Hand Over

WCDMA RAN

HandoverFeature Parameter Description Copyright Huawei Technologies Co., Ltd. 2010. All rights 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.

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WCDMA RAN Handover

Contents

Contents1 Introduction ................................................................................................................................1-11.1 Scope ............................................................................................................................................ 1-1 1.2 Intended Audience ........................................................................................................................ 1-1 1.3 Change History.............................................................................................................................. 1-1

2 Overview of Handover .............................................................................................................2-1 3 Intra-Frequency Handover .....................................................................................................3-13.1 Overview ....................................................................................................................................... 3-1 3.2 Intra-Frequency Handover Procedure .......................................................................................... 3-2 3.3 Intra-Frequency Handover Measurement ..................................................................................... 3-3 3.4 Intra-Frequency Handover Decision and Execution ..................................................................... 3-8 3.5 Rate Reduction After an SHO Failure ........................................................................................... 3-9 3.6 Signaling Procedures for Intra-Frequency Handover.................................................................. 3-11 3.6.1 Intra-NodeB Intra-Frequency Soft Handover Signaling Procedure .................................... 3-11 3.6.2 Intra-RNC Inter-NodeB Intra-Frequency Soft Handover Signaling Procedure................... 3-13 3.6.3 Inter-RNC Intra-Frequency Soft Handover Signaling Procedure ....................................... 3-14 3.6.4 Intra-RNC Inter-NodeB Intra-Frequency Hard Handover Signaling Procedure ................. 3-16 3.6.5 Inter-RNC Intra-Frequency Hard Handover Signaling Procedure...................................... 3-18

4 Inter-Frequency and Inter-RAT Handover ..........................................................................4-14.1 Overview ....................................................................................................................................... 4-1 4.2 Inter-frequency and Inter-RAT Handover Switches....................................................................... 4-2 4.3 Signaling Procedures for Inter-Frequency Handover.................................................................... 4-2 4.3.1 Inter-Frequency Handover Within One RNC........................................................................ 4-2 4.3.2 Inter-Frequency Handover Between RNCs.......................................................................... 4-4 4.4 Signaling Procedures for Inter-RAT Handover.............................................................................. 4-5 4.4.1 3G-to-2G Handover in the CS Domain................................................................................. 4-5 4.4.2 3G-to-2G Handover in the PS Domain................................................................................. 4-6 4.4.3 3G-to-2G Handover in Both CS Domain and PS Domain.................................................... 4-7 4.4.4 2G-to-3G Handover in the CS Domain................................................................................. 4-9 4.4.5 2G-to-3G Handover in the PS Domain............................................................................... 4-10

5 Coverage or QoS Handover ...................................................................................................5-15.1 Coverage or QoS Handover Procedure........................................................................................ 5-1 5.2 Coverage or QoS Handover Measurement .................................................................................. 5-2 5.2.1 Coverage or QoS Handover Measurement Report Modes .................................................. 5-2 5.2.2 Coverage or QoS Handover Measurement Quantity ........................................................... 5-2 5.2.3 Coverage or QoS Handover Measurement Events.............................................................. 5-3 5.2.4 BSIC Verification Requirements for 2G Cells ....................................................................... 5-7 5.3 Coverage or QoS Handover Decision and Execution................................................................... 5-7 5.3.1 Inter-Frequency Coverage or QoS Handover Decision and Execution ............................... 5-7

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WCDMA RAN Handover 5.3.2 3G-to-2G Coverage and QoS Handover Decision and Execution ....................................... 5-9

5.4 Rules for 3G-to-2G Coverage or QoS Handover .......................................................................... 5-9 5.5 3G-to-2G NACC .......................................................................................................................... 5-11 5.6 3G-to-2G PS Handover............................................................................................................... 5-12 5.7 2G-to-3G Handover..................................................................................................................... 5-12

6 Load Handover ..........................................................................................................................6-16.1 Inter-Frequency LDR Handover .................................................................................................... 6-1 6.1.1 Inter-Frequency LDR Handover Procedure.......................................................................... 6-1 6.1.2 Inter-Frequency LDR Handover Measurement .................................................................... 6-1 6.1.3 Inter-Frequency LDR Handover Decision and Execution .................................................... 6-1 6.2 Inter-RAT LDR Handover .............................................................................................................. 6-3 6.2.1 Inter-RAT LDR Handover Procedure.................................................................................... 6-3 6.2.2 Inter-RAT LDR Handover Measurement .............................................................................. 6-3 6.2.3 Inter-RAT LDR Handover decision and Execution ............................................................... 6-4 6.3 Inter-RAT Service Handover ......................................................................................................... 6-4 6.3.1 Switches for Inter-RAT Service Handover............................................................................ 6-4 6.3.2 Inter-RAT Service Handover Procedure ............................................................................... 6-5 6.4 Rules for Enabling Inter-RAT LDR or Service Handover .............................................................. 6-6 6.5 Interchanging Inter-RAT Load Information .................................................................................... 6-7

7 HSPA Handover .........................................................................................................................7-17.1 HSDPA Handover.......................................................................................................................... 7-1 7.1.1 HSDPA Intra-Frequency Handover ...................................................................................... 7-1 7.1.2 HSDPA Inter-Frequency Handover ...................................................................................... 7-2 7.1.3 HSDPA Inter-RAT Handover................................................................................................. 7-4 7.2 HSUPA Handover.......................................................................................................................... 7-4 7.2.1 HSUPA Intra-Frequency Handover ...................................................................................... 7-4 7.2.2 HSUPA Inter-Frequency Handover ...................................................................................... 7-8 7.2.3 HSUPA Inter-RAT Handover............................................................................................... 7-11 7.3 HSPA+ Handover ........................................................................................................................ 7-11 7.3.1 Overview............................................................................................................................. 7-11 7.3.2 Preselection Phase............................................................................................................. 7-11 7.3.3 Fallback Phase ................................................................................................................... 7-12 7.3.4 Retry Phase........................................................................................................................ 7-12 7.4 Anti-Frequent Serving Cell Change............................................................................................. 7-13 7.5 HSPA Retry ................................................................................................................................. 7-13

8 HCS Handover ...........................................................................................................................8-18.1 Overview ....................................................................................................................................... 8-1 8.2 HCS Handover Procedure ............................................................................................................ 8-2 8.3 UE Speed Estimation .................................................................................................................... 8-3 8.4 HCS Handover Measurement ....................................................................................................... 8-3 8.5 HCS Handover Execution ............................................................................................................. 8-4 iv Huawei Proprietary and Confidential Copyright Huawei Technologies Co., Ltd Issue 02 (2010-06-20)

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8.6 Signaling Procedure of HCS Handover ........................................................................................ 8-5 8.7 Interoperability Between HCS Handover and Other Handovers................................................... 8-5

9 Blind Handover..........................................................................................................................9-6 10 Handover Protection............................................................................................................10-110.1 Anti-Ping-Pong .......................................................................................................................... 10-1 10.2 Handover Retry ......................................................................................................................... 10-1 10.2.1 Inter-Frequency Handover Retry...................................................................................... 10-1 10.2.2 Inter-RAT (3G to 2G) Handover Retry.............................................................................. 10-2 10.3 Inter-RAT Multimedia Fallback .................................................................................................. 10-3 10.4 Transfering Event Report to Periodical Report ......................................................................... 10-4

11 Neighboring Cell Combination..........................................................................................11-1 12 Compressed Mode ...............................................................................................................12-1 13 Parameters .............................................................................................................................13-1 14 Counters .................................................................................................................................14-1 15 Glossary ..................................................................................................................................15-1 16 Reference Documents .........................................................................................................16-1

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1 Introduction

1 Introduction1.1 ScopeThe document describes the handover functional area. It provides an overview of the main functions and goes into details regarding handover.

1.2 Intended AudienceThis document is intended for: Personnel who are familiar with WCDMA basics Personnel who need to understand handover Personnel who work with Huawei products

1.3 Change HistoryThis 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 handover feature. Editorial change: refers to the change in wording or the addition of the information that was not described in the earlier version.

Document IssuesThe document issues are as follows: 02 (2010-06-20) 01 (2010-03-30) Draft (2009-12-05)

02 (2010-06-20)This is the document for the third commercial release of RAN11.0. Compared with 02 (2009-06-30) of RAN11.1, this issue incorporates no feature changes. Change Type Feature change Editorial change Change Description None. None. Parameter Change The parameter EHSPACMPermissionInd is added to 12 Compressed Mode. None.

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 optimizes the description.

Draft (2009-12-05)This is the draft of the document.Issue 02 (2010-06-20) Huawei Proprietary and Confidential Copyright Huawei Technologies Co., Ltd 1-1

1 Introduction

WCDMA RAN Handover

Compared with issue 02 (2009-06-30) of RAN11.0, this issue incorporates the changes described in the following table. Change Type Feature change Change Description HCS traffic absorption is removed. HSPA+ handover is moved from HSPA+ Feature Parameter Description to this document. Parameter Change The parameters deleted are as follows: INTER_FREQ_TA None

Compatibility Switch for Dual-frequency Receiver is The parameters added are as follows: introduced in RAN12.0 CMP_UU_ADJACENT_FREQ_CM_ SWITCH Editorial change None None

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2 Overview of Handover

2 Overview of HandoverHandover 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. 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. Figure 2-1 Handovers supported by the UMTS

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3 Intra-Frequency Handover

3 Intra-Frequency Handover3.1 OverviewIntra-frequency handover is classified into: Intra-frequency soft handover: Multiple radio links are connected to the UE at the same time. Intra-frequency hard handover: Only one radio link is connected to the UE.

Intra-Frequency Soft HandoverIntra-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 (WRFD-020201 Intra Node B Softer Handover, also known as softer handover) Intra-RNC inter-NodeB soft handover (WRFD-020202 Intra RNC Soft Handover) Inter-RNC soft handover (WRFD-020203Inter 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 time. Addition and/or release of radio links are controlled by the ACTIVE SET UPDATE procedure. Table 3-1 Differences between soft handover and softer handover Item Scenario Softer Handover 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 Uplink signal Using maximum-ratio combination Downlink signal Using maximum-ratio combination Soft Handover 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 Using selective combination Using maximum-ratio combination Occupying more Iub bandwidth

Resource use Occupying less 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 the NodeB decides not to perform maximum-ratio combination (softer combination), the RNC performs selective combination.

Intra-Frequency Hard HandoverIntra-frequency hard handover (WRFD-020301 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.

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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. 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. 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.

Inter RNC HandoverWhen the target cell under the target RNC fulfils the criteria for intra-frequency soft handover, intra- or inter-frequency hard handover, the conditions that the handover over Iur is triggered are as follows: Whether the Iur interface is available depends on the setting of the following two parameters according to handover types: Whether intra- or inter- frequency hard handover is allowed over the Iur interface depends on the setting of the HHOTRIG parameter. Whether inter RNC soft Handover is allowed depends on the setting of the SHOTRIG parameter. The SHOTRIG parameter consists of three subswitches: CS_SHO_SWTICH: If CS_SHO_SWTICH is checked, soft handover for CS service over the Iur interface is allowed. HSPA_SHO_SWTICH: If HSPA_SHO_SWTICH is checked, soft handover for HSPA service over the Iur interface is allowed. NON_HSPA_SHO_SWTICH: If NON_HSPA_SHO_SWTICH is checked, soft handover for non-HSPA PS service over the Iur interface is allowed. 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 parameter. Only if the switch is set to ON, can the cross-Iur soft handover be executed.

3.2 Intra-Frequency Handover ProcedureThe intra-frequency handover procedure involves 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.

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Figure 3-1 Intra-frequency handover procedure

3.3 Intra-Frequency Handover MeasurementIn 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.

Intra-Frequency Handover Measurement QuantitiesIntra-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.

Intra-Frequency Handover Measurement EventsIn intra-frequency handover, the UE reports measurement results to the RNC through event reporting. Event 1A Description 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. 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. 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. The best cell changes.

1B 1C

1D

Triggering of Event 1AEvent 1A is triggered under the following condition: 10 x Log(MNew) + CIONew W x 10 x Log(NA

Mi =1

i

) + (1 - W) x 10 x Log(MBest) - (R1a - H1a/2)

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

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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 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 HYSTFOR1A, the hysteresis value of event 1A Figure 3-2 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 3-2), 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 3-2 Triggering of event 1A

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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 1BEvent 1B is triggered under the following condition: 10 x Log(Mold) + CIOold W x 10 x Log(NB

Mi =1

i

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

MOld is the measurement value of the cell that becomes worse. 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. MBest is the measurement value of the best cell in the active set. 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 3-3 shows the triggering of event 1B. In this procedure, the default parameter values are used.

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Figure 3-3 Triggering of event 1B

A: signal quality curve of the best cell in the active set 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 1CEvent 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 3-4 shows the triggering of event 1C. In this procedure, the default parameter values are used.

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Figure 3-4 Triggering of event 1C

A: signal quality curve of the best cell in the active set 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 1DEvent 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. MBest is the measurement value of 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. Figure 3-5 shows the triggering of event 1D. In this procedure, the default parameter values are used.

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Figure 3-5 Triggering of event 1D

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

3.4 Intra-Frequency Handover Decision and ExecutionThe intra-frequency handover decision and execution procedure depends on the different measurement events that the RNC receives. 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. Table 3-2 lists different types of intra-frequency handover decision and execution based on different events. Table 3-2 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.

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Event Decision and Execution 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. 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. If any scenario is applicable, the RNC performs an intra-frequency hard handover.

3.5 Rate Reduction After an SHO FailureIf the radio link fails to be added for a soft handover, the rate reduction is triggered for R99 Non Real Time (NRT) services to increase the probability of a successful soft handover.

Estimation Procedure for Rate ReductionIf 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.

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Figure 3-6 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 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. the condition is not met, the RNC performs the next step (Step 2). is the CPICH Ec/No measurement value of the cell failing to be admitted. is the CPICH Ec/No measurement value of the best cell in the active set. is a parameter.

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

RelThdForDwnGrd

2. The RNC evaluates whether the number of SHO failures in the cell exceeds the ShoFailNumForDwnGrd. If the number of SHO failures in the cell is smaller than the ShoFailNumForDwnGrd: If If

the timer has not been started, the RNC starts it. the timer has been started, the RNC increments the SHO failure counter by one.

The timer length is set through the parameter ShoFailPeriod. 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,3-10 Huawei Proprietary and Confidential Copyright Huawei Technologies Co., Ltd Issue 02 (2010-06-20)

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Procedure of Rate Reduction ExecutionFigure 3-7 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 penalty timer (DcccShoPenaltyTime) 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. If the RNC fails to perform a soft handover again, it performs the estimation procedure and the execution procedure, as previously described.

3.6 Signaling Procedures for Intra-Frequency Handover3.6.1 Intra-NodeB Intra-Frequency Soft Handover Signaling ProcedureThis section describes the signaling procedure for intra-frequency soft handover within a NodeB. Figure 3-8 shows the procedure for intra-frequency soft handover when the UE moves from one cell to another cell within the same NodeB.

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Figure 3-8 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. Figure 3-9 Signaling procedure for intra-NodeB intra-frequency soft handover

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3.6.2 Intra-RNC Inter-NodeB Intra-Frequency Soft Handover Signaling ProcedureThis section describes the signaling procedure for intra-RNC inter-NodeB intra-frequency soft handover. Figure 3-8 shows the procedure for intra-RNC inter-NodeB intra-frequency soft handover. Figure 3-10 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. After the soft handover, only NodeB 2 is connected to the UE. The active set of NodeB 1 is removed.

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

3.6.3 Inter-RNC Intra-Frequency Soft Handover Signaling ProcedureThis section describes the signaling procedure for inter-RNC intra-frequency soft handover. Figure 3-8 shows the procedure for inter-RNC intra-frequency soft handover.

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Figure 3-12 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.

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

3.6.4 Intra-RNC Inter-NodeB Intra-Frequency Hard Handover Signaling ProcedureThe signaling procedure of intra-NodeB intra-frequency hard handover is similar to that of Intra-RNC inter-NodeB intra-frequency hard handover. This section describes the signaling procedure for only the intra-RNC inter-NodeB intra-frequency hard handover.

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Figure 3-14 Procedure for intra-RNC inter-NodeB intra-frequency hard handover

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

As shown in Figure 3-15, NodeB 1 is the source NodeB and NodeB 2 is the target NodeB.

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3.6.5 Inter-RNC Intra-Frequency Hard Handover Signaling ProcedureFigure 3-16 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 3-16 Procedure for inter-RNC intra-frequency hard handover

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

As shown in Figure 3-17, NodeB 1 is the source NodeB and NodeB 2 is the target NodeB.

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4 Inter-Frequency and Inter-RAT Handover

4 Inter-Frequency and Inter-RAT Handover4.1 OverviewBased on the handover triggering causes, the inter-frequency and Inter-RAT handover falls into five categories, as described in Table 4-1. Inter-RAT handover refers to the handover performed between 3G network and 2G network. This section mainly describes the 3G-to2G coverage handover and QoS handover. Except the cause of the triggering is different, the handover procedure is the same for the coverage handover and QoS handover. Table 4-1 Types of inter-frequency and inter-RAT handover Type Coverage handover Description Coverage handover involves the following features: WRFD-020302 Inter Frequency Hard Handover Based on Coverage WRFD-020303 Inter-RAT Handover Based on Coverage If a moving UE leaves the coverage of the current frequency, the RNC needs to trigger the coverage-based inter-frequency or inter-RAT handover to avoid call drops. For details, see 5 Coverage or QoS Handover. QoS handover QoS handover involves the following features: WRFD-020304 Inter Frequency Hard Handover Based on DL QoS WRFD-020309 Inter-RAT Handover Based on DL QoS If the link quality becomes worse, the Link Stability Control Algorithm may trigger the QoS-based inter-frequency or inter-RAT handover to avoid call drops. For details, see 5 Coverage or QoS Handover. LDR handover When the LDR function detects the basic congestion, the RNC chooses some UEs and performs the inter-frequency or inter-RAT handover according to user priorities and service priorities to balance the load between inter-frequency or inter-RAT cells. For details, see 6 Load Handover. Service handover Service handover involves the feature WRFD-020305 Inter-RAT Handover Based on Service 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. For details, see 6 Load Handover. HCS handover HCS handover involves the feature WRFD-021200 HCS. Inter-frequency or inter-RAT 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 details, see 8 HCS Handover.

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4.2 Inter-frequency and Inter-RAT Handover SwitchesSome 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 switches in the command SET UCORRMALGOSWITCH, as described below. HO_INTER_FREQ_HARD_HO_SWITCH: The switch decides whether the RNC allows inter-frequency handover. HO_INTER_RAT_PS_OUT_SWITCH: The switch decides whether the RNC allows inter-RAT handover of the PS domain from the UTRAN. HO_INTER_RAT_CS_OUT_SWITCH: The switch decides whether the RNC allows inter-RAT handover of the CS domain from the UTRAN. HHOTRIG: The switch decides whether intra- or inter- frequency hard handover is allowed over the Iur interface. HO_MC_SIGNAL_SWITCH: The switch decides when the RNC performs the active set signal quality measurement before the RB setup. If the UE is at the cell verge or the signal is weak signals after accessing the network, the RNC can trigger inter-frequency or inter-RAT handover when the UE sets up the RRC. 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_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.

4.3 Signaling Procedures for Inter-Frequency Handover4.3.1 Inter-Frequency Handover Within One RNCFigure 4-1 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.

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Figure 4-1 Inter-frequency handover between NodeBs within one RNC

Figure 4-2 Signaling procedure for inter-frequency handover between NodeBs within one RNC

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As shown in Figure 4-2, 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 original connection is released.

4.3.2 Inter-Frequency Handover Between RNCsFigure 4-3 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 4-3 Inter-frequency hard handover between the RNCs

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Figure 4-4 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 original connection is released.

4.4 Signaling Procedures for Inter-RAT Handover4.4.1 3G-to-2G Handover in the CS DomainFigure 4-5 shows the signaling procedure for the 3G-to-2G handover in the CS domain. The 2G messages shown in Figure 4-5 are for your reference only.

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Figure 4-5 3G-to-2G handover in the CS domain

4.4.2 3G-to-2G Handover in the PS DomainWhen 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 4-6.

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Figure 4-6 Example of the 3G-to-2G handover in the PS domain

4.4.3 3G-to-2G Handover in Both CS Domain and PS DomainThis 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 DomainFor 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.

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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 ResumeWhen 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 4-7 Intra-SGSN service suspend and resume

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Figure 4-8 Inter-SGSN service suspend and resume

4.4.4 2G-to-3G Handover in the CS DomainWhen 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. Then, 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.

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Figure 4-9 2G-to-3G handover in the CS domain

4.4.5 2G-to-3G Handover in the PS DomainFigure 4-10 shows the 2G-to-3G handover in the PS domain.

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Figure 4-10 2G-to-3G handover in PS domain

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5 Coverage or QoS Handover

5 Coverage or QoS HandoverIf a moving UE leaves the coverage area of the current frequency or the link quality degrades, the RNC triggers the coverage-based or QoS-based inter-frequency or inter-RAT handover to avoid call drops. The QoS handover procedure is the same as the coverage handover procedure.

5.1 Coverage or QoS Handover ProcedureFigure 5-1 shows the procedure for the coverage or QoS handover. Figure 5-1 Coverage or QoS handover procedure

In the triggering phase If the CPICH of the current cell becomes worse, the UE reports the event 2D. Then the RNC initiates the coverage handover. If the link quality of the current service deteriorates, the Link Stability Control Algorithm makes a QoS handover decision. Then the RNC initiate the QoS handover. 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.

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If the CPICH of the current cell becomes better, the UE reports the event 2F. Then the RNC stops the compressed mode and the coverage handover. 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 or 3A, 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.

5.2 Coverage or QoS Handover MeasurementIn the measurement phase of inter-frequency or inter-RAT 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. For detailed information on the quality estimation, see section "Frequency Quality Estimate" in 3GPP TS 25.331.

5.2.1 Coverage or QoS Handover Measurement Report ModesThe coverage-based and QoS-based handover use event-triggered or periodical measurement report mode. InterFreqReportMode: The measurement report mode of inter-frequency handover. InterRatReportMode: The measurement report mode of inter-RAT handover. PrdReportInterval: The periodical measurement report interval of inter-frequency handover. InterRATPeriodReportInterval: The periodical measurement report interval of inter-RAT handover. 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.

5.2.2 Coverage or QoS Handover Measurement QuantityMeasurement quantities vary according to the type of inter-frequency or inter-RAT handover. The used frequency belongs to a UMTS cell and the used frequency measurement quantities are set as follows: In inter-frequency or inter-RAT coverage or QoS handover, event 2B/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 or InterFreqCSThd2DRSCP is set to the minimum value, that is, -115. In inter-RAT coverage handover, the event 3A measurement quantity is set through the parameter MeasQuantityOf3A.

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In inter-RAT QoS handover, the event 3A measurement quantity is set through the parameter UsedFreqMeasQuantityForQos3A. The unused frequencies belong to a GSM cell, and the unused frequency measurement quantity is referred to as to GSM RSSI.

5.2.3 Coverage or QoS Handover Measurement EventsWhen the measurement thresholds are reached, the UE reports the events to the RNC to trigger related handover procedures. Table 5-1 describes the measurement events involved in inter-frequency or inter-RAT handover. Table 5-1 Measurement events involved in inter-frequency handover Event 2D 2F 2B Description The estimated quality of the currently used frequency is below a certain threshold. The estimated quality of the currently used frequency is above a certain threshold. 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. 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.

3A

Triggering of Event 2DAfter 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: Inter-frequencyparameters InterFreqCSThd2DEcN0 InterFreqR99PsThd2DEcN0 InterFreqHThd2DEcN0 InterFreqCSThd2DRSCP InterFreqR99PsThd2DRSCP InterFreqHThd2DRSCP

Inter-RAT parameter InterRATCSThd2DEcN0

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The parameters related to HSPA handover are valid only when the switch HO_ALGO_OVERLAY_SWITCH is set to ON. Otherwise, all the PS domain services will take the parameters related to R99 PS service as a measurement event threshold. For If

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

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 2FAfter 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, QUsed is the measured quality of the used frequency. 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: Inter-frequency parameters InterFreqCSThd2FEcN0 InterFreqCSThd2FRSCP InterFreqR99PsThd2FEcN0 InterFreqR99PsThd2FRSCP InterFreqHThd2FEcN0 InterFreqHThd2FRSCP

Inter-RAT parameters InterRATCSThd2FEcN0 InterRATR99PsThd2FEcN0 InterRATHThd2FEcN0 InterRATCSThd2FRSCP InterRATR99PsThd2FRSCP InterRATHThd2FRSCP

The parameters related to HSPA handover are valid only when the switch HO_ALGO_OVERLAY_SWITCH is set to ON. Otherwise, all the PS domain services will take the parameters related to R99 PS service as a measurement event threshold. For If

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

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.5-4 Huawei Proprietary and Confidential Copyright Huawei Technologies Co., Ltd Issue 02 (2010-06-20)

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Triggering of Event 2BAfter 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 QUsed TUsed2b - H2b/2 Where, QNoused is the measured quality of the cell that uses the other frequencies. QUsed is the measured quality of the used frequency. 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

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the RNC and TUsed2b of event 2B with the CPICH RSCP value is modified, TUsed2b is reset to 25 dBm.The parameters related to HSPA handover are valid only when the switch HO_ALGO_OVERLAY_SWITCH is set to ON. Otherwise, all the PS domain services will take the parameters related to R99 PS service 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.

Triggering of Event 3AWhen 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, QUsed is the measurement value of the cell at the currently used frequency. 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

In the Coverage-based handover, based on the measurement quantity (CPICH Ec/No or RSCP), TUsed is configured as follows: If

the measurement quantity is CPICH Ec/No:

If 2D is triggered by RSCP, TUsed is configured as the maximum value 0 dB. If 2D is triggered by Ec/No, TUsed is configured as the Ec/No threshold specified by the previous parameters. If

the measurement quantity is CPICH RSCP:

If 2D is triggered by RSCP, TUsed is configured as the RSCP threshold specified by the previous parameters.. If 2D is triggered by Ec/No, TUsed is configured as the maximum value -25 dBm. 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 If

the measurement quantity is CPICH Ec/No, TUsed is configured as the maximum value 0 dB. the measurement quantity is CPICH RSCP, TUsed is configured as the maximum value 25 dBm. the measurement quantity is CPICH Ec/No, TUsed is configured as the maximum value 0 dB.

In the downlink QoS-based handover: If If

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

UsedFreqCSThdRSCP

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and DlRscpQosHyst

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

5.2.4 BSIC Verification Requirements for 2G CellsDuring inter-RAT measurement, it is recommended that the UE report the 2G cell to the RNC after the Base Transceiver Station Identity Code (BSIC) of the cell is verified. This greatly enhances the reliability of handover. The parameter BSICVerify is the control switch for the BSIC verification.

5.3 Coverage or QoS Handover Decision and Execution5.3.1 Inter-Frequency Coverage or QoS Handover Decision and ExecutionThe coverage-based 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. HOCovPrio specifies the neighboring cell priority for coverage based inter-frequency handover.

Inter-Frequency Handover in Periodical Measurement Report ModeAfter 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, 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. is the cell individual offset value of the target cell. It is equal to the sum of CIO and

CIOother_Freq

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

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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 5-2. Figure 5-2 Selecting the cell with the highest CPICH RSCP

Inter-Frequency Handover in Event-Triggered Measurement Report ModeAfter 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.

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5.3.2 3G-to-2G Coverage and QoS Handover Decision and ExecutionThe 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.

3G-to-2G Coverage and QoS Handover in Periodical Report ModeAfter 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. is the cell individual offset value of the target cell. It is equal to the sum of CIO and

CIOother_RAT

CIOOffset. Tother_RAT

is the decision threshold of inter-RAT hard handover.

Based on the service type and measurement quantity, this threshold can be configured through the following parameters: TargetRatCsThd TargetRatR99PsThd TargetRatHThdH

is the inter-RAT handover hysteresis value set through HystforInterRAT. the PS and CS combined services, one or more handover thresholds for CS services are used.

For

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.

3G-to-2G Coverage and QoS Handover in Event Report ModeAfter 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.

5.4 Rules for 3G-to-2G Coverage or QoS HandoverThe rules for enabling the 3G-to-2G handover are based on the Service Handover Indicator and the capability requirement. The rules vary according to the types of inter-RAT handover.

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Capability RequirementBefore 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 required 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. 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 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 5-2 Impacts of different types of capability on handover decision 2G Cell Capability EDGE UE Capability Service Required Capability EDGE EDGE GPRS GSM Allowed Allowed Not allowed GPRS Allowed Allowed Not allowed Not allowed Allowed Allowed Not allowed Not allowed Not allowed Not allowed Not allowed Not allowed GSM Allowed Allowed Allowed Not allowed Allowed Allowed Allowed Not allowed Allowed Allowed Allowed Not allowed

Not supported by 2G Not allowed GPRS EDGE GPRS GSM Allowed Allowed Not allowed

Not supported by 2G Not allowed GSM EDGE GPRS GSM Not allowed Not allowed Not allowed

Not supported by 2G Not allowed

Service Handover IndicatorThe RNC initiates the coverage- or QoS-based UMTS-to-GSM handover only when Service Handover Indicator is as follows: HO_TO_GSM_SHOULD_BE_PERFORM HO_TO_GSM_SHOULD_NOT_BE_PERFORM

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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 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. 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 with 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).

5.5 3G-to-2G NACCThis section describes the feature WRFD-02030801 NACC (Network Assisted Cell Change). 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.

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5.6 3G-to-2G PS HandoverThis section describes the feature WRFD-02030802 PS Handover between UMTS and GPRS PS handover is similar to the inter-RAT handover in the CS domain. If the HO_INTER_RAT_PS_3G2G_RELOCATION_SWITCH is turned on, the PS handover from the 3G network to the 2G network is performed in the relocation process. When the switch is not on, the PS handover from the 3G network to the 2G network is performed in the cell change order process. 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.

5.7 2G-to-3G HandoverThe 2G-to-3G handover is initiated by the 2G network, where the dual-mode (GSM and WCDMA) mobile terminals are required. Both the GSM MSC and the GSM BSS must support the GSM-to-UMTS handover.

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6 Load Handover

6 Load HandoverLoad handover is used to balance the load among inter-frequency or inter-RAT cells. Load handover falls into the following categories: Inter-frequency LDR handover Inter-RAT LDR handover Inter-RAT service handover

6.1 Inter-Frequency LDR Handover6.1.1 Inter-Frequency LDR Handover ProcedureThe inter-frequency LDR handover (WRFD-020103 Inter Frequency Load Balance) suits co-sited cells covering the same area. In the triggering phase The Load Reshuffling (LDR) module detects that the current cell is in basic congestion and then initiates an inter-frequency handover. In the decision phase For Inter-frequency LDR blind handover, the RNC decides to trigger an inter-frequency blind handover if the corresponding conditions are met. 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 inter-frequency LDR measure-based 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. In the execution phase The RNC performs the handover according to the decision result. For details of LDR, see Load Control Feature Parameter Description.

6.1.2 Inter-Frequency LDR Handover MeasurementThe Inter-frequency LDR handover uses the periodical report mode. In Inter-frequency LDR blind handover, CPICH RSCP of the used frequency is measured. In inter-frequency LDR measure-based handover, both CPICH_RSCP and CPICH_Ec/No of the target frequency are measured.

6.1.3 Inter-Frequency LDR Handover Decision and ExecutionThe LDR algorithm may trigger an inter-frequency handover. The following describes the procedure for handover decision and execution. The inter-frequency LDR handover can be performed based on blind handover or measurement that can be decided by the parameter InterFreqLDHOMethodSelection.

Inter-Frequency LDR Blind Handover Decision1. 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 Inter-frequency LDR blind handover.Issue 02 (2010-06-20) Huawei Proprietary and Confidential Copyright Huawei Technologies Co., Ltd 6-1

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If the UE is in soft handover state, the RNC operates based on the following conditions: If the HO_ALGO_LDR_ALLOW_SHO_SWITCH is set to ON, The RNC determines whether the cell that triggers LDR is the best cell. If

this cell is the best cell, the RNC initiates an intra-frequency measurement for Inter-frequency LDR blind handover. The intra-frequency measurement is used to estimate quality of the inter-frequency cell of the same coverage. this cell is not the best cell, the RNC does not initiate a Inter-frequency LDR blind handover.

If

If the HO_ALGO_LDR_ALLOW_SHO_SWITCH is set to OFF, the RNC does not initiate a Inter-frequency LDR blind handover.

Inter-Frequency LDR Blind Handover ExecutionThe 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 The The The

reporting period is BlindHOIntrafreqMRInterval. number of measurement reports is BlindHOIntrafreqMRAmount. intra-frequency handover measurement quantity is CPICH RSCP. 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 If

the condition is met, the RNC increments the counter of the number of intra-frequency measurement reports for blind handover by 1. 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.

Inter-Frequency LDR Measure-based Handover Decision and Execution1. 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 report period is specified by the parameter PrdReportInterval. The target cell must meet the following conditions:

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6 Load Handover

CPICH RSCP value of the target cell is larger than TargetFreqThdRscp. CPICH Ec/No value of the target cell is larger than TargetFreqThdEcN0 target cell is not in the basic congestion state.

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

6.2 Inter-RAT LDR Handover6.2.1 Inter-RAT LDR Handover ProcedureWhen the load of the 3G network is heavy and all the RABs of the UE are supported by the 2G network, the Inter-RAT (3G-to-2G) LDR handover (WRFD-020306 Inter-RAT Handover Based on Load) is triggered. Figure 6-1 Inter-RAT LDR handover procedure

In the triggering phase When the load of the 3G cell that the UE a