an SRNC to another NodeB in a DRNC.

Figure 3-18 Procedure for inter-RNC intra-frequency hard handover


3-22

Figure 3-19 Signaling procedure for inter-RNC intra-frequency hard handover

As shown in Figure 3-19, NodeB 1 is the source NodeB and NodeB 2 is the target NodeB.

4 Inter-Frequency Handover

4-1

4 Inter-Frequency Handover 4.1 Inter-Frequency Handover Procedure

The inter-frequency handover procedure is divided into four phases: handover triggering,

handover measurement, handover decision, and handover execution. The procedure varies

according to handover types.

4.1.1 Coverage- or QoS-based Inter-Frequency and Inter-RAT Handover Procedure

The procedure for the coverage- or QoS-based inter-frequency handover is the same as that

for the coverage- or QoS-based inter-RAT handover, as shown in Figure 4-1.


4-2

Figure 4-1 Coverage- or QoS-based inter-frequency and inter-RAT handover procedure

� In the triggering phase

For the coverage-based handover, the RNC requests the UE to measure through an

inter-frequency measurement control message. If the CPICH Ec/No or CPICH RSCP of

the current cell is lower than the corresponding threshold, the UE reports event 2D.

For the QoS-based handover, if the service quality of the current cell deteriorates, the Link Stability Control Algorithm makes a handover measurement decision.

� In the measurement phase

The RNC sends an inter-frequency measurement control message to the UE, requesting

the NodeB and UE to start the compressed mode. The RNC also requests the UE to perform the inter-frequency or inter-RAT handover measurement .

In this phase, the method of either periodical measurement report or event-triggered

measurement report can be used.

� In the decision phase

After the UE reports event 2B, the RNC performs the handover. Or the UE periodically generates measurement reports, and the RNC makes a decision after evaluation.

� In the execution phase

The RNC executes the handover procedure.


4-3

4.1.2 Load-based Inter-Frequency Handover Procedure

The load-based inter-frequency handover suits best in the case of the co-sited cells covering

the same area.


The Load Reshuffling (LDR) module directly determines whether the current cell is in

basic congestion and whether an inter-frequency handover needs to be performed. The

LDR module provides the target cell information for the current cell, and the RNC

performs the handover procedure.

For details of LDR, see Load Control Feature Parameter Description.


For load-based inter-frequency blind handover, the RNC decides to trigger an inter-frequency blind handover if the corresponding conditions are met.

− If the inter-frequency blind handover can be triggered, the RNC enters the decision phase.

− If the inter-frequency blind handover cannot be triggered, the RNC does not perform

the handover.

After the inter-frequency handover is triggered, the RNC chooses a decision algorithm according to whether the conditions of direct blind handover are met.

For load- and measure-based inter-frequency handover, the RNC requests the UE to

perform the inter-frequency measurement. Based on the measurement results, the RNC

chooses a target cell to perform inter-frequency hard handover.


The RNC performs the handover according to the decision result.

For details of LDR, see Load Control Feature Parameter Description.

4.1.3 Speed-based Inter-Frequency Handover Procedure

Figure 4-2 shows speed-based inter-frequency handover procedure.


4-4

Figure 4-2 Speed-based inter-frequency handover procedure


The RNC receives the handover request according to the HCS speed estimation. The

handover based on HCS speed estimation is of two types: handover from the macro cell

to the micro cell and handover from the micro cell to the macro cell. For different types of handover, the RNC acts differently.

� In the measurement and decision phases

− If the handover is performed from a macro cell to a micro cell, the RNC sends an

inter-frequency measurement control message. After the UE reports event 2C, the

RNC performs the handover decision. For inter-RAT handover, the UE reports event

3C.

− If the handover is performed from a micro cell to a macro cell, the RNC directly performs blind handover, ignoring the measurement procedure.


The RNC initiates a handover procedure.

− If the handover is performed from a micro cell to a macro cell and the target cell of

blind handover is configured (through the parameter BlindHOFlag), the RNC

performs blind handover to the target cell.

− If the blind handover fails or the handover is performed from a macro cell to a micro

cell, the RNC starts the inter-frequency (or inter-RAT) measurement procedure. If the

inter-frequency measurement mode is employed, the RNC performs the


4-5

inter-frequency handover procedure to the cell with the best quality after receiving

event 2C from the UE.

4.2 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.

4.2.1 Inter-Frequency Handover Measurement Switches

Some switches are important for inter-frequency handover because they decide whether the

handover can be performed successfully. These switches are the parameter values of

Handover algorithm switch in the command SET UCORRMALGOSWITCH, as described

below.

HO_MC_SIGNAL_SWITCH: The switch decides when the RNC performs the active set

signal quality measurement.

� If the switch is set to ON, the RNC initiates the active set quality measurement after the RRC connection setup is completed (before the RB setup).

� If the switch is set to OFF, the RNC initiates the active set quality measurement after the RB setup is completed.

� The switch is set to OFF by default.

HO_INTER_FREQ_HARD_HO_SWITCH: The switch decides whether to enable the

inter-frequency handover measurement.

� If the switch is set to ON, the RNC enables the inter-frequency handover measurement and the load-based inter-frequency handover.

� If the switch is set to OFF, the RNC disables the inter-frequency handover measurement.

� The switch is set to ON by default.

HO_MC_MEAS_BEYOND_UE_CAP_SWITCH: The switch decides whether the

neighboring cell will be sent in the inter-frequency measurement control message when the

frequency of the neighboring cell is not included in the measurement capability of the UE.

The reported measurement capability of the UE is not the same as the actual measurement

capability of the UE. Measurement capability at some frequencies may not be reported due to

the limitation of the version of UE protocol.

� If the switch is set to ON, the RNC sends the inter-frequency measurement control

message with the neighboring cell, whose frequency is not included in the measurement

capability of the UE.

� If the switch is set to OFF, the RNC sends the inter-frequency measurement control

message without the neighboring cell, whose frequency is not included in the measurement capability of the UE.

� The switch is set to OFF by default.


4-6

4.2.2 Inter-Frequency Handover Measurement Report Modes

The event-triggered measurement report mode applies to various handovers. The periodical

measurement report mode applies to only load-based and speed-based inter-frequency

handovers.

� The measurement report mode of inter-frequency handover is configured through the

parameter InterFreqReportMode.

� The interval of the measurement reports is configured through the parameter

PrdReportInterval.

The advantage of periodical measurement report is that if the handover fails, the RNC

reattempts the handover to the same cell after receiving the periodical measurement report

from the UE. This increases the probability of the success of inter-frequency handover.

Based on the measurement control message received from the RNC, the UE periodically

reports the measurement quality of the target cell. Then, based on the measurement report, the

RNC makes the handover decision and performs handover.

4.2.3 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 the triggering phase, events 2D and 2F that correspond to CPICH_Ec/No and CPICH_RSCP are sent from the UE.

− In the measurement phase, event 2B or periodical measurement that correspond to

CPICH_Ec/No and CPICH_RSCP are sent from the UE.

− In inter-frequency handover based on coverage, the system delivers both CPICH

Ec/No and RSCP as measurement quantities to perform 2D/2F measurement. To

restrict the types of reported measurement quantities, set the measurement triggering

threshold to the minimum value. For example, if the reporting of event 2D of CS

service Ec/No is allowed but that of RSCP is restricted, you can set InterFreqCSThd2DRSCP to the minimum value, that is, –115.

� In inter-frequency handover based on QoS, event 2B or periodical measurement takes both CPICH Ec/No and RSCP as measurement quantities.

� In inter-frequency handover based on speed, event 2C takes only CPICH Ec/No as

measurement quantity.

� 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

The UE performs the layer 3 (L3) filtering of measurement values before it judges the

measurement event and sends the measurement report. The inter-frequency measurement

model is similar to the intra-frequency measurement model. For detailed information, see3.2.1

Intra-Frequency Handover Measurement Quantities for Intra-Frequency Handover. The

parameter InterFreqFilterCoef is the filtering coefficient of the inter-frequency measurement

value, which is configured on the basis of inter-frequency handover types.


4-7

4.2.4 Inter-Frequency Handover Measurement Events

When the measurement thresholds are reached, the UE reports the events to the RNC to

trigger related handover procedures.

Table 4-1 describes the measurement events involved in inter-frequency handover.

Table 4-1 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.

2C The estimated quality of a non-used frequency is above a certain threshold.

1F A Primary CPICH becomes worse than an absolute threshold.

Frequency Quality Estimation for Inter-Frequency Handover

In inter-frequency handover, the reporting criteria of measurement events are based on the

frequency quality estimation. The parameter Weight for used frequency specifies the

frequency weighing factor that is used to measure the quality of the current frequency. This

parameter is used for all event-triggered inter-frequency measurements but not for periodical

inter-frequency measurements. The event-triggered measurement events include events 2D,

2F, 2B, and 2C.

For detailed information on the quality estimation formula, see section "Frequency Quality

Estimate" in 3GPP TS 25.331.


After the conditions of event 2D are fulfilled and maintained until the TimeToTrig2D is

reached, the UE sends the event 2D measurement report message.

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

QUsed ≤ TUsed2d - H2d/2

� QUsed is the measured quality of the used frequency.

� TUsed2d is the absolute quality threshold of the cell that uses the current frequency.

Based on the service type and measurement quantity, this threshold can be configured through one of the following parameters:

− InterFreqCSThd2DEcN0

− InterFreqR99PsThd2DEcN0

− InterFreqHThd2DEcN0

− InterFreqCSThd2DRSCP

− InterFreqR99PsThd2DRSCP

− InterFreqHThd2DRSCP


4-8

The parameters InterFreqHThd2DRSCP and InterFreqHThd2DEcN0 are valid

only when the switch HO_ALGO_OVERLAY_SWITCH is set to ON. Otherwise,

the PS domain services will take InterFreqR99PsThd2DEcN0 or InterFreqR99PsThd2DRSCP as a measurement event threshold.

− For the PS and CS combined services, the threshold is set to the higher one of CS or

PS services.

− If the UE has only signaling connections currently, the thresholds for CS services are used.

� H2d is the event 2D hysteresis value set through the parameter HystFor2D.

Triggering of Event 2F

After the conditions of event 2F are fulfilled and maintained until the parameter

TimeToTrig2F is reached, the UE reports the event 2F measurement report message.

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

QUsed ≥ TUsed2f + H2f/2

where


� TUsed2f is the absolute quality threshold of the cell that uses the current frequency.

Based on the service type and measurement quantity, this threshold can be configured

through one of the following parameters:

− InterFreqCSThd2FEcN0

− InterFreqCSThd2FRSCP

− InterFreqR99PsThd2FEcN0

− InterFreqR99PsThd2FRSCP

− InterFreqHThd2FEcN0

− InterFreqHThd2FRSCP

The parameters InterFreqHThd2FEcN0 and InterFreqHThd2FRSCP are valid

only when the switch HO_ALGO_OVERLAY_SWITCH is set to ON. Otherwise,

the PS domain services will take InterFreqR99PsThd2FEcN0 or InterFreqR99PsThd2FRSCP as a measurement event threshold.

− For the PS and CS combined services, the threshold is set to the higher one of CS or

PS services.

− If the UE has only signaling connections currently, the thresholds for CS services are used.

� H2f is the event 2F hysteresis value set through the parameter HystFor2F.

Conditions of event 2F are as follows: TUsed2d - H2d/2 < TUsed2f + H2f/2, for example,

(InterFreqCSThd2DEcN0–HystFor2D/ 2) < (InterFreqCSThd2FEcN0+ HystFor2F / 2).

Triggering of Event 2B

After the conditions of event 2B are fulfilled and maintained until the parameter

TimeToTrig2B is reached, the UE reports the event 2B measurement report message.

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

QNoused ≥ TNoused2b + H2b/2


4-9

QUsed ≤ TUsed2b - H2b/2

where

� QNoused is the measured quality of the cell that uses the other frequencies.


� H2b is the event 2B hysteresis value set through the parameter HystFor2B.

� TNoused2b is the absolute quality threshold of the cell that uses the other frequencies.

Based on the service type and measurement quantity, this threshold can be configured through one of the following parameters:

− TargetFreqCsThdEcN0

− TargetFreqCsThdRscp

− TargetFreqR99PsThdEcN0

− TargetFreqR99PsThdRscp

− TargetFreqHThdEcN0

− TargetFreqHThdRscp

� TUsed2b is the absolute quality threshold of the cell that uses the current frequency.

TUsed2b is set in the following way:

� Based on the service type and measurement quantity, this threshold can be configured

through one of the following parameters:

If event 2D with the CPICH RSCP value is received by the RNC:

− TUsed2b of event 2B with the CPICH RSCP value can be:

UsedFreqCSThdRSCP

UsedFreqR99PsThdRSCP

UsedFreqHThdRSCP

− TUsed2b of event 2B with the CPICH Ec/No value is configured as the maximum value

0 dB.

According to 3GPP specifications, TUsed2b of event 2B with the CPICH Ec/No

value should be configured as the maximum value 0 dB. If the event 2F with the

CPICH Ec/No value is received by the RNC and TUsed2b of event 2B with the

CPICH Ec/No value is modified, TUsed2b is reset to 0 dB.

If event 2D with the CPICH Ec/No value is received by the RNC:

− TUsed2b of event 2B with the CPICH Ec/No value can be:

UsedFreqCSThdEcN0

UsedFreqR99PsThdEcN0

UsedFreqHThdEcN0

− TUsed2b of event 2B with the CPICH RSCP value is configured as the maximum value –25 dBm.

According to 3GPP specification, TUsed2b of event 2B with the CPICH RSCP value

should be configured as the maximum value –25 dBm. If event 2F with the CPICH

RSCP value is received by the RNC and TUsed2b of event 2B with the CPICH RSCP

value is modified, TUsed2b is reset to –25 dBm.


4-10

� For the PS and CS combined services, the threshold is set to the higher one of CS or PS services.

� If the UE has only signaling connections currently, the thresholds for CS services are used.

The parameters TargetFreqHThdEcN0, TargetFreqHThdRscp, UsedFreqHThdRSCP,

and UsedFreqHThdEcN0 are valid only when the switch HO_ALGO_OVERLAY_SWITCH is

set to ON. Otherwise, the PS domain R99 services take UsedFreqR99PsThdEcN0, UsedFreqR99PsThdRSCP, TargetFreqR99PsThdEcN0, or TargetFreqR99PsThdRscp as a measurement event threshold.


After the conditions of event 2C are fulfilled and maintained until the parameter TrigTime2C

is reached, the UE reports the event 2C measurement report message..

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

QNoused ≥ TNoused2c + H2c/2

where

� QNoused is the measured quality of the cell that uses the other frequencies.

� TNoused2c is the absolute quality threshold of the cell that uses the other frequencies, namely, InterFreqNCovHOThdEcN0.

� H2c is the event 2C hysteresis value Hystfor2C.


After the conditions of event 1F are fulfilled and maintained until the parameter TrigTime1F

is reached, the UE reports the event 1F measurement report message.


10LogMOld ≤ T1f - H1f/2

Where:

� MOld is the measurement value of the cell that becomes worse.

� T1f is an absolute threshold. It is set through the parameter IntraAblThdFor1FRSCP or

IntraAblThdFor1FecNo.

� H1f is the event 1F hysteresis value set through the parameter Hystfor1F.

4.2.5 Inter-Frequency Handover Neighboring Cell Combination Algorithm

See section 3.2.3 Intra-Frequency Handover Neighboring Cell Combination Algorithm.

4.2.6 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.


4-11

If the UE has a dual-frequency receiver, it can perform inter-frequency measurement without

starting the compressed mode if all of the following conditions are met:

� The MP_UU_ADJACENT_FREQ_CM_SWITCH is on.

� The value of the IE "Adjacent frequency measurements without compressed mode"

reported by the UE is TRUE.

� For the UE that supports dual-carrier HSDPA(DC-HSDPA):

− If the UE has a DC-HSDPA service, all the cells involved in inter-frequency measurement are at the same frequency as the supplementary carrier.

− If the UE does not have a DC-HSDPA service, all the cells involved in

inter-frequency measurement are at the same frequency, with a 5 MHz spacing from the current cell, but within the same band as the current cell.

Each physical frame can provide three to seven timeslots for the inter-frequency or inter-RAT

cell measurement.

Compressed Mode Switches

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,

CMCF_UL_PRECFG_TOLERANCE_SWITCH under CmcfSwitch determines whether

to set up the RB of SF4 during the preparation for SF/2 compressed mode.

� If CMCF_UL_PRECFG_TOLERANCE_SWITCH is set to ON, the RB of SF4 can

be set up during the preparation for SF/2 compressed mode. The inter-frequency or

inter-RAT handover measurement, however, cannot be triggered, because SF4 cannot be compressed to SF2.

� If CMCF_UL_PRECFG_TOLERANCE_SWITCH is set to OFF, the RB of SF4

cannot be set up during the preparation for SF/2 compressed mode. The system can trigger the SF/2 compressed mode measurement.

CMCF_WITHOUT_UE_CAP_REPORT_SWITCH under CmcfSwitch determines

whether to use the frequencies beyond the range of UE reports on the compressed mode

measurement.

The compressed mode is of the following types:

� Spreading factor reduction (SF/2)

� High layer scheduling

Which type of compressed mode to use is automatically decided by the RNC on the basis of

the spreading factor used in the uplink or the downlink.

� When the downlink spreading factor is greater than or equal to the parameter

DlSFTurnPoint, the SF/2 approach is preferred. Otherwise, the high layer scheduling is used.


4-12

� When the uplink spreading factor is greater than or equal to the parameter

UlSFTurnPoint, the SF/2 approach is preferred. Otherwise, the high layer scheduling is used.

To initiate the high layer scheduling, set the following two switches:

� If the algorithm switch CMCF_DL_HLS_SWITCH in the command SET

UCORRMALGOSWITCH is set to ON, the DL high-layer scheduling for the compressed mode is allowed.

� If the algorithm switch CMCF_UL_HLS_SWITCH in the command SET

UCORRMALGOSWITCH is set to ON, the UL high-layer scheduling for the compressed mode is allowed.

Measurement Timer Length

When the UE takes a long time to perform the inter-frequency measurement in compressed

mode, the radio network will be affected. To avoid the influence, the RNC stops the

inter-frequency measurement and disables the compressed mode if no inter-frequency

handover occurs upon expiry of the inter-frequency measurement timer.

� The timer is specified by InterFreqMeasTime in inter-frequency handover based on

coverage, load or HCS.

� The timer is specified by InterRATMeasTime in inter-RAT handover based on

coverage, load, or service.

� The timer is specified by DLQosMcTimerLen or ULQosMcTimerLen in inter-RAT handover based on downlink or uplink QoS respectively.

4.3 Inter-Frequency Handover Decision and Execution This section describes the procedure for decision and execution of different types of

inter-frequency handover.

4.3.1 Coverage- and QoS-based Inter-Frequency Handover Decision and Execution

The coverage- and QoS-based inter-frequency handovers are categorized into two types

according to the following two measurement report modes: periodical measurement report

mode and event-triggered measurement report mode. Each mode corresponds to a different

decision and execution procedure.

Coverage- and QoS-based Inter-Frequency Handover in Periodical Measurement Report Mode

After receiving the periodical measurement report of the inter-frequency cell, the RNC starts

the following decision procedures:

1. 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 listed below:

Mother_Freq + CIOother_Freq ≥ Tother_Freq + H/2

where


4-13

− Mother_Freq is the CPICH Ec/No or CPICH RSCP measurement value of the target cell

reported by the UE. Both of the two measurement values of the inter-frequency cell must satisfy the formula.

− CIOother_Freq is the cell individual offset value of the target cell. It is equal to the sum of CIO and CIOOffset.

− Tother_Freq is the decision threshold of inter-frequency hard handover. Based on the

service type and measurement quantity, this threshold can be configured through one of the following parameters:

� TargetFreqCsThdEcN0

TargetFreqCsThdRscp

TargetFreqR99PsThdEcN0

TargetFreqR99PsThdRscp

TargetFreqHThdEcN0

TargetFreqHThdRscp

These thresholds are the same as the quality threshold of event 2B..

− H is the inter-frequency hard handover hysteresis value set through the parameter HystForPrdInterFreq.

2. Start the hard handover time-to-trigger timer, which is configured through the parameter TimeToTrigForPrdInterFreq.

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

4. Select the cells in sequence, that is, from high quality cells to low quality ones, to initiate

inter-frequency handover in the cells where the hard handover time-to-trigger timer expires.

Each cell in the measurement report shall be evaluated as mentioned previously. When the

hard handover time-to-trigger timers of more than one cell expire at the same time, the latest

measurement report is used for selecting the best inter-frequency neighboring cell for

handover. For example, the cell with the highest CPICH RSCP in the latest measurement

report is selected, as shown in Figure 4-3.


4-14

Figure 4-3 Selecting the cell with the highest CPICH RSCP

Coverage- and QoS-based Inter-Frequency Handover in 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:

1. 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.

2. Select the cells in turn from the cell set to perform inter-frequency handover.

4.3.2 Load-based Inter-Frequency Handover Decision and Execution

The LDR algorithm may trigger an inter-frequency handover. The following describes the

procedure for handover decision and execution.

Load-based Inter-Frequency Blind Handover Decision

1. The LDR algorithm learns that a cell is in basic congestion and provides target cells and the UE with low priority for handover.

2. The RNC determines to trigger an inter-frequency blind handover.

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.


4-15

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

load-based inter-frequency blind handover. The intra-frequency measurement is used to estimate quality of the inter-frequency cell of the same coverage.

− 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

The inter-frequency cells with the same coverage area have the same CPICH RSCP values.

By measuring the CPICH RSCP of the cell, the quality of the cells with the same coverage

area can be determined, which increases the probability of successful blind handover.

1. The RNC initializes the timer of intra-frequency measurement for blind handover. The

timer is specified by internal algorithm and need not be configured.

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

The measurement report mode is set to periodical report.

− The reporting period is BlindHOIntrafreqMRInterval.

− The number of measurement reports is BlindHOIntrafreqMRAmount.

− The intra-frequency handover measurement quantity is CPICH RSCP.

− The list of measured cells contains only the cells that trigger LDR.

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.

4. When the counter reaches the value of BlindHOIntrafreqMRAmount, the RNC

initiates a blind handover to the target cell.

If the counter does not reach this value, the RNC waits for the next intra-frequency

measurement report from the UE.

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.

If the inter-frequency handover based on coverage or QoS is triggered, the RNC stops the

intra-frequency measurement for conditional blind handover.

Load- and Measure-based Inter-Frequency Handover Decision and Execution

1. The LDR algorithm learns that a cell is in basic congestion and provides target cells and

the UE with low priority for handover.

2. The RNC selects the target cell based on the measurement results.

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.


4-16

3. The RNC performs an inter-frequency hard handover to the target cell directly.

4.3.3 Speed-based Inter-Frequency Handover Decision and Execution

This section covers the decision and execution of micro cell to macro cell, as well as that of

macro cell to micro cell.

Decision and Execution of Micro Cell to Macro Cell Handover

If the handover is performed from a micro cell to a macro cell and a target cell for blind

handover is configured, the RNC performs a blind handover to the target cell. If the blind

handover fails, the RNC continues to perform a blind handover. The blind handover procedure

is as follows:

1. The RNC selects the neighboring cells with a lower HCSPrio to generate a cell set. The

neighboring cells whose frequency band is not supported by the UE are not taken into

account. If there are neighboring cells with several candidate frequencies, then the RNC

selects one of the frequencies randomly.

2. The RNC searches for neighboring cells for blind handover according to BlindHOFlag.

3. The RNC chooses a neighboring cell whose BlindHOQualityCondition value is the smallest for blind handover.

4. The RNC determines whether the target cell supports the current service. If the target cell does not support the current service, the RNC does not perform the blind handover.

Decision and Execution of Macro Cell to Micro Cell Handover

If the blind handover fails or the handover is performed from a macro cell to a micro cell, the

RNC starts the inter-frequency (or inter-RAT) measurement procedure. If the inter-frequency

measurement mode is employed, the RNC starts the following procedure:

1. Add all the pilot cells that trigger event 2C to a cell set and arrange the cells according to the measurement quality in descending order.

2. Select the cells in turn from the cell set to perform inter-frequency handover.

4.3.4 Blind Handover Decision and Execution Based on Event 1F

When there is only one cell in the active set, the RNC performs inter-frequencey blind

handover after receiving event 1F.

1. The RNC gets the actual best cell from event 1F. If the quality of the best cell meets the

Blind handover condition (BlindHOQualityCondition), the RNC gets neighboring cells

for blind handover of the best cell, and filtrate the cells which belong to the frequency

bands that UEs don't support.

2. If there are multiple neighboring cells for blind handover, the RNC chooses the cell with

the lowest value of BlindHOQualityCondition and the cell must support all the current

services of UE. When there are multiple such cells, the RNC choose the neighboring cell

for blind handover randomly.


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4.3.5 Inter-Frequency Anti-Ping-Pong Algorithm

After an inter-frequency handover based on coverage or an inter-frequency blind handover

based on event 1F occurs, the RNC starts the anti-ping-pong algorithm to prevent frequent

switching between inter-frequency handovers triggered by different causes.

The inter-frequency anti-ping-pong algorithm is as follows:

1. When a coverage-based inter-frequency handover or an inter-frequency blind handover

based on event 1F occurs, the RNC starts the timer specified by

IFAntiPingpangTimerLength for the UE.

2. When a non-coverage-based inter-frequency handover is triggered, first, the RNC

determines whether the timer specified by IFAntiPingpangTimerLength expires.

− If the timer does not expire, the RNC cancels the handover.

− If the timer expires, the RNC performs the handover.

4.3.6 Inter-Frequency Handover Retry

If an inter-frequency handover based on event-triggered measurement report mode fails, the

RNC initiates the inter-frequency handover attempt according to an inter-frequency retry

algorithm.

� After the inter-frequency handover fails, the retry timer for the cell is started.

� After the retry timer expires, the UE makes a handover attempt to the cell again until the

retry number exceeds the maximum allowed retry number. If the handover succeeds or two new event 2B reports are received, the periodical retry is stopped.

For the inter-frequency handover based on coverage or QoS, the following two parameters

determine the retry period and the maximum number of retry times:

� Retry timer:PeriodFor2B

� Maximum number of retry times:AmntOfRpt2B

For the inter-frequency handover based on speed, the following two parameters determine the

retry period and the maximum number of retry times:

� Retry timer:PeriodFor2C

� Maximum number of retry times:AmntOfRpt2C

4.4 Signaling Procedures for Inter-Frequency Handover

4.4.1 Inter-Frequency Handover Within One RNC

Figure 4-4 shows the inter-frequency handover for a UE that moves from NodeB 1 to NodeB

2 within one RNC. Before the handover, the UE sets up a connection to NodeB 1.After the

handover, the UE sets up a connection to NodeB 2.

The signaling procedure of inter-frequency handover within one NodeB is similar to that

between NodeBs within one RNC.


4-18

Figure 4-4 Inter-frequency handover between NodeBs within one RNC

Figure 4-5 Signaling procedure for inter-frequency handover between NodeBs within one RNC


4-19

As shown in Figure 4-5, NodeB 1 is the source NodeB, whereas NodeB 2 is the target NodeB.

From step 1 through step 6, a new connection is set up. From step 7 through step 9, the old

connection is released.

4.4.2 Inter-Frequency Handover Between RNCs

Figure 4-6 shows the signaling procedure for inter-frequency hard handover for a UE that

moves from a NodeB to another NodeB between the RNCs. Before the handover, the UE sets

up a connection to NodeB 1.After the handover, the UE sets up a connection to NodeB 2.

Figure 4-6 Inter-frequency hard handover between the RNCs


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Figure 4-7 Signaling procedure for inter-frequency hard handover between the RNCs

NodeB 1 is the source NodeB, whereas NodeB 2 is the target NodeB. From step 1 through

step 10, a new connection is set up. From step 11 through step 13, the old connection is

released.

5 Inter-RAT Handover

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5 Inter-RAT Handover 5.1 3G-to-2G Handover Procedure

The 3G-to-2G handover procedure is divided into four phases: handover triggering, handover

measurement, handover decision, and handover execution. The procedure varies according to

handover types.

5.1.1 Coverage-based 3G-to-2G Handover Procedure

For details, see 4.1.1 Coverage- or QoS-based Inter-Frequency and Inter-RAT Handover

Procedure.

5.1.2 Load-based 3G-to-2G Handover Procedure

Figure 5-1 Load-based 3G-to-2G handover procedure



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When the load of the 3G cell that the UE accesses is higher than the related threshold,

the Load Reshuffling (LDR) algorithm makes a handover decision. For detailed

information of the LDR, see Load Reshuffling in the Load Control Feature Parameter

Description.


The RNC enables the compressed mode and starts the inter-RAT handover measurement.


After the UE reports event 3C, the RNC makes a handover decision.



5.1.3 Service-based 3G-to-2G Handover Procedure

Figure 5-2 Service-based 3G-to-2G handover procedure


When a service is established, the RNC requests the handover to the GSM based on the service type and service handover indicator assigned by the CN.


The RNC enables the compressed mode and starts the inter-RAT handover measurement.


After the UE reports event 3C, the RNC makes a handover decision.



5.1.4 Speed-based 3G-to-2G Handover Procedure

For details, see 4.1.3 Speed-based Inter-Frequency Handover Procedure.


5-3

5.2 3G-to-2G Handover Measurement

5.2.1 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.

5.2.2 3G-to-2G Handover Measurement Report Modes

For coverage or QoS based UMTS-to-GSM handover, there are two measurement report

modes: event-triggered measurement report mode and periodical measurement report mode.

For load or service-based 3G-to-2G handover, the measurement report is event-triggered only.

� The measurement report mode is configured through the parameter InterRatReportMode.

� In periodical measurement report mode, the UE sends measurement reports periodically

to the RNC according to the values of the report interval. The report interval needs to be configured through the parameter InterRATPeriodReportInterval.

5.2.3 3G-to-2G Handover Measurement Quantity

There is a choice of multiple measurement quantities used to measure the CPICH quality.

� 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. To deliberately limit the types of

measurement quantity, you can set the corresponding threshold of the limited

measurement quantity to the minimum value. For example, if event 2D of CS service

Ec/No can be reported but the RSCP cannot, the parameter

InterRATCSThd2DRSCP is set to the minimum value, that is, -115.

− 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.

The unused frequencies refer to GSM frequency signals, and the unused frequency

measurement quantity refers to GSM RSSI.

The UE performs the layer 3 (L3) filtering of measurement values before it judges the

measurement event and sends the measurement report. The inter-RAT measurement model is

similar to the intra-frequency measurement model. For detailed information, see 3.2.1

Intra-Frequency Handover Measurement Quantities for Intra-Frequency Handover. The


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smoothed filter coefficient for layer 3 inter-RAT measurement is InterFreqFilterCoef, and

the smoothed filter coefficient for events 2D and 2F is FilterCoefOf2D2F.

5.2.4 3G-to-2G Handover Measurement Events

When the measurement thresholds are reached, the UE reports the events to the RNC to

trigger the related handover procedures.

Table 5-1 Events in inter-RAT 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 Frequency Quality Estimation

In 3G-to-2G handover, the report criteria of event 3A are based on the quality estimation of

the frequency. The parameter WeightForUsedFreq is the frequency weighting factor used to

calculate the quality of the current frequency. This parameter is used for event 3A only.

For detailed information about the quality estimation formula, see section "Frequency Quality

Estimate" in 3GPP TS 25.331.


When the conditions for event 2D are met and maintained in time-to-trigger specified by the

parameter TimeToTrig2D, the UE sends the measurement report of event 2D.

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

QUsed ≤ TUsed2d - H2d/2

where

� QUsed is the measurement value of the cell at the currently used frequency.

� TUsed2d is the absolute quality threshold of the cell at the currently used frequency.

Based on the service type and measurement quantity, this threshold can be configured through the following parameters:

− InterRATCSThd2DEcN0

− InterRATR99PsThd2DEcN0

− InterRATHThd2DEcN0

− InterRATCSThd2DRSCP

− InterRATR99PsThd2DRSCP


5-5

− InterRATHThd2DRSCP

� H2d is the event 2D hysteresis value set through the parameter HystFor2D.

� For the PS and CS combined services, the threshold(s) for CS services is (are) used.


When the conditions for event 2F are met and maintained in time-to-trigger specified by

TrigTime2F, the UE sends the measurement report of event 2F.


QUsed ≥ TUsed2f + H2f/2

where


� TUsed2f is the absolute quality threshold of the cell at the currently used frequency.


− InterRATCSThd2FEcN0

− InterRATR99PsThd2FEcN0

− InterRATHThd2FEcN0

− InterRATCSThd2FRSCP

− InterRATR99PsThd2FRSCP

− InterRATHThd2FRSCP

� H2f is the event 2F hysteresis value set through the parameter HystFor2F.


Triggering of Event 3A

When the conditions for event 3A are met and maintained in time-to-trigger specified by

TrigTime3A the UE sends the measurement report of event 3A.

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

QUsed ≤ TUsed - H3a/2 and MOtherRAT + CIOOtherRAT ≥ TOtherRAT + H3a/2

where


TUsed is the absolute quality threshold of the cell that uses the current frequency. Based

on the service type and measurement quantity in the coverage-based handover, TUsed can be configured through the following parameters

− UsedFreqCSThdEcN0

− UsedFreqCSThdRSCP

− UsedFreqHThdEcN0

− UsedFreqHThdRSCP

− UsedFreqR99PsThdEcN0

− UsedFreqR99PsThdRSCP


5-6

In the uplink QoS-based handover, based on the measurement quantity (CPICH Ec/No or

RSCP), TUsed is configured as the maximum value according to 3GPP specifications, as described below:

− If the measurement quantity is CPICH Ec/No, TUsed is configured as the maximum value 0 dB.

− If the measurement quantity is CPICH RSCP, TUsed is configured as the maximum

value –25 dBm.

In the downlink QoS-based handover:

− If the measurement quantity is CPICH Ec/No, TUsed is configured as the maximum value 0 dB.

− If the measurement quantity is CPICH RSCP, based on the service type , TUsed can be configured as one of the following sums:

− UsedFreqCSThdRSCP and DlRscpQosHyst

� UsedFreqR99PsThdRSCP and DlRscpQosHyst

� UsedFreqHThdRSCP and DlRscpQosHyst

− MOtherRAT is the measurement value of the cell (in another RAT) in the reporting range.

− CIOOtherRAT is the cell individual offset value of the cell (in another RAT) in the

reporting range which is equal to the sum of CIO and CIOOffset.

− TOtherRAT is the absolute inter-RAT handover threshold. Based on different service

types (CS , PS domain R99 service, or PS domain HSPA service), this threshold can be configured through the following parameters:

− TargetRatCsThd

− TargetRatR99PsThd

− TargetRatHThd

� H3a is 3A hysteresis, the hysteresis value of event 3A.



When the conditions for event 3C are met and the delay requirement specified by the

TrigTime3C parameter can be satisfied, the UE sends the measurement report of event 3C.

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

MOtherRAT + CIOOtherRAT ≥ TOtherRAT + H3c/2

where

� MOtherRAT is the measurement value of the cell (in another RAT) in the reporting range.

� CIOOtherRAT is the cell individual offset value of the cell (in another RAT) in the

reporting range, which is equal to the sum of CIO and CIOOffset.

� TOtherRAT is the absolute inter-RAT handover threshold. Based on different service

types (CS , PS domain R99 service, or PS domain HSPA service), this threshold can be configured through the following parameters:

− TargetRatCsThd

− InterRATNCovHOPSThd

� H3c is 3C hysteresis, the hysteresis value of event 3C.



5-7

5.2.5 3G-to-2G Handover Neighboring Cell Combination Algorithms

For details, see 3.2.3 Intra-Frequency Handover Neighboring Cell Combination Algorithm.

5.2.6 3G-to-2G Handover Compressed Mode

For details, see 4.2.6 Inter-Frequency Handover Compressed Mode.

5.2.7 BSIC Verification Requirements for 2G Cells

During inter-RAT measurement, it is recommended that the UE report the 2G cell after the

Base Transceiver Station Identity Code (BSIC) of the cell is verified. This greatly enhances

the reliability of handover. The related parameter is BSICVerify.

5.3 3G-to-2G Handover Decision and Execution

5.3.1 Coverage and QoS-based UMTS-to-GSM Handover Decision and Execution

The coverage-based and QoS-based 3G-to-2G handover is categorized into two types

according to the following two measurement report modes: periodical measurement report

mode and event-triggered measurement report mode. Each mode corresponds to a different

decision and execution procedure.

Coverage- and QoS-based 3G-to-2G Handover in Periodical Measurement Report Mode

After receiving the periodical measurement report of GSM cells, the RNC performs the

following decision and execution procedures:

1. Decide whether the quality of 2G cells meets the conditions of inter-RAT handover.

The evaluation formula is listed below:

Mother_RAT + CIOother_RAT ≥ Tother_RAT + H/2

where

− Mother_RAT is the measurement result of inter-RAT handover received by the RNC.

− CIOother_RAT is the cell individual offset value of the target cell. It is equal to the

sum of CIO and CIOOffset.

− Tother_RAT is the decision threshold of inter-RAT hard handover.


TargetRatCsThd

TargetRatR99PsThd

TargetRatHThd

− H is the inter-RAT handover hysteresis value set through HystforInterRAT.

− For the PS and CS combined services, one or more handover thresholds for CS services are used.


5-8

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

The length of the time-to-trigger timer is configured through the parameter

TimeToTrigForVerify (with BSIC acknowledged) or the parameter

TimeToTrigForNonVerify (with BSIC unacknowledged).

3. Select the cells in sequence, that is, from high quality cells to low quality ones, to initiate 3G-to-2G handover in the cells where the handover time-to-trigger timer expires.

Coverage- and QoS-based 3G-to-2G Handover in Event-Triggered Measurement Report Mode

After receiving the event 3A measurement report of 2G cells, the RNC performs the following

decision and execution procedures:

1. 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.

2. Select the cells in sequence from the cell set to perform inter-RAT handover.

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

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 of Load- or Service-Based 3G-to-2G Handover

After receiving the event 3C measurement report of 2G cells, the RNC performs the following

handover decision and execution procedure:

1. 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.

2. Select the cells in sequence from the cell set.

To avoid the impact of the UE (in long-term measurement of compressed mode) on the radio

network, the parameter InterRATHOAttempts is set to restrict the maximum attempts of the

3G-to-2G load-based or service-based handover. The parameter indicates the handover

attempts made to the same cell or different cells. If the number of attempts exceeds the

parameter value, the RNC does not initiate the handover.

Interchanging Load Information in Load- or Service-based 3G-to-2G Handover

The procedure for load information interchanging between the 3G source cell and 2G target

cell is described as follows:

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.


5-9

If the switch SndLdInfo2GsmInd is set to OFF, then the RELOCATION REQUIRED

message does not include the Old BSS To New BSS Information IE.

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 by reading the Inter-System Information Transparent Container IE, which is included in the RELOCATION COMMAND message.

− If the 2G load is lower than CSHOOut2GloadThd (for CS service), or if the 2G load

is lower than PSHOOut2GloadThd (for PS service), 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.

5.3.3 3G-to-2G Handover Retry

In case of inter-RAT handover failure, if the cause of the failure is not a configuration failure

and the retry timer expires, the UE makes handover attempts to the cell again until the retry

number exceeds the maximum retry number.

The inter-RAT handover retry algorithm works in the following two signaling procedures:

Signaling Procedure for Iu Relocation

1. The RELOCATION REQUIRED message is initiated on the Iu interface.

2. If the RNC receives the RELOCATION PREPARATION FAILURE message, the

inter-RAT handover fails.

If the cause of the failure is one of the following configuration failure, the RNC does not make a handover retry to the cell.

− Relocation Failure in Target CN/RNC or Target System, or

− Relocation not supported in Target RNC or Target System, or

− Relocation Target not allowed

Otherwise, the related retry timer for the cell is started. After the retry timer expires, the

UE makes handover attempts to the cell again until the retry number exceeds the maximum retry number.

3. If the RNC receives the RELOCATION COMMAND message, the handover on the Uu

interface continues.

4. If the handover succeeds or the new event 3A or 3C report is received, the periodical retry is stopped.

Signaling Procedure for Service-based Handover on the Uu Interface � For CS services or CS and PS combined services, the HANDOVER FROM UTRAN

signaling procedure on the Uu interface is performed only when the handover based on CS services is made.


5-10

� For a PS service or combined PS services, the CELL CHANGE ORDER FROM

UTRAN or HANDOVER FROM UTRAN signaling procedure on the Uu interface is performed.

� If the HANDOVER FROM UTRAN FAILURE or CELL CHANGE ORDER FROM UTRAN FAILURE message is received, the handover on the Uu interface fails.

If the "Inter-RAT handover failure cause" in HANDOVER FROM UTRAN FAILURE

message is "Configuration unacceptable", or if the "Inter-RAT change failure cause" in CELL

CHANGE ORDER FROM UTRAN FAILURE message is "Configuration unacceptable", the

RNC does not make a handover retry to the cell.

Otherwise, the related retry timer for the cell is started. After the retry timer expires, the UE

makes a handover attempt to the cell again until the retry number exceeds the maximum

number.

If the handover succeeds or the new event 3A or 3C report is received, the periodical retry is

stopped.

The retry timer and maximum retry number for coverage-based and QoS-based inter-RAT

handover are:

� PeriodFor3A

� AmntOfRpt3A

The retry timer and maximum retry number for load-based and service-based inter-RAT

handover are:

� PeriodFor3C

� AmntOfRpt3C

5.3.4 3G-to-2G Multimedia Fallback

Before the RNC performs handover for the UE that is enjoying the video phone (VP) service,

the RNC initiates multimedia fallback to change the VP service to the Adaptive Multi Rate

(AMR) speech service, that is, to perform the 3G-to-2G handover based on the CS AMR

speech service.

Overview of Fallback Service

Compared with the traditional speech service of the GSM, the VP service of the UMTS can

transmit not only speech services between the calling party and the called party, but also the

images and videos captured by both parties. Since the actual implementation is limited by

terminals and networks, the VP service sometimes carries only speech and may fail to

transmit images or videos. In this scenario, the Service Change and Unrestricted Digital

Information Fallback (SCUDIF) provides the fallback mechanism that changes a video call to

a common speech call.

As specified in 3GPP TS 23.172, the fallback service of the VP is categorized into the

following two types:

� The process of changing multimedia services back to speech services during call setup.

The RNC does not take part in the process. Therefore, the detailed description of fallback process is not given hereinafter.

� The process of changing multimedia services back to speech services during the call.


5-11

Triggering of Fallback Service

Currently, the network-initiated multimedia fallback is performed only for the 3G-to-2G

handover. Service changes triggered by the UEs are not supported.

Fallback is initiated when both of the following occasions are met:

� The RNC decides to send an inter-RAT handover request after receiving periodical measurement reports of event 1A, 3A, or 3C.

� The service is combined with a VP, and the "Alternative RAB Parameters" in the RAB ASSIGNMENT message is a valid AMR speech format.

Procedure of Service Change

Figure 5-3 shows the service change procedure for the 3G-to-2G handover. The network

initiates the service change, that is, the RNC initiates the change from the VP service to the

speech service during the call.

Figure 5-3 Service change procedure for the 3G-to-2G handover in the CS domain

1. The CN sends the SRNC a RANAP RAB ASSIGNMENT REQUEST message to set up the VP service.

2. During 3G-to-2G handover, the SRNC sends a RANAP RAB MODIFY REQUEST

message to change the VP service to the AMR speech service. In the 3GPP R6 protocol,

the information element (IE) Alternative RAB Configuration Request is also added to the

RAB MODIFY REQUEST message, which enables the RNC to request the CN to change the VP service to the AMR speech service.

3. The MSC initiates the Bearer Capability (BC) negotiation with the UE.

4. After the negotiation, the RNC is requested to perform service change.

When the multimedia fallback ends, the RNC decides whether to perform the 3G-to-2G

handover according to the current measurements reported by the UE.

At the beginning of the service setup, the RNC saves the RAB parameters.


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The CN initiates the RAB reconfiguration to request both parties to perform the multimedia

fallback. The single VP service falls back to the single AMR speech service. The multi-RAB

service combined with VP falls back to the multi-RAB service combined with AMR. If the

multimedia fallback succeeds, that is, the video phone in the service falls back to speech

successfully, the inter-RAT handover is initiated. Otherwise, the inter-RAT handover fails.

5.3.5 3G-to-2G Handover in the PS Domain with NACC

The Network Assisted Cell Change (NACC) function can efficiently reduce the delay of

UMTS-to-GSM handover.

Some services have requirements for the delay. If the handover takes too long, TCP may start

slowly or data transmission of the service stream may be interrupted due to the overflow of

the UE buffer. The introduction of NACC enables the system information exchange between

different BSSs, or between BSS and RAN. Thus the inter-system delay, especially

inter-system delay in PS domains, can be reduced. With NACC, the RNC sends the UE a cell

change order, which contains the GSM EDGE Radio Access Network (GERAN) system

information, when the 3G-to-2G handover in the PS domain is triggered.

To enable the NACC function, do as follows:

� Run the SET UCORRMALGOSWITCH command to set HoSwitch:

HO_INTER_RAT_PS_3G2G_CELLCHG_NACC_SWITCH to ON.

� Run the ADD UEXT2GCELL / MOD UEXT2GCELL command to set SuppRIMFlag to TRUE.

5.3.6 3G<->2G Handover in the PS Domain with PS Handover

PS handover is similar to the inter-RAT handover in the CS domain.

To enable the PS HO function, do as follows:

� Run the SET UCORRMALGOSWITCH command to set HoSwitch: HO_INTER_RAT_PS_3G2G_RELOCATION_SWITCH parameter to ON.

� Run the ADD UEXT2GCELL / MOD UEXT2GCELL command to set

SuppPSHOFlag to TRUE.

5.4 2G-to-3G Handover The 2G-to-3G handover is initiated by the 2G network, where the dual-mode (GSM and

WCDMA) MSs are required. Both the GSM MSC and the GSM BSS must support the

GSM-to-UMTS handover.

2G-to-3G Handover Penalty Algorithm

For the 2G-to-3G handover, the measurement control message is delivered through a system

information broadcast of 2G when the 2G cell has a neighboring 3G cell. The dual-mode MS

performs the inter-RAT measurement in idle timeslots and reports the measurement results.

Based on the reported measurement values, the BSC decides whether to perform the handover

to the 3G network.

To avoid the ping-pong handover between 2G and 3G, the 2G-to-3G handover penalty

algorithm is used.


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When the UE is handed over from 2G to 3G and if any CS domain service exists, the system

increases the hysteresis of event 3A through the parameter InterRATPingPongHyst to

prevent the UE from the ping-pong handover between 2G and 3G in the period specified by

the parameter InterRATPingPongTimer.

Interchange of Load Information in 2G-to-3G Load or Service-based Handover

In 2G-to-3G handover based on load or service, the RNC can make a decision about

admission considering the load information of the 3G target cell. This can avoid the

worsening of the 3G system performance caused by 2G-to-3G handover based on load or

service if the 3G system load is high.

The procedure is described as follows:

1. When the RNC sends a RELOCATION REQUEST ACKNOWLEDGE message to the 3G CN,

− If the switch SndLdInfo2GsmInd is set to ON, the RELOCATION REQUEST

ACKNOWLEDGE message includes the New BSS To Old BSS Information IE, which includes the load information of the 3G target cell.

− If the switch SndLdInfo2GsmInd is set to OFF, the RELOCATION REQUEST

ACKNOWLEDGE message does not include the New BSS To Old BSS Information

IE.

Depending on the network requirement, the 2G network decides whether to use the load

information sent to the 3G network for judgment.

2. When the RNC receives the RELOCATION REQUEST message from the 3G CN,

− If the 3G cell is not in the basic congestion state, the RNC continues the inter-RAT handover procedure.

− If the 3G cell is in the basic congestion state, the RNC returns RELOCATION

FAILURE message to the CN to cancel the inter-RAT handover.

For the concept of "basic congestion", see the Load Control Feature Parameter Description.

5.5 Interoperability Between Inter-RAT Handover and Inter-Frequency Handover

During the coverage-based and QoS-based 3G-to-2G handover, the measurements on both

inter-frequency and inter-RAT neighboring cells can be made, which enables the cells to

provide continuous coverage and high quality.

The preconditions for the measurements are as follows:

� Both inter-frequency and inter-RAT neighboring cells are available.

� InterFreqRATSwitch is set to SIMINTERFREQRAT.

If InterFreqRATSwitch is set to:

� Inter-frequency measurement (INTERFREQ), the RNC allows the UE to perform only

this type of measurement.

� Inter-RAT measurement (INTERRAT), the RNC allows the UE to perform only this type of measurement.


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� Concurrent inter-frequency and inter-RAT measurement (SIMINTERFREQRAT), the

RNC allows the UE to perform both types of measurement at the same time.

During the concurrent inter-frequency and inter-RAT measurement, the values of the

parameter CoexistMeasThdChoice for event 2D are chosen as follows:

� When the value COEXIST_MEAS_THD_CHOICE_INTERFREQ is chosen, the

inter-frequency measurement threshold for event 2D is used.

� When the value COEXIST_MEAS_THD_CHOICE_INTERRAT is chosen, the inter-RAT measurement threshold for event 2D is used.

5.6 Signaling Procedures for Inter-RAT Handover

5.6.1 3G-to-2G Handover in CS Domain

Figure 5-4 shows the signaling procedures for the 3G-to-2G handover in the CS domain. The

2G messages shown in Figure 5-4 are for your reference only.


5-15

Figure 5-4 3G-to-2G handover in the CS domain

5.6.2 3G-to-2G Handover in PS Domain

For a UE in idle mode or connected mode, if the SGSN changes with the shift of the system

that the UE accesses from 3G network to 2G network, the inter-SGSN handover will be

performed.

The handover procedures are different in the following two cases:

� When the UE is in CELL_DCH state

The 3G-to-2G handover in the PS domain is triggered after the UTRAN sends a CELL CHANGE ORDER FROM UTRAN message.

� When the UE is in CELL_FACH, CELL_PCH, or URA_PCH state

The 3G-to-2G handover in the PS domain is triggered through the cell reselection.

The following figure shows an example of handover for the UE in CELL_FACH, CELL_PCH,

or URA_PCH state. When the UE is in idle mode, the cell reselection procedure does not

include the elementary procedures marked "UE CONNECTED" in Figure 5-5.


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Figure 5-5 Example of the 3G-to-2G handover in the PS domain

5.6.3 3G-to-2G Handover in Both CS Domain and PS Domain

This section describes the 3G-to-2G handover in both CS domain and PS domain in detail.

Inter-RAT Handover in Both CS Domain and PS Domain

For a UE in CELL_DCH state using both CS and PS domain services, the inter-RAT handover

procedure is based on the measurement reports from the UE but is initiated from the UTRAN.


5-17

The UE performs the inter-RAT handover from UTRA RRC connected mode to GSM

connected mode first. After the UE sends a handover complete message to the GSM/BSS, the

UE initiates a temporary block procedure towards the GPRS to suspend the GPRS services.

After the CS domain services are released on the GSM side, the inter-RAT handover in the PS

domain is initiated and then completed.

If the inter-RAT handover from UTRA RRC Connected Mode to GSM Connected Mode

succeeds, the handover is regarded as successful, no matter whether the UE initiates a

temporary block procedure towards the GPRS.

In case of inter-RAT handover failure, the UE may go back to the UTRA RRC Connected

Mode and re-establish the connection in the original state.

SGSN Service Suspend and Resume

When the CS connection is terminated, the BSS may send a RESUME message to the SGSN.

However, resume is impossible since the radio access system has changed. Therefore, the

SGSN acknowledges the resume through a RESUME NACK message.

The UE sends a ROUTING AREA UPDATE REQUEST message to the SGSN to resume the

GPRS service. The update mode depends on the network operation mode in use.

Figure 5-6 Intra-SGSN service suspend and resume


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Figure 5-7 Inter-SGSN service suspend and resume

5.6.4 2G-to-3G Handover in CS Domain

When a GSM cell has a neighboring UMTS cell, the measurement control information is

contained in the system information. The dual-mode MS performs the inter-RAT

measurement in idle timeslots and reports the measurement result. The BSC decides whether

to start the inter-RAT handover according to the measurement result.

The GSM system uses time division multiple access technology, and the inter-RAT

measurement is performed in idle timeslots. Therefore, the GSM need not support the

compressed mode.


5-19

Figure 5-8 2G-to-3G handover in CS domain

5.6.5 2G-to-3G Handover in PS Domain

Figure 5-9 shows the 2G-to-3G handover in the PS domain.


5-20

Figure 5-9 2G-to-3G handover in PS domain


5-1

6 Glossary

6-1

6 Glossary For the acronyms, abbreviations, terms, and definitions, see the Glossary.

7 Reference Documents

2

7 Reference Documents [1] 3GPP TS 23.122: Non Access Stratum functions related to Mobile

Station (MS) in idle mode

[2] 3GPP TS 24.008: Mobile radio interface layer 3 specification; Core Network Protocols - Stage 3

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

Reselection in Connected Mode

[4] 3GPP TS 25.331: RRC Protocol Specification

[5] 3GPP TS 23.060: General Packet Radio Service (GPRS); Service description

[6] 3GPP TS 25.931: UTRAN Functions, Examples on Signalling Procedures

[7] BSC6900 UMTS Performance Counter Reference

[8] NodeB Performance Counter Reference

[9] Glossary

2G 3G Handover Algorithms

Documents

g handover

huawei trademarks

overview of handover

handover types

frequency handover procedure

rat handover introduction

copyright huawei technologies

huawei industrial base