interoperability between gsm and lte

GSM BSS

Interoperability Between GSM and LTE Feature Parameter Description

Copyright © Huawei Technologies Co., Ltd. 2011. 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.

Trademarks and Permissions

and other Huawei trademarks are trademarks of Huawei Technologies Co., Ltd.

All other trademarks and trade names mentioned in this document are the property of their respective holders.

Notice

The purchased products, services and features are stipulated by the commercial contract made between Huawei and the customer. All or partial products, services and features described in this document may not be within the purchased scope or the usage scope. Unless otherwise agreed by the contract, all statements, information, and recommendations in this document are provided “AS IS” without warranties, guarantees or representations of any kind, either express or implied.

The information in this document is subject to change without notice. Every effort has been made in the preparation of this document to ensure accuracy of the contents, but all statements, information, and recommendations in this document do not constitute the warranty of any kind, express or implied.

Huawei Proprietary and Confidential Copyright © Huawei Technologies Co., Ltd

i

GSM BSS Interoperability Between GSM and LTE 1 Introduction

Issue Draft A (2011-01-15) Huawei Proprietary and Confidential Copyright © Huawei Technologies Co., Ltd

1-1

Content 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

3 Related Concepts......................................................................................................................3-1 3.1 SI2quater....................................................................................................................................... 3-1 3.2 Measurement of Neighboring LTE Cells ....................................................................................... 3-1

4 Inter-RAT Cell Reselection Between GSM and LTE .........................................................4-1 4.1 Overview ....................................................................................................................................... 4-1 4.2 Cell Reselection from LTE to GSM ............................................................................................... 4-1

4.2.1 LTE-to-GSM Cell Reselection............................................................................................... 4-1 4.2.2 LTE-to-GSM eNACC ............................................................................................................ 4-1

4.3 Cell Reselection from GSM to LTE ............................................................................................... 4-2 4.4 Fast LTE Reselection at 2G CS Call Release............................................................................... 4-4 4.5 eNC2 Between GSM and LTE ...................................................................................................... 4-4

4.5.1 Service-Based Cell Reselection Algorithm........................................................................... 4-6 4.5.2 Quality-Based Cell Reselection Algorithm............................................................................ 4-7 4.5.3 Load-Based Cell Reselection Algorithm............................................................................... 4-7 4.5.4 Coverage-Based Cell Reselection Algorithm ....................................................................... 4-8 4.5.5 RAT Priority-Based Cell Reselection Algorithm.................................................................... 4-8 4.5.6 Neighboring Cell Priority-Based Cell Reselection Algorithm................................................ 4-8

5 GSM/LTE Inter-RAT PS Handover.........................................................................................5-1 5.1 GSM-to-LTE PS Handover ............................................................................................................ 5-1

5.1.1 Overview............................................................................................................................... 5-1 5.1.1 Procedure ............................................................................................................................. 5-2 5.1.2 Fast PS Handover Between GSM and LTE ......................................................................... 5-5 5.1.3 Service-Based PS Handover................................................................................................ 5-5 5.1.4 Quality-Based PS Handover ................................................................................................ 5-6 5.1.5 Load-Based PS Handover.................................................................................................... 5-6 5.1.6 Coverage-Based PS Handover ............................................................................................ 5-7 5.1.7 RAT Priority-Based PS Handover......................................................................................... 5-7 5.1.8 Neighboring Cell Priority-Based PS Handover..................................................................... 5-8

5.2 PS Handover from LTE to GSM .................................................................................................... 5-8 5.2.1 Overview............................................................................................................................... 5-8 5.2.2 Procedure ............................................................................................................................. 5-8

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



1-2

6.2 Procedure...................................................................................................................................... 6-1

7 CS Fallback.................................................................................................................................7-1 7.1 Overview ....................................................................................................................................... 7-1 7.2 Procedure...................................................................................................................................... 7-1

7.2.1 MOC CSFB (PS Handover).................................................................................................. 7-2 7.2.2 MOC CSFB (Cell Reselection) ............................................................................................. 7-3 7.2.3 MTC CSFB (Idle Mode) ........................................................................................................ 7-5 7.2.4 MTC CSFB (Connected Mode + PS Handover)................................................................... 7-6 7.2.5 MTC CSFB (Connected Mode + Cell Reselection) .............................................................. 7-8

8 Engineering Guidelines...........................................................................................................8-1 8.1 Related Parameters in the System Information ............................................................................ 8-1 8.2 Neighboring LTE Cell Configuration.............................................................................................. 8-1 8.3 Optimized Inter-RAT Cell Reselection Between GSM and LTE.................................................... 8-1 8.4 GSM/LTE Inter-RAT NC2 and PS Handover................................................................................. 8-1 8.5 CS Service Connectivity................................................................................................................ 8-2

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

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

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

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



1-1

1 Introduction 1.1 Scope This document describes Global System for Mobile communications/Long Term Evolution (GSM/LTE) interoperability of Huawei GSM Base Station Subsystem (BSS). It covers the functions of and technologies related to this feature, including measurement of neighboring LTE cells, GSM/LTE cell reselection, and GSM/LTE inter-RAT Packet Switched (PS) handover.

The following features are involved:

GBFD-511301 Cell Reselection Between GSM and LTE GBFD-511302 PS Handover Between GSM and LTE Based on Coverage GBFD-511303 PS Handover Between GSM and LTE Based on Quality GBFD-511304 PS Handover Between GSM and LTE Based on Cell Load GBFD-511305 PS Handover Between GSM and LTE Based on Mode Priority GBFD-511306 GSM/LTE Service Based PS Handover GBFD-511307 eNC2 Between GSM and LTE GBFD-511308 eNACC Between GSM and LTE GBFD-511309 SRVCC GBFD-511310 Multi Technology Neighbour Cell Based Handover GBFD-511312 Fast LTE Reselection at 2G CS Call Release GBFD-511313 CSFB

1.2 Intended Audience It is assumed that users of this document are familiar with GPRS basics and have a working knowledge of GPRS telecommunication.

This document is intended for:

Personnel working on Huawei GPRS products or systems System operators who need a general understanding of this feature

1.3 Change History The change history provides information on the changes made to the Interoperability between GSM and LTE feature in different document versions.

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

Feature change Feature change refers to the change in the Interoperability between GSM and LTE feature of a specific product version.

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

Document Issues The document issue is as follows:

Draft A (2011-01-15)



1-2

Draft A (2011-01-15) BSS13.0.

f GBSS12.0, this issue incorporates the changes described in

This is the first release of G

Compared with issue 01 (2010-06-30) othe following table.

Change Type Change Description Parameter Change

Feature change

Added a description of the neighboring cell priority-

based handover between GSM and LTE. For details, see section 5.1.9 "Neighboring Cell Priority-Based PS Handover". Added a description of the fast PS handover between GSM and LTE. For details, see section 5.1.3 "Fast PS Handover Between GSM and LTE". Added a description of the fast LTE reselection at 2G CS call release. For details, see section 4.4 "Fast LTE Reselection at 2G CS Call Release". Added a description of the CSFB. For details, see chapter 7 "CS Fallback".

Added the following parameter:TrafficReselAllow

Editorial T ptimized: ection 4.2.2

None change

he following contents are o eNACC procedure. For details, see s"LTE-to-GSM eNACC".

GSM-to-LTE cell reselection. For details, see section 4.3 "Cell Reselection from GSM to LTE".

SRVCC procedure. For details, see chapter 6 "SRVCC". Setting of GSM and LTE configuration parameters. For details, see chapter 8 "Engineering Guidelines".

GSM BSS Interoperability Between GSM and LTE 2 Overview


2-1

2 Overview With the development of radio access technologies, the GSM or EDGE network is evolved to the Wideband Code Division Multiple Access (WCDMA) or Time Division-Synchronous Code Division Multiple Access (TD-SCDMA) network. Currently, main-stream operators start to deploy LTE network.

EDGE is an enhancement of GSM.

Actually, a continuous coverage cannot be achieved in the initial phase of LTE deployment. To achieve good network coverage, operators can use their GSM network as a supplement for the LTE network. Therefore, GSM/LTE interoperability is introduced. With this feature, mobile stations (MSs) in areas without LTE coverage or areas with heavy traffic load can reselect or be handed over to the GSM network.

When the LTE network is deployed with the GSM network, MSs in idle mode can perform inter-RAT cell reselection; MSs in packet transfer mode can perform inter-RAT cell reselection and inter-RAT handover.

Huawei provides the GSM/LTE interoperability feature, supporting bidirectional inter-RAT (GSM/LTE) cell reselection and bidirectional PS handover.

The co-existence of the GSM, UMTS, and LTE is not described in this document.

All MSs involved in this feature are GSM/LTE dual-mode MSs. The FDD-based LTE is not distinguished from the TDD-based LTE in this document.

GSM BSS Interoperability Between GSM and LTE 3 Related Concepts


3-1

3 Related Concepts 3.1 SI2quater The System Information 2quater (SI2quater) is sent on the BCCH to all the MSs in the cell. SI2quater contains the parameters related to the measurement of GSM and neighboring LTE cells and the measured results.

There are 504 Physical Layer Cell Identities (PCIDs) in an LTE network. The SI2quater contains the LTE frequencies and the prohibited PCIDs (if any) corresponding to each frequency. All these frequencies and PCIDs are recorded in the LTE Cell Reselection List. A maximum of eight frequencies and related information are contained in the LTE Cell Reselection List.

Priorities of neighboring cells are also broadcast to MSs through the SI2quater. The priority information is used for the priority-based GSM or LTE cell reselection. In the SI2quater, the priority of neighboring GSM cells must be different from that of neighboring LTE cells. The priority of neighboring GSM cells is determined by NCELLPRI for GSM neighboring cells in the neighboring cell relationship; the priority of neighboring LTE cells is determined by NCELLPRI for neighboring LTE cells in the neighboring cell relationship.

The information on neighboring LTE cells can be split and transmitted through multiple consecutive SI2quaters. A start flag is marked in the first SI2quater containing the neighboring LTE cell information, and an end flag is marked in the last SI2quater containing the neighboring LTE cell information. In this way, the MS can decode these consecutive SI2quaters together to obtain the complete information on neighboring LTE cells. This accelerates the cell reselection.

When the parameter LTECELLRESELEN is set to YES, the information on neighboring LTE cells and network priorities is carried in the SI2quater.

3.2 Measurement of Neighboring LTE Cells The purpose of measuring neighboring LTE cells is to obtain the signal quality of neighboring LTE cells, ensuring that the MS can select a proper cell for cell reselection and handover.

To facilitate MS performing GSM/LTE inter-RAT cell reselection and handover, related system information (SI) is required. It contains a list of neighboring LTE cells and parameters related to LTE cell reselection and handover, based on which the MS measures the signal quality of neighboring cells and performs cell reselection and handover. The SI is the SI2quater sent on the Broadcast Control Channel (BCCH).

The MSs in a GSM cell measure the signal quality of both neighboring GSM cells and neighboring inter-RAT cells. Neighboring inter-RAT cells include neighboring UMTS and LTE cells. In this document, however, only neighboring LTE cells are described. To reduce unnecessary measurements and power consumption of MSs, the BSS controls the neighboring cell measurement using the parameter THRPRISEARCH.

The MS determines whether to measure neighboring LTE cells based on THRPRISEARCH and receive level of the serving cell. The condition for triggering the measurement differs with the value of THRPRISEARCH.

If THRPRISEARCH is set to a value within the range of 0 to 14, the measurement is triggered when the receive level of the serving cell is lower than THRPRISEARCH.

If THRPRISEARCH is set to 15, MSs always measure the neighboring LTE cell information.

GSM BSS Interoperability Between GSM and LTE 4 Inter-RAT Cell Reselection Between GSM and LTE


4-1

4 Inter-RAT Cell Reselection Between GSM and LTE 4.1 Overview This chapter describes the features GBFD-511301 Cell Reselection Between GSM and LTE, GBFD-511307 eNC2 Between GSM and LTE, GBFD-511308 eNACC Between GSM and LTE, GBFD-511312 Fast LTE Reselection at 2G CS Call Release, and GBFD-511313 CSFB.

GSM/LTE cell reselection involves the cell reselection from GSM to LTE and the cell reselection from LTE to GSM. Cell reselection is mainly performed by MSs.

For MSs in idle mode, an MS camping on a GSM cell can reselect an LTE cell. Similarly, an MS camping on an LTE cell can reselect a GSM cell. The MS measures the information about neighboring LTE cells, and then decides whether to reselect an LTE cell according to cell reselection parameters.

For MSs in packet transfer mode, cell reselection modes include network-controlled mode 0 (NC0), network-controlled mode 1 (NC1), and external network-controlled mode 2 (eNC2). MSs can reselect an LTE cell for PS services. NC0 cell reselection and NC1 cell reselection are performed by MSs without the intervention of the BSS. In eNC2 cell reselection, the BSS sends signaling to steer MSs towards desired camping cells.

The LTECELLRESELEN parameter specifies whether to enable GSM/LTE inter-RAT cell reselection. When LTECELLRESELEN is set to No, the BSS does not send the neighboring LTE cell list and the parameters related to GSM/LTE cell reselection. In this case, MSs in a GSM cell cannot reselect an LTE cell.

4.2 Cell Reselection from LTE to GSM 4.2.1 LTE-to-GSM Cell Reselection When an MS in idle or connected mode moves from an LTE coverage area to a GSM coverage area, it may reselect a GSM cell.

After reselecting a GSM cell, the MS initiates the location update and route area update in the GSM network. The GSM network handles the location update and route area update regardless of whether the MS is from an LTE cell or a GSM cell.

For the BSS, the LTE-to-GSM cell reselection procedure is the same as that between GSM cells. It is not repeated in this document.

4.2.2 LTE-to-GSM eNACC This section describes the feature GBFD-511308 eNACC Between GSM and LTE.

The LTE-to-GSM eNACC procedure is specified in 3GPP specifications. The GSM-to-LTE eNACC procedure, however, is not specified in 3GPP specifications.



4-2

Figure 4-1 eNACC procedure

The eNodeB decides to reselect the MS to a GSM cell, and sends a MobilityFromEUTRACommand message to the MS. If the LTE-to-GSM eNACC procedure is applied, the MobilityFromEUTRACommand message carries cellChangeOrder in the purpose IE, instructing the MS to perform cell reselection. In addition, the message carries the ID and SI (including SI1, SI3, and SI13) of the target GSM cell.

Before performing LTE-to-GSM eNACC, the eNodeB obtains the SI of the target GSM cell through the RAN Information Management (RIM) procedure. The RIM procedure consists of SI request and SI update procedures.

SI request procedure: This procedure is initiated by the source eNodeB, requesting the SI about the target GSM cell.

SI update procedure: This procedure is initiated by the target BSC, instructing the source eNodeB to update the SI about the target GSM cell.

After receiving the Mobility From EUTRA Command message, the MS leaves the LTE cell and reselects the GSM cell. After the cell reselection is complete, the MS uses the SI about the target GSM cell in the initial packet access procedure. In this manner, the period of packet service disruption is shortened.

During the LTE-to-GSM eNACC procedure, the RIM procedure must be supported on the Gb interface. To support the RIM procedure, the BSC must be configured with the RIMSUP parameter of the NSE to indicate whether the RIM procedure is supported.

4.3 Cell Reselection from GSM to LTE This section describes the feature GBFD-511301 Cell Reselection Between GSM and LTE.



4-3

This function is introduced in 3GPP Release 8.

1. The BSC is configured with the following priority information for the cell reselection based on cell priority:

LTE frequency priority. Involved parameter: EUTRANPRI.

LTE frequency thresholds. Involved parameters: THRPRISEARCH, UTRANQRXLEVMIN, THREUTRANHIGH, THREUTRANLOW, HPRIO, and TRESEL.

Priority of the GSM serving cell. Involved parameter: GERANPRI.

Serving cell threshold. Involved parameter: THRGSMLOW.

Where,

EUTRANPRI is the common priority of LTE cells.

THRPRISEARCH is the threshold for priority-based inter-RAT cell search. If the receive level of the serving cell is higher than this threshold, MSs do not search for neighboring LTE cells whose priority is lower than that of the GSM serving cell.

THRPRISEARCH does not take effect for neighboring cells whose priority is higher than the priority of the GSM serving cell.

EUTRANQRXLEVMIN is used to calculate the Reference Signal Received Power (RSRP) of the target cell during a GSM-to-LTE cell reselection decision:

RSRP = Measured RSRP - EUTRANQRXLEVMIN

THREUTRANHIGH is the upper threshold for priority-based GSM-to-LTE cell reselections. MSs can reselect a neighboring LTE cell whose EUTRANPRI is greater than GERANPRI and whose RSRP is greater than THREUTRANHIGH.

THREUTRANLOW is the lower threshold for priority-based GSM-to-LTE cell reselections. If the receive levels of the serving cell and all neighboring GSM cells are lower than THRGSMLOW, MSs can reselect a neighboring LTE cell whose EUTRANPRI is smaller than GERANPRI and whose RSRP is greater than THREUTRANLOW.

HPRIO is the level hysteresis for priority-based cell reselections.

TRESEL is the time hysteresis for priority-based cell reselections. During priority-based inter-RAT cell reselections, this parameter is used to specify the period for which the cell reselection condition must be met.

GERANPRI is the common priority of GSM cells.

THRGSMLOW is the lower threshold for GSM cells during priority-based cell reselections. When receive levels of the serving cell and all neighboring GSM cells are lower than this threshold, MSs can reselect a neighboring LTE cell whose priority is lower than GERANPRI.

2. The MS has obtained the priority information for inter-RAT cell reselection. MSs in a GSM cell obtain the neighboring LTE cell list and cell reselection priorities from SI2quater, and then measure neighboring LTE cells according to the list and priorities. MSs in idle and packet transfer modes use the same GSM-to-LTE NC0/NC1 cell reselection mechanism.

3. The MS supports priority-based GSM-to-LTE cell reselection. GSM/LTE dual-mode MSs always support priority-based GSM-to-LTE cell reselection. The target cell in a priority-based GSM-to-LTE cell reselection is selected as follows:



4-4

If within the period specified by TRESEL, multiple neighboring LTE cells meet the condition of EUTRANPRI > GERANPRI and RSRP > THREUTRANHIGH, the MS selects the neighboring LTE cell with the highest priority. If multiple cells have the highest priority, the MS selects the cell with the highest RSRP from these cells.

If within the period specified by TRESEL, the serving GSM cell is lower than THRGSMLOW of the serving GSM cell and all measured neighboring GSM cells, the MS reselects an LTE cell according to the following rules:

If multiple neighboring LTE cells meet the conditions of EUTRANPRI < GERANPRI and RSRP > THREUTRANLOW for the period specified by TRESEL, the MS selects the neighboring LTE cell with the highest priority. If multiple cells have the highest priority, the MS selects the cell with the highest RSRP from these cells.

If none of neighboring cells meet the preceding condition, the MS selects the neighboring LTE cell whose RSRP is greater than the receive level of the serving GSM cell plus HPRIO. If there are many cells whose RSRP is greater than the receive level of the serving GSM cell plus HPRIO, the MS selects the cell with the greatest RSRP from these cells.

When EUTRANPRI is greater than GERANPRI, and THREUTRANHIGH is small, the condition for priority-based GSM-to-LTE cell reselection is easy to meet. In this case, there is a decrease in the number of MSs that camp on GSM cells.

4.4 Fast LTE Reselection at 2G CS Call Release This section describes the feature GBFD-511312 Fast LTE Reselection at 2G CS Call Release.

In general, when an MS terminates a call in the GSM network, it camps on a cell in which the call is released and then starts neighboring cell measurement. When a neighboring LTE cell meets the requirements for cell reselection, the MS reselects the LTE cell. Before initiating the cell reselection to the LTE cell, the MS must receive system information and calculate cell reselection parameters. This procedure takes a long time.

After the Fast LTE Reselection at 2G CS Call Release feature is activated, the MS attempts to select an LTE cell after terminating a CS call, thereby speeding up cell reselection, improving the user experience and increasing the revenue of operators from the LTE network.

This feature is activated when SPTRAPIDSEL is set to SUPPORT. This feature enables an MS to select an LTE cell immediately after it terminates a call in a GSM cell or immediately after the DTM service releases an RR connection.

After an MS terminates a call in a GSM cell, the BSC sends the CHANNEL RELEASE message. The message carries the information element (IE) "cell selection indicator after release of all TCH and SDCCH" that contains the neighboring LTE cells whose SPTRAPIDSEL is set to SUPPORT.

After the DTM service releases an RR connection, the MS can reselect the specified LTE cell according to the IE "Cell selection indicator after release of all TCH and SDCCH" carried in the CHANNEL RELEASE message, if the network or the MS does not support the enhanced DTM CS release procedure.

4.5 eNC2 Between GSM and LTE This section describes the feature GBFD-511307 eNC2 Between GSM and LTE.

MSs in packet transfer mode can perform eNC2 inter-RAT cell reselection.

The GSM-to-LTE eNC2 cell reselection is triggered by the BSC.

NC2 is enabled when NCO is set to NC2.



4-5

In eNC2 mode, an MS performs inter-RAT neighboring LTE cell measurements based on QPEUTRAN, BESTEUTRANCELLNUM, and THREUTRANRPT and reports the measurement reports.

QPEUTRAN is the threshold for MSs in packet transfer mode to search for LTE cells. MSs start to search for neighboring LTE cells when the level of the serving GSM cell is lower than the value of QPEUTRAN (when QPEUTRAN is set to a value within the range of 0 to 6) or higher than the value of QPEUTRAN (when QPEUTRAN is set to a value within the range of 8 to 14). When QPEUTRAN is set to 7, MSs always search for neighboring LTE cells.

BESTEUTRANCELLNUM is the number of LTE cells that should be contained in the best cell list which is carried in the measurement report from an MS.

THREUTRANRPT is the threshold for reporting the LTE cell information. The MS reports only the information of LTE cells whose RSCP is greater than this threshold.

Figure 4-2 shows the procedure for eNC2 cell reselection from GSM to LTE.

Figure 4-2 eNC2 cell reselection from GSM to LTE

1. An MS in the GMM Ready state periodically sends Packet Measurement Report messages or Packet Enhanced Measurement Report messages to the BSC. These measurement reports contain the RSRP of neighboring LTE cells.

2. After receiving a packet measurement report, the BSC processes the measurement results. Then, the BSC determines whether to perform a cell reselection.

3. If the BSC determines to initiate a cell reselection, it sends the Packet Cell Change Order message to the MS to instruct the MS to reselect the specified target LTE cell. Target cell reselection is based on the eNC2 cell reselection algorithm.

4. If a cell reselection fails, the MS sends the Packet Cell Change Failure message to the BSC. 5. The eNC2 cell reselection algorithms include the service-based eNC2 cell reselection algorithm,

quality-based eNC2 cell reselection algorithm, load-based eNC2 cell reselection algorithm, RAT-



4-6

based eNC2 cell reselection algorithm, and neighboring cell priority-based eNC2 cell reselection algorithm.

4.5.1 Service-Based Cell Reselection Algorithm The service-based cell reselection is activated when TrafficReselAllow is set to PERMIT.

The BSC may find the IE "Service UTRAN CCO" in multiple DL-UNITDATA PDUs, CREATE-BSS-PFC PDUs, or PS-HANDOVER-REQUEST PDUs sent from the SGSN. The BSS considers that the last received IE "Service UTRAN CCO" is of the highest priority. The IE "Service UTRAN CCO" carries Service UTRAN CCO Value part and Service E-UTRAN CCO Value part, which indicates the most suitable RAT for the current service. Table 4-1 and Table 4-2 respectively list the values of Service UTRAN CCO Value part and Service E-UTRAN CCO Value part and their meanings.

Table 4-1 Values of Service UTRAN CCO Value part and their meanings

Coding Bits Semantic

000 Network initiated cell change order to UTRAN or PS handover to UTRAN procedure should be performed

001 Network initiated cell change order to UTRAN or PS handover to UTRAN procedure should not be performed

010 Network initiated cell change order to UTRAN or PS handover to UTRAN procedure shall not be performed

111 If received, shall be interpreted as no information available (bits 4-5 valid)

Other values If received, shall be interpreted as no information available

Table 4-2 Values of Service E-UTRAN CCO Value part and their meanings


01 Network initiated cell change order to E-UTRAN or PS handover to E-UTRAN procedure should be performed

10 Network initiated cell change order to E-UTRAN or PS handover to E-UTRAN procedure should not be performed

11 Network initiated cell change order to E-UTRAN or PS handover to E-UTRAN procedure shall not be performed

00 If received, shall be interpreted as no information available

If the value of Service UTRAN CCO Value part is 000 or the value of Service E-UTRAN CCO Value part is 01, the MS triggers a service-based cell reselection. When the value of Service E-UTRAN CCO Value part is 01, the MS selects a neighboring LTE cell with the highest neighboring cell priority and the best receive quality. If no neighboring LTE cells are available, the MS proceeds to perform a quality-based, load-based, or coverage-based eNC2 cell reselection. If the value of Service UTRAN CCO Value part is not 000 and the value of Service E-UTRAN CCO Value part is not 01, the MS triggers a quality-based, load-based, or coverage-based cell reselection.



4-7

4.5.2 Quality-Based Cell Reselection Algorithm The quality-based cell reselection is activated when URGENTRESELALLOW is set to PERMIT. When the conditions for triggering a service-based cell reselection are not met, the BSC determines whether to initiate a cell reselection based on the receive quality of the radio link on the Um interface. The measurement reports or bit error rate (BER) indicates the receive quality on the radio link. If the BER increases, the possible cause is that the signal level is too low or there is interference on the channel. In this case, the BSC instructs the MS to reselect a neighboring cell with higher signal level. In a receive quality measurement period, if the MS receive quality deterioration ratio is greater than the CELLRXQUALWORSENRATIOTHRSH parameter, a quality-based cell reselection is initiated.

MS receive quality deterioration ratio = Times of bad radio link quality/Number of radio link quality measurement reports

The MS selects the highest level candidate cell within the highest priority cells as the target cell. When Service E-UTRAN CCO Value part is set to 10 or 11, none of the LTE cells can be selected as a target cell.

4.5.3 Load-Based Cell Reselection Algorithm The load-based cell reselection is activated when LOADRESELALLOW is set to PERMIT. When neither the conditions for initiating a service-based cell reselection nor the conditions for initiating a quality-based cell reselection are met, a load-based cell reselection is initiated to balance the load among the cells in the network. In a load-based cell reselection, some MSs in cells with heavy load are reselected to cells with light load. In addition, the MSs in neighboring cells should not be reselected to these heavily-loaded cells. Figure 4-3 shows the load-based cell reselection.

Figure 4-3 Load-based cell reselection

When the serving cell is overloaded and the receive level in this cell is lower than LOADRESELMAXRXLEV, load-based cell reselection is triggered.

If the channel multiplexing rate of a cell is higher than LOADRESELSTARTTHRSH, the load in the cell is heavy. Then, the load-based cell reselection should be enabled.

In a load-based cell reselection, only the MS whose signal level is lower than LOADRESELMAXRXLEV can be reselected to a neighboring cell.

The MS selects the highest level candidate cell within the highest priority cells as the target cell

When the value of Service E-UTRAN CCO Value part is 10 or 11, none of the LTE cells can be selected as a target cell.



4-8

4.5.4 Coverage-Based Cell Reselection Algorithm The coverage-based cell reselection is activated when NORMALRESELALLOW is set to PERMIT.

A coverage-based cell reselection is initiated when none of the conditions for initiating a service-based, quality-based, and load-based cell reselection are met and the P/N criterion for initiating a coverage-based cell reselection is met.

The P/N criterion for initiating a coverage-based eNC2 cell reselection is as follows: In the period specified by RESELWATCHPERIOD, the number of times that the receive level of the serving cell is lower than the value of MINACCRXLEV reaches the value of RESELWORSENLEVTHRSH.

The MS selects the highest level candidate cell within the highest priority cells as the target cell. When the value of Service E-UTRAN CCO Value part is 10 or 11, none of the LTE cells can be selected as a target cell.

4.5.5 RAT Priority-Based Cell Reselection Algorithm In the RAT priority-based cell reselection algorithm, neighboring cells are ranked based on their RATs.

The RAT priority-based neighboring cell ranking is applicable to quality-based, load-based, and coverage-based PS handovers.

The value of GERANPRI or EUTRANPRI (depends on the RAT of the cell) is used as the RAT priority of a cell.

The priority of neighboring GSM cells must be different from that of neighboring LTE cells.

If the priority of GSM is higher than that of LTE, then a neighboring GSM cell is preferentially selected as a candidate cell. If the priority of LTE is higher than that of GSM, then a neighboring LTE cell is preferentially selected as a candidate cell.

4.5.6 Neighboring Cell Priority-Based Cell Reselection Algorithm In the neighboring cell priority-based cell reselection algorithm, neighboring cells are ranked based on their priorities.

The neighboring cell priority-based neighboring cell ranking is involved in quality-based, load-based, and coverage-based eNC2 cell reselections.

Neighboring cell priority is determined by the NCELLPRI parameter.

When NCELLPRI is set to an invalid value, the value of GERANPRI or EUTRANPRI (depends on the RAT of the cell) is used as the value of this parameter.


Neighboring cells with the highest priority are selected as candidate cells.

GSM BSS Interoperability Between GSM and LTE 5 GSM/LTE Inter-RAT PS Handover


5-1

5 GSM/LTE Inter-RAT PS Handover GSM/LTE inter-RAT PS handover is introduced in 3GPP Release 8.

GSM/LTE inter-RAT PS handover involves LTE-to-GSM and GSM-to-LTE PS handovers.

5.1 GSM-to-LTE PS Handover This section describes the features GBFD-511302 PS Handover Between GSM and LTE Based on Coverage, GBFD-511303 PS Handover Between GSM and LTE Based on Quality, GBFD-511304 PS Handover Between GSM and LTE Based on Cell Load, GBFD-511305 PS Handover Between GSM and LTE Based on Mode Priority, GBFD-511306 GSM/LTE Service Based PS Handover, and GBFD-511310 Multi Technology Neighbour Cell Based Handover.

5.1.1 Overview The PS handover from GSM to LTE is initiated by the BSC. PS handovers have two phases: handover preparation and handover execution.

The GSM-to-LTE PS handover is supported when SPTLTEOUTBSCPSHO is set to SUPPORT.

The triggering conditions of a GSM-to-LTE handover are as follows:

The MS supports PS handover. The radio access capability reported by the MS contains the PS handover field, which indicates that the MS supports the PS handover.

The BSC supports PS handover. The BSC supports PS handover when PSHOSUP is set to YES, and SPTLTEOUTBSCPSHO is set to SUPPORT. NACCSPT is set to YES if NCO is set to NC0 or NC1 because NC0 and NC1 are based on NACC.NC2SPT is set to YES if NCO is set to NC2.

The SGSN supports PS handover. The BVC RESET and BVC RESET ACK messages sent over the Gb interface contain the Extended Feature Bitmap field, which specifies whether the Network Service Entity (NSE) supports PS handover: − If the BVC RESET or BVC RESET ACK message sent by the SGSN does not contain the Extended Feature Bitmap field, or if the Extended Feature Bitmap field specifies that PS handover is not supported, none of the cells under the NSE of the SGSN supports PS handover. That is, the source cell does not support PS handover.

− If the Extended Feature Bitmap field specifies that PS handover is supported, all cells under the NSE of the SGSN support PS handover. That is, the source cell supports PS handover.

Through the preceding negotiation procedure, the BSC determines whether the SGSN supports PS handover.

The BSC and the SGSN support the PFC procedure. PFCSUP is set to YES.

The triggering conditions for a GSM-to-LTE PS handover vary according to the setting of NCO:

When NCO is set to NC0 or NC1: NACCSPT is set to YES. The MS sends the BSC a PACKET CELL CHANGE NOTIFICATION message, and target cell information contained in the message indicates that the target cell is an LTE cell. SPTLTEOUTBSCPSHO is set to SUPPORT.

When NCO is set to NC2:



5-2

The MS sends the BSC a measurement report, and the BSC detects that the target cell is an LTE cell using the PS handover algorithm. SPTLTEOUTBSCPSHO is set to SUPPORT.

The BSC determines whether the handover is a service-based handover based on the DL-UNITDATA PDU, CREATE-BSS-PFC PDU, or PS-HANDOVER-REQUEST PDU sent by the SGSN. If the handover is not a PS handover, the BSC selects the neighboring cell with the highest priority in the measurement report, and then initiates a quality-based, load-based, or coverage-based PS handover to that neighboring cell. The priority of a neighboring cell is specified by NCELLPRI. When NCELLPRI is set to an invalid value, the value of GERANPRI, UTRANPRI, or EUTRANPRI (depends on the RAT of the cell) is used as the value of this parameter.

5.1.1 Procedure On the BSS side, the GSM-to-LTE PS handover procedure is similar to the inter-BSC PS handover procedure. The differences are as follows:

The target cell is an LTE cell. The PS Handover Required message carries the Source BSC to Target eNodeB Transparent Container, which contains such IEs as MS radio access capability, INTER RAT HANDOVER INFO, LTE INTER RAT HANDOVER INFO, and target cell.

The PS Handover Required Acknowledge message carries the Source eNodeB to Target BSC Transparent Container, which contains such IEs as handover command and RRCConnectionReconfiguration.

Figure 5-1 shows the signaling procedure during GSM-to-LTE PS handover preparation.

Figure 5-1 Signaling procedure during GSM-to-LTE PS handover preparation



5-3

1. The source BSS decides to initiate a PS handover to an LTE cell. At this point both uplink and downlink user data is transmitted through the following: Bearers between MS and Source BSS, BSSGP PFC tunnel(s) between source BSS and source SGSN, GTP tunnel(s) between Source SGSN, Serving GW and PDN GW.

2. The source BSS sends the PS handover Required message to the source SGSN to request the CN to reserve resources in the target eNodeB, target MME, and the serving GW.

3. The source SGSN analyzes the IE "Target eNodeB Identifier" and determines that the type of handover is an inter-RAT PS handover to LTE. The source SGSN sends a Forward Relocation Request message which carries a PFI list to the target MME, requesting the target MME to reserve resources for the service.

The target MME determines if the serving GW is to be relocated, for example, due to PLMN change. If the serving GW is to be relocated, the target MME selects the target serving GW and then sends a Create Bearer Request message to the target serving GW.

4a. The target serving GW allocates its local resources and returns them the target MME with a Create Bearer Response message carrying the address of the serving GW.

5. The target MME requests the target eNodeB to establish the bearer(s) by sending the message Handover Request to the target eNodeB.

5a. The target eNodeB allocates the request resources and returns the applicable parameters to the target MME in the message Handover Request Acknowledge (Target to Source Transparent Container, S1AP Cause, EPS Bearers setup list, EPS Bearers failed to setup list). Upon sending the Handover Request Acknowledge message the target eNodeB shall be prepared to receive downlink GTP PDUs from the Serving GW for the accepted EPS bearers.

6./6a. If indirect forwarding is applied, the target MME starts to create an indirect data forwarding tunnel.

7. The target MME sends the Forward Relocation Response message to the source SGSN. Serving GW change indication indicates whether a new Serving GW has been selected.

8./8a. If indirect forwarding is applied, the source SGSN starts to create an indirect data forwarding tunnel.

Figure 5-2 shows the GSM-to-LTE PS handover execution.



5-4

Figure 5-2 GSM-to-LTE PS handover execution

The source SGSN continues to receive downlink and uplink user plane PDUs. When the source SGSN receives the Forward Relocation Response message it may start downlink N-PDU relay, make a copy, and send the copy to the target eNodeB (for direct forwarding) or through the serving GW (for indirect forwarding), and the target eNodeB may start blind transmission of downlink user data towards the MS over the allocated radio channels.

1. The source SGSN completes the preparation phase towards source BSS by sending the PS HO Required Acknowledge message. This message includes all PFIs that could be established on the target side. The SGSN may suspend downlink data transfer before sending the PS HO Required Acknowledge message. The PS HO Required Acknowledge message also carries the handover command. The BSS attempts to empty the downlink buffer related to PFCs before sending the handover command to the MS.

2. The source BSS sends a PS Handover Command message, instructing the MS to hand over to the target LTE cell.

3. The MS moves to the LTE cell and performs access procedures toward the target eNodeB.

4. When the MS has got access to the target eNodeB, it sends the RRCConnectionReconfigurationComplete message to the target eNodeB.

5. When the MS has successfully accessed the target eNodeB, the target eNodeB sends a Handover Notify message to the target MME.



5-5

6./6a. After detecting that the MS has accessed the target cell, the target MME sends a Forward Relocation Complete message to the source SGSN. The source SGSN then responds with a Forward Relocation Complete Acknowledge message. After that, the source SGSN stops forwarding data to the source MME.

7./7a. The target MME completes the handover.

8. The source SGSN releases related resources through the BSS packet flow delete procedure.

9. The MS initiates the tracking area update procedure.

5.1.2 Fast PS Handover Between GSM and LTE This feature is applicable to the GSM/LTE co-site and co-coverage scenarios. To enable the fast handover from GSM to LTE, set NACCSPT to NO, set NCO to NC0 or NC1, set PSHOSUP to YES, set SPTBLINDHO to YES, and set SPTLTEOUTBSCPSHO to YES.

The fast handover between GSM and LTE is triggered when any of the following conditions is met:

The DL-UNITDATA, CREATE-BSS-PFC, or PS-HANDOVER-REQUEST carries the IE "Service UTRAN CCO", in which the value of Service UTRAN CCO Value part is not 000 and the value of Service E-UTRAN CCO Value part is 01.

The channel multiplexing rate of the cell is higher than LOADRESELSTARTTHRSH, and the neighboring cell that has the greatest NCELLPRI value is an LTE cell. In addition, the value of Service E-UTRAN CCO Value part is 01.

The target cell for the GSM-to-LTE fast handover is determined by the GSM configuration. That is, no algorithm is required to select the target cell.

5.1.3 Service-Based PS Handover This section describes the feature GBFD-511306 GSM/LTE Service Based PS Handover. The service-based PS handover is activated when TrafficReselAllow is set to PERMIT.

The BSC may find the IE "Service UTRAN CCO" in multiple DL-UNITDATA PDUs, CREATE-BSS-PFC PDUs, or PS-HANDOVER-REQUEST PDUs sent from the SGSN. The BSS considers that the last received IE "Service UTRAN CCO" is of the highest priority. The IE "Service UTRAN CCO" carries Service UTRAN CCO Value part and Service E-UTRAN CCO Value part, which indicates the most suitable RAT for the current service. Table 5-1 and Table 5-2 respectively list the values of Service UTRAN CCO Value part and Service E-UTRAN CCO Value part and their meanings.

Table 5-1 Values of Service UTRAN CCO Value part and their meanings


000 Network initiated cell change order to UTRAN or PS handover to UTRAN procedure should be performed

001 Network initiated cell change order to UTRAN or PS handover to UTRAN procedure should not be performed

010 Network initiated cell change order to UTRAN or PS handover to UTRAN procedure shall not be performed

111 If received, shall be interpreted as no information available (bits 4-5 valid)

Other values If received, shall be interpreted as no information available



5-6

Table 5-2 Values of Service E-UTRAN CCO Value part and their meanings


01 Network initiated cell change order to E-UTRAN or PS handover to E-UTRAN procedure should be performed

10 Network initiated cell change order to E-UTRAN or PS handover to E-UTRAN procedure should not be performed

11 Network initiated cell change order to E-UTRAN or PS handover to E-UTRAN procedure shall not be performed

00 If received, shall be interpreted as no information available

If the value of Service UTRAN CCO Value part is 000 or the value of Service E-UTRAN CCO Value part is 01, the MS triggers a service-based PS handover. When the value of Service E-UTRAN CCO Value part is 01, the MS selects a neighboring LTE cell that has the highest neighboring cell priority and the best receive quality. If no neighboring LTE cell is unavailable, the MS proceeds to perform a quality-based, load-based, or coverage-based PS handover. When the value of Service UTRAN CCO Value part is not 000 and the value of Service E-UTRAN CCO Value part is not 01, the MS triggers a quality-based, load-based, or coverage-based PS handover.

5.1.4 Quality-Based PS Handover This section describes the feature GBFD-511303 PS Handover Between GSM and LTE Based on Quality.

The quality-based PS handover is activated when URGENTRESELALLOW is set to PERMIT. When the conditions for triggering a service-based PS handover are not met, the BSC determines whether to initiate a PS handover based on the receive quality of the radio link on the Um interface. The measurement reports or bit error rate (BER) indicates the receive quality of a radio link. If the BER increases, the signal level may be too low or interference exists on the channel. In this case, the BSC instructs the MS to reselect a neighboring cell with higher signal level. Within a receive quality measurement period, if the MS receive quality deterioration ratio is greater than CELLRXQUALWORSENRATIOTHRSH, a quality-based PS handover is initiated. MS receive quality deterioration ratio = Times of bad radio link quality/Number of radio link quality measurement reports

The MS selects the highest level candidate cell within the highest priority cells as the target cell. When the value of Service E-UTRAN CCO Value part is 10 or 11, none of LTE cells can be selected as a target cell.

5.1.5 Load-Based PS Handover This section describes the feature GBFD-511304 PS Handover Between GSM and LTE Based on Cell Load.

The load-based PS handover is activated when LOADRESELALLOW is set to PERMIT. When neither the conditions for initiating a service-based PS handover nor the conditions for initiating a quality-based PS handover are met, a load-based PS handover is initiated to balance the load among the cells in the network. In a load-based PS handover, some MSs in cells with heavy load are handed over to cells with light load. In addition, the MSs in neighboring cells should not be handed over to these heavily-loaded cells. Figure 5-3 shows the load-based PS handover.



5-7

Figure 5-3 Load-based PS handover

When the serving cell is overloaded and the receive level in this cell is lower than LOADRESELMAXRXLEV, load-based PS handover is triggered.

If the channel multiplexing rate of a cell is higher than the value of the LOADRESELSTARTTHRSH parameter, the load in the cell is heavy, and the load-based PS handover should be enabled.

In a load-based PS handover, only the MS whose signal level is lower than LOADRESELMAXRXLEV can be handed over to a neighboring cell.


5.1.6 Coverage-Based PS Handover This section describes the feature GBFD-511302 PS Handover Between GSM and LTE Based on Coverage.

The coverage-based PS handover is activated when NORMALRESELALLOW is set to PERMIT.

When none of the conditions for initiating a service-based, quality-based, and load-based PS handover are met and the P/N criterion for initiating a coverage-based PS handover is met, a coverage-based PS handover is initiated.

The P/N criterion for initiating a coverage-based PS handover is as follows: In the period specified by RESELWATCHPERIOD, the number of times that the receive level of the serving cell is lower than the value of MINACCRXLEV reaches the value of RESELWORSENLEVTHRSH.


5.1.7 RAT Priority-Based PS Handover This section describes the feature GBFD-511305 PS Handover Between GSM and LTE Based on Mode Priority.

In the RAT priority-based PS handover algorithm, neighboring cells are ranked based on their RATs.

The RAT priority-based neighboring cell ranking is involved in quality-based, load-based, and coverage-based PS handovers.



5-8

The value of GERANPRI or EUTRANPRI (depends on the RAT of the cell) is used as the RAT priority of a neighboring cell.

The priority of neighboring GSM cells must be different from the priority of neighboring LTE cells.

If the priority of GSM is higher than that of LTE, then a neighboring GSM cell is preferentially selected as a candidate cell. If the priority of LTE is higher than that of GSM, then a neighboring LTE cell is preferentially selected as a candidate cell.

5.1.8 Neighboring Cell Priority-Based PS Handover This section describes the feature GBFD-511310 Multi Technology Neighbour Cell Based Handover.

In the neighboring cell priority-based PS handover algorithm, neighboring cells are ranked based on their priorities.

The neighboring cell priority-based neighboring cell ranking is involved in quality-based, load-based, and coverage-based PS handovers.

Neighboring cell priority is specified by the NCELLPRI parameter.

When NCELLPRI is set to an invalid value, the value of GERANPRI or EUTRANPRI (depends on the RAT of the cell) is used as the value of this parameter.


Neighboring cells with the highest priority are selected as candidate cells.

5.2 PS Handover from LTE to GSM 5.2.1 Overview The handover from LTE to GSM is triggered by the eNodeB.

The LTE-to-GSM PS handover is activated when SPTLTEINBSCPSHO is set to SUPPORT.

5.2.2 Procedure On the BSS side, the LTE-to-GSM PS handover procedure is similar to the inter-BSC PS handover procedure. The differences are as follows:

The PS Handover Request message carries the Source to Target Transparent Container, which contains IEs such as MS radio access capability, INTER RAT HANDOVER INFO, LTE INTER RAT HANDOVER INFO, and the target cell.

The PS Handover Request Acknowledge message carries the Source to Target Transparent Container, which contains IEs such as MobilityFromEUTRACommand and the ciphering algorithm.

Figure 5-4 shows the signaling procedure during LTE-to-GSM handover preparation.



5-9

Figure 5-4 LTE-to-GSM PS handover preparation

1. The source eNodeB decides to initiate a PS handover to a GSM cell. At this point both uplink and downlink user data is transmitted over the following: bearer(s) between MS and source eNodeB, GTP tunnel(s) between source eNodeB, serving GW and PDN GW.

2. The source eNodeB sends the source MME a Handover Required message which carries the target BSC identifier, source eNodeB identifier, and transparent container.

3. Based on the target BSC identifier, the source MME detects that the MS needs to be handed over to GSM and then sends a Forward Relocation Request message to the target SGSN. The target SGSN maps the EPS bearers to PDP contexts 1-to-1 and maps the EPS Bearer QoS parameter values of an EPS bearer to the pre-Rel-8 QoS parameter values of a bearer context

4. The target SGSN determines whether the Serving GW is to be relocated, for example, due to PLMN change. If the serving GW is to be relocated, the target SGSN selects the target serving GW, and sends a Create Session Request message to the target serving GW.

4a. The target serving GW allocates resources to the service and then sends a Create Session Response message to the target SGSN.

5. The target SGSN creates the EPS Bearer context(s), and then sends a PS Handover Request to the target BSS, requesting the target BSS to set up PFC resources for the service. Based upon the ABQP for each PFC the target BSS makes a decision about which PFCs to assign radio resources. Then, the target BSS allocates TBFs for each PFC that it can accommodate and prepares the Target to Source Transparent Container.

5a. The target BSS sends a PS Handover Request Acknowledge message, which carries the handover command, to the target SGSN. Upon sending the PS Handover Request Acknowledge message the



5-10

target BSS shall be prepared to receive downlink LLC PDUs from the target SGSN for the accepted PFCs.

6./6a. If indirect forwarding is applied, the target SGSN starts to create an indirect data forwarding tunnel.

7. The target SGSN sends the source MME a Forward Relocation Response message which carries the Target to Source Transparent Container.

8./8a. If indirect forwarding is applied, the source MME starts to create an indirect data forwarding tunnel.

Figure 5-5 shows the signaling procedure during handover execution.

Figure 5-5 LTE-to-GSM PS handover execution

1. The Source MME completes the preparation phase towards source eNodeB by sending the Handover Command message that carries the Target to Source Transparent Container (PS Handover Command, PFI list).

2. The source eNodeB sends the MobilityFromEUTRACommand message to the MS, instructing the MS to hand over to the target access system. Upon the reception of that message, the MS associates its bearer IDs to the respective PFIs and suspends the uplink transmission of the user plane data.

3. The MS moves to the target GSM system and executes the handover.



5-11

4. After accessing the cell, the MS sends an XID response message to the target SGSN, and recovers the data transfer.

5. After receiving the first correct RLC/MAC block from the MS, the target BSS informs the target SGSN by sending the PS Handover Complete message.

6. The target BSS also relays the XID Response message to the target SGSN. Note that the message in step 6 and 7 may arrive in any order in the target SGSN.

7.-8. After receiving the PS Handover Complete message, the target SGSN informs the source MME by sending the Forward Relocation Complete Notification message. The source MME then returns the Forward Relocation Complete Acknowledge message.

9.-10. The CN adjusts the user plane bearer. At this stage the user plane path is established for all EPS Bearer contexts between the MS, Target BSS, Target SGSN, Target Serving GW and PDN GW. The SGSN releases the non-accepted EPS Bearer contexts.

11./12a. The target SGSN may initiate an LLC/SNDCP XID negotiation.

13. The MS updates the routing area.

14. After receiving the PS Handover Complete message with Request for Inter RAT Handover Info setting to 1, the target SGSN returns a PS Handover Complete Acknowledge message, which carries the INTER RAT HANDOVER INFO. If the target SGSN cannot identify the Request for Inter RAT Handover Info, it does not return the PS Handover Complete Acknowledge message. If the target BSS receives the PS Handover Complete Acknowledge message, it sets the IE "Reliable INTER RAT HANDOVER" in the PS Handover Required message to 1. If the PS Handover Complete Acknowledge message is not received, the target BSS sets the IE "Reliable INTER RAT HANDOVER" to 0.

15. The source MME requests the source eNodeB and source serving GW to release related resources. If indirect forwarding was applied, the source MME release temporary resources used for indirect forwarding.

GSM BSS Interoperability Between GSM and LTE 6 SRVCC


6-1

6 SRVCC 6.1 Overview This section describes the feature GBFD-511309 SRVCC.

In Single Radio Voice Call Continuity (SRVCC), speech services are implemented in LTE PS network, so technically the SRVCC feature can be regarded as a real LTE VoIP technique.

The SRVCC feature enables the speech services that are carried on the IP Multimedia Subsystem (IMS) to be handed over to the GSM, maintaining the speech services.

The SRVCC feature supports only handover of speech services from LTE to GSM that covers the same area.

The SRVCC feature is activated when SRVCCHOEN is set to YES. In addition, the parameters LTESAIMCC, LTESAIMNC, LTESAILAC, and LTESAISAC must be set based on the setting of these parameters on the MSC server.

The following figure shows the Network Elements (NEs) involved in SRVCC. As shown in the figure, the IMS must be deployed at the Core Network (CN) and must be capable of providing speech services to implement the SRVCC feature. With the assistance of the IMS in VoIP speech service routing, control, and triggering, and the assistance of the Mobile Management Entity (MME) in handover control, the speech service in the LTE network can be handed over to the GSM/UMTS smoothly.

Figure 6-1 NEs involved in SRVCC

6.2 Procedure On the BSS side, the SRVCC procedure is similar to the handover preparation and handover execution of an incoming GSM inter-RAT handover. The difference is that in SRVCC procedure, the source cell SAI carried in the Handover Request is the default SAI configured in SRVCC. If the source cell SAI carried in the Handover Request is not the default SAI configured in SRVCC, the BSC handles the SRVCC as a normal incoming inter-RAT handover and sends a handover response message to the MSC.

Figure 6-2 shows the procedure of LTE-to-GSM SRVCC.



6-2

Figure 6-2 SRVCC from LTE to GSM without DTM/PSHO support

1. The source LTE makes the decision to perform a handover to the GSM based on measurement reports from the MS.

2. The source LTE sends a Handover Required message that carries the Source to Target Transparent Container to the MME. This message also shows that the SRVCC procedure is applied.

3. The MME separates speech data from other data based on the QoS Class Identifier (QCI) and the SRVCC handover indication. Then, the MME sends a Forward Relocation Request message to the MSC server to start a PS handover for speech data. The Forward Relocation Request message carries the VDN, MSISDN, Source to Target Transparent Container, and MM Context.

4. The MSC server handles the handover as an inter-MSC CS handover, and sends a Prepare Handover Request message to the target MSC.



6-3

5. The target MSC starts resource reservation in the target BSS cell. That is, the MSC sends a Handover Request message to the BSS, and then the BSS responds with a Handover Acknowledge message.

6. After resources are reserved in the target BSS cell, the target MSC sends a Prepare Handover Response message to the source MSC server.

7. The source MSC server sets up the circuit connection between the target MSC and the MGW associated with the MSC server.

8. The MSC server sends the ISUP IAM (VDN) to initiate the session transfer from IP Multimedia Subsystem (IMS) to CS domain.

9. The MSC server sends the MME a Forward Relocation Response message that carries the Target to Source Transparent Container, which contains resource information of the target cell.

10a. The source MME sends the source LTE a Handover Command message that carries the Target to Source Transparent Container to the source LTE. This handover involves only CS services.

10b. The source MME instructs the serving GW to release all S1-U bearers of the EPS Bearer to deactivate CS bearers and keep the non-GBR bearers. After that, the MME does not send paging messages to the MS after receiving the paging data from the serving GW.

11. The source LTE sends a Handover from LTE Command message to instruct the MS to start handover.

12. The MS starts to access the GSM cell.

13. After detecting that the MS has accessed the target cell, the target BSS sends a Handover Complete message the target MSC.

14. The target MSC sends an SES (Handover Complete) message to the MSC server.

15. The circuit connection between the target MSC and the MGW associated with the MSC Server is released. For example, the target MSC sends the MSC server an ISDN User Part (ISUP) Answer message.

16. The MSC server sends a Forward Relocation Complete message to inform the source MME that the MS has accessed the target cell. The source MME then responds with a Forward Relocation Complete Acknowledge message.

17. The MSC server may start the MAP Update Location procedure to update the MS location information in the HSS or HLR.

GSM BSS Interoperability Between GSM and LTE 7 CS Fallback


7-1

7 CS Fallback 7.1 Overview This chapter describes the feature GBFD-511313 CSFB.

If the CN is not deployed with an IMS, the LTE network fails to carry CS services through VoIP. The Circuit Switch FallBack (CSFB) feature enables an MS camping on the LTE network to access the GSM network and then process the Mobile Originated (MO) or Mobile Terminated (MT) CS services. CSFB optimizes the migration of an MS to a GSM cell through PS handover or PS eNACC.

In the initial stage of LTE deployment, the operator can use CSFB to carry CS services in the existing GSM network and carry PS services in the LTE network. The CSFB feature is available only when the LTE and GSM networks cover the same area.

If this feature is used together with the feature GBFD-511312 Fast LTE Reselection at 2G CS Call Release, the MS migrated to a GSM cell by CSFB can quickly return to the LTE cell after the CS call is terminated, ensuring the high PS service quality.

Figure 7-1 shows the NEs involved in CSFB.

Figure 7-1 NEs involved in CSFB

MS MSC sever

GERAN

SGSN

E-UTRAN MME

A

S3

Gs

GbUm

LTE-Uu

S1-MMESGs

To enable CSFB, the SGs interface between the MSC server and the MME must be configured. The SMS and LCS are processed in the LTE network after the SGs interface is configured.

7.2 Procedure The call procedure in CSFB is similar to that when the MS camps on a GSM cell. The differences are as follows:

In CSFB, an MS camps on an LTE cell firstly, and is migrated to a GSM cell using CSFB if the MS starts an MO CS call or receives a CS paging message. An MS can be migrated to a GSM cell through eNACC or PS handover.

In MSC pool networking mode, the BSC do as follows after receiving a message in response to the CSFB paging message: − If the response message carries the Temporary Mobile Subscriber Identity (TMSI), that is, the CSFB paging message from the eNodeB carries the S-TMSI, the BSC obtains the signaling point of the MSC according to the Network Resource Identifier (NRI) carried in the TMSI and forwards the response message to the MSC.



7-2

− If the response message carries the International Mobile Subscriber Identity (IMSI), that is, the CSFB paging message from the eNodeB carries the IMSI, and if CSFBPAGRSPBCSWITCH is set to YES, that is, the MSC supports roaming retry, the BSC selects an MSC from the MSC pool and forwards the response to the MSC. If CSFBPAGRSPBCSWITCH is set to NO, the BSC discards the response message.

CSFB can be triggered in the following scenarios:

An MS in idle mode or during a PS service originates a CS call in an LTE network. In this case, the eNodeB initiates CSFB to migrate the MS to a GSM cell through cell reselection or PS handover to proceed with the call procedure. The involved scenarios are as follows: − Mobile Originated Call (MOC) CSFB (PS handover) − MOC CSFB (cell reselection)

An MS in idle mode receives a CS Paging Notification message in an LTE network. In this case, the eNodeB initiates CSFB to migrate the MS to a GSM cell through cell reselection or PS handover to proceed with the call procedure. The involved scenario is as follows:

Mobile Terminated Call (MTC) CSFB (idle mode) An MS during a PS service receives a CS Paging Notification message in an LTE network. In this case, the eNodeB initiates CSFB to migrate the MS to a GSM cell through cell reselection or PS handover to proceed with the call procedure. The involved scenarios are as follows: − MTC CSFB (connected mode + PS handover) − MTC CSFB (connected mode + cell reselection)

7.2.1 MOC CSFB (PS Handover) The procedure of the CSFB for MOCs through PS handover is shown in Figure 7-2. The procedure for MSs in idle mode is similar to that for MSs in connected mode.

Figure 7-2 Procedure of MOC CSFB through PS handover



7-3

1a. The MS sends an Extended Service Request message that carries the CS Fallback Indicator to inform the MME to initiate CSFB. The MS only transmits this request if it is attached to CS domain (with a combined EPS/IMSI Attach) and cannot initiate an IMS voice session (because for example the MS is not IMS registered or IMS voice services are not supported by the serving IP-CAN, home PLMN or MS).

1b. The MME sends an S1-AP Request message that carries the CS Fallback indicator to the eNodeB. This message indicates to the eNodeB that the MS should be moved to GSM.

2. The eNodeB may optionally solicit a measurement report from the MS to determine the target GSM cell to which PS handover will be performed.

3. The eNodeB initiates a PS handover from LTE to GSM.

4. The MS originates an MOC setup procedure in the target GSM cell. After the main DCCH is set up, the MS enters the DTM or Dedicated (not supporting DTM) mode.

5. If the MSCs that the MS is attached in the LTE cell before and after CSFB are different and no location area update is performed, the MSC rejects the MOC. After receiving the CM Service Reject message, the MS triggers location area update (LAU) or combined routing area (RA)/location area (LA) update.

6. The MS initiates a CS call setup procedure.

7. The MS camps on the GSM cell, and the PS handover is complete. After that, the MS initiates an RAU procedure to recover PS services (if the MS supports DTM) or suspends PS services (if the MS does not support DTM).

If the MS remains in the GSM cell after the CS voice call is terminated, the MS performs normal mobility management (MM) procedures.

7.2.2 MOC CSFB (Cell Reselection) The procedure of the CSFB for MOCs through cell reselection is shown in Figure 7-3.



7-4

Figure 7-3 Procedure of MOC CSFB through cell reselection

1a. The MS sends an Extended Service Request message that carries the CS Fallback Indicator to inform the MME to initiate CSFB. The MS only transmits this request if it is attached to the CS domain (with a combined EPS/IMSI Attach) and cannot initiate an IMS voice session (because for example the MS is not IMS registered or IMS voice services are not supported by the serving IP-CAN, home PLMN or MS).

1b. The MME sends an S1-AP Request message that carries the CS Fallback indicator to the eNodeB. This message indicates to the eNodeB that the MS should be moved to GSM.

2. The eNodeB may optionally solicit a measurement report from the MS to determine the target GSM cell to which the redirection procedure will be performed.

3. The eNodeB triggers cell reselection from LTE to GSM.

3a. If both the MS and the network support cell reselection from LTE to GSM, the eNodeB sends a MobilityFromEUTRACommand message to the MS. If the eNACC procedure is applied, the MobilityFromEUTRACommand message indicates that the purpose is cellChangeOrder. In addition, the message carries the GSM cell ID and the SI including SI1, SI3, and SI13.

3b. If the MS or the network does not support cell reselection from LTE to GSM, the eNodeB sends an RRC connection release message to redirect the MS to a GSM or UMTS cell.

4-5. The eNodeB releases S1 MS Context.

6. The MS accesses the target GSM cell and triggers LAU or combined RA/LA update if the location area is changed.

7a-8. If the MS does not support DTM, it suspends PS services.

9. The MS initiates a CS call setup procedure.

10a-10c. If the MSC that the MS is attached in the LTE cell before CSFB is different from the MSC that the MS is attached in the GSM cell after CSFB, and the MS has not performed LAU, the MSC rejects



7-5

the MOC. After receiving the CM Service Reject message, the MS triggers LAU, and then proceeds with the call procedure.

11. After the CS call is complete, the MS initiates RAU to recover PS services if there are PS services being suspended.

If the MS remains on GSM after the CS voice call is terminated, the MS performs normal mobility management (MM) procedures.

7.2.3 MTC CSFB (Idle Mode) Figure 7-4 Procedure of MTC CSFB through PS handover for MSs in idle mode

1-6. The MS in an LTE cell receives a paging message that carries an S-TMSI or IMSI.

1a. The MS sets up an RRC connection and sends an Extended Service Request message that carries the CS Fallback Indicator to inform the MME to initiate CSFB. The MME sends an SGs Service Request message to the MSC, requesting the MSC to stop retransmitting the SGs interface Paging message.

7b. The MME sends an Initial MS Context Setup message that carries the CS Fallback indicator to the eNodeB. This message indicates to the eNodeB that the MS should be moved to GSM. After receiving the Initial MS Context Setup message, the eNodeB does as follows:

8a. If both the MS and the network support PS handover, the eNodeB triggers the LTE-to-GSM PS handover. The eNodeB may optionally solicit a measurement report from the MS to determine the target GSM cell to which the PS handover procedure will be performed

8a. If the MS or the network does not support PS handover, the eNodeB triggers the LTE-to-GSM cell reselection.

If both the MS and the network support cell reselection from LTE to GSM, the eNodeB sends a MobilityFromEUTRACommand message to the MS. If the eNACC procedure is applied, the



7-6

MobilityFromEUTRACommand message indicates that the purpose is cellChangeOrder. In addition, the message carries the GSM cell ID and the SI including SI1, SI3, and SI13.

If the MS or network does not support cell reselection from LTE to GSM, the eNodeB sends an RRC connection release message to redirect the MS to a GSM cell.

8c. The MS accesses the target GSM cell and triggers LAU or combined RA/LA update if it cannot decide whether the location area is changed.

8d. If the MS does not initiate the LAU procedure, it sends a paging response message to the MSC through the BSS.

9a. After the LAU or after the MSC receives a paging response, the MSC starts the CS call setup if the call is allowed to access the location area.

9b. If the MS is not registered in the MSC or the MS is not allowed to access the location area, the MSC rejects the paging response and releases the A interface links. Then, the BSC releases the signaling channel on the air interface. After the signaling channel on the air interface is released, the MS obtains the LAI and performs LAU.


7.2.4 MTC CSFB (Connected Mode + PS Handover) Figure 7-5 Procedure of MTC CSFB through PS handover for MSs in connected mode

1a. The MS in connected mode receives a CS Paging Notification message.

1b./1d. The MS sends an Extended Service Request message that carries the CS Fallback Indicator to inform the MME to initiate CSFB. Then, the MME sends an S1-AP Request message that carries the



7-7

CS Fallback indicator to the eNodeB. This message indicates to the eNodeB that the MS should be moved to GSM.

1c. If the MS rejects the CSFB procedure, the MME sends a Paging Reject message to inform the MSC to stop paging and CSFB.

2. The eNodeB may optionally solicit a measurement report from the MS to determine the target GSM cell to which the PS handover will be performed.

3. The eNodeB initiates a PS handover from LTE to GSM.

4a. The MS accesses the target GSM cell and triggers LAU or combined RA/LA update if it cannot decide whether the location area is changed.

4b. If the MS does not initiate the LAU procedure, it sends a paging response message to the MSC through the BSS.


5b. If the MS is not registered in the MSC or the MS is not allowed to access the location area, the MSC rejects the paging response and releases the A interface links. Then, the BSC releases the signaling channel on the air interface. After the signaling channel on the air interface is released, the MS obtains the LAI and performs LAU.

6. The MS continues to perform other operations. If the MS does not support DTM, it suspends PS services.




7-8

7.2.5 MTC CSFB (Connected Mode + Cell Reselection) Figure 7-6 Procedure of MTC CSFB through cell reselection for MSs in connected mode

1a. The MS in connected mode receives a CS Paging Notification message.

1b./1d. The MS sends an Extended Service Request message that carries the CS Fallback Indicator to inform the MME to initiate CSFB. Then, the MME sends an S1-AP Request message that carries the CS Fallback indicator to the eNodeB. This message indicates to the eNodeB that the MS should be moved to GSM.

1c. If the MS rejects the CSFB procedure, the MME sends a Paging Reject message to inform the MSC to stop paging and CSFB.

2. The eNodeB may optionally solicit a measurement report from the MS to determine the target GSM cell to which the redirection procedure will be performed.

3. The eNodeB triggers cell reselection from LTE to GSM.

3a. If the MS and network support cell reselection from LTE to GSM, the eNodeB sends a MobilityFromEUTRACommand message to the MS. If the eNACC procedure is applied, the MobilityFromEUTRACommand message indicates that the purpose is cellChangeOrder. In addition, the message carries the GSM cell ID and the SI including SI1, SI3, and SI13.



7-9

3b. If the MS or network does not support cell reselection from LTE to GSM, the eNodeB sends an RRC connection release message to redirect the MS to a GSM/UMTS cell.

4-5. The eNodeB releases S1 MS Context.

6. The MS accesses the target GSM cell and triggers LAU or combined RA/LA update if the location area is changed.

7a-8. If the MS does not support DTM, it suspends PS services.

9. If the MS does not initiate the LAU procedure, it sends a paging response message to the MSC through the BSS.


9b. If the MS is not registered in the MSC or the MS is not allowed to access the location area, the MSC rejects the paging response and releases the A interface links. Then, the BSC releases the signaling channel on the air interface.

9c. After the signaling channel on the air interface is released, the MS obtains the LAI and performs LAU. The LAU triggers the Roaming Retry procedure in the CN.

10a-10c. If the MSC that the MS is attached in the LTE cell before CSFB is different from the MSC that the MS is attached in the GSM cell after CSFB, and the MS has not performed LAU, the MSC rejects the MOC. After receiving the CM Service Reject message, the MS triggers LAU, and then proceeds with the call procedure.

After the CS call is complete, the MS initiates RAU to recover PS services if there are PS services being suspended.


GSM BSS Interoperability Between GSM and LTE 8 Engineering Guidelines


8-1

8 Engineering Guidelines 8.1 Related Parameters in the System Information The setting of the parameters in SI affects the cell reselection between GSM and LTE. Assume that a telecom operator requires that MSs preferentially access LTE (when available), the telecom operator is advised to set THRPRISEARCH to 15 (the neighboring LTE cell search is always performed) and set EUTRANPRI greater than GERANPRI.

LTE cells can be configured with same or different EUTRANPRI values, but EUTRANPRI cannot be set to the same value as GERANPRI or UTRANPRI.

8.2 Neighboring LTE Cell Configuration To enable GSM/LTE interoperability, neighboring LTE cells must be configured. A GSM cell can be configured with a maximum of 64 neighboring LTE cells. These neighboring cells can work in a maximum of eight frequencies, and a maximum of 16 cells can work in a same frequency.

If SPTRESEL is set to UNSUPPORT for a neighboring LTE cell of a GSM cell, the cell reselection from the source GSM cell to this LTE cell is not allowed. You need to set SPTRESEL for each neighboring LTE cell that does not support cell reselection.

If SPTRESEL is set to SUPPORT for a neighboring LTE cell of a GSM cell, the cell reselection from the source GSM cell to this LTE cell is allowed.

8.3 Optimized Inter-RAT Cell Reselection Between GSM and LTE The Fast LTE Reselection at 2G CS Call Release feature accelerates the cell reselection to LTE. This feature is activated when SPTRAPIDSEL is set to SUPPORT. MSs in connected mode in a GSM cell cannot measure neighboring LTE cells. Therefore, the BSC does not select a neighboring cell based on measurement reports but sends a list of neighboring LTE cells whose SPTRAPIDSEL is set to SUPPORT in the IE "cell selection indicator after release of all TCH and SDCCH" of the CHANNEL RELEASE message.

The eNACC Between GSM and LTE feature helps reduce the service interruption duration during the LTE-to-GSM PS cell reselection or CSFB for MSs in connected mode. During the eNACC procedure, the RIM procedure must be supported on the Gb interface. The BSC is configured with the RIMSUP parameter of the network service entity (NSE), indicating whether the NSE supports the RIM procedure.

8.4 GSM/LTE Inter-RAT NC2 and PS Handover GSM/LTE Inter-RAT PS handover needs the support of MS, eNodeB, BSC, and CN.

NC2 cell reselection is enabled when NCO is set to NC2.

PS handover is enabled when PSHOSUP is set to YES. You are also advised to set PFCSUP to YES. After PS handover is enabled, you can set SPTLTEOUTBSCPSHO to SUPPORT to enable the GSM-to-LTE PS handover.

If NCO is set to NC0 or NC1, NACC is applied, and NACCSPT must be set to YES. If NCO is set to NC2, the BSC makes PS handover decision based on measurement reports from the MS and indications from the SGSN.

After PS handover is enabled, you can enable the LTE-to-GSM PS handover by setting SPTLTEINBSCPSHO to SUPPORT.

GSM BSS Interoperability Between GSM and LTE 8 Engineering Guidelines


8-2

After NC2 cell reselection and PS handover are enabled, you can enable different types of cell reselection and handovers as follows:

To enable quality-based NC2 cell reselection and quality-based handover, set URGENTRESELALLOW to PERMIT.

To enable load-based NC2 cell reselection and load-based handover, set LOADRESELALLOW to PERMIT.

To enable coverage-based NC2 cell reselection and coverage-based handover, set NORMALRESELALLOW to PERMIT.

To enable priority-based NC2 cell reselection and priority-based handover, set GERANPRI and EUTRANPRI. You can also set NCELLPRI for each cell to enable neighboring cell priority-based NC2 cell reselection and neighboring cell priority-based PS handover. When NCELLPRI is set to an invalid value, the value of GERANPRI or EUTRANPRI (depends on the RAT of the cell) is used as the value of this parameter.

After PS handover is enabled, you can enable quick PS handover by setting SPTBLINDHO to SUPPORT. You can set SPTBLINDHO of only one LTE cell to SUPPORT, and NCELLPRI of this cell must be set to a greatest value.

8.5 CS Service Connectivity The SRVCC feature enables the speech services that are carried on the IMS to be handed over to the GSM, maintaining the speech services. The SRVCC feature is activated when SRVCCHOEN is set to YES. In addition, the default value of Service Area Identifier (SAI), that is, LTESAIMCC, LTESAIMNC, LTESAILAC, and LTESAISAC, must be set based on the setting on the MSC server.

If the CN is not deployed with an IMS, CS services are not supported in the LTE network. The CSFB feature enables an MS camping on the LTE network to access the GSM network to process the MO or MT CS services.

To enable CSFB, the SGs interface between the MSC server and the MME must be configured. CSFB optimizes the migration of an MS to a GSM cell through PS handover or PS eNACC. If CSFB is used together with the feature GBFD-511312 Fast LTE Reselection at 2G CS Call Release, the MS migrated to a GSM network by CSFB can quickly return to the LTE cell after the CS call is terminated, ensuring the high PS service quality.

In MSC pool networking mode, BSC does as follows after receiving a CSFB paging response message, − If the paging response message carries the TMSI, the BSC obtains the MSC signaling point according to the NRI in the TMSI and then sends the paging response message to the MSC.

− If the paging response message carries the IMSI, and if CSFBPAGRSPBCSWITCH is set to YES, that is, the MSC supports roaming retry, the BSC selects an MSC from the MSC pool and forwards the response message to the MSC. If CSFBPAGRSPBCSWITCH is set to NO, the BSC discards the response message.

GSM BSS Interoperability Between GSM and LTE 9 Parameters


9-1

9 Parameters Figure 9-1 Parameter description

Parameter ID NE MML Command Description

NCELLPRI BSC6900 ADD G2GNCELL(Optional) MOD G2GNCELL(Optional)

Meaning: Priority of the neighboring 2G cell. Value 0 indicates the lowest priority, and value 7 indicates the highest priority. Value 255 is invalid. GUI Value Range: 0~7, 255 Actual Value Range: 0~7, 255 Unit: None Default Value: 255

NCELLPRI BSC6900 ADD G3GNCELL(Optional) MOD G3GNCELL(Optional)

Meaning: Priority of the neighboring 3G cell. Value 0 indicates the lowest priority, and value 7 indicates the highest priority. Value 255 is invalid. GUI Value Range: 0~7, 255 Actual Value Range: 0~7, 255 Unit: None Default Value: 255

NCELLPRI BSC6900 ADD GLTENCELL(Optional) MOD GLTENCELL(Optional)

Meaning: Priority of the neighboring LTE cell. The priority is used in cell reselection and PS handover, which are based on priority of the neighboring cell. Value 0 indicates the lowest priority, and value 7 indicates the highest priority. Value 255 GUI Value Range: 0~7, 255 Actual Value Range: 0~7, 255 Unit: None Default Value: 255

LTECELLRESELEN

BSC6900 SET GCELLHOBASIC(Optional)

Meaning: Whether to allow cell reselection from GSM to LTE. GUI Value Range: NO(No), YES(Yes) Actual Value Range: NO, YES Unit: None Default Value: NO



9-2


THRPRISEARCH BSC6900 SET GCELLPRIEUTRANSYS(Optional)

Meaning: When the receive level of the serving cell is higher than the value of this parameter, the MS does not search for neighboring cells in UTRAN or EUTRAN whose priority is lower than the GERAN priority. The values of this parameter correspond to the followin GUI Value Range: 0~15 Actual Value Range: 0~15 Unit: None Default Value: 15

RIMSUP BSC6900 ADD NSE(Optional) MOD NSE(Optional)

Meaning: Whether to support RAN information management (RIM). IN the RIM procedure, RANs (Radio Access Network) can exchange messages through the core network. GUI Value Range: NO(No Support), YES(Support) Actual Value Range: NO, YES Unit: None Default Value: NO

EUTRANPRI BSC6900 SET GCELLPRIEUTRANSYS(Optional)

Meaning: Priority of EUTRAN. Value 0 indicates the lowest priority, and value 7 indicates the highest priority. GUI Value Range: 0~7 Actual Value Range: 0~7 Unit: None Default Value: 0

UTRANQRXLEVMIN

BSC6900 SET GCELLPRIEUTRANSYS(Optional)

Meaning: Used to calculate the RSCP threshold for the target cell when a priority-based decision to perform GSM to UTRAN cell reselection is made. The values of this parameter correspond to the following decibel values: 0: -119 dBm, 1: -117 dBm, 2: -115 dBm, .. GUI Value Range: 0~31 Actual Value Range: 0~31 Unit: None Default Value: 9



9-3


THREUTRANHIGH


Meaning: If the measured RSRP value of one or more neighboring EUTRAN cells is higher than the value of this parameter, the MS is allowed to reselect a neighboring cell in EUTRAN whose priority is higher than the GERAN priority. The values of this parameter corre GUI Value Range: 0~31 Actual Value Range: 0~31 Unit: None Default Value: 20

THREUTRANLOW


Meaning: If the receive levels of the serving cell and all neighboring GSM cells are lower than "Low GSM Threshold Based on Priority", and if the measured RSRP value of one or more neighboring EUTRAN cells is higher than the value of this parameter, the MS is allo GUI Value Range: 0~31 Actual Value Range: 0~31 Unit: None Default Value: 20

HPRIO BSC6900 SET GCELLPRIEUTRANSYS(Optional)

Meaning: The MS is allowed to reselect a neighboring cell in UTRAN or EUTRAN whose priority is lower than the GERAN priority when all the following conditions are fulfilled: 1)The receive levels of the serving cell and all neighboring GSM cells are lower than "Lo GUI Value Range: 0~3 Actual Value Range: 0~3 Unit: None Default Value: 0

TRESEL BSC6900 SET GCELLPRIEUTRANSYS(Optional)

Meaning: Period during which the measured RSCP (or RSRP) value must meet the cell reselection condition when a priority-based decision to perform a GSM to UTRAN (or EUTRAN) cell reselection is made. The values of this parameter correspond to the following time va GUI Value Range: 0~3 Actual Value Range: 0~3 Unit: None Default Value: 0



9-4


GERANPRI BSC6900 SET GCELLPRIEUTRANSYS(Optional)

Meaning: Priority of GERAN. Value 0 indicates the lowest priority, and value 7 indicates the highest priority. GUI Value Range: 0~7 Actual Value Range: 0~7 Unit: None Default Value: 7

THRGSMLOW BSC6900 SET GCELLPRIEUTRANSYS(Optional)

Meaning: If the receive levels of the serving cell and all neighboring GSM cells are lower than the value of this parameter, the MS is allowed to reselect a neighboring cell in UTRAN or EUTRAN whose priority is lower than the GERAN priority. The values of this par GUI Value Range: 0~15 Actual Value Range: 0~15 Unit: None Default Value: 0

EUTRANQRXLEVMIN


Meaning: Used to calculate the RSRP threshold for the target cell when a priority-based decision to perform GSM to EUTRAN cell reselection is made. The values of this parameter correspond to the following decibel values: 0: -140 dBm, 1: -138 dBm, 2: -136 dBm, . GUI Value Range: 0~31 Actual Value Range: 0~31 Unit: None Default Value: 9

SPTRAPIDSEL BSC6900 ADD GLTENCELL(Optional) MOD GLTENCELL(Optional)

Meaning: Whether a quick reselection from the source GSM cell to the target LTE cell is allowed. Quick reselection from the source GSM cell to the target LTE cell indicates that the CHANNEL RELEASE message sent to the MS carries the information abo GUI Value Range: UNSUPPORT(UNSUPPORT), SUPPORT(SUPPORT) Actual Value Range: UNSUPPORT, SUPPORT Unit: None Default Value: UNSUPPORT



9-5


QPEUTRAN BSC6900 SET GCELLPRIEUTRANSYS(Optional)

Meaning: Threshold of signal level at which a mobile station starts to search for the target EUTRAN cell during cell reselection. In packet mode, if this parameter is set to a value lower than 7, the mobile station starts to search for an EUTRAN cell when the sign GUI Value Range: 0~15 Actual Value Range: 0~15 Unit: None Default Value: 15

BESTEUTRANCELLNUM


Meaning: Number of neighboring EUTRAN cells that need to be contained in the measurement report sent by an MS. GUI Value Range: 0~3 Actual Value Range: 0~3 Unit: None Default Value: 2

THREUTRANRPT


Meaning: A measurement report is valid only when the receive level of an LTE cell in the measurement report exceeds the value of this parameter. The values of this parameter correspond to the following decibel values: 0: 0 dB, 1: 6 dB, ..., 6: 36 dB, 7: positive GUI Value Range: 0~7 Actual Value Range: 0~7 Unit: None Default Value: 0

TrafficReselAllow BSC6900 SET GCELLNC2PARA(Optional)

Meaning: Whether to allow the cell service reselection. When this parameter is set to "PERMIT", the radio access technology (RAT) of the candidate cell is involved in the algorithm for cell service reselection. GUI Value Range: FORBID(Forbid), PERMIT(Permit) Actual Value Range: FORBID, PERMIT Unit: None Default Value: PERMIT



9-6


URGENTRESELALLOW

BSC6900 SET GCELLNC2PARA(Optional)

Meaning: Whether to allow cell urgent reselection. If this parameter is set to PERMIT and [NC2 Load Reselection Switch is set to Support, the load of the target cell is involved in the algorithm for NC2 cell reselection. GUI Value Range: FORBID(Forbid), PERMIT(Permit) Actual Value Range: FORBID, PERMIT Unit: None Default Value: PERMIT

CELLRXQUALWORSENRATIOTHRSH


Meaning: The number of times that the downlink transmission quality of the MS is lower than the transmission quality threshold of the MS ("EDGE GMSK Quality Threshold", "EDGE 8PSK Quality Threshold", or "GPRS Quality Threshold" by TBF type) is calculated accumulat GUI Value Range: 0~100 Actual Value Range: 0~100 Unit: % Default Value: 30

LOADRESELALLOW


Meaning: Whether to allow the cell load reselection. If this parameter is set to PERMIT and "NC2 Load Reselection Switch" is set to Support, the load of the target cell is involved in the algorithm for NC2 cell reselection. GUI Value Range: FORBID(Forbid), PERMIT(Permit) Actual Value Range: FORBID, PERMIT Unit: None Default Value: PERMIT

LOADRESELMAXRXLEV


Meaning: Threshold for allowing the MS to reselect a cell during load reelection. When the receive level of the serving cell is lower than this threshold, the load reselection is triggered. GUI Value Range: 0~63 Actual Value Range: 0~63 Unit: None Default Value: 40



9-7


LOADRESELSTARTTHRSH


Meaning: When the uplink load or downlink load of the cell exceeds this threshold, the load reselection decision is made. GUI Value Range: 0~100 Actual Value Range: 0~100 Unit: % Default Value: 85

NORMALRESELALLOW


Meaning: Whether to allow the cell normal reselection. If this parameter is set to PERMIT and "NC2 Load Reselection Switch" is set to Support, the load of the target cell is involved in the algorithm for NC2 cell reselection. GUI Value Range: FORBID(Forbid), PERMIT(Permit) Actual Value Range: FORBID, PERMIT Unit: None Default Value: PERMIT

RESELWATCHPERIOD


Meaning: The number of received Packet Measurement Report messages on the receive level of the serving cell is measured continuously. When the statistical value is greater than or equal to the value of this parameter, the normal reselection decision is made. GUI Value Range: 1~32 Actual Value Range: 1~32 Unit: None Default Value: 10

MINACCRXLEV BSC6900 SET GCELLNC2PARA(Optional)

Meaning: Minimum receive level for a neighbor cell to become a candidate cell during cell reselection. When the receive level of the serving cell is lower than the value of this parameter, it indicates that the normal cell reselection level is bad. In this case, t GUI Value Range: 0~63 Actual Value Range: 0~63 Unit: None Default Value: 15



9-8


RESELWORSENLEVTHRSH


Meaning: If the number of times when the receive level of the serving cell within "Normal Cell Reselection Watch Period" is lower than "Cell Reselection Level Threshold" is greater than the value of this parameter, the normal cell reselection is triggered. GUI Value Range: 1~32 Actual Value Range: 1~32 Unit: None Default Value: 1

SPTLTEOUTBSCPSHO

BSC6900 SET GCELLGPRS(Optional) Meaning: Whether to allow a PS handover from a GSM cell to an LTE cell GUI Value Range: UNSUPPORT(Not Support), SUPPORT(Support) Actual Value Range: UNSUPPORT, SUPPORT Unit: None Default Value: UNSUPPORT

PSHOSUP BSC6900 ADD NSE(Optional) MOD NSE(Optional)

Meaning: Whether to support PS Handover(PS HO). The PS HO is used to reduce the interval of the cell reselection of the MS. GUI Value Range: NO(No Support), YES(Support) Actual Value Range: NO, YES Unit: None Default Value: NO

NACCSPT BSC6900 SET GCELLGPRS(Optional) Meaning: Whether to support the network assisted cell change (NACC). The NACC is used in the network control modes NC0, NC1 or NC2. The NACC enables the network to notify the MS of the system information of the neighboring cell when the MS is in the packet transmi GUI Value Range: NO(No), YES(Yes) Actual Value Range: NO, YES Unit: None Default Value: NO



9-9


SPTBLINDHO BSC6900 ADD GLTENCELL(Optional) MOD GLTENCELL(Optional)

Meaning: Whether to support the blind handover from the source GSM cell to the target LTE cell. The blind handover from the source GSM cell to the target LTE cell indicates that the MS in the GSM cell is handed over to the target LTE cell without m GUI Value Range: UNSUPPORT(UNSUPPORT), SUPPORT(SUPPORT) Actual Value Range: UNSUPPORT, SUPPORT Unit: None Default Value: UNSUPPORT

SPTLTEINBSCPSHO

BSC6900 SET GCELLGPRS(Optional) Meaning: Whether to allow a PS handover from an LTE cell to a GSM cell GUI Value Range: UNSUPPORT(Not Support), SUPPORT(Support) Actual Value Range: UNSUPPORT, SUPPORT Unit: None Default Value: UNSUPPORT

SRVCCHOEN BSC6900 SET GCELLHOBASIC(Optional)

Meaning: This parameter indicates whether the SRVCC handover is supported. If this parameter is set to "YES", the speech call handled by the IMS can be handed over a GSM cell. In this manner, the continuity of the speech service is maintained. GUI Value Range: NO(No), YES(Yes) Actual Value Range: NO, YES Unit: None Default Value: NO

LTESAIMCC BSC6900 SET GCELLHOBASIC(Optional)

Meaning: If SRVCC handover is allowed and the source cell ID type in the incoming BSC handover request message is SAI and the values of "LTE SAI MCC","LTE SAI MNC","LTE SAI LAC","LTE SAI SAC" in the message are consistent with those configured at the BSC, then the GUI Value Range: None Actual Value Range: 3 digits Unit: None Default Value: None



9-10


LTESAIMNC BSC6900 SET GCELLHOBASIC(Optional)

Meaning: If SRVCC handover is allowed and the source cell ID type in the incoming BSC handover request message is SAI and the values of "LTE SAI MCC","LTE SAI MNC","LTE SAI LAC","LTE SAI SAC" in the message are consistent with those configured at the BSC, then the GUI Value Range: None Actual Value Range: 3 digits Unit: None Default Value: None

LTESAILAC BSC6900 SET GCELLHOBASIC(Optional)

Meaning: If SRVCC handover is allowed and the source cell ID type in the incoming BSC handover request message is SAI and the values of "LTE SAI MCC","LTE SAI MNC","LTE SAI LAC","LTE SAI SAC" in the message are consistent with those configured at the BSC, then the GUI Value Range: 1~65533, 65535 Actual Value Range: 1~65533, 65535 Unit: None Default Value: None

LTESAISAC BSC6900 SET GCELLHOBASIC(Optional)

Meaning: If SRVCC handover is allowed and the source cell ID type in the incoming BSC handover request message is SAI and the values of "LTE SAI MCC","LTE SAI MNC","LTE SAI LAC","LTE SAI SAC" in the message are consistent with those configured at the BSC, then the GUI Value Range: 0~65535 Actual Value Range: 0~65535 Unit: None Default Value: None

CSFBPAGRSPBCSWITCH

BSC6900 SET GCELLSOFT(Optional) Meaning: When the paging response message carries IMSI, the BSC cannot obtain the mapping between the IMSI and the MSC signaling point because the paging message is not delivered from the BSC. If this parameter is set to "YES", the BSC sends the paging response me GUI Value Range: NO(No), YES(Yes) Actual Value Range: NO, YES Unit: None Default Value: NO

GSM BSS Interoperability Between GSM and LTE 10 Counters


10-1

10 Counters For details, see the BSC6900 GSM Performance Counter Reference.

GSM BSS Interoperability Between GSM and LTE 11 Glossary


11-1

11 Glossary For the acronyms, abbreviations, terms, and definitions, see the Glossary.

GSM BSS Interoperability Between GSM and LTE 12 Reference Documents


12-1

12 Reference Documents [1] 3GPP TS 45.008 Radio subsystem link control [2] 3GPP TS 44.018 Mobile radio interface layer 3 specification; Radio Resource Control (RRC)

protocol [3] 3GPP TS 48.008 Mobile Switching Centre - Base Station system (MSC-BSS) interface; Layer 3

specification [4] BSC6900 Feature List [5] BSC6900 Optional Feature Description [6] GBSS Reconfiguration Guide [7] BSC6900 GSM Parameter Reference [8] BSC6900 GSM MML Command Reference [9] BSC6900 GSM Performance Counter Reference

interoperability between gsm and lte

Documents

huawei trademarks

huawei proprietary

gsm cell reselection

purchased scope

rat cell reselection

purchased products

usage scope

ltdigsm bss interoperability