Interoperability Between UMTS and LTE(RAN14.0_04)

Interoperability Between UMTS and LTE RAN14.0

Feature Parameter Description

Issue 04

Date 2013-05-10

HUAWEI TECHNOLOGIES CO., LTD.

Copyright Huawei Technologies Co., Ltd. 2013. All rights reserved.

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WCDMA RAN

Interoperability Between UMTS and LTE Contents

Issue 04 (2013-05-10) Huawei Proprietary and Confidential

Copyright Huawei Technologies Co., Ltd.

i

Contents

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

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

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

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

2 Overview...................................................................................................................................... 2-1

2.1 Background ................................................................................................................................... 2-1

2.2 Function Classification .................................................................................................................. 2-1

2.3 Deployment Phases of Interoperability Between UMTS and LTE ................................................ 2-1

2.3.1 Phase 1: Only Data Cards, Only Data Services, LTE Coverage Still Incomplete ................ 2-1

2.3.2 Phase 2: Not Only Data Cards, Only Data Services, CSFB Supported, LTE Coverage Still

Incomplete ..................................................................................................................................... 2-2

2.3.3 Phase 3: Data and VoIP Services Supported, LTE Coverage Still Incomplete .................... 2-3

3 Cell Reselection Between UMTS and LTE .......................................................................... 3-1

3.1 UMTS-to-LTE Cell Reselection ..................................................................................................... 3-1

3.1.1 Criteria for Starting Measurements ....................................................................................... 3-1

3.1.2 Criteria for Triggering Cell Reselection ................................................................................. 3-2

3.2 LTE-to-UMTS Cell Reselection ..................................................................................................... 3-3

3.3 UMTS-to-LTE Fast Return............................................................................................................. 3-3

3.3.1 Principles .............................................................................................................................. 3-3

3.3.2 Related Features .................................................................................................................. 3-4

3.4 UMTS-to-LTE Quick Cell Reselection ........................................................................................... 3-5

4 PS Redirections and Handovers Between UMTS and LTE ............................................ 4-1

4.1 LTE-to-UMTS PS Redirections and Handovers ............................................................................ 4-1

4.2 Service-based UMTS-to-LTE PS Redirections and Handovers .................................................... 4-1

4.2.1 Overview ............................................................................................................................... 4-1

4.2.2 Measurements on LTE Signal Quality .................................................................................. 4-2

4.2.3 Target Cell Selection and Execution of Redirections or Handovers ..................................... 4-3

5 CS Fallback Guarantee for LTE Emergency Calls ............................................................ 5-1

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

5.2 Policy ............................................................................................................................................. 5-2

6 CS Fallback Guarantee for LTE Common Calls ................................................................ 6-1

6.1 Overview ....................................................................................................................................... 6-1

6.2 Policy ............................................................................................................................................. 6-1

7 Impact on the Network............................................................................................................. 7-1

7.1 WRFD-140226 UMTS-to-LTE Fast Return (a Trial Feature) ......................................................... 7-1

7.2 WRFD-020129 Service-Based PS Service Redirection from UMTS to LTE ................................. 7-1

7.3 WRFD-140218 Service-Based PS Handover from UMTS to LTE ................................................ 7-1

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Interoperability Between UMTS and LTE Contents



ii

7.4 WRFD-140102 CS Fallback Guarantee for LTE Emergency Calls ............................................... 7-1

8 Engineering Guidelines ........................................................................................................... 8-1

8.1 WRFD-020126 Mobility Between UMTS and LTE Phase 1 .......................................................... 8-1

8.1.1 When to Use Mobility Between UMTS and LTE Phase 1 .................................................... 8-1

8.1.2 Feature Deployment ............................................................................................................. 8-1

8.2 WRFD-140226 UMTS-to-LTE Fast Return (a Trial Feature) ......................................................... 8-3

8.2.1 When to Use UMTS-to-LTE Fast Return .............................................................................. 8-3

8.2.2 Information to Be Collected .................................................................................................. 8-4

8.2.3 Network Planning ................................................................................................................. 8-4


8.2.5 Performance Monitoring ....................................................................................................... 8-6

8.2.6 Parameter Optimization ........................................................................................................ 8-6

8.2.7 Troubleshooting .................................................................................................................... 8-7

8.3 WRFD-020129 Service-Based PS Service Redirection from UMTS to LTE ................................. 8-7

8.3.1 When to Use Service-based PS Redirection or Handover from UMTS to LTE .................... 8-7


8.3.3 Performance Optimization .................................................................................................. 8-10

8.4 WRFD-140218 Service-Based PS Handover from UMTS to LTE .............................................. 8-10

8.4.1 Feature Deployment ........................................................................................................... 8-10


8.5 WRFD-140102 CS Fallback Guarantee for LTE Emergency Calls ............................................. 8-14

8.5.1 When to Use CS Fallback Guarantee for LTE Emergency Calls ....................................... 8-14

8.5.2 Feature Deployment ........................................................................................................... 8-14


9 Parameters.................................................................................................................................. 9-1

10 Counters.................................................................................................................................. 10-1

11 Glossary .................................................................................................................................. 11-1

12 Reference Documents ......................................................................................................... 12-1

WCDMA RAN

Interoperability Between UMTS and LTE 1 Introduction



1-1

1 Introduction

1.1 Scope

This document describes Interoperability Between UMTS and LTE, which includes cell reselection, handovers, and redirections between UMTS and LTE. Details are provided about how these functions work and how to deploy them.

This document addresses the following features:

WRFD-020126 Mobility Between UMTS and LTE Phase 1

WRFD-020129 PS Service Redirection from UMTS to LTE

WRFD-140218 Service-Based PS Handover from UMTS to LTE

WRFD-140102 CS Fallback Guarantee for LTE Emergency Calls

1.2 Intended Audience

This document is intended for:

Personnel who are familiar with WCDMA basics

Personnel who need to understand Interoperability Between UMTS and LTE

Personnel who work with Huawei WCDMA products

1.3 Change History

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

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

Feature change: refers to a change in the Interoperability Between UMTS and LTE feature of a specific product version.

Editorial change: refers to a change in wording or the addition of information that was not described in the earlier version.

Document Issues

The document issues are as follows:

04 (2013-05-10)

03 (2012-11-30)

02 (2012-07-20)

01 (2012-04-30)

Draft A (2012-02-15)

04 (2013-05-10)

This is the fourth commercial release for RAN14.0.

Compared with issue 03 (2012-11-30) for RAN14.0, this issue incorporates the changes described in the following table.

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Change Type Change Description Parameter Change

Feature change

None None

Editorial change

Added the descriptions about SRB data rate. For details, see section 5.2 Policy and 6.2 Policy.

Added the CSFBSRBRate parameter.

03 (2012-11-30)

This is the third commercial release for RAN14.0.



Feature change

Changed the UMTS-to-LTE fast return function to a trial feature.

None

Editorial change

Optimized the descriptions in section 3.1.2 "Criteria for Triggering Cell Reselection."

None

Added the following sections for the UMTS-to-LTE fast return function

3.3.2 "Related Features"

7.1 "WRFD-140226 UMTS-to-LTE Fast Return (a Trial Feature)"

8.2 "WRFD-140226 UMTS-to-LTE Fast Return (a Trial Feature)"

02 (2012-07-20)

This is the second commercial release for RAN14.0.

Compared with issue 01 (2012-04-30) for RAN14.0, this issue incorporates the changes described in the following table:


Feature change

Added descriptions of UMTS-to-LTE quick cell reselection. For details, see section 3.4 "UMTS-to-LTE Quick Cell Reselection."

Added descriptions of the CS fallback guarantee for LTE common calls. For details, see chapter 6 "CS Fallback Guarantee for LTE Common Calls."

Added the following parameters:

RsvSwitch0: RESERVED_SWITCH_0_BIT10

RsvSwitch0: RESERVED_SWITCH_0_BIT8

PerfEnhanceSwitch: PERFENH_L2U_CSFB_COMMCALL_SWITCH

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Editorial change

Added the information about how to deploy related features to interoperability between UMTS and LTE. For details, see 8 "Engineering Guidelines."

None

01 (2012-04-30)

This is the first commercial release for RAN14.0.

Compared with issue Draft A (2012-02-15) for RAN14.0, this issue incorporates the changes described in the following table:


Feature change None None

Editorial change The document description is optimized to improve readability.

None

Draft A (2012-02-15)

This is the first draft of the document for RAN14.0.



Feature change Added the following functions:

Service-Based PS Handover from UMTS to LTE. For details, see chapter 4 "PS Redirections and Handovers Between UMTS and LTE."

CS Fallback Guarantee for LTE Emergency Calls. For details, see chapter 5 "CS Fallback Guarantee for LTE Emergency Calls."

UMTS-to-LTE Fast Return. For details, see section 3.3 "UMTS-to-LTE Fast Return."

Added the following parameters:

SuppPSHOFlag

HO_LTE_SERVICE_PSHO_OUT_SWITCH

HO_L2U_EMGCall_Switch

HO_UMTS_TO_LTE_FAST_RETURN_SWITCH

Editorial change The document description is optimized to improve readability.

None

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Interoperability Between UMTS and LTE 2 Overview



2-1

2 Overview

2.1 Background

As wireless data services rapidly grow and conditions mature for LTE commercial use, telecom operators are beginning to execute plans to build LTE networks upon existing UMTS networks. These two types of networks will have to coexist for a long time, so interoperability between UMTS and LTE is important. This feature helps make the most of existing network equipment, provide diversified services, and achieve smooth network evolution. Huawei products support interoperability between UMTS and time division duplex (TDD) LTE and between UMTS and frequency division duplex (FDD) LTE. However, interoperability between UMTS and LTE is not currently an option if both TDD LTE and FDD LTE are deployed.

2.2 Function Classification

Interoperability between UMTS and LTE functions are classified by UE status, as shown in Table 2-1.

Table 2-1 Interoperability between UMTS and LTE functions classified by UE status

UE Status Interoperability Between UMTS and LTE Function

Idle mode UMTS-to-LTE cell reselection

LTE-to-UMTS cell reselection. See LTE document Mobility Management in Idle Mode Feature Parameter Description for details.

Connected mode

Data services

LTE-to-UMTS PS redirections or handovers. See LTE document Mobility Management in Connected Mode Feature Parameter Description for details.

Service-based UMTS-to-LTE PS redirections and handovers

Voice services

LTE-to-UMTS circuit-switched fallback (CSFB) specified by 3GPP Release 8. See LTE document CS Fallback Feature Parameter Description for details.

CSFB guarantee for emergency calls originated on the LTE network

NOTE

Currently, LTE does not support voice services. Therefore, interoperability between UMTS and LTE does not address UMTS-to-LTE handovers of CS services or CS/PS combined services.

2.3 Deployment Phases of Interoperability Between UMTS and LTE

2.3.1 Phase 1: Only Data Cards, Only Data Services, LTE Coverage Still Incomplete

Description

UMTS/LTE dual-mode UEs only support PS services and PS handovers.

No IP Multimedia Subsystem (IMS) has been deployed on the LTE network and therefore VoIP services are not supported.

LTE coverage is still incomplete.

UE camping policy

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An LTE-first policy is recommended for UE camping, because commercial UMTS/LTE dual-mode UEs are all in data-card mode.

Cell reselection is performed to shift UEs in idle mode or the CELL_PCH/URA_PCH state between UMTS and LTE. For details, see chapter 3 "Cell Reselection Between UMTS and LTE."

CS service policy

CS services are not supported, because commercial UMTS/LTE dual-mode UEs are all in data-card mode.

PS service policy

Since LTE coverage is still incomplete, when a UE processing a PS service on the LTE network moves out of the LTE coverage area, a PS handover or redirection to the UMTS network is performed for the UE and the PS service. For details, see section 4.1 "LTE-to-UMTS PS Redirections and Handovers."

When a UE processing a PS service on the UMTS network moves to a UMTS/LTE overlapping coverage area, a PS handover or redirection to the LTE network is not performed.

2.3.2 Phase 2: Not Only Data Cards, Only Data Services, CSFB Supported, LTE Coverage Still Incomplete

Description

Commercial UMTS/LTE dual-mode UEs in data-card mode and non-data-card mode are in use.

No IMS has been deployed on the LTE network and therefore VoIP services are not supported.

The networks and UEs support CSFB.


UE camping policy

Huawei products support either the LTE network or the UMTS network as the preferred choice for UE camping. An LTE-first policy is recommended for this phase.

CS service policy

When a UE initiates a voice service on the LTE network, both the UE and the voice service will fall back to the UMTS network. Emergency calls initiated on the LTE network are ensured a high CSFB success rate. For details, see chapter 5 "CS Fallback Guarantee for LTE Emergency Calls."

A UE processing a CS service or CS/PS combined service on the UMTS network remains on the UMTS network to ensure CS service continuity.

PS service policy

Since LTE coverage is still incomplete in this phase, when a UE processing a PS service on the LTE network moves out of LTE coverage, a PS handover or redirection to the UMTS network will be performed. For details, see section 4.1 "LTE-to-UMTS PS Redirections and Handovers." When a UE processing a PS service on the UMTS network moves to a UMTS/LTE overlapping coverage area, the UE can remain on the UMTS network. For details, see section 4.1 "LTE-to-UMTS PS Redirections and Handovers."

A UMTS-first policy can be adopted for UE camping. Under this policy, when a UE initiates a PS service in a UMTS/LTE overlapping coverage area, a service-based UMTS-to-LTE PS handover or redirection is performed to shift the UE and the PS service to the LTE network. This mechanism makes efficient use of the LTE network. For details, see section 4.2 "Service-based UMTS-to-LTE PS Redirections and Handovers."

When a UE processing a PS service initiates a CS service, CSFB is performed and a PS handover or redirection is used to shift the PS service to the UMTS network. If the PS service is still in progress

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2-3

when the CS service is complete and the LTE signal quality meets specific conditions, a service-based UMTS-to-LTE PS handover or redirection is performed to shift the UE and the PS service back to the LTE network. For details, see section 4.2 "Service-based UMTS-to-LTE PS Redirections and Handovers."

2.3.3 Phase 3: Data and VoIP Services Supported, LTE Coverage Still Incomplete

Description

An IMS has been deployed on the IMS. Therefore, both PS data services and VoIP services are supported.


UE Camping Policy

An LTE-first policy is recommended. If the delay caused by CSFB is too long to ensure service quality, adopt a UMTS-first policy.

CS service policy

When a UE processing a VoIP service on the LTE network moves out of the LTE coverage area, the Single Radio Voice Call Continuity (SRVCC) feature converts the VoIP service to a CS service on the UMTS network. This mechanism ensures voice service continuity.

A UE processing a CS service or CS/PS combined service remains on the UMTS network to ensure CS service continuity.

PS service policy

Since LTE coverage is still incomplete, when a UE processing a PS service on the LTE network moves out of the LTE coverage area, a PS handover or redirection to the UMTS network is performed. For details, see section 4.1 "LTE-to-UMTS PS Redirections and Handovers." When a UE processing a PS service on the UMTS network moves to a UMTS/LTE overlapping coverage area, the UE can remain on the UMTS network. For details, see section 4.1 "LTE-to-UMTS PS Redirections and Handovers."

A UMTS-first policy can be adopted for UE camping. Under this policy, when a UE initiates a PS service in a UMTS/LTE overlapping coverage area, a service-based UMTS-to-LTE PS handover or redirection is performed to shift the UE and the PS service to the LTE network. This mechanism makes efficient use of the LTE network. For details, see section 4.2 "Service-based UMTS-to-LTE PS Redirections and Handovers."

When a UE processing a PS service initiates a CS service, CSFB is performed and a PS handover or redirection is used to shift the PS service to the UMTS network. If the PS service is still in progress when the CS service is complete and the LTE signal quality meets specific conditions, a service-based UMTS-to-LTE PS handover or redirection is performed to shift the UE and the PS service back to the LTE network. For details, see section 4.2 "Service-based UMTS-to-LTE PS Redirections and Handovers."

NOTE

To adopt an LTE-first policy for UE camping, set high priorities for LTE frequencies so that the LTE network is preferred during cell reselection. To adopt a UMTS-first policy for UE camping, set low priorities for LTE frequencies so that the UMTS network is preferred during cell reselection.

WCDMA RAN

Interoperability Between UMTS and LTE 3 Cell Reselection Between UMTS and LTE



3-1

3 Cell Reselection Between UMTS and LTE

This chapter describes the WRFD-020126 Mobility Between UMTS and LTE Phase 1 feature.

Cell reselection between UMTS and LTE includes UMTS-to-LTE cell reselection, LTE-to-UMTS cell reselection, UMTS-to-LTE fast return, and UMTS-to-LTE quick cell reselection.

When camping on the UMTS network, a UMTS/LTE dual-mode UE receives system information from the serving UMTS cell. System information block 19 (SIB19) carries the absolute priorities of the serving UMTS cell and LTE frequencies. If the absolute priorities of one or more LTE frequencies are higher than the absolute priority of the serving UMTS cell, the corresponding LTE cell or cells are the preferred target cells for cell reselection. If the absolute priorities of all LTE frequencies are lower than the absolute priority of the serving UMTS cell, UMTS cells are the preferred target cells for cell reselection.

UMTS-to-LTE fast return improves user experience by accelerating reselection. However, it can only be used if UMTS and LTE are deployed together.

When camping on the LTE network, a UMTS/LTE dual-mode UE receives system information from the serving LTE cell. SIB3 carries the absolute priority of the serving LTE cell, SIB5 carries the absolute priorities of the LTE frequencies, and SIB6 carries the absolute priorities of the UMTS frequencies. You can manipulate these priorities to favor UMTS or LTE cells as target cells for reselection.

When camping on the UMTS network, a UMTS/LTE dual-mode UE can initiate UMTS-to-LTE cell reselection only when it is in the CELL_PCH or idle state. To accelerate the reselection process, you need to enable fast state transition from CELL_DCH to CELL_PCH or from CELL_DCH to the idle state. With this function, the UMTS/LTE dual-mode UE can transit to the CELL_PCH or idle state within a short period of time after data transmission is complete, thereby initiating the UMTS-to-LTE cell reselection.

The SibCfgBitMap parameter in the ADD/MOD UCELLSIBSWITCH command specifies whether to broadcast SIB19.

3.1 UMTS-to-LTE Cell Reselection

When a UE camping on the UMTS network receives SIB19 and specific conditions are met, the UE starts measuring the LTE signal quality. Based on the measurement results, the UE camps on the best cell by performing reselection.

3.1.1 Criteria for Starting Measurements

SIB19 carries the absolute priority of the serving UMTS cell, the absolute priorities of the LTE frequencies, and the cell reselection thresholds. Different radio access technologies (RATs) must have different priorities. Upon receipt of SIB19, the UE does the following:

If the absolute priorities of one or more LTE frequencies are higher than the absolute priority of the serving UMTS cell, the UE starts measuring the signal quality of the LTE frequencies.

The SPriority parameter in the ADD UCELLSELRESEL or MOD UCELLSELRESEL command specifies the absolute priority of the serving UMTS cell.

The NPriority parameter in the ADD UCELLNFREQPRIOINFO or MOD UCELLNFREQPRIOINFO command specifies the absolute priorities of the LTE frequencies.

If the absolute priorities of one or more LTE frequencies are lower than the absolute priority of the serving UMTS cell and the formula SrxlevServingCell Sprioritysearch1 or SqualServingCell Sprioritysearch2 is true, the UE starts measuring the signal quality of the LTE frequencies.

Details about these two formulas are as follows:

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3-2

The ThdPrioritySearch1 and ThdPrioritySearch2 parameters in the ADD UCELLSELRESEL or MOD UCELLSELRESEL command specify the values of Sprioritysearch1 and Sprioritysearch2, respectively.

Sprioritysearch1 is a threshold for the received signal code power (RSCP) of the serving UMTS cell. If the serving cell's RSCP measured by the UE minus Qrxlevmin is not larger than Sprioritysearch1, the UE starts measuring the signal quality of the LTE frequencies whose absolute priorities are lower than the absolute priority of the serving UMTS cell. The larger the value of this parameter, the more likely the UEs are to start the measurements.

Sprioritysearch2 is a threshold for the Ec/No of the serving UMTS cell. If the serving cell's Ec/No measured by the UE minus Qqualmin is not larger than Sprioritysearch2, the UE starts measuring the signal quality of the LTE frequencies whose absolute priorities are lower than the absolute priority of the serving UMTS cell. The larger the value of this parameter, the more likely the UEs are to start the measurements.

The meanings of the other variables are as follows:

Srxlev: Cell Selection RX level value (dB).

Squal: Cell Selection quality value (dB), Applicable only for FDD cells.

Qrxlevmin: required minimum RX level.

Qqualmin: required minimum quality level.

SrxlevServingCell: the serving cell's RSCP measured by the UE minus Qrxlevmin.

SqualServingCell: the serving cell's Ec/No measured by the UE minus Qqualmin.

The UE should not perform cell reselection to a cell for which cell selection criterion S is not fulfilled. For details about criterion S, see UE Behaviors in Idle Feature Parameter Description.

3.1.2 Criteria for Triggering Cell Reselection

After measuring the UMTS serving cell and LTE frequencies, the UE shifts to the best cell by performing reselection.

SIB19 carries the absolute priority of the serving UMTS cell, the absolute priorities of the LTE frequencies, and the cell reselection thresholds. The UE performs cell reselection based on the absolute priorities.

3GPP TS 25.304 specifies three sets of criteria for cell reselection based on the absolute priorities. However, criteria set 2 is used for inter-frequency scenarios, not for inter-RAT scenarios, and SIB19 does not carry the absolute priorities of UMTS frequencies in Huawei products. Therefore, criteria set 2 is not supported by Huawei products.

Criteria sets 1 and 3 apply to UMTS-to-LTE reselection:

Criteria set 1 (both need to be fulfilled)

The absolute priority of an LTE frequency is higher than the absolute priority of the serving UMTS cell.

The Srxlev value of the LTE frequency, SrxlevnonServingCell, has remained at or above the threshold Threshhigh for a period of time longer than Treselection.

Criteria set 3 (all need to be fulfilled)

The absolute priority of an LTE frequency is lower than the absolute priority of the serving UMTS cell.

SrxlevnonServingCell has remained above Threshlow for a period of time longer than Treselection.

SrxlevServingCell has remained below Threshserving,low for a period of time longer than Treselection, or SqualServingCell has remained below 0 for a period of time longer than Treselection.

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Details about these parameters are as follows:

Threshhigh is the threshold for the target cell's signal level relative to EQrxlevmin during reselection to a cell using a frequency with a higher absolute priority. The ThdToHigh parameter in the ADD UCELLNFREQPRIOINFO or MOD UCELLNFREQPRIOINFO command specifies the value of Threshhigh. The larger the value of this parameter, the less likely that reselection occurs.

Threshlow is the threshold for the target cell's signal level relative to EQrxlevmin during reselection to a cell using a frequency with a lower absolute priority. The ThdToLow parameter in the ADD UCELLNFREQPRIOINFO or MOD UCELLNFREQPRIOINFO command specifies the value of Threshlow. The larger the value of this parameter, the less likely that reselection occurs.

EQrxlevmin is the minimum required signal level for the target cell. It is set by running the ADD UCELLNFREQPRIOINFO or MOD UCELLNFREQPRIOINFO command.

Treselection is the reselection delay. The Treselections parameter in the ADD UCELLSELRESEL or MOD UCELLSELRESEL command specifies the value of Treselection.

Threshserving,low is the threshold for the serving cell's RSCP during reselection to an LTE cell working at an LTE frequency with a lower absolute priority. The ThdServingLow parameter in the ADD UCELLSELRESEL or MOD UCELLSELRESEL command specifies the value of Threshserving,low. When the LTE frequencies of lower absolute priorities are being measured, if the signal quality of the serving UMTS cell constantly remains below Threshserving,low and the signal quality of an LTE frequency satisfies the formula SrxlevnonServingCell > Threshlow, the UE triggers reselection to the cell working at this LTE frequency. The larger the value of this parameter, the more likely reselection is to occur.

To summarize:

If both criteria in criteria set 1 are fulfilled, the UE performs reselection to a cell working at an LTE frequency with a higher absolute priority.

If all criteria in criteria set 3 are fulfilled, the UE performs reselection to a cell working at an LTE frequency with a lower absolute priority.

If the criteria in neither group are fulfilled, the UE remains on the UMTS network.

If multiple cells fulfill a set of criteria, the UE performs reselection to the cell with the highest absolute priority. If multiple cells have the highest absolute priority, the UE performs reselection to the cell with the largest SrxlevnonServingCell value.

3.2 LTE-to-UMTS Cell Reselection

LTE-to-UMTS cell reselection is used when the LTE network is new and provides incomplete coverage, but the UMTS coverage is complete. LTE-to-UMTS cell reselection is based on absolute priorities and mainly involves the LTE network.

For details, see LTE document Idle Mode Management Feature Parameter Description.

3.3 UMTS-to-LTE Fast Return

This section describes WRFD-140226 UMTS-to-LTE Fast Return (a trial feature).

3.3.1 Principles

Before RAN14.0, if UMTS and LTE are deployed together and the absolute priority of a neighboring LTE cell's LTE frequency is higher than that of the serving UMTS cell, UE accesses UMTS due to CSFB, when RRC connection is released (CS or PS is finished) in UMTS. The UE generally camps on the UMTS cell, if the neighboring LTE cell fulfills the criteria for reselection, UE camps on the neighboring LTE cell by reselection. The UE needs to receive system information and make decisions before performing UMTS-to-LTE reselection. As a result, the process takes a longer time. To reduce delay, UMTS-to-LTE fast return has been introduced.

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UMTS-to-LTE fast return is applicable for scenes below:

A UE starting voice call in LTE is handed over to UMTS due to CSFB. The cause in RELOCATION RQEUSET is "CS Fallback triggered (268)" or CSFB information carried in the RELOCATION REQUEST message is set to "CSFB" or "CSFB High Priority" and RRC connection is released in UMTS.

A UE that complies with 3GPP Release 9.4.0 or later starting voice call in LTE is redirected to UMTS due to CSFB, and the first RAB setup in UMTS is the CS domain. The RRC connection is released in UMTS.

In RAN14.0, for these UEs, when the RRC connection is released, the RNC sends an RRC CONNECTION RELEASE message carrying neighboring LTE cells' frequencies whose absolute priorities are higher than the absolute priority of the serving UMTS cell. After releasing the RRC connection, the UE attempts to camp on one of the suitable LTE cells whose frequencies are carried in the RRC CONNECTION RELEASE message. This mechanism reduces the reselection delay from UMTS to LTE in idle state and improves user experience.

The algorithm is recommended in scenes with good LTE coverage. However, if no suitable cell on the frequencies carried in the RRC CONNECTION RELEASE message is found within 10s, the UE attempts to camp on a suitable cell on any LTE frequency it supports. If no suitable LTE cell is found, UE camps on a suitable GSM cell or UMTS cell. When UE is searching for an LTE signal, it cannot start a call or be paged. If there is no LTE coverage, Huawei's UE E398 keeps searching LTE signals for 23s before camping on a UMTS cell.

Relationship with other algorithms:

After receiving SCRI, RRC connection is released, RNC sends RRC CONNECTION RELEASE message, carrying LTE frequencies information. The UE selects and camps on LTE network on receiving the message.

UMTS-to-LTE Fast Return is applicable for UEs accessing to UMTS due to CSFB, and the RRC CONNECTION RELEASE message contains all the LTE neighboring cell frequencies of higher priority than the serving cell. While "Service-based UMTS-to-LTE PS Redirections and Handovers" is suitable for PS only services, the RRC CONNECTION RELEASE message contains only LTE neighbor cell frequency with the best signal.

HO_UMTS_TO_LTE_FAST_RETURN_SWITCH under the HoSwitch parameter is the switch for UMTS-to-LTE fast return. The SPriority parameter in the ADD UCELLSELRESEL or MOD UCELLSELRESEL command specifies the absolute priority of the serving UMTS cell. The NPriority parameter in the ADD UCELLNFREQPRIOINFO or MOD UCELLNFREQPRIOINFO command specifies the absolute priorities of the LTE frequencies.

3.3.2 Related Features

Required Features

This feature depends on the LTE feature LOFD-001033 CS Fallback to UTRAN.

Mutually Exclusive Features

None

Affected Features

None

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3-5

3.4 UMTS-to-LTE Quick Cell Reselection

A UMTS/LTE dual-mode UE camping on the UMTS network can initiate UMTS-to-LTE cell reselection only when it is in the CELL_PCH or idle state. In RAN14.0 and earlier versions, state transition to the CELL_PCH or idle state is slow because the state transition is triggered only when the UE does not transmit or receive service data during the time length of an inactivity timer.

The inactivity timer can be:

PsInactTmrForCon (conversational services), PsInactTmrForStr (streaming services), PsInactTmrForInt (interactive services), or PsInactTmrForBac (background services) for UEs that are not enabled with enhanced fast dormancy

PsInactTmrForFstDrmDch for UEs that are enabled with enhanced fast dormancy and in the CELL_DCH state

PsInactTmrForFstDrmFach for UEs that are enabled with enhanced fast dormancy and in the CELL_FACH state

To accelerate the UMTS-to-LTE cell reselection, you need to enable the UMTS-to-LTE quick cell reselection function by running the SET UALGORSVPARA command with RESERVED_SWITCH_0_BIT10 under RsvSwitch0 set to ON. The details of this function are as follows:

For UEs that are not enabled with enhanced fast dormancy

State transition to the CELL_PCH or idle state is triggered when the UE does not transmit or receive service data during the time length specified by PsInactTmrForFstDrmDch, not the time length specified by PsInactTmrForCon. The default value of PsInactTmrForFstDrmDch is smaller than that of PsInactTmrForCon and therefore the cell reselection process is faster.

State transition from CELL_DCH to CELL_PCH or the idle state by running the SET UALGORSVPARA command with RESERVED_SWITCH_0_BIT8 set to an appropriate value under RsvSwitch0. When RESERVED_SWITCH_0_BIT8 is set to OFF, the UE transits from CELL_DCH to CELL_PCH. When RESERVED_SWITCH_0_BIT8 is set to ON, the UE transits from CELL_DCH to the idle state.

The default value of RESERVED_SWITCH_0_BIT8 under RsvSwitch0 is OFF. Set it to ON if some UEs in the network do not support state transition from CELL_DCH to CELL_PCH.

For UEs that are enabled with enhanced fast dormancy and in the CELL_DCH state

When RSVDBIT1_BIT29 under RsvdPara1 is set to OFF by running the SET URRCTRLSWITCH command, the UE transits from CELL_DCH to CELL_FACH when it does not transmit or receive service data during the time length specified by PsInactTmrForFstDrmDch and then transits from CELL_FACH to CELL_PCH or the idle state when it does not transmit or receive service data during the time length specified by PsInactTmrForFstDrmFach. After UMTS-to-LTE quick cell reselection is enabled, the UE is able to transit from CELL_DCH directly to CELL_PCH or the idle state when it does not transmit or receive service data during the time length specified by PsInactTmrForFstDrmDch, without the need to wait until PsInactTmrForFstDrmFach expires. This shortens the duration of the UMTS-to-LTE cell reselection.

When RSVDBIT1_BIT29 under RsvdPara1 is set to ON, UMTS-to-LTE quick cell reselection does not provide gains for these UEs. State transition from CELL_DCH to CELL_PCH or the idle state is triggered when the UE does not transmit or receive service data during the time length specified by PsInactTmrForFstDrmDch, regardless of whether UMTS-to-LTE quick cell reselection is enabled.

For UEs that are enabled with enhanced fast dormancy and in the CELL_FACH state

UMTS-to-LTE quick cell reselection does not provide gains for these UEs. State transition from CELL_FACH to CELL_PCH or the idle state is triggered when the UE does not transmit or receive service data during the time length specified by PsInactTmrForFstDrmFach, regardless of whether UMTS-to-LTE quick cell reselection is enabled.

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Changing the value of PsInactTmrForFstDrmDch or PsInactTmrForFstDrmFach affects this feature and the Enhanced Fast Dormancy feature. For details about enhanced fast dormancy, see Enhanced Fast Dormancy Feature Parameter Description.

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Interoperability Between UMTS and LTE

4 PS Redirections and Handovers Between UMTS

and LTE



4-1

4 PS Redirections and Handovers Between UMTS and LTE

This chapter describes PS directions and handovers from UMTS to LTE and from LTE to UMTS.

4.1 LTE-to-UMTS PS Redirections and Handovers

When a UE processing a PS service on the LTE network moves out of the LTE coverage area or the LTE signal quality falls below a specific threshold, a PS redirection or handover is performed to shift the UE to the UMTS network. The choice between a PS redirection and a PS handover depends on the UE capability.

LTE-to-UMTS PS handovers or redirections are performed mainly by the LTE network. For details, see LTE document Idle Mode Management Feature Parameter Description.

If certain UL/LTE dual-mode UEs do not support UMTS network measurements when in connected mode, the LTE network needs to support LTE-to-UMTS blind redirections or blind handovers.

4.2 Service-based UMTS-to-LTE PS Redirections and Handovers

This chapter corresponds to the features WRFD-020129 PS Service Redirection from UMTS to LTE and WRFD-140218 Service-Based PS Handover from UMTS to LTE.

4.2.1 Overview

Service-based UMTS-to-LTE PS redirections have the same characteristics as service-based UMTS-to-LTE PS handovers. After a UE sets up a PS service on the UMTS network, a PS redirection or handover is used to shift the UE and the PS service to the LTE network when the LTE signal quality fulfills the criteria.

During a UMTS-to-LTE PS redirection, the RNC sends the UE an RRC Connection Release message, which contains LTE frequencies. After the connection is released, the UE enters idle mode on the UMTS network, selects the LTE network, and sets up a PS service on it.

During a UMTS-to-LTE PS handover, the RNC sends a handover request to the LTE network through the core network (CN). When the LTE network finishes preparing resources, the UE and the PS service are handed over to the LTE network.

If the UE and networks support UMTS-to-LTE PS handovers and the SuppPSHOFlag parameter for the target LTE cell is set to support PS handovers, PS handovers are preferred over PS redirections. Otherwise, PS redirections are preferred.

NOTE

PS handovers cause heavy signaling traffic and require smooth collaboration between network elements, but such collaboration is not readily available yet. If telecom operators care about these issues, run the ADD ULTECELL command

to set the SuppPSHOFlag parameter to disable UMTS-to-LTE handovers for LTE cells.

Service-based UMTS-to-LTE PS handovers or redirections are mainly used in the following two situations:

A UE that has fallen back to the UMTS network by using CSFB is still processing PS services and the LTE signal quality is good when the UE's voice services are complete, that is, the RNC receives the RADIO BEARER RELEASE COMPLETE message of the voice service or the Iu Release message in the CS domain. In this scenario, if RNC receives the 3C event report, a UMTS-to-LTE PS handover or redirection will be performed.

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4-2

A UE only initiates a PS service on the UMTS network in a UMTS/LTE overlapping coverage area and the LTE signal quality is good. In this scenario, if RNC receives the 3C event report, a UMTS-to-LTE PS handover or redirection will be performed.

To minimize the possibility of redirection or handover failures, UMTS-to-LTE PS redirections and handovers are based on the LTE signal quality measurements. Redirections or handovers are only triggered if the LTE signal quality is good.

4.2.2 Measurements on LTE Signal Quality

After receiving Radio Bearer Setup, Radio Bearer Reconfiguration (except for D2F, D2P and RAB DRD), Radio Bearer Release message or inter-frequency hard handover or the Iu Release message in the CS domain. RNC determines whether LTE measurement is started. RNC start LTE measurement if all the following conditions are met:

There are no CS RABs among the UE's RABs.

The value of the information element E-UTRAN Service Handover in a certain PS RAB of the UE is not "Handover to E-UTRAN shall not be performed."

The value of the service handover attribute EUTRANSHIND of a certain PS RAB of the UE is not set to HO_TO_EUTRAN_SHALL_NOT_BE_PERFORM.

The neighboring LTE cells are configured for UMTS serving cell.

The UE supports both UMTS and LTE.

The UE supports LTE measurements in connected mode.

The UE supports UMTS-to-LTE PS redirection or handover.

The general switch for UMTS-to-LTE PS handovers is turned on. This switch is configured by HO_LTE_PS_OUT_SWITCH under the HoSwitch parameter.

Service-based UMTS-to-LTE PS redirections are controlled by HO_LTE_SERVICE_PS_OUT_SWITCH under the HoSwitch parameter, and PS handovers are controlled by HO_LTE_SERVICE_PSHO_OUT_SWITCH under the HoSwitch parameter.

Where

The information element E-UTRAN Service Handover is optional and specifies which RABs cannot be shifted to the LTE network through a redirection or handover. If one or more of the PS RABs for the UE cannot be shifted to the LTE network, the UE cannot be redirected or handed over to the LTE network.

The parameters EUTRANSHIND and TrafficClass in MML ADD UTYPRABBASIC command are used for controlling whether the type of services can be handed over or redirected to LTE network. The parameter EUTRANSHIND can be set to HO_TO_EUTRAN_SHOULD_BE_PERFORM or HO_TO_EUTRAN_SHALL_NOT_BE_PERFORM, and the parameter TrafficClass can be set to conversational, streaming, interactive, or background. For example, if the parameter TrafficClass is set to conversational and the parameter EUTRANSHIND is set to HO_TO_EUTRAN_SHALL_NOT_BE_PERFORM, the conversational services are not allowed to hand over or redirect to LTE network.

If all these conditions are met and a UMTS-to-PS redirection or handover is allowed, the RNC sends a measurement control command to the UE, instructing the UE to measure the LTE signal quality. Event 3C is triggered when the LTE signal quality satisfies the following formula:

MOtherRAT TOtherRAT + H3c/2

where

MOtherRAT is the measured quality of the LTE cell after filtering. The LTEMeasQuanOf3C parameter specifies which of the following is used as the measured quantity of the LTE cell: Reference Signal Received Power (RSRP) or Reference Signal Received Quality (RSRQ). U2LTEFilterCoef is the filter

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4-3

coefficient for the measurement results. A larger value for this parameter results in a greater smoothing effect and higher anti-fading capabilities, but also lower capabilities of tracking signal fluctuations. A smaller value for this parameter results in more unnecessary handovers.

TOtherRAT is the threshold that the LTE signal must reach before a redirection or handover to the LTE network can be performed. The TargetRatThdRSRP or TargetRatThdRSRQ parameter specifies the TOtherRAT value. The TargetRatThdRSRP parameter is the RSRP threshold, and the TargetRatThdRSRQ parameter is the RSRQ parameter.

If the LTEMeasQuanOf3C parameter is set to RSRP, event 3C is reported when the RSRP of the LTE cell has remained greater than or equal to the sum of TargetRatThdRSRP and H3c/2 for a period of time longer than TrigTime3C.

If the LTEMeasQuanOf3C parameter is set to RSRQ, event 3C is reported when the RSRQ of the LTE cell has remained greater than or equal to the sum of TargetRatThdRSRQ and H3c/2 for a period of time longer than TrigTime3C.

The TrigTime3C parameter is the hysteresis for the UE triggering event 3C. The value of this parameter relates to slow fading. A larger value for this parameter results in a lower possibility of handovers and unnecessary handovers and a stronger resistance to instantaneous signal fluctuations. An excessively large value for this parameter results in a higher possibility of call drops.

H3c is the hysteresis for reporting event 3C, and it is configured by the Hystfor3C parameter. The value of this parameter relates to slow fading. A larger value for this parameter results in stronger resistance to signal fluctuations. This curbs the ping-pong effect but slows the handover algorithm's response to signal fluctuations.

These parameters can be configured at the RNC or cell level with the SET UU2LTEHONCOV command or the ADD UCELLU2LTEHONCOV command, respectively. If these parameters are configured at both RNC and cell levels, cell-level settings override RNC-level settings.

4.2.3 Target Cell Selection and Execution of Redirections or Handovers

The event 3C report from the UE to the RNC carries the LTE cell or cells that meet the conditions for event 3C. If the report carries multiple LTE cells, the one with the best signal quality is selected as the target cell. The RNC shifts the UE to the target cell by using a redirection or handover.

Figure 4-1 shows the procedure for a UMTS-to-LTE PS redirection.

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4-4

Figure 4-1 UMTS-to-LTE PS redirection

Figure 4-2 shows the procedure for a UMTS-to-LTE PS handover.

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4-5

Figure 4-2 UMTS-to-LTE PS handover

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Interoperability Between UMTS and LTE 5 CS Fallback Guarantee for LTE Emergency Calls



5-1

5 CS Fallback Guarantee for LTE Emergency Calls

This chapter describes the feature WRFD-140102 CS Fallback Guarantee for LTE Emergency Calls.

5.1 Overview

When a UE within the LTE coverage area attempts to initiate a CS service, the Circuit Switched Fallback (CSFB) enables the UE to be redirected or handed over to the UMTS network for CS service access. In this way, the existing UMTS network can be reused to provide traditional voice services for UEs on the LTE network.

CSFB applies to scenarios where the LTE network does not support voice services because the IP Multimedia Subsystem (IMS) is not available for use. The eNodeB can instruct a UE to fall back to the UMTS network when the UE attempts to process voice services on the LTE network. A UE in idle mode needs to transit to connected mode and then fall back to the UMTS network.

When a UE is attaching to LTE network, MME sends an ATTACH ACCEPT message to the UE, carrying IE "EPS attach result" to indicate whether the LTE network supports CSFB. If this IE value is "combined EPS/IMSI attach", it indicates that the LTE network supports CSFB. For details, see 3GPP TS 24.301.

When a UE in connected mode initiates a CS service on the LTE network, it sends an Extended Service Request message that contains a CS Fallback Indicator to the Mobility Management Entity (MME), indicating that CSFB is required for the CS service. The MME instructs the eNodeB to initiate a CSFB procedure so that the UE can fall back to the UMTS network.

Each UE maintains a default PS connection on the LTE network, regardless of whether it is processing PS services. Upon receiving the CSFB indication from the MME, the eNodeB performs an LTE-to-UMTS PS handover or redirection to execute CSFB. After falling back to the UMTS network, the UE re-initiates the CS service. The procedure is as follows:

If a UE is to fall back to the UMTS network by using the LTE-to-UMTS PS redirection, the eNodeB sends the UE an RRC Connection Release message containing the UMTS frequency to be used by the UE. The UE accesses the UMTS network using the received UMTS frequency, and then re-initiates the CS and PS services on the UMTS network.

If a UE is to fall back to the UMTS network by using the LTE-to-UMTS PS handover, the RNC performs resource reservation and service admission for the PS service of the UE upon receiving a PS handover request. If resource reservation and service admission are successful, the eNodeB instructs the UE to perform an inter-RAT handover for UMTS network access. After falling back to the UMTS network, the UE re-initiates the CS service. The PS service or default PS connection is set up by using an LTE-to-UMTS PS handover.

Upon receiving the CS fallback indicator from the MME, the eNodeB decides whether to perform the fallback by using an LTE-to-UMTS PS handover or redirection, based on the capability of the network and UE.

For details about message exchange during the procedure, see 3GPP TS 23.272.

For CSFB for an emergency call:

If the UE is to fall back to the UMTS network by using the LTE-to-UMTS PS redirection, the LTE network will send an RRC connection release message to the UE and the UE re-initiates an emergency call on the UMTS network. CSFB should be successful once the UE has accessed the UMTS network. The feature WRFD-021104 Emergency Call ensures that emergency calls are granted access to the UMTS network before other call types.

If a UE is to fall back to the UMTS network by using the LTE-to-UMTS PS handover, the RNC performs resource reservation and service admission for the PS service of the UE. Then the eNodeB instructs the UE to perform an inter-RAT handover for UMTS network access. After falling back to the UMTS

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Interoperability Between UMTS and LTE 5 CS Fallback Guarantee for LTE Emergency Calls



5-2

network, the UE re-initiates an emergency call. CSFB should be successful once resource reservation and service admission are successful for the PS service on the RNC. The feature WRFD-140102 CS Fallback Guarantee for LTE Emergency Calls ensures that resource reservation and service admission are successful for PS services, by decreasing the PS service rate, performing resource preemption, or both.

This document only describes resource reservation and service admission for PS services. For details about implementation of the feature WRFD-021104 Emergency Call, see Load Control Feature Parameter Description.

The HO_L2U_EMGCall_Switch field has been added to the HoSwitch parameter in the SET UCORRMALGOSwitch command. The feature WRFD-140102 CS Fallback Guarantee for LTE Emergency Calls is enabled when this switch is turned on.

5.2 Policy

If a UE is to fall back to the UMTS network by using the LTE-to-UMTS PS handover, the eNodeB sends the MME a Handover Required message. This message carries a transparent container, Source RNC to Target RNC Transparent Container, which contains an IE referred to as CSFB Information. If this IE value is CSFB, it indicates a PS handover caused by CSFB for a common CS service. If this IE value is CSFB High Priority, it indicates a PS handover caused by CSFB for an emergency call.

The transparent container is forwarded by the CN to the destination RNC. When the destination RNC receives CSFB Information whose value is CSFB High Priority, the RNC determines that an incoming LTE-to-UMTS PS handover is caused by CSFB for an emergency call. In this case, the RNC decreases the service rate or performs resource preemption for the PS service. The specific policy is as follows:

For a best effort (BE) PS service, such as an interactive or background service, the RNC attempts to admit it on the DCH with the 8 kbit/s access rate in UL and DL regardless of the capability of the UE (even if the UE is HSPA-capable). If the admission attempt fails, the RNC preempts the resources of low-priority user. For a non-BE PS service, such as a streaming service, the RNC attempts to admit it based on the GBR. If the admission attempt fails, the RNC preempts the resources of low-priority user.

After the PS service admission succeeds, the PS service rate is gradually increased if there are available resources in the UMTS network.

For details about service admission, see Call Admission Control Feature Parameter Description. For details about resource preemption, see Load Control Feature Parameter Description.

For a CSFB procedure during which a UE falls back to the UMTS network through an LTE-to-UMTS PS handover, the CSFB delay can be reduced by increasing the bearing data rate on the signaling radio bearer (SRB). The bearing data rate is set by CSFBSRBRate of the SET UFRC command.

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Interoperability Between UMTS and LTE 6 CS Fallback Guarantee for LTE Common Calls



6-1

6 CS Fallback Guarantee for LTE Common Calls

6.1 Overview

RAN14.0 provides a CSFB guarantee for LTE emergency calls and common calls. This reduces admission failures and increases successful handovers for CS services.

To enable CSFB guarantee for LTE common calls, users need to set PERFENH_L2U_CSFB_COMMCALL_SWITCH under PerfEnhanceSwitch to ON by running the SET UCORRMPARA command.

6.2 Policy

The RNC determines that an incoming LTE-to-UMTS PS handover is caused by CSFB for a common call when either of the following conditions is met:

The cause value is CS Fallback triggered (268) in the Relocation Request message received at the RNC.

The value of the IE "CSFB Information" is CSFB in the IE "Source RNC To Target RNC Transparent Container" of the Relocation Request message.

In this case, the RNC decreases the service rate or performs resource preemption for the PS service. The specific policy is as follows:

For a non-real-time PS service, the RNC attempts to admit it on the DCH with the 8 kbit/s access rate. If the admission attempt fails, the RNC preempts the resources of a low-priority service for the non-real-time PS service.

For a real-time PS service, the RNC attempts to admit it based on the GBR. If the admission attempt fails, the RNC preempts the resources of a low-priority service for the real-time PS service.

After the PS service admission succeeds, the PS service rate is gradually increased if there are available resources in the UMTS network.

For details about service admission, see Call Admission Control Feature Parameter Description. For details about resource preemption, see Load Control Feature Parameter Description.

For a CSFB procedure during which a UE falls back to the UMTS network through an LTE-to-UMTS PS handover, the CSFB delay can be reduced by increasing the bearing data rate on the signaling radio bearer (SRB). The bearing data rate is set by CSFBSRBRate of the SET UFRC command.

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Interoperability Between UMTS and LTE 7 Impact on the Network



7-1

7 Impact on the Network

7.1 WRFD-140226 UMTS-to-LTE Fast Return (a Trial Feature)

Impact on System Capacity

No impact.

Impact on Network Performance

This feature reduces the time required for UEs to return to the LTE network from the serving UMTS network, improving user experience.

7.2 WRFD-020129 Service-Based PS Service Redirection from UMTS to LTE

Impact on System Capacity

No impact.

Impact on Network Performance

This feature provides an alternative to PS handovers in UMTS/LTE hybrid networks. If the network or UEs do not support PS handovers from UMTS to LTE, this feature redirects UEs performing only PS services from UMTS to LTE to improve user experience.

7.3 WRFD-140218 Service-Based PS Handover from UMTS to LTE

System Capacity

No impact.

Network Performance

With this feature, some PS services on the UMTS network can be handed over to the LTE network. In this way, this feature eases the traffic load on the UMTS network, and increases the UMTS access success rate and throughput for admitted users.

7.4 WRFD-140102 CS Fallback Guarantee for LTE Emergency Calls

System Capacity

No impact.

Network Performance

This feature increases the success rate for LTE-to-UMTS PS handovers caused by CSFB for LTE emergency calls.

When the destination UMTS cell is congested, too many CSFB requests caused by LTE emergency calls may preempt the UMTS resources, leading to an increased call drop rate on the UMTS network.

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Interoperability Between UMTS and LTE 8 Engineering Guidelines



8-1

8 Engineering Guidelines

8.1 WRFD-020126 Mobility Between UMTS and LTE Phase 1

8.1.1 When to Use Mobility Between UMTS and LTE Phase 1

This feature is required when UEs move back and forth between UMTS and LTE in a UMTS/LTE overlapping coverage area.

8.1.2 Feature Deployment

This section describes how to activate, verify, and deactivate the optional feature WRFD-020126 Mobility Between UMTS and LTE Phase 1. For details about how to configure this feature on the LTE side, see the related documents provided by the LTE equipment vendor. (This feature cannot be configured using the CME.)

Prerequisites

Dependencies on Hardware

The UE is a UMTS&LTE dual-mode terminal.

Dependencies on Other Features

This feature does not depend on other features.

License

The license " Mobility Between UMTS and LTE Phase 1" on the RNC side has been activated. For details about the license items and how to activate the license, see License Management Feature Parameter Description.

Other Prerequisites

The UE supports both UMTS and LTE.

The LTE network supports this feature.

Procedure

Activation Procedure

1. Run the RNC MML command ADD UCELLSIBSWITCH or MOD UCELLSIBSWITCH. In this step, set SIB Switch to SIB19.

After the information about the frequencies of neighboring LTE cells is configured and SIB Switch is set to SIB19, the RNC sends SIB19 messages to UEs. The SIB19 message contains the neighboring LTE cell list and LTE cell reselection parameters.

2. Run the RNC MML command ADD UCELLSELRESEL or MOD UCELLSELRESEL. In this step, set Absolute priority level of the serving cell to an appropriate value.

Inter-RAT measurement is performed based on the settings of RSCP threshold for low-prio-freq measurement initiation and Ec/No threshold for low-prio-freq measurement initiation. The measurement result provides a reference to cell reselection.

3. Run the RNC MML command ADD UCELLNFREQPRIOINFO or MOD UCELLNFREQPRIOINFO to configure the information about the frequencies of neighboring cells.

The UE makes cell reselection decisions based on the configured information about the frequencies of neighboring cells.

4. Configure the related data, such as the neighboring cell relationships between cells, on the LTE side.

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8-2

For details about how to configure this feature on the LTE side, see the related documents provided by the LTE equipment vendor. If the LTE equipment is provided by Huawei, see the LTE document Mobility Management in Connected Mode Parameter Description.

5. Run the RNC MML command ADD UNODEB or MOD UNODEB. In this step, set NodeB Protocol Version to R8 or the higher version.

Verification Procedure

6. In the Navigation Tree pane on the RNC LMT, click the Trace tab. In the displayed Trace Navigation Tree pane, double-click UMTS Services. On the unfolded list, double-click Uu Interface Trace. In the displayed Uu Interface Trace dialog box, select RRC_SYS_INFO_TYPE19 to trace Uu interface SIB19 message.

Figure 8-1 Uu Interface Trace dialog box

7. Analyze the traced messages.

If the SIB19 message has been traced on the Uu interface, as shown in Figure 8-2, this feature has been activated.

If the SIB19 message is not traced on the Uu interface, this feature is not activated.

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8-3

Figure 8-2 SIB message tracing

Deactivation Procedure

To deactivate this feature, you can either turn off the SIB19 switch or deactivate the license.

To deactivate this feature in a specific cell, you are advised to turn off the SIB19 switch.

To deactivate this feature in all cells under a RNC, deactivate the license. This method is not recommended.

1. Run the RNC MML command MOD UCELLSIBSWITCH. In this step, deselect the SIB19 check box under the parameter SIB Switch to turn off the SIB19 switch in a cell. After the switch is turned off, the RNC stops sending SIB19 messages to UEs. In such a case, the configured absolute priority of the serving cell and the configured information about the frequencies of neighboring cells become ineffective.

2. Run the RNC MML command SET LICENSE to deactivate the license controlling the feature Mobility Between UMTS and LTE Phase 1.

----End

Example

//Activating Mobility Between UMTS and LTE Phase 1

MOD UCELLSIBSWITCH: CellId=1, SibCfgBitMap=SIB19-1;

MOD UCELLSELRESEL: CellId=1, QualMeas=CPICH_ECNO, QrxlevminExtSup=FALSE,

NonhcsInd=NOT_CONFIGURED, ThdPrioritySearch1=2, ThdPrioritySearch2=2;

MOD UCELLNFREQPRIOINFO: CellId=1, EARFCN=1, NPriority=2, BlacklstCellNumber=D0;

MOD UNODEB: NodeBId=1, NodeBProtclVer=R9;

//Deactivating Mobility Between UMTS and LTE Phase 1

MOD UCELLSIBSWITCH: CellId=1, SibCfgBitMap=SIB19-0;

SET LICENSE: SETOBJECT=UMTS, ISPRIMARYPLMN=YES, FUNCTIONSWITCH5=LQW1ULM01-0;

8.2 WRFD-140226 UMTS-to-LTE Fast Return (a Trial Feature)

This section describes how to activate, verify, and deactivate the trial feature WRFD-140226 UMTS-to-LTE Fast Return. For details about how to configure this feature on the LTE side, see the LTE document CS Fallback Feature Parameter Description.

8.2.1 When to Use UMTS-to-LTE Fast Return

This feature is recommended in the areas where UMTS and LTE coexist.

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8.2.2 Information to Be Collected

Collect the following information before deploying this feature:

Information about areas where UMTS and LTE coexist and areas where UMTS and LTE coverage overlap.

Duration for a UE to return to LTE from UMTS. The duration starts when the UE receives an RRC Connection Release message from the UTRAN and ends when the UE sends an RRC Connection Request message to the EUTRAN. The duration is in the UE logs.

8.2.3 Network Planning

Not involved


Requirements

Requirements for other features

The LTE feature LOFD-001033 CS Fallback to UTRAN has been activated on the LTE side. For details about how to activate this feature, see the LTE document CS Fallback Feature Parameter Description.

Requirements for other NEs as well as for network equipment and transmission devices from other vendors:

To enable a UE to fall back to UMTS by means of the LTE-to-UMTS PS handover, the eNodeB and MME must carry either of the following information elements (IEs) in the Relocation Request message:

Cause, whose value is CS Fallback triggered (268).

CSFB Information, whose value is CSFB or CSFB High Priority.

The UE must comply with 3GPP Release 9.4.0 or later so that it can fall back to UMTS by means of the LTE-to-UMTS redirection.

Requirements for the license

UMTS-to-LTE Fast Return is a trial feature and is not under license control.

Data Preparation

Parameter Name

Parameter ID

Setting Description Data Source

HandOver Switch

HoSwitch Select HO_UMTS_TO_LTE_FAST_RETURN_SWITCH of this parameter to activate the feature.

Default/Recommended Value

Precautions

None

Feature Activation (Using the MML Command)

Run the SET UCORRMALGOSWITCH command on the RNC with the HO_UMTS_TO_LTE_FAST_RETURN_SWITCH check box of the HandOver Switch parameter selected.

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Example

//Turning on the switch for UMTS-to-LTE Fast Return

SET UCORRMALGOSWITCH: HoSwitch=HO_UMTS_TO_LTE_FAST_RETURN_SWITCH-1;

Feature Activation (Using the CME)

NOTE

When configuring the UMTS-to-LTE Fast Return feature on the CME, you must perform a single configuration first, and then perform batch modifications if required.

You must perform a single configuration for a parameter before batch modifications of the parameter. You are advised to perform batch modifications before logging out of the parameter setting interface.

Step 1 Configure a single object on the CME. (CME single configuration)

Set parameters on the CME configuration interface according to the operation sequence described in Table 8-1. For the method of performing the CME single configuration, see the CME Single Configuration Operation Guide.

Step 2 (Optional) Modify objects in batches on the CME. (CME batch modification center)

To modify objects, such as RNCs, NodeBs, cells, and TRXs, in batches, click on the CME configuration interface to start the batch modification wizard. For details about how to perform batch modifications on the CME batch modification center, press F1 on the wizard interface to obtain online help.

----End

Table 8-1 Turning on the switch on the CME

SN Managed Object (MO)

NE Parameter Name

Parameter ID

Supports CME Batch Modification Center

1 UCORRMALGOSWITCH

RNC HandOver Switch

HoSwitch YES

Activation Observation

With this feature activated, if a UE that has fallen back to UMTS from LTE has released all services on the UMTS network, the RNC sends the UE an RRC Connection Release message. The Redirection info IE in this message carries the information about the frequency used by the neighboring LTE cell, as shown in Figure 8-3.

Figure 8-3 RRC Connection Release message tracing

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Deactivation (Using the MML Command)

Run the SET UCORRMALGOSWITCH command on the RNC with the HO_UMTS_TO_LTE_FAST_RETURN_SWITCH check box of the HandOver Switch parameter cleared.

Example

//Turning off the switch for UMTS-to-LTE Fast Return

SET UCORRMALGOSWITCH: HoSwitch=HO_UMTS_TO_LTE_FAST_RETURN_SWITCH-0;

Deactivation (Using the CME)

NOTE

When configuring the UMTS-to-LTE Fast Return feature on the CME, you must perform a single configuration first, and then perform batch modifications if required.

You must perform a single configuration for a parameter before batch modifications of the parameter. You are advised to perform batch modifications before logging out of the parameter setting interface.

Step 1 Configure a single object on the CME. (CME single configuration)

Set parameters on the CME configuration interface according to the operation sequence described in Table 8-2. For the method of performing the CME single configuration, see the CME Single Configuration Operation Guide.

Step 2 (Optional) Modify objects in batches on the CME. (CME batch modification center)

To modify objects, such as RNCs, NodeBs, cells, and TRXs, in batches, click on the CME configuration interface to start the batch modification wizard. For the method of performing batch modifications through the CME batch modification center, press F1 on the wizard interface to obtain online help.

----End

Table 8-2 Turning on the switch on the CME

SN Managed Object (MO)

NE Parameter Name

Parameter ID

Supports CME Batch Modification Center

1 UCORRMALGOSWITCH

RNC HandOver Switch

HoSwitch YES

8.2.5 Performance Monitoring

In the UE logs, check the duration for a UE to return to LTE from UMTS. The duration starts when the UE receives an RRC Connection Release message from the UTRAN and ends when the UE sends an RRC Connection Request message to the EUTRAN.

If the duration shortens after the feature is activated, the feature has brought positive gains.

8.2.6 Parameter Optimization

Not involved

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8.2.7 Troubleshooting

Not involved

8.3 WRFD-020129 Service-Based PS Service Redirection from UMTS to LTE

8.3.1 When to Use Service-based PS Redirection or Handover from UMTS to LTE

This feature is recommended in UMTS/LTE overlapping coverage areas. Determine whether to enable the UMTS-to-LTE PS redirection or handover based on the UE capabilities in the live network. If only a few UEs support the UMTS-to-LTE PS handover, enable only UMTS-to-LTE PS redirection. If a majority of UEs support the UMTS-to-LTE PS handover, enable both UMTS-to-LTE PS redirection and handover. In the latter case, UEs supporting handovers use the UMTS-to-LTE PS handover and UEs not supporting handovers use the UMTS-to-LTE PS redirection.

If UEs preferentially camp on the UMTS network, this feature must be used. Otherwise, UEs can camp on the LTE network by cell reselection only in weak UMTS coverage areas, which leads to an idle LTE network.

If the target LTE network is a MOCN network and the UMTS and LTE networks of the operator are different PLMNs, do not enable service-based UMTS-to-LTE PS handovers, because they may cause call drops.


This section describes how to activate, verify, and deactivate the optional feature WRFD-020129 Service-Based PS Service Redirection from UMTS to LTE.

Prerequisites


There is no requirement for RNC and NodeB.



License

The license " Service-Based PS Service Redirection from UMTS to LTE" on the RNC side has been activated. For details about the license items and how to activate the license, see License Management Feature Parameter Description.

Others

The UE must support 3GPP Release 8 (Sept. 2008) or later. It also must support both UMTS and LTE.

The SGSN support this feature.

CN should support cooperation from UMTS to LTE.

The neighboring LTE cell has been configured. For details, see Configuring a Neighboring LTE Cell section in BSC6900 UMTS Initial Configuration Guide.

Procedure


1. Run the RNC MML command MOD ULTECELL (CME single configuration: Object Group > UMTS Service Configuration and Maintenance Management > External Cell Configuration > RNC LTE

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External Cell; CME batch modification center: not supported) to set an LTE cell. In this step, set LTE Cell Supporting PS HO Indicator to NotSupport and set BlackCell List Flag to False.

2. Run the RNC MML command SET UU2LTEHONCOV (CME single configuration: UMTS Radio Global Configuration Express > HandOver Parameter Configuration > RNC-Oriented Non-Coverage-Based UMTS-LTE Handover Measurement Algorithm Parameters; CME batch modification center: not supported) to set RNC-oriented non-coverage-based UMTS-LTE handover measurement algorithm parameters. The RNC sends these parameters to the UE by means of a measurement control message.

3. Optional: Run the RNC MML command ADD UCELLU2LTEHONCOV (CME single configuration: UMTS Cell Configuration Express > Cell Parameters > Cell-Oriented Non-Coverage-Based UMTS-LTE Handover Measurement Algorithm Parameters; CME batch modification center: Modifying UMTS Cell Parameters in Batches) to set the cell-level non-coverage-based UMTS-to-LTE handover measurement parameters for a cell.

4. Run the RNC MML command MOD UTYPRABBASIC (CME single configuration: UMTS Radio Global Configuration Express > Typical Service Configuration > Basic Information for Typical Traffic Radio Access Bearer; CME batch modification center: not supported) to modify the basic configuration of a typical radio access bearer (RAB). In this step, set EUTRANSHIND to HO_TO_EUTRAN_SHOULD_BE_PERFORM.

5. Run the RNC MML command SET UCORRMALGOSWITCH (CME single configuration: UMTS Radio Global Configuration Express > Connection_Oriented RRM Switch Configuration > Connection Oriented Algorithm Switches; CME batch modification center: Modifying RNC Parameters in Batches) to select HO_LTE_PS_OUT_SWITCH and HO_LTE_SERVICE_PS_OUT_SWITCH from HandOver Switch drop list.

Verification Procedure

1. Start Uu interface tracing on the LMT to trace messages on the Uu interface.

2. View the RRC_MEAS_CTRL message, as shown in Figure 8-4. If the measurementCommand message contains the information element (IE) e-UTRA-FrequencyInfo, this feature takes effect. The measurement control message sent by the RNC contains the LTE cell information.

After receiving the message, the UE measures the signal quality in the LTE cell. The measurement result serves as the basis for handover decision.

Figure 8-4 Viewing the IE e-UTRA-FrequencyInfo

3. View the RRC_CONN_REL message, as shown in Figure 8-5. If in the message the rrcConnectionRelease message contains the IE EUTRA-TargetFreqInfo, the RRC connection release message carries the LTE cell information.

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After receiving this message, the UE is handed over to the LTE network and the UE reestablishes PS services in the LTE cell.

Figure 8-5 Viewing the IE EUTRA-TargetFreqInfo

Deactivation Procedure

Run the RNC MML command SET UCORRMALGOSWITCH (CME single configuration: UMTS Radio Global Configuration Express > Connection_Oriented RRM Switch Configuration > Connection Oriented Algorithm Switches; CME batch modification center: Modifying RNC Parameters in Batches) to deselect HO_LTE_SERVICE_PS_OUT_SWITCH from the HandOver Switch drop list.

----End

Example

//Activation procedure

/Configuring an LTE cell

MOD ULTECELL: LTECellIndex=1, SuppPSHOFlag=NotSupport, BlackFlag=False;

//Setting the parameters related to the RNC-oriented non coverage-based UMTS-to-LTE handover

measurement algorithm

SET UU2LTEHONCOV:

LTEMeasTypOf3C=MeasurementQuantity, U2LTEFilterCoef=D6, U2LTEMeasTime=30,

LTEMeasQuanOf3C=RSRP, Hystfor3C=2, TrigTime3C=D10, TargetRatThdRSRP=20, TargetRatThdRSRQ=30;

//Setting the parameters related to the cell-oriented non coverage-based UMTS-to-LTE handover

measurement algorithm

ADD UCELLU2LTEHONCOV: CellId=1, LTEMeasTypOf3C=MeasurementQuantity, U2LTEFilterCoef=D6,

U2LTEMeasTime=30, LTEMeasQuanOf3C=RSRP, Hystfor3C=2, TrigTime3C=D10, TargetRatThdRSRP=20,

TargetRatThdRSRQ=30;

//Modifying the basic configuration of a typical RAB

MOD UTYPRABBASIC: RabIndex=1, EUTRANSHIND=HO_TO_EUTRAN_SHOULD_BE_PERFORM;

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//Enabling HO_LTE_PS_OUT_SWITCH and HO_LTE_SERVICE_PS_OUT_SWITCH

SET UCORRMALGOSWITCH: HoSwitch=HO_LTE_PS_OUT_SWITCH-1&HO_LTE_SERVICE_PS_OUT_SWITCH-1;

//Deactivation procedure

//Disabling HO_LTE_SERVICE_PS_OUT_SWITCH

SET UCORRMALGOSWITCH: HoSwitch=HO_LTE_SERVICE_PS_OUT_SWITCH-0;

8.3.3 Performance Optimization

Monitoring

The added counter involved in the feature WRFD-020129 PS Service Redirection from UMTS to LTE is as follows:

Counter Measurement Object

Measurement Unit

Description

VS.U2LTEHO.RRCRelease.Service

CELL U2LTE.HO.CELL Number of service-based redirections to LTE through RRC connection release for a cell

8.4 WRFD-140218 Service-Based PS Handover from UMTS to LTE


This section describes how to activate, verify, and deactivate the optional feature WRFD-140218 Service-Based PS Handover from UMTS to LTE.

Prerequisites


This feature does not have any special requirements for hardware.



License

The license " PS Service Redirection from UMTS to LTE " on the RNC side has been activated. For details about the license items and how to activate the license, see License Management Feature Parameter Description.

Other Prerequisites

The eNodeB, Mobility Management Entity (MME), Serving GPRS Support Node (SGSN), and UE support this feature. The UE supports LTE measurements.

The neighboring LTE cell has been configured. For details, see Configuring a Neighboring LTE Cell section in BSC6900 UMTS Initial Configuration Guide.

Procedure


1. Run the RNC MML command MOD ULTECELL (CME single configuration: Object Group > UMTS Service Configuration and Maintenance Management > External Cell Configuration > RNC LTE

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External Cell; CME batch modification center: not supported) to set an LTE cell. In this step, set LTE Cell Supporting PS HO Indicator to Support(Support) and set BlackCell List Flag to False.

2. Run the RNC MML command SET UU2LTEHONCOV (CME single configuration: UMTS Radio Global Configuration Express > HandOver Parameter Configuration > RNC-Oriented Non-Coverage-Based UMTS-LTE Handover Measurement Algorithm Parameters; CME batch modification center: not supported) to set the RNC-level non-coverage-based UMTS-to-LTE handover measurement parameters. These parameter settings are to be delivered in the measurement control infor

Interoperability Between UMTS and LTE(RAN14.0_04)

Documents

huawei trademarks

huawei proprietary

data services

lte coverage

lte contents issue

huawei industrial base

lte ran14

data cards