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Directed Retry DecisionFeature Parameter Description

Copyright Huawei Technolog ies Co., Ltd. 2010. All righ ts reserved.

No part of this document may be reproduced or transmitted in any form or by any means without prior written

consent of Huawei Technologies Co., Ltd.

Trademarks and Permissions

and other Huawei trademarks are the property of Huawei Technologies Co., Ltd. All other trademarksand trade names mentioned in this document are the property of their respective holders.

Notice

The purchased products, services and features are stipulated by the commercial contract made between

Huawei and the customer. All or partial products, services and features described in this document may not be

within the purchased scope or the usage scope. Unless otherwise agreed by the contract, all statements,

information, and recommendations in this document are provided AS IS without warranties, guarantees or

representations of any kind, either express or implied.

The information in this document is subject to change without notice. Every effort has been made in the

preparation of this document to ensure accuracy of the contents, but all statements, information, andrecommendations in this document do not constitute the warranty of any kind, express or implied.

Huawei Proprietary and Confidential

Copyright Huawei Technologies Co., Ltd.


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Directed Retry Decision Contents

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iii

Contents

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

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

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

1.3 Change History..............................................................................................................................1-1

2 Overview of DRD .......................................................................................................................2-1

3 RRC DRD .....................................................................................................................................3-1

4 Non-periodic DRD .....................................................................................................................4-1

4.1 Overview .......................................................................................................................................4-1

4.1.1 Blind-handover-based Non-periodic DRD............................................................................ 4-1

4.1.2 Measurement-based Non-periodic DRD ..............................................................................4-1

4.2 Inter-Frequency DRD Procedure .................................................................................................. 4-2

4.3 DRD for Technological Satisfaction............................................................................................... 4-3

4.3.1 Overview...............................................................................................................................4-3

4.3.2 Priority Sequence of HSPA+ Technologies .......................................................................... 4-4

4.3.3 Procedure of DRD for Technological Satisfaction ................................................................ 4-4

4.4 Inter-Frequency DRD for Service Steering ...................................................................................4-5

4.4.1 Cell Service Priorities ........................................................................................................... 4-5

4.4.2 Procedure of DRD for Service Steering................................................................................ 4-6

4.5 Inter-Frequency DRD for Load Balancing..................................................................................... 4-8

4.5.1 Overview of DRD for Load Balancing................................................................................... 4-8

4.5.2 Power-Based DRD for Load Balancing................................................................................4-8

4.5.3 Code-Based DRD for Load Balancing................................................................................ 4-12

4.6 Inter-RAT DRD ............................................................................................................................ 4-14

4.7 MBDR..........................................................................................................................................4-15

4.7.1 Overview of the MBDR Algorithm....................................................................................... 4-15

4.7.2 MBDR Algorithm Switches ................................................................................................. 4-15

4.7.3 Procedure for the MBDR Algorithm.................................................................................... 4-15

5 Periodic DRD..............................................................................................................................5-1

5.1 Overview .......................................................................................................................................5-1

5.1.1 Switches for Periodic DRD................................................................................................... 5-1

5.1.2 Triggering of Periodic DRD................................................................................................... 5-1

5.2 Periodic DRD Procedure............................................................................................................... 5-2

5.2.1 Blind-Handover-Based Periodic DRD ..................................................................................5-2

5.2.2 Measurement-Based Periodic DRD .....................................................................................5-3

6 Parameters .................................................................................................................................6-1

7 Counters ......................................................................................................................................7-1


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Directed Retry Decision 1 Introduction



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1 Introduction

1.1 Scope

This document describes Directed Retry Decision (DRD). It covers both the RRC DRD and the RABDRD, and furthermore provides parameter descriptions.

1.2 Intended Audience

This document is intended for:

Personnel who are familiar with WCDMA basics

Personnel who need to understand DRD

Personnel who work with Huawei products

1.3 Change History

This section provides information on the changes in different document versions.

There are two types of changes, which are defined as follows:

Feature change: refers to the change in the DRD feature.

Editorial change: refers to the change in wording or the addition of the information that was notdescribed in the earlier version.

Document Issues

The document issues are as follows:

03 (2010-12-20)

02 (2010-06-20)

01 (2010-03-30)

Draft (2009-12-05)

03 (2010-12-20)

This is the document for the third commercial release of RAN12.0.

Compared with issue 02 (2010-06-20) of RAN12.0, this issue optimizes the description.

02 (2010-06-20)

This is the document for the second commercial release of RAN12.0.

Compared with issue 01 (2010-03-30) of RAN12.0, this issue corrects the error in 4.6 Inter-RAT DRD.

01 (2010-03-30)

This is the document for the first commercial release of RAN12.0.

Compared with issue Draft (2009-12-05) of RAN12.0, this issue incorporates the changes described inthe following table.


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Change Type Change Descrip tion Parameter Change

Feature change The description aboutmeasurement-based non-periodicDRD (MBDR) is added. Fordetails, see 4.7 MBDR.

The added parameters are listedas follows:

InterFreqActiveType InterRatActiveType

UlNonCtrlThdForAMR

UlNonCtrlThdForNonAMR

UlNonCtrlThdForOther

DlConvAMRThd

DlConvNonAMRThd

DlOtherThd

InterFreqUlMbdrTrigThreshold

InterFreqDlMbdrTrigThreshold

InterRatUlMbdrTrigThreshold

InterRatDlMbdrTrigThreshold

UserPercentage

MBDRPrio

MaxAttNum

MBDRFlag

InterFreqReportMode

TrigTime2C

InterFreqMeasQuantity

HOThdEcN0

HOThdRscp

InterRatReportMode

InterRATPeriodReportInterval

InterRATHOThd

TrigTime3C

Editorial change None. None.

Draft (2009-12-05)

This is the draft of the document for RAN12.0.

This is a new document. The description about RRC DRD and non-periodic DRD is separated from theLoad Control Feature Parameter Description; the description about periodic DRD is newly added.


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Directed Retry Decision 2 Overview of DRD

2 Overview of DRD

Directed Retry Decision (DRD) is used to select a suitable cell for a UE to access. Different types of DRDcan be adopted during different phases of service processing. In this way, the system capacity can be

maximized, and better services can be provided.

Figure 2-1shows the different types of DRD.

Figure 2-1 Types of DRD

RAB DRD is performed during the RAB phase, which starts from RAB setup processing and ends inRAB release. There are two types of RAB DRD, non-periodic DRD and periodic DRD, as shown inFigure 2-1.

DRD Type Appl icationScenario

Description

RRC DRD During RRCsetup

RRC DRD is used to select a suitable inter-frequency neighboringcell for a UE to set up an RRC connection in either of the followingsituations:

The RRC connection setup fails in the cell that the UE tries toaccess.

The cell that the UE tries to access does not support signalingradio bearer (SRB) over HSPA when SRB over HSPA is selectedas the bearer scheme.

RRC DRD is based on blind handover.



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DRD Type App lication Descrip tionScenario

Non-periodicDRD

During RABsetup, RABmodification, orDCCC channelreconfiguration

Non-periodic DRD can be performed based on blind handover ormeasurement.

Blind-handover-based non-periodic DRD is used to select asuitable cell for a UE to access according to the HSPA+technological satisfaction, service priority, and cell load. Itenables the UE to be served with the best technologicalsatisfaction and implements load balancing and service steering.

Measurement-based non-periodic DRD, that is, MeasurementBased Directed Retry (MBDR) is used to select a signal qualifiedcell for a UE according to the measurement result. Comparedwith blind-handover-based non-periodic DRD, MBDR canincrease the DRD success rate when the current cell and theDRD target cell cover different areas.

NOTE:Blind-handover-based non-periodic DRD cannot work with MBDR. WhenMBDR is enabled, this type of DRD is disabled automatically.

PeriodicDRD

After RAB setupor after thebearer scheme ischanged

Periodic DRD is triggered by the HSPA/HSPA+ retry or cell servicepriority. It can be performed to select a suitable cell when the RNCdetermines that the UE can be served by a better HSPA/HSPA+technology or when a neighboring cell has a higher service prioritythan the current cell. Note that only measurement-based periodicDRD can be triggered by cell service priority.

After periodic DRD is triggered, it can be performed through eitherof the following two ways:

Blind-handover-based periodic DRD: It mainly applies to theinter-frequency same-coverage scenarios. It selects the targetcell that support blind handover and does not consider the signalquality of the target cell.

Measurement-based periodic DRD: It applies to both theinter-frequency different-coverage scenarios and theinter-frequency same-coverage scenarios. It selects the targetcell according to the signal measurement results. Only the cellthat meets the specified signal conditions can be selected as thetarget cell.

NOTE:

Blind-handover-based periodic DRD cannot work with measurement-based

periodic DRD. When the latter is enabled, the former is disabledautomatically.


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Directed Retry Decision 3 RRC DRD

3 RRC DRD

RRC DRD is performed during RRC connection setup. When a UE fails to access the current cell, theRNC performs RRC DRD. The purpose is to instruct the UE to set up an RRC connection in a suitable

inter-frequency neighboring cell.

The DR_ RRC_DRD_SWITCH subparameter of theDrSwitchparameter determines whether RRCDRD is enabled.

The RRC DRD procedure is as follows:

1. The RNC selects the intra-band inter-frequency neighboring cells of the current cell. Theseneighboring cells are suitable for blind handovers. Whether the neighboring cells support blindhandover is specified by the parameter BlindHoFlag.

2. The RNC generates a list of candidate DRD-supportive inter-frequency cells according to thefollowing condition

(CPICH_EcNo)RACH > DRD_EcNOnbcell

Here:

(CPICH_EcNo)RACHis the cached CPICH Ec/N0 value included in the RACH measurement report.Note that this value is of the current cell.

DRD_EcNOnbcellis the DRD threshold (DRDEcN0Threshhold) of the neighboring cell.

3. The RNC selects a target cell from the candidate cells for UE access. If the candidate cell list isempty, the RRC DRD fails. The RNC performs RRC redirection. If the candidate cell list containsmore than one cell, the UE tries a cell randomly.

If the admission is successful, the RNC continues the RRC connection setup procedure.

If the admission to a cell fails, the UE tries admission to another cell in the candidate cell list until anadmission is successful or all admission attempts fail.

If all the admission attempts fail, then

The RNC makes an RRC redirection decision when the function of RRC redirection after DRD failureis enabled.

The RRC connection setup fails when the function of RRC redirection after DRD failure is disabled.

For information about RRC redirection after DRD failure, see the Load Control Feature ParameterDescription.



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Directed Retry Decision 4 Non-periodic DRD

4 Non-periodic DRD

This section involves the following features:

WRFD-02040001 Intra System Direct Retry

WRFD-02040002 Inter System Direct Retry

WRFD-01061112 HSDPA DRD

WRFD-020402 Measurement based Direct Retry

4.1 Overview

Non-periodic DRD is used to select a suitable cell for UE access. It can be performed during RAB setup,RAB modification, or DCCC channel reconfiguration.

Non-periodic DRD can be performed based on measurement or blind handover. Blind-handover-basednon-periodic DRD and measurement-based non-periodic DRD (that is, MBDR) can not be used

simultaneously. When the MBDR algorithm is enabled, other non-periodic DRD algorithms areautomatically disabled.

4.1.1 Blind-handover-based Non-periodic DRD

Blind-handover-based non-periodic DRD involves inter-frequency DRD (WRFD-02040001 Intra SystemDirect Retry) and inter-RAT DRD (WRFD-02040002 Inter System Direct Retry).

The following parameters determine whether to enable blind-handover-based non-periodic DRD:

For a single service, blind-handover-based non-periodic DRD is enabled by theDR_RAB_SING_DRD_SWITCHsubparameter of the DrSwitchparameter.

For a service combination, blind-handover-based non-periodic DRD is enabled by the

DR_RAB_COMB_DRD_SWITCH subparameter of the DrSwitchparameter.

Note that if the measurement-based periodic DRD switch BasedOnMeasHRetryDRDSwitchis set toON, blind-handover-based non-periodic DRD is also controlled by the BlindDrdExceptHRetrySwitchparameter.

For example, when the DR_RAB_SING_DRD_SWITCHsubparameter of the DrSwitchparameter is setto ONand the BasedOnMeasHRetryDRDSwitchparameter is set to ON, blind-handover-basednon-periodic DRD for a single service is enabled only if the BlindDrdExceptHRetrySwitchparameter isset to ON.

For detailed information about blind-handover-based non-periodic DRD, see the following sections:

4.2 Inter-Frequency DRD Procedure 4.3 DRD for Technological Satisfaction

4.4 Inter-Frequency DRD for Service Steering

4.5 Inter-Frequency DRD for Load Balancing

4.6 Inter-RAT DRD

4.1.2 Measurement-based Non-periodic DRD

Measurement-based non-periodic DRD (MBDR) is a feature introduced in RAN12.0. It can increase thesuccess rate of DRD, reduce the service drops caused by DRD with blind handover, and improve thenetwork performance.



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After an RRC connection is set up, the RNC decides whether to establish the requested service in aninter-frequency or inter-RAT cell based on the current cell load and the type of service to be established.If the RNC decides to establish the service in such a neighboring cell, the RNC sends an inter-frequencyor inter-RAT measurement control message to the UE, instructing the UE to measure the signal qualityof neighboring cells. If the signal quality of a neighboring cell meets the specified requirements, the RNC

establishes the service in this cell. Otherwise, the RNC attempts to establish the service in the currentcell.

For a type of service, whether MBDR can be performed can be set through the parametersInterFreqActiveTypeand InterRatActiveTyp .

For detailed information about blind-handover-based non-periodic DRD, see 4.7 MBDR.

4.2 Inter-Frequency DRD Procedure

An inter-frequency DRD procedure consists of DRD for technological satisfaction, DRD for servicesteering, and DRD for load balancing. The RNC performs these DRDs in sequence, as shown in Figure4-1.

Figure 4-1 Performing DRDs in sequence

If one of the DRD function is disabled, the RNC does not consider the conditions based on which thistype of DRD is performed. For example, if DRD for load balancing is disabled, the RNC does notconsider the cell load when selecting a cell based on inter-frequency DRD.

DRD for technological satisfaction is efficient, but it is applicable only to UEs requesting HSPA+ services.DRD for service steering and DRD for load balancing are controlled by the related parameters.

If all the DRD functions are enabled, the RNC performs the following steps:

1. The RNC determines the candidate cells to which a blind handover can be performed. Whether theneighboring cells support blind handover is specified by the parameter BlindHoFlag. A candidate

cell must meet the following conditions:

The candidate cell supports the requested service.

The frequency of the candidate cell is within the band supported by the UE.

The current cell meets the quality requirements of inter-frequency DRD. For details, see 3 "RRCDRD."

2. The RNC selects a target cell from the candidate cells for UE access as follows:

(1) The RNC selects a cell with the highest technological satisfaction.

(2) If multiple cells have the highest technological satisfaction or the requested service is not anHSPA+ one, the RNC selects a cell based on DRD for service steering as described in section 4.4Inter-Frequency DRD for Service Steering.


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(3) If multiple cells have the highest service priority, the RNC selects a cell based on DRD for loadbalancing as described in section 4.4 "Inter-Frequency DRD for Service Steering."

3. The CAC algorithm makes an admission decision based on the resource status of the cell.

If the admission attempt is successful, the RNC initiates an inter-frequency blind handover to the cell.

If the admission attempt fails, the RNC removes the cell from the candidate cells and then checkswhether all candidate cells are tried.

a. If there is any candidate cell that has not been tried, the algorithm goes back to step 2 to try thiscell.

b. If all candidate cells haven been tried, then:

If the service request is an HSPA one, the HSPA request falls back to a DCH one. Then, the algorithmgoes back to step 1 to retry admission based on R99 service priorities.

If the service request is a DCH one, the RNC initiates an inter-RAT DRD.

For UEs requesting the non-HSPA+ services, If both DRD for service steering and DRD for loadbalancing are disabled, the RNC performs the following steps:

1. The UE attempts to access the current cell when its service priority is not 0. If the service priority ofthe current cell is 0, the UE attempts to access a neighboring cell with the highest priority of blindhandover. The blind handover priority of the cell is specified by the parameter BlindHOPrio.

2. The CAC algorithm makes an admission decision based on the cell status. For details about the CACprocedure, see the Call Admission Control Feature Parameter Description.

If the admission attempt is successful, the RNC admits the service request.

If the admission attempt fails, the UE attempts to access another candidate cell randomly.

3. If any request for access to a candidate cell is rejected, then:

If the service request is an HSPA one, the HSPA request falls back to a DCH one. Then, the algorithmgoes back to step 1 to retry admission based on R99 service priorities.

If the service request is a DCH one, the RNC initiates an inter-RAT DRD. For details about inter-RATDRD, see section 4.6 "Inter-RAT DRD."

4.3 DRD for Technological Satisfaction

4.3.1 Overview

DRD for technical satisfaction is used to select a suitable cell and HSPA+ technologies for a UE basedon the HSPA+ technologies supported by the UE and attributes of the requested service such as thebearer channel, service type, and service rate.

DRD for technical satisfaction consists of the following phases:

1. The RNC determines the HSPA+ technologies that can be configured for the UE, based on theHSPA+ technologies supported by the UE and attributes of the requested service, as described in

the Radio Bearers Feature Parameter Description.

2. The RNC determines the HSPA+ technical satisfaction of each candidate cell based on the prioritiesof HSPA+ technologies and the intersection of the HSPA+ technologies that can be configured forthe UE and supported by the cell.

3. The RNC selects a suitable cell for the UE based on the priority sequence of HSPA+ technologies. Inaddition, the RNC determines the HSPA+ technologies for the UE, which are the intersection of theHSPA+ technologies that can be configured for the UE and supported by this cell.



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4.3.2 Priori ty Sequence of HSPA+ Technologies

From a UE perspective, the technical satisfaction of a cell is determined by the intersection of the HSPA+technologies that can be configured for the UE and supported by the cell. If the HSPA+ technologies inthe intersection have a high priority, the cell has high technical satisfaction.

The HSPA+ technologies comprise DC-HSDPA, enhanced layer 2 (L2), MIMO, 64QAM, DTX+DRX, UL16QAM, and HS-SCCH Less Operation. The priority sequences of the technologies in a cell supportingHSPA+ are as follows:

When MIMO64QAMorDCHSDPASwitch is set to DC-HSDPAand MIMOor64QAMSwitch to MIMO,the priority sequence is DC-HSDPA (with downlink 64QAM activated in at least one cell) >MIMO+64QAM > DC-HSDPA (with downlink 16QAM activated in at least one cell) > MIMO+DL16QAM > DL 64QAM > DL enhanced L2 > UL 16QAM > UL enhanced L2 > DTX+DRX > HS-SCCHLess Operation.

When MIMO64QAMorDCHSDPASwitch is set to DC-HSDPAand MIMOor64QAMSwitch to 64QAM,the priority sequence is DC-HSDPA (with downlink 64QAM activated in at least one cell) >

MIMO+64QAM > DC-HSDPA (with downlink 16QAM activated in at least one cell) > DL 64QAM >MIMO+DL 16QAM > DL enhanced L2 > UL 16QAM > UL enhanced L2 > DTX+DRX > HS-SCCH LessOperation.

When MIMO64QAMorDCHSDPASwitch is set to MIMO_64QAM and MIMOor64QAMSwitch toMIMO, the priority sequence is MIMO+64QAM > DC-HSDPA (with downlink 64QAM activated in atleast one cell) > MIMO+DL 16QAM > DL 64QAM > DC-HSDPA (with downlink 16QAM activated in atleast one cell) > DL enhanced L2 > UL 16QAM > UL enhanced L2 > DTX+DRX > HS-SCCH LessOperation.

When MIMO64QAMorDCHSDPASwitch is set to MIMO_64QAM and MIMOor64QAMSwitch to64QAM, the priority sequence is MIMO+64QAM > DC-HSDPA (with downlink 64QAM activated in atleast one cell) > DL 64QAM > MIMO+DL 16QAM > DC-HSDPA (with downlink 16QAM activated in atleast one cell) > DL enhanced L2 > UL 16QAM > UL enhanced L2 > DTX+DRX > HS-SCCH Less

Operation.

4.3.3 Procedure of DRD for Technological Satisfaction

The procedure for performing DRD for technological satisfaction is as follows:

1. The RNC determines the candidate cells to which blind handovers can be performed. Whether theneighboring cells support blind handover is specified by the parameter BlindHoFlag. A candidatecell must meet the following conditions:



The current cell meets the quality requirements of inter-frequency DRD. For details, see 3 "RRC

DRD."

2. The RNC selects a cell with the highest technical satisfaction as the target cell. If multiple cells havethe highest technical satisfaction, the RNC selects a suitable cell based on DRD for service steering.Then, if multiple cells have the highest service priority, the RNC selects a suitable cell based on DRDfor load balancing.

The RNC also determines the HSPA technologies for the UE in this step.

If the UE requires the DC-HSPA technology, the RNC searches for a DC-HSPA cell group based on the target cell. Ifmultiple DC-HSPA cell groups have the highest technical satisfaction, the RNC selects a suitable cell group based onDRD for service steering. Then, if multiple cell groups have the highest service priority, the RNC selects a suitable cellgroup based on DRD for load balancing.


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3. The CAC algorithm makes an admission decision based on the resource status of the cell or cellgroup.

If the admission attempt is successful, the RNC initiates an inter-frequency blind handover to the cellor cell group.

If the admission attempt fails, the RNC removes the cell or cell group from the candidate cells andthen checks whether all candidate cells are tried.

a. If there is any candidate cell that has not been tried, the algorithm goes back to step 2to try thiscell.

b. If all candidate cells have been tried and the service request is an HSPA one, the HSPA requestfalls back to a DCH one to retry admission based on R99 service priorities according to the DRD forservice steering and load balancing.

4.4 Inter-Frequency DRD for Service Steering

This section describes the features WRFD-02040004 Traffic Steering and Load Sharing During RABSetup.

If the UE requests a service in an area covered by multiple frequencies, the RNC selects the cell with thehighest service priority for UE access, based on the service type of RAB and the definitions of servicepriorities in the cells.

The availability of DRD for service steering is specified by the ServiceDiffDrdSwitchparameter.

Inter-Frequency DRD for service steering can also be called Inter-Frequency DRD for traffic steering.

"Inter-frequency DRD for service steering" is called "DRD for service steering" for short in this section.

4.4.1 Cell Service Priorities

A cell service priority is a service-specific priority of a cell among cells under the same coverage. Cellservice priorities help achieve traffic absorption in a hierarchical way.

The service priorities of a cell are set as follows:

1. Run the ADD USPGcommand to add a service priority group, which is identified by SpgId. Thisgroup includes the service priorities of a cell.

2. Run the ADD UCELLSETUP, MOD UCELLSETUP, or ADD UCELLQUICKSETUP command toassign the SPG identity to the cell, that is, set the service priorities for the cell.

The SPG to which a cell belongs is independent of DRD for service steering. For example, if the priority of a service is setto 0 in an SPG, the establishment of this service is impossible in the cells belonging to the SPG, regardless of whether

DRD for service steering is activated or not.

When selecting a target cell for RAB processing, the RNC selects a cell with a high priority, that is, a cellthat has a small value of service priority.

The service priority of a DC-HSDPA cell group is determined by the highest service priority of the twocells in the group.

Assume that the service priority groups given in the following table are defined on an RNC.



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Cell SPGIdentity

Service Priorityof R99 RT Service

Service Priorityof R99 NRTService

Service Priorityof HSDPAService

Service Priorityof HSUPAService

ServicePriority ofOtherServices

A 1 2 1 1 1 0

B 2 1 2 0 0 0

As shown in the following figure, cell B has a higher service priority of the R99 RT service than cell A. Ifthe UE requests an R99 RT service in cell A, preferably the RNC selects cell B for the UE to access.

Figure 4-2 Example of DRD for service steering

If the requested service is a combination of multiple services, the RAB with the highest priority is used when a cell isselected for RAB processing. In addition, the target cell must support all these services.

4.4.2 Procedure of DRD for Service Steering

This section describes the procedure of DRD for service steering when DRD for load balancing is disabled.


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Figure 4-3 Procedure of DRD for service steering

The procedure of DRD for service steering is as follows:

1. The RNC determines the candidate cells to which blind handovers can be performed and sorts thecandidate cells in descending order according to service priority.

A candidate cell must meet the following conditions:

The candidate cell supports blind handover. Whether the neighboring cells support blind handover isspecified by the parameter BlindHoFlag.




2. The RNC selects a target cell from the candidate cells in order of service priority for the UE to access.

If there is more than one cell with the same service priority,

When the cell, in which the UE requests the service, is one of the candidate cells with the sameservice priority, preferably, the RNC selects this cell for admission decision.

Otherwise, the RNC randomly selects a cell as the target cell.

3. The CAC algorithm makes an admission decision based on the status of the target cell.

If the admission attempt is successful, the RNC accepts the service request.


If there are any cells where no admission decision has been made, the algorithm goes back to step 2.

If admission decisions have been made in all the candidate cells, then:

a. If the service request is an HSPA one, the HSPA request falls back to a DCH one. Then, thealgorithm goes back to step 1to make an admission decision based on R99 service priorities.

b. If the service request is a DCH one, the RNC initiates an inter-RAT DRD.

In the case of DC-HSDPA services, if multiple DC-HSDPA cell groups have the highest technicalsatisfaction, the RNC selects a cell group with the highest service priority.



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The service priority of a DC-HSDPA cell group is determined by the highest service priority of the twocells.

4.5 Inter-Frequency DRD for Load Balancing

This section involves the feature WRFD-02040004 Traffic Steering and Load Sharing During RAB Setup.

If the UE requests a service setup or channel reconfiguration in an area covered by multiple frequencies,the RNC sets up the service on a carrier with a light load to achieve load balancing among the cells onthe different frequencies.

Inter-Frequency DRD for load balancing also can be called Inter-Frequency DRD for load sharing.

"Inter-frequency DRD for load balancing" is called "DRD for load balancing" for short in this section.

This section describes the procedure of DRD for load balancing when DRD for service steering is disabled.

4.5.1 Overview of DRD for Load Balancing

DRD for load balancing considers two resources: power and code.

The availability of DRD for load balancing is specified by the associated parameters as follows:

The availability of power-based DRD for load balancing for DCH service is specified by theLdbDRDSwitchDCHparameter.

The availability of power-based DRD for load balancing for HSDPA service is specified by theLdbDRDSwitchHSDPAparameter.

The availability of code-based DRD for load balancing is specified by the CodeBalancingDrdSwitchparameter.

In practice, it is recommended that only either a power-based DRD for load balancing or a code-basedDRD for load balancing be activated. If both are activated, power-based DRD for load balancing takesprecedence over code-based DRD for load balancing.

Code-based DRD for load balancing is applicable to only R99 services because HSDPA services usereserved codes.

4.5.2 Power-Based DRD for Load Balancing

In the Case of Non-DC-HSDPA Services

The following two algorithms are available for power-based load balancing. The algorithm used isspecified by the LdbDRDchoiceparameter.

Algorithm 1: DRD for load balancing is performed according to the cell measurement values about theDL non-HSDPA power and DL HS-DSCH GBP.

For DCH service, the RNC sets up the service on a carrier with a light load of non-HSDPA power toachieve load balancing among the cells at the different frequencies.

For HSDPA service, the RNC sets up the service on a carrier with a light load of HS-DSCH GBP toachieve load balancing among the cells at different frequencies.

Algorithm 2: DRD for load balancing is performed according to the DCH equivalent number of users(ENU) and HSDPA user number.

For DCH service, the RNC sets up the service on a carrier with a light load of DCH ENU to achieveload balancing among the cells on different frequencies.

For HSDPA service, the RNC sets up the service on a carrier with a light load of HSDPA user toachieve load balancing among the cells on different frequencies.


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Figure 4-4shows the procedure of power-based DRD for load balancing.

Figure 4-4 Procedure of power-based DRD for load balancing

The procedure of power-based DRD for load balancing is as follows:

1. The RNC determines the candidate cells to which blind handovers can be performed.

A candidate cell must meet the following conditions. Note that the selection of target cell is also basedon the resources of the DC-HSDPA cell group when the cell group is involved.





2. If the current cell meets the preceding conditions, the RNC proceeds to step 3. Otherwise, the RNCselects the cell with lowest load from the candidate cell list and goes to step 5.

3. The RNC determines whether the current cell meets the following condition (condition 1).

For algorithm 1, condition 1 is as follows:



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a. For DCH service

(ThdAMR,cutcell-Pnon-H,cutcell) > Thdnon-H

Here,

ThdAMR,cutcellis specified by DlConvAMRThd.

Pnon-H,cutcellis the Non-HSDPA power load of the current cell.

Thdnon-His specified by LdbDRDLoadRemainThdDCH.

b. For HSDPA service

(Thdtotal,cutcell-PGBP,cutcell) > ThdH

Here,

Thdtotal,cutcellis specified by DlCellTotalThd.

PGBP,cutcellis the HS-DSCH GBP load of the current cell.

ThdHis specified by LdbDRDLoadRemainThdHSDPA.


a. For DCH service

(ThdAMR,cutcell-PD-enu,cutcell) > Thdnon-H

Here, PD-enu,cutcellis DCH ENU load of the current cell.

b. For HSDPA service

(ThdH-ue,cutcell-PH-ue,,cutcell) / ThdH-ue,cutcell> ThdH

Here,

ThdH-ue,cutcellis specified by MaxHsdpaUserNum.

PH-ue,,cutcellis the total number of HSDPA users of the current cell.

If... Then...

Condition 1 is met For non-DC-HSDPA services:

If the current cell does not support DC-HSDPA, the service triesadmission to the current cell. Goes to step 5.

If the DC-HSDPA cell group is selected, the cell with the lowest load isselected. Goes to step 5.

Condition 1 is not met Goes to step 4.

4. The RNC selects a target cell for the UE to access.

The RNC determines whether any inter-frequency neighboring cell meets the following condition(condition 2):


For DCH service

(ThdAMR,nbcell- Pnon-H,nbcell) - (ThdAMR,cutcell- Pnon-H,cutcell) > ThdD,loadoffset

(Thdtotal,cutcell- Pload,cutcell) - (Thdtotal,nbcell- Pload,nbcell) < Thdtotal,loadoffset

Here,

ThdAMR,nbcellis specified by DlConvAMRThd.

Pnon-H,nbcellis the Non-HSDPA power load of the neighboring cell.


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ThdD,loadoffsetis specified by LdbDRDOffsetDCH.

Pload,cutcellis the sum of the non-HSDPA power and the GBP load of the current cell.

Thdtotal,nbcellis specified by DlCellTotalThd.

Pload,nbcellis the sum of the non-HSDPA power and the GBP load of the neighboring cell.Thdtotal,loadoffsetis specified by LdbDRDTotalPwrProThd.

For HSDPA service

(Thdtotal,nbcell-PGBP,nbcell) - (Thdtotal,cutcell-PGBP,cutcell)> ThdH,loadoffset

(Thdtotal,cutcell-Pload,cutcell) - (Thdtotal,nbcell-Pload,nbcell) < Thdtotal,loadoffset

Here,

PGBP,nbcellis the HS-DSCH GBP load of the neighboring cell.

ThdH,loadoffsetis specified by LdbDRDOffsetHSDPA .


For a DCH service

(ThdAMR,nbcell PD-enu,nbcell) - (ThdAMR,cutcell PD-enu,cutcell) > ThdD,loadoffset

Here, PD-enu,nbcellis the DCH ENU load of the neighboring cell.

For an HSDPA service

(ThdH-ue,nbcell PH-ue,nbcell) / ThdH-ue,nbcell- (ThdH-ue,cutcell PH-ue,cutcell) / ThdH-ue,cutcell> ThdH,loadoffset

Here,

ThdH-ue,nbcellis specified by MaxHsdpaUserNum.

PH-ue,nbcellis the total number of HSDPA users of the neighboring cell.

Then, the RNC selects the target cell as follows:

If there is only one inter-frequency neighboring cell that meets the condition 2, the RNC selects thiscell as the target cell. If there are multiple such cells:

For a DCH service

a. If algorithm 1 is used, the RNC selects the cell with the lightest non-HSDPA load as the target cell.

b. If algorithm 2 is used, the RNC selects the cell with the lightest load of DCH ENU as the target cell.

For an HSDPA service

a. If algorithm 1 is used, the RNC selects the cell with the lightest load of HS-DSCH required poweras the target cell.

b. If algorithm 2 is used, the RNC selects the cell with the lightest load of HSDPA user as the targetcell.

If there is no such cell, the RNC selects the current cell as the target cell.


If the admission attempt is successful, the RNC admits the service request.

If the admission attempt fails, the RNC checks whether admission decisions have been made in allcandidate inter-frequency neighboring cells.

If there is any cell where no admission decision is made, the algorithm goes back to step 2.

If admission decisions have been made in all the candidate cells:

a. When the service request is an HSPA one, the HSPA request falls back to a DCH one. Then, thealgorithm goes back to step 1to make an admission decision based on R99 service priorities.

b. When the service request is a DCH one, the RNC initiates an inter-RAT DRD.



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In the Case of DC-HSDPA Services

If multiple DC-HSDPA cell groups are available after DRD for technical satisfaction and DRD for servicesteering, the RNC performs DRD for load balancing.

DRD for load balancing in the case of DC-HSDPA services is similar to that in the case ofnon-DC-HSDPA services. The difference is that the former considers cell groups (not individual cells),calculates the load factors of cell groups, and finally selects a suitable cell group.

After the RNC selects a suitable DC-HSDPA cell group, it determines the primary cell based on thetechnical satisfaction and service priorities of the two cells. If the two cells have the same technicalsatisfaction and service priority, the RNC performs the following operations:

If the uplink load balancing switch ULLdbDRDSwitchDcHSDPAis turned off, the RNC selects eitherof the two cells as the primary cell.

If this switch is turned on, the RNC determines the primary cell based on uplink load balancing.

The uplink load balancing mechanism is introduced to prevent RNC from selecting the same cell as the

primary cell for multiple UEs requesting DC-HSDPA services.

The uplink load balancing between the two cells is performed based on the uplink ENU:

During Uplink load balancing, if the serving cell is not in the target DC-HSDPA cell group, the RNCselects a primary cell with lower load. Otherwise, the RNC checks whether the UL load margin of theserving cell is higher than the value of ULLdbDRDLoadRemainThdDCHSDPA:

If the condition is met, the RNC selects the serving cell as the primary cell.

If the condition is not met, the RNC calculates the difference between the UL load margin of theserving cell and that of the target cell. Then,

If the difference is greater than the value of ULLdbDRDOffsetDcHSDPA, the RNC selects the targetcell as the primary cell.

Otherwise, the RNC selects the serving cell as the primary cell.

4.5.3 Code-Based DRD for Load Balancing

The procedure of code-based DRD for load balancing is similar to that of power-based DRD for loadbalancing. The difference is that the RNC considers code resources when selecting a target cell.

The following figure shows the procedure for selecting a target cell based on code resource.


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Figure 4-5 Procedure of code-based DRD for load balancing

The procedure is as follows:

1. The RNC determines whether the minimum remaining SF of the current cell is smaller than theminimum SF threshold of DRD for code balancing (CodeBalancingDrdMinSFThd).

If the minimum SF is smaller than this threshold, the RNC tries the admission of the service request tothe current cell.

If the minimum SF is not smaller than this threshold, the RNC goes to the next step.

2. The RNC determines whether the code load of the current cell is lower than the code occupation ratethreshold of DRD for code balancing (CodeBalancingDrdCodeRateThd).

If the code load is lower than this threshold, the service tries the admission to the current cell.

If the code load is higher than or equal to this threshold, the RNC selects the cell as follows:

If the minimum SF supported by the cell with the lightest code load is the same as that supported bythe current cell, and the difference between the code resource occupancies of the two is larger thanor equal to the value of DeltaCodeOccupiedRate, the RNC selects the cell with the lightest codeload as the target cell. Otherwise, the RNC selects the current cell as the target cell.



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If the minimum SF supported by the cell with the lightest code load is smaller than the minimum SFsupported by the current cell, the RNC selects the cell with the lightest code load as the target cell.

4.6 Inter-RAT DRD

When all admission attempts for inter-frequency DRD during RAB processing fail, the RNC determineswhether to initiate an inter-RAT DRD.

The following figure shows the inter-RAT DRD procedure.

Figure 4-6 Inter-RAT DRD procedure

The inter-RAT DRD procedure is as follows:

1. If the current cell is configured with any neighboring GSM cell suitable for blind handover, and if the"service handover" IE that is contained in the RAB assignment signaling assigned by the CN is set to

"handover to GSM should be performed" or "handover to GSM should not be performed" , then theRNC performs step 2. Otherwise, the service request undergoes preemption and queuing.

Whether the neighboring cells support blind handover is specified by the parameter BlindHoFlag.

2. The RNC generates a list of candidate DRD-supportive inter-RAT cells that fulfill the qualityrequirement. For details, see 3 "RRC DRD". If the candidate cell list does not include any cell, theservice request undergoes preemption and queuing.

3. The RNC selects target GSM cells for the service request according to the blind handover priority.The blind handover priority of the cell is specified by the parameter BlindHOPrio.

4. If all admission attempts fail or the number of inter-RAT handover retries exceeds the value ofDRMaxGSMNum, the service request undergoes preemption and queuing.


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The Inter-RAT DRD is not applicable to RABs of combined services, R99 PS services, and HSPA services.

4.7 MBDR

This section describes the feature WRFD-020402 Measurement based Direct Retry.

4.7.1 Overview of the MBDR Algorithm

When an RAB is set up, the DRD algorithm uses the blind handover procedure to achieve load balancingand service steering. In this situation, if the current cell and the DRD target cell cover different areas, theUE DRD may fail.

After the Measurement Based Directed Retry (MBDR) function is implemented, inter-frequency orinter-RAT measurement is performed. This ensures good signal quality of the DRD target cell. With thisfunction, the success rate of inter-frequency or inter-RAT DRD can be ensured even if the current celland the DRD target cell cover different areas. The UE access delay, however, is increased.

Note that the MBDR algorithm cannot be used with other non-periodic DRD algorithms simultaneously.When the MBDR algorithm is enabled, other non-periodic DRD algorithms are automatically disabled.

4.7.2 MBDR Algor ithm Switches

The MBDR algorithm switches are InterFreqActiveTypeand InterRatActiveType . They specifywhether a type of service can use MBDR.

The following types of service support inter-frequency MBDR:

CS AMR

CS non-AMR

PS R99

PS HSPA

Only CS AMR services support inter-RAT MBDR.

4.7.3 Procedure for the MBDR Algori thm

Overview

After an RRC connection setup, the RNC determines whether to establish services in inter-frequency orinter-RAT cells based on the current cell load and the type of services to be established. If required, theRNC sends the UE an inter-frequency or inter-RAT measurement control message, instructing the UE tomeasure the signal quality of the target cell. If the signal quality of the target cell meets the specified

requirements, the RNC establishes services in the target cell. Otherwise, the RNC attempts to establishservices in the current cell.

The procedure for the inter-frequency MBDR algorithm is as follows:

1. After an RRC connection setup, the MBDR algorithm triggers the measurement of an inter-frequencyMBDR cell if the corresponding MBDR algorithm switch is turned on and the current cell loadexceeds the MBDR congestion decision threshold.

2. The RNC sends the UE an inter-frequency measurement control message, instructing the UE tomeasure the signal quality of the inter-frequency MBDR cell. If the signal quality of theinter-frequency MBDR cell meets the specified requirements, the RNC establishes services in thiscell.

If several inter-frequency MBDR cells are qualified, the RNC prioritizes these cells and establishesservices in the cell with the highest priority.



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3. If services are established successfully, the RAB is set up successfully. Otherwise, the RNC attemptsto establish services in the cell with the second highest priority.

The procedure for the inter-RAT MBDR algorithm is similar to that for the inter-frequency MBDRalgorithm.

Trigger Conditions of MBDR

After an RRC connection setup, if the MBDR algorithm switch for the service type to which this RABbelongs is turned on, the RNC triggers MBDR when either of the following conditions is met:

The uplink admission control switch NBMUlCacAlgoSelSwitch is not set toALGORITHM_OFF, andthe cell is in the MBDR congestion state, that is, the formula {Uplink admission threshold MBDRcongestion decision threshold Current cell load factor Uplink admission threshold } is fulfilled.

The downlink admission control switch NBMDlCacAlgoSelSwitch is not set toALGORITHM_OFF,and the cell is in the MBDR congestion state, that is, the formula {Downlink admission threshold MBDR congestion decision threshold Current cell load factor Downlink admission threshold } isfulfilled.

In the above two formulas:

The uplink admission threshold is specified by the UlNonCtrlThdForAMR,UlNonCtrlThdForNonAMR,or UlNonCtrlThdForOther parameter. The downlink admissionthreshold is specified by the DlConvAMRThd,DlConvNonAMRThd,or DlOtherThd parameter.

The MBDR congestion decision threshold is specified by the InterFreqUlMbdrTrigThreshold,InterFreqDlMbdrTrigThreshold, InterRatUlMbdrTrigThreshold, or InterRatDlMbdrTrigThresholdparameter.

The current cell load factor indicates the percentage of the used cell capacity to the total cell capacity.The current cell load factor in both uplink and downlink is calculated by the RNC according to the cellload measurement results reported by the NodeB. For details, see the Load Control ParameterDescription.

In the case of inter-RAT MBDR, the RNC triggers MBDR for only a certain percentage of UEs that meetthe trigger conditions. This percentage is specified by the UserPercentageparameter.

MBDR Target Cell Selection

After MBDR is triggered, the RNC starts target cell selection.

If the current cell has only one MBDR neighboring cell, the RNC sends the UE a measurement request,instructing the UE to measure the signal quality of this neighboring cell. If the measured signal qualitymeets the specified requirements, the RNC establishes services in this neighboring cell. If serviceestablishment fails, the RNC establishes services in the current cell.

If the current cell has more than one MBDR neighboring cell, the following procedure is triggered:

1. The RNC sends the UE a measurement request, instructing the UE to measure the signal quality ofall the MBDR neighboring cells.

2. According to the measurement results, the RNC selects the neighboring cells that meet the specifiedrequirements as target cells. Note that the neighboring cell in the MBDR congestion state can not beselected as target cell.

If only one neighboring cell meets the specified requirements, the RNC establishes services in thisneighboring cell.

If more than one neighboring cell meets the specified requirements, the RNC prioritizes these cellsbased on the value of the MBDRPrio parameter and then establishes services in the cell with thehighest priority. If these cells have the same priority, the RNC randomly selects one of them and then

establishes services in this cell. A smaller value of MBDRPrio indicates a higher priority.


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3. If services fail to be established in the cell with the highest priority, the RNC attempts to establishservices in the cell with the second highest priority. If service establishment still fails, the RNC triesthe neighboring cell with the third highest priority. By this analogy, the RNC establishes services inthe current cell only after the number of attempts exceeds the value of the MaxAttNum parameter orafter the RNC tries all the target cells.

MBDR neighboring cells are specified by the MBDRFlagparameter.

Measurement Control Items

After MBDR is triggered, the RNC sends the UE a measurement control message, instructing the UE tomeasure the signal quality of the target cell. After measurement, the UE reports the measurement resultsto the RNC.

The parameters associated with measurement control items, for example, the measurement reportmode and trigger threshold, can be configured by running theADD CELLMBDRINTERFREQorADDCELLMBDRINTERRATcommand.

In the case of inter-frequency MBDR, you can:

Set the InterFreqReportModeparameter to PERIODICAL_REPORTINGor EVENT_TRIGGER.

If the InterFreqReportModeparameter is set to PERIODICAL_REPORTING, the UE reportsmeasurement results to the RNC at an interval of PrdReportInterval. Then, the RNC determineswhether the signal quality of this inter-frequency cell meets the specified requirements according tothe measurement results and the tigger conditions.

If the InterFreqReportModeparameter is set to EVENT_TRIGGER, the UE sends the RNC ameasurement report (indicating that the signal quality of the inter-frequency cell meets theinter-frequency handover requirements) when the signal quality of the inter-frequency cell is higherthan the trigger threshold for the period specified by TrigTime2C.

Set the InterFreqMeasQuantity parameter to Ec/No, RSCP, or BOTH.

The InterFreqMeasQuantityparameter cannot be set to BOTHif the InterFreqReportModeparameter is set toEVENT_TRIGGER.

If the InterFreqMeasQuantity parameter is set to Ec/No, the Ec/No value of the target cell mustreach the inter-frequency handover trigger threshold, which is specified by the HOThdEcN0parameter.

If the InterFreqMeasQuantity parameter is set to RSCP, the RSCP value of the target cell mustreach the inter-frequency handover trigger threshold, which is specified by the HOThdRscpparameter.

If the InterFreqMeasQuantity parameter is set to BOTH, both the Ec/No and RSCP values of the

target cell must reach the corresponding inter-frequency handover trigger threshold.

In the case of inter-RAT MBDR, you can set the InterRatReportModeparameter toPERIODICAL_REPORTINGor EVENT_TRIGGER.

If the InterRatReportModeparameter is set to PERIODICAL_REPORTING, the UE reportsmeasurement results to the RNC at an interval of InterRATPeriodReportInterval . Then, the RNCcompares the measurement results with InterRATHOThdto determine whether the signal quality ofthis inter-RAT cell meets the specified requirements.

If the InterRatReportModeparameter is set to EVENT_TRIGGER, the UE sends the RNC ameasurement report (indicating that the signal quality of the inter-RAT cell meets the inter-RAThandover requirements) when the signal quality of the inter-RAT cell is higher than the triggerthreshold for the period specified by TrigTime3C.



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The measurement mechanism for inter-frequency or inter-RAT MBDR is the same as that for handover.For details about the measurement mechanism, see the Handover Parameter Description.


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Directed Retry Decision 5 Periodic DRD

5 Periodic DRD

5.1 Overview

5.1.1 Switches for Periodic DRD

The DR_RAB_SING_DRD_SWITCH andDR_RAB_COMB_DRD_SWITCHsubparameters of theDrSwitch parameter determine whether to enable RAB DRD for a single service and a servicecombination respectively. The BasedOnMeasHRetryDRDSwitchparameter further determineswhether to enable blind-handover-based non-periodic DRD, blind-handover-based periodic DRD, ormeasurement-based periodic DRD.

When the subparameter DR_RAB_SING_DRD_SWITCH orDR_RAB_COMB_DRD_SWITCHis set toON, the functions of the BasedOnMeasHRetryDRDSwitchparameter are as follows:

When the BasedOnMeasHRetryDRDSwitchparameter is set to ON:

Measurement-based periodic DRD is enabled.Blind-handover-based periodic DRD is disabled.

Blind-handover-based non-periodic DRD is further controlled by the BlindDrdExceptHRetrySwitchparameter.

When the BasedOnMeasHRetryDRDSwitchparameter is set to OFF:

Measurement-based periodic DRD is disabled.

Blind-handover-based periodic DRD is enabled if the ChannelRetryTimerLen parameter is not setto 0.

Blind-handover-based non-periodic DRD is enabled.

5.1.2 Triggering of Periodic DRD

Periodic DRD is triggered by the HSPA/HSPA+ retry. The HSPA/HSPA+ retry can be performed after thebearer scheme of a service is changed, for example, after RAB setup, RAB modification, soft handover,hard handover, or best cell change.

After the bearer scheme of a service is changed, the RNC determines whether the UE can be served bya better HSPA/HSPA+ technology by considering the technological satisfaction. If a better HSPA/HSPA+technology can be used, the HSPA/HSPA+ retry is performed and consequently periodic DRD istriggered. In this way, a suitable cell can be selected to serve the UE with a better HSPA/HSPA+technology.

Measurement-based periodic DRD can also be triggered when a neighboring cell has a higher servicepriority than the current cell. In this way, service steering is achieved.

In different situations, HSPA/HSPA+ technologies that can trigger HSPA/HSPA+ retry and consequentlyperiodic DRD are different. The conditions on which an HSPA/HSPA+ technology can triggerHSPA/HSPA+ retry and consequently periodic DRD are as follows:

The HSPA+ technology must be selected through RetryCapability parameter.

This condition does not apply to the HSPA technologies.

The HSPA/HSPA+ technology must be supported by periodic DRD.

Note that different types of periodic DRD support different HSPA/HSPA+ technologies.



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For blind-handover-based periodic DRD, the supported HSPA/HSPA+ technologies are HSUPA,HSDPA, 64QAM, MIMO, and DC-HSDPA.

For measurement-based periodic DRD, the supported HSPA/HSPA+ technologies are HSDPA,HSUPA, uplink enhanced L2, uplink 16QAM, downlink enhanced L2, CPC, 64QAM, DC-HSDPA, and

MIMO.The reason why measurement-based periodic DRD supports more HSPA+ technologies thanblind-handover-based periodic DRD is as follows: When measurement-based periodic DRD is enabled,non-periodic DRD may not be applied. In such a case, the HSPA+ technologies that are supported bynon-periodic DRD can be supported by measurement-based periodic DRD. In this way, the function ofnon-periodic DRD can be indirectly implemented through measurement-based periodic DRD.

When measurement-based periodic DRD is enabled, whether non-periodic DRD can be applied is further determined bythe BlindDrdExceptHRetrySwitch parameter. For details, see 4 Non-periodic DRD.

5.2 Periodic DRD Procedure

5.2.1 Blind-Handover-Based Periodic DRD

Blind-handover-based periodic DRD applies to the inter-frequency same-coverage scenarios. It isperformed at regular intervals. The interval is specified by the ChannelRetryTimerLen parameter.

Figure 5-1shows the procedure of blind-handover-based periodic DRD.

Figure 5-1 Procedure of blind-handover-based periodic DRD

The procedure of blind-handover-based periodic DRD is as follows:

1. The RNC decides whether candidate cells that the UE can retry accessing exist. The candidate cellsare selected from the same-coverage neighboring cells of the current best cell. A candidate cell mustmeet the following conditions:


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The frequency of the cell is within the band supported by the UE.

The cell supports the requested service.

The cell is not overloaded.

The HSPA+ technological satisfaction of the cell is higher than that of the current cell.

If such candidate cells do not exist, the procedure of blind-handover-based periodic DRD fails. In sucha case, the RNC waits for the next DRD period.

If such candidate cells exist, the following step is performed.

2. The RNC sequences the candidate cells according to the HSPA+ technological satisfaction.

3. The RNC selects a target cell for UE access according to the sequence from the highest to thelowest.


If the admission attempt is successful, the RNC accepts the service request.



If admission decisions fail in all the candidate cells, the procedure of blind-handover-based periodicDRD fails. In such a case, the RNC waits for the next DRD period.

If the UE fails to access the target cell after RNC accepts the service request, blind-handover-based periodic DRD will notbe performed for the UE.

5.2.2 Measurement-Based Periodic DRD

In a multi-band network, the cells that operate on different frequency bands have different coverageareas. When a UE needs to perform an inter-frequency handover in a multi-band network, it normallydoes not perform a blind handover as the success rate of the blind handover is relatively low. Instead,the UE performs handover decision according to the signal of each inter-frequency cell.Measurement-based periodic DRD is introduced to select a signal-qualified cell for the UE to access.

Measurement-based periodic DRD applies to both the inter-frequency same-coverage scenarios and theinter-frequency different-coverage scenarios. It can increase the DRD success rate in both thesame-coverage scenarios and the different-coverage scenarios.

Figure 5-2shows the procedure of measurement-based periodic DRD.



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Figure 5-2 Procedure of measurement-based periodic DRD

The procedure of measurement-based periodic DRD is as follows:

1. Based on HSPA+ technological satisfaction and cell service priority, the RNC decides whethercandidate cells that the UE can retry accessing exist. The candidate cells are selected from the bestcell and its neighboring cells.

A candidate cell must meet the following conditions:

The frequency of the cell is within the band supported by the UE.

The cell supports the requested service.

The DrdOrLdrFlagparameter of the cell is set toTrue, indicating that the cell can be measured.

The HSPA+ technological satisfaction of the cell is higher than that of the current cell, or the servicepriority of the cell is higher than or equal to that of the current cell.

For details about the HSPA+ technological satisfaction and cell service priority, see the Load Control

Feature Parameter Description.If such candidate cells exist, the following step is performed.

2. The RNC starts the timer for periodic DRD. The length of the timer is specified by theHRetryTimerLength parameter.

If there is only one candidate cell and it is the current cell, the UE retries higher HSPA+ technologiesin the current cell when the timer expires.

In other situations, the RNC issues a measurement control message, requesting the UE to measurethe signal quality of all candidate cells.

3. The UE measures the RSCP and Ec/No of the candidate cells and periodically reports themeasurement results to the RNC. The reporting period is specified by the PrdReportIntervalparameter.


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4. Based on the received measurement results, the RNC selects the candidate target cells.

A candidate target cell must meet the following conditions:

The cell is not overloaded.

The measured RSCP is higher than the RSCP threshold that is specified by the TargetFreqThdRscp

parameter.

The measured Ec/No is higher than the Ec/No threshold that is specified by the TargetFreqThdEcN0parameter.

If such candidate target cells do not exist, the procedure of measurement-based periodic DRD fails. Insuch a case, the RNC waits for the DRD timer to expire.

If such candidate target cells exist, the following step is performed.

5. The RNC sequences the candidate target cells according to the HSPA+ technological satisfactionand cell service priority.

6. The RNC selects a candidate target cell for UE access according to the sequence from the highest tothe lowest.

7. The CAC algorithm makes an admission decision based on the status of the candidate target cell. If the admission attempt is successful, the RNC accepts the service request.

If the admission attempt fails, the RNC removes the cell from the candidate target cells and thenchecks whether all candidate target cells are tried.


If admission decisions fail in all the candidate target cells, the procedure of measurement-basedperiodic DRD fails. In such a case, the RNC waits for the DRD timer to expire.

If the measurement or retry fails during the procedure of measurement-based periodic DRD, a failurepenalty timer is started when the DRD timer expires. During the penalty time, such a procedure cannotbe performed and the UE can retry accessing only the current cell. The length of the penalty timer is

specified by multiplying the value of the HRetryTimerLength parameter by the value of theDrdFaiPenaltyPeriodNum parameter.



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Directed Retry Decision 6 Parameters

6 Parameters

Table 6-1 Parameter description

Parameter ID NE MML Command MeaningBasedOnMeasHRetryDRDSwitch

BSC6900

SETUDRD(Optional)

Meaning: Controls the validity of themeasurement-based DRD algorithm. Assume thatthe DRD algorithm is enabled. If the switch is on, theRNC uses the DRD algorithm based on themeasurement (for measuring the signals in theneighboring cell of the best cell). You can run the"SET UMCDRD" command to configure the relatedparameters. If the switch is off, the RNC implementsthe DRD algorithm based on blind handovers. Note:When the measurement-based DRD algorithm isused, you need to measure the signal quality of the

target cell before a DRD retry. This cell can act as theactual target cell only when its signal quality meetsthe preset threshold. The measurement-based DRDis performed only for the periodic retry flow.

GUI Value Range: OFF, ONActual Value Range: OFF, ONUnit: NoneDefault Value: OFF

BlindDrdExceptHRetrySwitch

BSC6900

ADDUCELLMCDRD(Optional)

Meaning: When the measurement-based DRD isperformed, this parameter is used to determinewhether the DRD retry for blind handover isperformed in aperiodic mode. The aperiodic retryincludes the setup of the RAB, modification of theRAB, and DCCC channel handover.If this parameter is set to "ON", the DRD retry forblind handover is performed in aperiodic mode.If this switch is set to "OFF", the DRD retry for blindhandover is not performed in aperiodic mode.

GUI Value Range: OFF, ONActual Value Range: OFF, ONUnit: NoneDefault Value: OFF

BlindDrdExceptHRetrySwitch

BSC6900

SETUMCDRD(Optional)

Meaning: When the measurement-based DRD isperformed, this parameter is used to determinewhether the DRD retry for blind handover isperformed in aperiodic mode. The aperiodic retryincludes the setup of the RAB, modification of theRAB, and DCCC channel handover.If this parameter is set to "ON", the DRD retry forblind handover is performed in aperiodic mode.If this switch is set to "OFF", the DRD retry for blindhandover is not performed in aperiodic mode.

GUI Value Range: OFF, ONActual Value Range: OFF, ON



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Parameter ID NE MML Command Meaning

Unit: NoneDefault Value: OFF

ChannelRetryTimerLen BSC6900 SETUCOIFTIMER(Optional)

Meaning: This parameter specifies the value of thechannel retry timer. The timer will start when traffic isset up or reconfigured and some higher technique isnot configured by some reason except for thecapbility of UE or cell. Channel retry will beperformed after this timer expires.

GUI Value Range: 0~180Actual Value Range: 0~180Unit: sDefault Value: 5

CodeBalancin

gDrdCodeRateThd

BSC69

00

ADD

UCELLDRD(Optional)

Meaning: One of the triggering conditions of code

balancing DRD. The other condition is the minimumspreading factor. Code balancing DRD is appliedonly when the code occupancy in the best cell is notlower than the value of this parameter.

GUI Value Range: 0~100Actual Value Range: 0~100Unit: %Default Value: 13

CodeBalancingDrdCodeRateThd

BSC6900

SETUDRD(Optional)

Meaning: One of the triggering conditions of codebalancing DRD. The other condition is the minimumspreading factor. Code balancing DRD is appliedonly when the code occupancy in the best cell is notlower than the value of this parameter.

GUI Value Range: 0~100Actual Value Range: 0~100Unit: %Default Value: 13

CodeBalancingDrdMinSFThd

BSC6900

ADDUCELLDRD(Optional)

Meaning: One of the triggering conditions of codebalancing DRD. The other condition is the codeoccupancy threshold. Code balancing DRD is appliedonly when the minimum spreading factor in the best

cell is not lower than the value of this parameter.

GUI Value Range: SF4, SF8, SF16, SF32, SF64,SF128, SF256Actual Value Range: SF4, SF8, SF16, SF32, SF64,SF128, SF256Unit: NoneDefault Value: SF8

CodeBalancingDrdMinSFThd

BSC6900

SETUDRD(Optional)

Meaning: One of the triggering conditions of codebalancing DRD. The other condition is the codeoccupancy threshold. Code balancing DRD is appliedonly when the minimum spreading factor in the best

cell is not lower than the value of this parameter.


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GUI Value Range: SF4, SF8, SF16, SF32, SF64,SF128, SF256

Actual Value Range: SF4, SF8, SF16, SF32, SF64,SF128, SF256Unit: NoneDefault Value: SF8

CodeBalancingDrdSwitch

BSC6900


Meaning: Whether to apply the code balancing DRDalgorithm. The "DR_RAB_SING_DRD_SWITCH"parameter in "SET UCORRMALGOSWITCH" needsto be enabled. For combination services, the"DR_RAB_COMB_DRD_SWITCH" parameter needsto be enabled.

GUI Value Range: ON, OFFActual Value Range: ON, OFFUnit: NoneDefault Value: OFF

CodeBalancingDrdSwitch

BSC6900

SETUDRD(Optional)

Meaning: Whether to apply the code balancing DRDalgorithm. The "DR_RAB_SING_DRD_SWITCH"parameter in "SET UCORRMALGOSWITCH" needsto be enabled. For combination services, the"DR_RAB_COMB_DRD_SWITCH" parameter needsto be enabled.

GUI Value Range: ON, OFF

Actual Value Range: ON, OFFUnit: NoneDefault Value: OFF

ConnectFailRrcRedirSwitch

BSC6900

SETUDRD(Optional)

Meaning: RRC redirection switch used in the case ofadmission failure. It is valid only when the"DR_RRC_DRD_SWITCH" parameter is set to ON.- OFF indicates that the RRC redirection is notallowed.- Only_To_Inter_Frequency indicates that only RRCredirection to inter-frequency cells is allowed.- Allowed_To_Inter_RAT indicates that both RRCredirection to inter-frequency cells and redirection to

inter-RAT cells are allowed.

GUI Value Range: OFF, Only_To_Inter_Frequency,Allowed_To_Inter_RATActual Value Range: OFF,Only_To_Inter_Frequency, Allowed_To_Inter_RATUnit: NoneDefault Value: Only_To_Inter_Frequency

DeltaCodeOccupiedRate

BSC6900

SETUDRD(Optional)

Meaning: Threshold of code occupancy offsetbetween the current cell and the target cell whencode balancing DRD is applied. Only when the cell

code occupancy offset reaches this threshold can aneighboring cell be selected to be a candidate cell for



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DRD.

GUI Value Range: 0~100

Actual Value Range: 0~100Unit: %Default Value: 7

DlCellTotalThd

BSC6900

ADDUCELLCAC(Optional)

Meaning: Admission threshold of the total celldownlink power. If the value is too high, too manyusers will be admitted. However, the throughput of asingle user is easy to be limited. If the value is toolow, cell capacity will be wasted.

GUI Value Range: 0~100Actual Value Range: 0~1, step:0.01Unit: %Default Value: 90

DlConvAMRThd

BSC6900


Meaning: The percentage of the conversational AMRservice threshold to the 100% downlink load. It isapplicable to algorithm 1 and algorithm 2. Theparameter is used for controlling the AMR serviceadmission. That is, when an AMR service isaccessing, the RNC evaluates the measurementvalue of the downlink load after the service isaccessed. If the DL load of a cell is higher than thisthreshold after the access of an AMR speech service,this service will be rejected. If the DL load of a cell will

not be higher than this threshold, this service will beadmitted.The DL load factor thresholds include parameters of[DL threshold of Conv non_AMR service], [DLhandover access threshold] and [DL threshold ofother services]. The four parameters can be used tolimit the proportion between the conversationalservice, handover user and other services in aspecific cell, and to guarantee the access priority ofthe conversational AMR service.


DlConvNonAMRThd

BSC6900


Meaning: The percentage of the conversationalnon-AMR service threshold to the 100% downlinkload. It is applicable to algorithm 1 and algorithm 2.The parameter is used for controlling the non-AMRservice admission. That is, when a non-AMR serviceis accessing, the RNC evaluates the measurementvalue of the downlink load after the service isaccessed. If the DL load of a cell is higher than thisthreshold after the access of a non-AMR speech

service, this service will be rejected. If the DL load of


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a cell will not be higher than this threshold, thisservice will be admitted.The DL load factor thresholds include parameters of

[DL threshold of Conv non_AMR service], [DLhandover access threshold] and [DL threshold ofother services]. The four parameters can be used tolimit the proportion between the conversationalservice, handover user and other services in aspecific cell, and to guarantee the access priority ofthe conversational non-AMR service.


DlOtherThd BSC6900


Meaning: The percentage of other service thresholdsto the 100% downlink load. The services refer toother admissions except the conversational AMRservice, conversational non-AMR service, andhandover scenarios. It is applicable to algorithm 1and algorithm 2. The parameter is used forcontrolling other service admissions. That is, when aservice is accessing, the RNC evaluates themeasurement value of the downlink load after theservice is accessed. If the DL load of a cell is higherthan this threshold after the access of a service, thisservice will be rejected. If the DL load of a cell will not

be higher than this threshold, this service will beadmitted.The DL load factor thresholds include parameters of[DL threshold of Conv non_AMR service], [DLhandover access threshold] and [DL threshold ofother services]. The four parameters can be used tolimit the proportion between the conversationalservice, handover user and other services in aspecific cell, and to guarantee the access priority ofother services.

GUI Value Range: 0~100

Actual Value Range: 0~1, step:0.01Unit: %Default Value: 75

DRDEcN0Threshhold

BSC6900

ADDU2GNCELL(Optional)

Meaning: DRD Ec/No threshold for determiningwhether to perform the blind handover. The DRD ispermitted if Ec/No of the current cell is greater thanthe DRD Ec/No threshold of ainter-RAT/inter-frequency neighboring cell.

GUI Value Range: -24~0Actual Value Range: -24~0Unit: dB

Default Value: -18



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DRDEcN0Threshhold

BSC6900

ADDUINTERFREQNCELL(Optional)

Meaning: DRD Ec/No threshold for determiningwhether to perform the blind handover. If themeasured Ec/No of the current cell is greater thanthis parameter, this cell can be the candidate cell forDRD.

GUI Value Range: -24~0Actual Value Range: -24~0Unit: dBDefault Value: -18

DrdFaiPenaltyPeriodNum

BSC6900

ADDUCELLMCDRD(Optional)

Meaning: Number of retry periods in the intervalbetween a failure of a measurement-based DRDre-attempt and the initiation of the next DRDre-attempt. If this parameter is set to a great value,

the probability of a user re-accessing a cell with ahigh priority becomes low; If this parameter is set to asmall value, the probability of a user re-accessing acell with a high priority becomes high; however, theperformance is greatly affected. Note: The processof a measurement-based DRD retry is as follows: Atthe beginning, the RNC determines to enable theDRD retry; then, it starts inter-frequencymeasurement control; next, the RNC receives themeasurement report from a UE; after that, the RNCretries the access to a cell in the reported DRD celllist. The process ends until the cell access succeeds.GUI Value Range: 1~65535Actual Value Range: 1~65535Unit: NoneDefault Value: 10

DrdFaiPenaltyPeriodNum

BSC6900

SETUMCDRD(Optional)

Meaning: Number of retry periods in the intervalbetween a failure of a measurement-based DRDre-attempt and the initiation of the next DRDre-attempt. If this parameter is set to a great value,the probability of a user re-accessing a cell with ahigh priority becomes low; If this parameter is set to asmall value, the probability of a user re-accessing a

cell with a high priority becomes high; however, theperformance is greatly affected. Note: The processof a measurement-based DRD retry is as follows: Atthe beginning, the RNC determines to enable theDRD retry; then, it starts inter-frequencymeasurement control; next, the RNC receives themeasurement report from a UE; after that, the RNCretries the access to a cell in the reported DRD celllist. The process ends until the cell access succeeds.GUI Value Range: 1~65535Actual Value Range: 1~65535Unit: None


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Default Value: 10

DrdOrLdrFlag BSC69

00

ADD

UINTERFREQNCELL(Optional)

Meaning: Specify the flags of the cells that the DRD

measurement or LDR measurement is performed.The value "TRUE" indicates that the cell can beconsidered as the measurement object in the DRDmeasurement algorithm or LDR measurementalgorithm. The value "FALSE" indicates that the cellis invalid.

GUI Value Range: FALSE(Do not send),TRUE(Send)Actual Value Range: FALSE, TRUEUnit: NoneDefault Value: False

DRMaxGSMNum

BSC6900


Meaning: Maximum number of inter-RAT RABdirected retries. It decides the size of the candidateset for inter-RAT DRD. The value 0 indicates thatinter-RAT RAB DRD is not applicable. Thisparameter can be cell-oriented.

GUI Value Range: 0~5Actual Value Range: 0~5Unit: NoneDefault Value: 2

DRMaxGSMNum

BSC6900

SETUDRD(Optional)

Meaning: Maximum number of inter-RAT RABdirected retries. It decides the size of the candidateset for inter-RAT DRD. The value 0 indicates thatinter-RAT RAB DRD is not appl

Documents

Directed Retry Decision