GSMLTE Interoperability

GSM BSS

GSM/LTE Interoperability Feature Parameter Description

Copyright © Huawei Technologies Co., Ltd. 2011. All rights reserved.

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Issue 01 (2010-06-30) Huawei Proprietary and Confidential Copyright © Huawei Technologies Co., Ltd. i

GSM BSS GSM/LTE Interoperability Contents

Issue 01 (2010-06-30) Huawei Proprietary and Confidential Copyright © Huawei Technologies Co., Ltd.

ii

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

1.1 Scope ............................................................................................................................................ 1-1 1.2 Intended Audience ........................................................................................................................ 1-1 1.3 Change History.............................................................................................................................. 1-1

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

3 Measurement of Neighboring EUTRAN Cells ...................................................................3-1 3.1 Overview of Measurement of Neighboring EUTRAN Cells........................................................... 3-1 3.2 SI2quater....................................................................................................................................... 3-1 3.3 Measurement of Neighboring EUTRAN Cells of MS .................................................................... 3-1

4 Inter-RAT Cell Reselection between GERAN and EUTRAN...........................................4-1 4.1 Overview ....................................................................................................................................... 4-1 4.2 Cell Reselection from EUTRAN to GERAN .................................................................................. 4-1 4.3 Cell Reselection from GERAN to EUTRAN .................................................................................. 4-1 4.4 Fast Cell Reselection to EUTRAN Cells ....................................................................................... 4-2 4.5 eNACC .......................................................................................................................................... 4-2 4.6 eNC2 ............................................................................................................................................. 4-5

5 Inter-RAT Handover Between the GERAN and the EUTRAN ........................................5-1

6 SRVCC .........................................................................................................................................6-1

7 CS Fallback.................................................................................................................................7-1

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

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

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

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

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

GSM BSS GSM/LTE Interoperability 1 Introduction


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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 describes the functions of and technologies related to this feature, including measurement of neighboring Evolved Universal Terrestrial Radio Access Network (EUTRAN) cells, GSM/EDGE Radio Access Network (GERAN)/EUTRAN cell reselection, and inter-RAT PS (Packet Switched) handover.

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 This section provides information on the changes 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 GSM/LTE interoperability 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 issues are as follows:

01 (2010-06-30) Draft (2010-03-30)

01 (2010-06-30) This is the first release of GBSS12.0.

Compared with the draft (2010-03-30) of GBSS12.0, issue 01 (2010-06-30) of GBSS12.0 incorporates the changes described in the following table.

GSM BSS GSM/LTE Interoperability 1 Introduction


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Change Type Change Description Parameter Change

Feature Change

The cell reselection and handover algorithms are optimized. Priority of neighboring cells replaces RAT priority andcarries the highest weight in target cell selection.

The added parameters are listed as follows:

NCELLPRI for GERAN neighboring cells

NCELLPRI for UTRAN neighboring cells

NCELLPRI for EUTRAN neighboring cells

Editorial change

None None

Draft (2010-03-10) This is the draft release of GBSS12.0.

GSM BSS GSM/LTE Interoperability 2 Overview


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2 Overview With the development of radio access technologies, the GSM- or EDGE-based GSM/EDGE Radio Access Network (GERAN) is gradually evolving to the Universal Terrestrial Radio Access Network (UTRAN) with two technical standards, namely Wideband Code Division Multiple Access (WCDMA) and Time Division-Synchronous Code Division Multiple Access (TD-SCDMA). Currently, main-stream operators start to deploy LTE-based EUTRAN network.

EDGE is an enhancement of GSM. The WCDMA network is a FDD-based UTRAN, and the TD-SCDMA is a TDD-based UTRAN.

Actually, a continuous coverage cannot be achieved in the initial phase of EUTRAN deployment. To achieve good network coverage, operators can use their GERAN as a supplement for EUTRAN. Therefore, GSM/LTE interoperability is introduced to facilitate the co-existence of GERAN and EUTRAN. With this feature, the Mobile Station (MS) or User Equipment (UE) out of the EUTRAN coverage can be served by GERAN. In addition, MSs or UEs can be handed over from EUTRAN to GERAN when the traffic load in EUTRAN is heavy.

Huawei takes a phase-in strategy for EUTRAN deployment. In this manner, GERAN must co-exist with EUTRAN in earlier phases. The phase-in of the EUTRAN deployment is a process in which the EUTRAN is deployed at hot spots in the initial phase and then is expanded to other areas in later phases. In the phase for coverage in hot spots, the EUTRAN provides high-speed mobile broadband access services for subscribers, whereas the GERAN provides medium- or low-speed seamless broadband services and voice services in wider coverage. With such a network combination, operators can flexibly make operation policies and provide diverse services. In this way, operators can take full advantages of both EUTRAN and GERAN.

By means of GSM/LTE interoperability, a smooth evolution from GERAN to EUTRAN can be achieved, thus reducing the CAPEX for operators. For operators who deploy both EUTRAN and GERAN, GSM/LTE interoperability can be performed to make GERAN and EUTRAN work as a supplement to each other, thus expanding the network coverage and improving the service quality. For example, when a dual-mode MS moves to an area out of the EUTRAN coverage, it can reselect or be handed over to GERAN through GSM/LTE interoperability. This improves the user experience.

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

This document describes GSM/LTE interoperability. It covers the functions of and technologies related to this feature, including measurement of neighboring EUTRAN cells, GERAN/E-URAN cell reselection, and inter-RAT PS handover. The co-existence of the GERAN, UTRAN, and EUTRAN is not described in this document.

All the MSs involved in this feature are dual-mode MSs supporting both GERAN and EUTRAN. The FDD-based EUTRAN is not distinguished from the TDD-based EUTRAN in this document.

GSM BSS GSM/LTE Interoperability 3 Measurement of Neighboring EUTRAN Cells


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3 Measurement of Neighboring EUTRAN Cells 3.1 Overview of Measurement of Neighboring EUTRAN Cells The purpose of measuring neighboring EUTRAN cells is to obtain the signal quality of neighboring EUTRAN cells, ensuring that the MS can select a proper cell during cell reselection and handover.

To enable the MS to perform inter-RAT (GERAN/EUTRAN) cell reselection and handover, the system information needs to contain a list of neighboring EUTRAN cells and parameters related to EUTRAN cell reselection and handover. Based on the system information, the MS measures the signal quality of neighboring cells and performs cell reselection and handover. The system information is the System Information 2quater (SI2quater) sent on the Broadcast Control Channel (BCCH).

When EUTRAN is deployed with GERAN, the MS in idle or PS transfer mode can perform inter-RAT cell reselection; the MS in PS transfer mode can perform inter-RAT handovers.

The BSS controls the MS for neighboring cell measurement through parameter settings.

The following sections describe the functions and parameters of the S12quater, as well as how the MS in different states measures the neighboring EUTRAN cells.

3.2 SI2quater The system information SI2quater is sent to all the MSs in a cell through the BCCH. SI2quater includes the parameters related to the measurement and reporting of neighboring GSM and EUTRAN.

There are 504 Physical Layer Cell Identities (PCIDs) in the EUTRAN. SI2quater contains the EUTRAN frequencies and the prohibited PCIDs, which correspond to each frequency if they exist. These frequencies and prohibited PCIDs are recorded in the EUTRAN Cell Reselection List. A maximum of eight frequencies and related information are carried in the EUTRAN Cell Reselection List.

Priorities of neighboring cells are also broadcast to MSs through the SI2quater. The priority information is used for the algorithms of GERAN and EUTRAN cell reselection based on priority. In the SI2quater, the priority of neighboring GERAN cells must be different from the priority of neighboring EUTRAN cells. The priority of neighboring GERAN cells is determined by NCELLPRI for GERAN neighboring cells in neighboring cell relationship; the priority of neighboring EUTRAN cells is determined by NCELLPRI for EUTRAN neighboring cells in neighboring cell relationship.

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

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

3.3 Measurement of Neighboring EUTRAN Cells of MS The MS in a GERAN cell measures the signal quality of both neighboring GERAN cells and neighboring inter-RAT cells. Neighboring inter-RAT cells include neighboring UTRAN and EUTRAN cells. In this document, however, they refer only to neighboring EUTRAN cells. To reduce unnecessary measurements and power consumption of the MS, the BSS controls the MS for neighboring cell measurement using the parameter THRPRISEARCH.

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

GSM BSS GSM/LTE Interoperability 3 Measurement of Neighboring EUTRAN Cells


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If THRPRISEARCH is set to a value between 0 and 14, the measurement is triggered when the receive level of the serving cell is below THRPRISEARCH.

If THRPRISEARCH is set to 15, the MS measures the neighboring EUTRAN cells regardless of the receive level of the serving cell.

GSM BSS GSM/LTE Interoperability

4 Inter-RAT Cell Reselection between GERAN and EUTRAN


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4 Inter-RAT Cell Reselection between GERAN and EUTRAN 4.1 Overview Inter-RAT cell reselection between GERAN and EUTRAN involves the cell reselection from GERAN to EUTRAN and the cell reselection from EUTRAN to GERAN. Cell reselection is performed mainly by the MS.

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

For an MS in packet transfer mode, it can reselect an EUTRAN cell for data services through autonomous cell reselection, Network Assisted Cell Change (NACC), or Network Control Mode 2 (NC2). The autonomous cell reselection procedure in packet transfer mode is the same as that in idle mode. In NACC and NC2, the network controls the cell reselection so that the MS will camp on the desired cell.

The parameter LTECELLRESELEN determines whether cell reselection between GERAN and EUTRAN is enabled. When LTECELLRESELEN is set to No, the BSS does not send the neighboring EUTRAN cell list and the parameters related to Inter-RAT (GERAN/EUTRAN) cell reselection. In this situation, the MS in a GERAN cell cannot reselect an EUTRAN cell.

4.2 Cell Reselection from EUTRAN to GERAN When an MS moves into the GERAN coverage area and reselects a GERAN cell, the MS initiates the location area update in the GERAN network. The GERAN network handles the location area update regardless of whether the MS is from an EUTRAN cell or a GERAN cell. If another GERAN cell is available five seconds after the MS reselects a GERAN cell from the EUTRAN cell, the MS is not allowed to reselect an EUTRAN cell again.

For the BSS, the cell reselection procedure from EUTRAN to GERAN is the same as that between GERAN cells. Thus, it is not repeated in this document.

4.3 Cell Reselection from GERAN to EUTRAN The MS in a GERAN cell obtains the neighboring EUTRAN cell list and cell reselection parameters through System Information 2Quater (SI2quater), and then measures the neighboring EUTRAN cells according to the list and parameters.

The GERAN/EUTRAN cell reselection is priority-based when the MS is in idle mode or packet transfer mode. Based on the RAT priority and cell reselection parameters, the network controls the GERAN-to-UTRAN cell reselection of the MS.

Reference Signal Received Power (RSRP) is a measurement item commonly used during the measurement of neighboring EUTRAN cells. The parameter EUTRANQRXLEVMIN determines the lowest receive quality of an EUTRAN candidate cell for reselection. The parameter is used to ensure the signal quality of the candidate EUTRAN cell. An EUTRAN cell can serve as the candidate reselection cell only when the receive level of the EUTRAN cell is greater than EUTRANQRXLEVMIN. When EUTRANQRXLEVMIN is set to a relatively small value, the condition of inter-RAT cell reselection from GERAN to EUTRAN is easily met. Thus, the MS is likely to reselect an EUTRAN cell, and the number of MSs that camp on GERAN is decreased. Contrarily, when EUTRANQRXLEVMIN is set to a great value, the cell reselection condition is difficult to meet. In this way, the number of MSs that camp on GERAN is increased.




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Whether an MS reselects an EUTRAN neighboring cell depends on the priorities of GERAN and EUTRAN neighboring cells.

The priority of GERAN neighboring cells is lower than that of EUTRAN neighboring cells, that is, Priority of Neighboring Cell for GERAN neighboring cells is lower than that for EUTRAN neighboring cells in neighboring cell relationship. In this case, the MS, within a given time, reselects the EUTRAN cell that has the best RSRP measurement result if the following condition is met: RSRP > THREUTRANHIGH + EUTRANQRXLEVMIN

The priority of GERAN neighboring cells is higher than that of EUTRAN neighboring cells, that is, NCELLPRI for GERAN neighboring cells is higher than that for EUTRAN neighboring cells in neighboring cell relationship. In this case, the MS initiates a cell reselection from GERAN to EUTRAN if the receive levels of all GERAN cells are lower than THRGSMLOW. If an EUTRAN cell, within a given time, meets the following condition, the MS reselects the EUTRAN cell that has the best RSRP measurement result: RSRP > THREUTRANLOW + EUTRANQRXLEVMIN If such cell does not exist, the MS reselects the EUTRAN cell that meets the following condition: RSRP > THREUTRANLOW + EUTRANQRXLEVMIN

In case of a reselection attempt towards a barred EUTRAN cell, the MS abandons further reselection attempts towards this EUTRAN cell for a period of up to 20 minutes. In case the MS attempts reselection to an EUTRAN cell which is not suitable due to being part of the "list of forbidden tracking areas for roaming", and if the MS has not received the PCID to TA Mapping information element for the frequency of the cell, the MS may abandon further reselection attempts towards this EUTRAN cell and all other cells on the same frequency, for a period of up to 20 minutes. For details, see 3GPP TS 45.008.

4.4 Fast Cell Reselection to EUTRAN Cells Normally, after an MS terminates a call in a GSM cell, it camps on the GSM cell. When a neighboring EUTRAN cell meets the requirements for cell reselection, the MS camps on the EUTRAN cell after the cell reselection. Before initiating the cell reselection to the EUTRAN cell, the MS must receive system information and make the cell reselection decision.

Fast Cell Reselection to EUTRAN Cells is a feature through which the MS preferentially selects an EUTRAN cell during cell reselection. This feature accelerates the cell reselection from GSM to EUTRAN. In this way, the period of time during which the MS camps on the EUTRAN network is prolonged, and the revenue of operators in the EUTRAN network is increased.

The feature of Fast Cell Reselection to EUTRAN Cells is enabled only when the SPTRAPIDSEL parameter is set to SUPPORT. An MS can select an EUTRAN cell in a fast way 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 to the MS. The message carries the information element (IE) "cell selection indicator after release of all TCH and SDCCH". If the IE specifies the neighboring EUTRAN cell to be reselected, the MS attempts to reselect the specified cell as soon as possible. If the IE carries only the information about an EUTRAN frequency, the MS attempts to select a cell operating at the specified frequency as soon as possible.

After the DTM service releases an RR connection, the MS can reselect the specified EUTRAN 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 eNACC This section describes the feature GBFD-511308 eNACC Between GSM and LTE.




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The eNACC between the EUTRAN and GERAN, which is short for External Network Assisted Cell Change, functions as follows: In NC0/NC1 mode and packet transfer mode, if an MS determines to perform cell reselection, it requests the system information (SI) about the target cell from the BSC. Then, the BSC sends the requested SI through the Cell Change Notification (CCN) procedure. According to the SI about the target cell, the MS accelerates the packet service access in the target cell. In this way, the period of PS service disruption during a cell reselection is shortened.

An MS supports only the EUTRAN-to-GERAN eNACC but does not support the GERAN-to-EUTRAN eNACC. The EUTRAN-to-GERAN eNACC requires the BSC to support the RIM procedure over the Gb interface. That is, the parameter RIMSUP of the corresponding NSE must be set to YES on the BSC side.

Before an MS initiates an NACC procedure, the source BSC obtains the SI about the target cell from the target eNodeB. During the NACC procedure, the MS obtains the SI about the target cell directly from the source BSC, thus accelerating the packet service access in the target cell. Figure 4-1 shows the procedure of GERAN-to-EUTRAN NACC.

Figure 4-1 NACC procedure

The dashed lines in Figure 4-1 indicate optional procedures. A GERAN-to-EUTRAN NACC procedure is described as follows:

1. After the MS decides to initiate an autonomous cell reselection, it enters the CCN mode if the conditions of starting CCN are fulfilled. The MS does not change the cell immediately. Instead, it sends a PACKET CELL CHANGE NOTIFICATION message to the BSC to request the SI about the target cell. The conditions of starting CCN are as follows:

− Both the serving cell and the target cell support CCN. − The MS operates in NC0 or NC1 mode. − The MS is in packet transfer mode.




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When the MS is in CCN mode, the BSC cannot change the target cell that the MS determines to reselect by sending a PACKET CELL CHANGE ORDER message.

2. After receiving the PACKET CELL CHANGE NOTIFICATION message, the BSC sends a PACKET NEIGHBOR CELL DATA message to the MS. This message contains SI1, SI3, and SI13 of the target cell. Then, the BSC sends the MS a PACKET CELL CHANGE CONTINUE message, instructing the MS to continue the cell reselection.

3. After receiving the PACKET NEIGHBOR CELL DATA message, the MS saves the SI contained in this message. After receiving the PACKET CELL CHANGE CONTINUE message, the MS leaves the CCN mode, enters the NC0/NC1 mode and continues the cell reselection.

4. After the MS changes the cell, the MS uses the SI about the target cell in the initial packet access procedure.

5. If the target cell supports the PACKET SI STATUS procedure, and the MS does not have all SI about the target cell after the MS reselects the target cell, the MS sends a PACKET SI STATUS message to the BSC to request the required SI about the serving cell.

6. When the BSC receives the PACKET SI STATUS message, it sends a PACKET SERVING CELL DATA message to the MS. This message carries all required SI about the serving cell.

7. After receiving the PACKET SERVING CELL DATA message, the MS saves the SI contained in this message. With all SI about the serving cell, the MS can ensure the current packet service procedure and avoid service delay or disruption.

The RIM procedure shown in Figure 4-1 can be of the following types:

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

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

RAN SI Request Procedure Figure 4-2 shows the RAN SI request procedure.

Figure 4-2 RAN SI request procedure

BSC eNodeB

RAN-INFORMATION-REQUEST(Multiple Report)

RAN-INFORMATION(Multiple Report-Initial)

1. When the serving cell controlled by the source BSC is activated and the transmission link over the Gb interface is set up, the source BSC sends a RAN-INFORMATION-REQUEST (Multiple Report) message to the target eNodeB through the SGSN to request the setup of the RIM association and to request the SI about the target cell if the serving cell is configured with external neighboring cells and the RIM association between the serving cell and the target cell is not set up. A RIM association is an association between a cell under the target eNodeB and a cell under the source BSC that requests




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the application information about the target cell. A RIM association is identified by the ID of the source cell, ID of the target cell, and ID of the RIM application.

2. After the target eNodeB receives the RAN-INFORMATION-REQUEST (Multiple Report) message, it sends the source BSC a RAN-INFORMATION (Multiple Report-Initial) message, containing the information about the established RIM association and the SI (including SI1, SI3, and SI13) about the target cell.

3. After receiving the RAN-INFORMATION (Multiple Report-Initial) message, the source BSC saves the information about the RIM association and the SI about the target cell. The SI about the target cell is used in the subsequent NACC procedure.

RAN SI Update Procedure Figure 4-3 shows the RAN SI update procedure.

Figure 4-3 RAN SI update procedure

BSC eNodeB

RAN-INFORMATION(Multiple Report)

RAN-INFORMATION-ACK

1. After the RIM association is set up, the target eNodeB sends a RAN-INFORMATION (Multiple Report) message to the source BSC through the SGSN if the SI about the target cell is changed. This message contains the updated SI (including SI1, SI3, and SI13) about the target cell.

2. After receiving the RAN-INFORMATION (Multiple Report) message, the source BSC updates the SI about the target cell and sends a RAN-INFORMATION-ACK message to the target eNodeB. The SI about the target cell is used in the subsequent NACC procedure.

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

In a GSM and LTE hybrid network, the MS in a GSM cell periodically sends packet measurement reports to the BSC if the serving cell is in NC2 mode and packet connection state. On receiving the reports from the MS, the BSC triggers a network-controlled cell reselection based on the receive level, cell load, receive quality, priority of neighboring cells, and service priority indicated by the message from the core network. If the target cell is an LTE cell, the BSC triggers a procedure of eNC2 from GSM to LTE. Compared with the autonomous cell reselection of the MS, the network-controlled cell reselection comprehensively considers such factors as the receive level and load status in the serving cell and the neighboring cells so that the MS can reselect a proper cell. In this way, the loads in the cells can be balanced.

If the PDU (DL-UNITDATA PDU, CREATE-BSS-PFC PDU, or PS-HANDOVER-REQUEST PDU) sent from the SGSN to the BSS indicates a suitable RAT for the current service, the MS performs a service-based cell reselection during eNC2. Otherwise, the MS performs a quality-based, load-based, or




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coverage-based cell reselection. The target cell is the neighboring cell with the highest neighboring cell priority. Priority of a neighboring cell is determined by the setting of NCELLPRI in neighboring cell relationship. When the parameter is set to an invalid value (255), the priority of the neighboring cell depends on the setting of the parameter for neighboring cells of the same RAT, namely the setting of GERANPRI, UTRANPRI, or EUTRANPRI. For example, if NCELLPRI for a GERAN neighboring cell is set to an invalid value (255), the priority of the neighboring cell depends on the setting of the parameter for neighboring cells of the same RAT, namely the setting of GERANPRI.

The detailed cell reselection schemes are as follows:

If the PDU sent from the SGSN to the BSS indicates that the most suitable RAT for the current service is EUTRAN, then the MS is triggered to perform a service-based cell reselection and the target cell is an EUTRAN cell. If a suitable target cell is not found, then the MS performs a quality-based, load-based, or coverage-based cell reselection and the target cell is the GERAN neighboring cell with the highest neighboring cell priority.

If the PDU sent from the SGSN to the BSS does not indicate any suitable RAT for the current service, then the MS performs a quality-based, load-based, or coverage-based cell reselection and the target cell is the neighboring cell with the highest neighboring cell priority.

The BSC may find the Service UTRAN CCO IE 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 Service UTRAN CCO IE is of the highest priority. The Service UTRAN CCO IE, consisting of Service UTRAN CCO Value part and Service EUTRAN CCO Value part, indicates the most suitable RAT for the current service. Table 4-1 and Table 4-2 respectively describe the Service UTRAN CCO Value part and Service EUTRAN CCO Value part.

Table 4-1 Service UTRAN CCO Value part

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 Service EUTRAN CCO Value part

Coding Bits Semantic

01 Network initiated cell change order to EUTRAN or PS handover to EUTRAN procedure should be performed

10 Network initiated cell change order to EUTRAN or PS handover to EUTRAN procedure should not be performed

11 Network initiated cell change order to EUTRAN or PS handover to EUTRAN procedure shall not be performed

00 If received, shall be interpreted as no information available




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When the Service UTRAN CCO Value part is set to 000 or when the Service EUTRAN CCO Value part is set to 01, a service-based cell reselection is initiated. When the Service EUTRAN CCO Value part is set to 01, the MS can reselect the EUTRAN neighboring cell with the highest NCELLPRI and best signal quality. If the EUTRAN neighboring cell is not found, the MS proceeds to perform a quality-based, load-based, or coverage-based cell reselection. When Service UTRAN CCO Value part is not set to 000 and Service EUTRAN CCO Value part is not set to 01, the MS performs a quality-based, load-based, or coverage-based cell reselection according to NCELLPRI.

Quality-Based Cell Reselection Algorithm The URGENTRESELALLOW parameter specifies whether to allow the quality-based cell reselection algorithm. When the conditions of 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 receive quality 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 measurement period of the receive quality, 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 indicates the ratio of times of bad MS downlink quality to number of downlink quality measurement reports.

In a quality-based cell reselection, the EUTRAN neighboring cell with the highest NCELLPRI and the best signal quality is selected as the target cell. When the Service EUTRAN CCO Value part is set to 10 or 11, no EUTRAN cells can be selected as the target cell.

Load-Based Cell Reselection Algorithm The LOADRESELALLOW parameter specifies whether to allow the load-based cell reselection algorithm. When neither the triggering conditions of a service-based cell reselection are met nor the triggering conditions of a quality-based cell reselection are met, a load-based cell reselection is initiated to balance the load among the cells on the network. In a load-based cell reselection, some MSs in heavily-loaded cells are redirected to light-loaded cells. In addition, the MSs in neighboring cells should not be reselected to heavily-loaded cells. Figure 4-4 shows the load-based cell reselection.

Figure 4-4 Load-based cell reselection

Cell with heavy load



Cell with light load




To determine the traffic load of a cell, compare the channel multiplexing rate with the predefined threshold:

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




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If the average channel multiplexing rate of a cell is lower than LOADRESELRXTHRSH, the traffic load in the cell is light and some loads in heavily-loaded cells can be redirected to this cell.

In a load-based cell reselection, an MS with very high signal level cannot be reselected to a neighboring cell. By setting the LOADRESELMAXRXLEV parameter, only the MS whose signal level is lower than the LOADRESELMAXRXLEV parameter can be reselected to a neighboring cell. A load-based cell reselection can be initiated only when the serving cell is overloaded and the receive level in this cell is lower than the LOADRESELMAXRXLEV parameter.

In a load-based cell reselection, the EUTRAN neighboring cell with the highest NCELLPRI and the best signal quality is selected as the target cell. When the Service EUTRAN CCO Value part is set to 10 or 11, no EUTRAN cells can be selected as the target cell.

Coverage-Based Cell Reselection Algorithm The NORMALRESELALLOW parameter specifies whether to allow the coverage-based cell reselection algorithm. When the triggering conditions of a service-based cell reselection, quality-based cell reselection, and load-based cell reselection are not met, a coverage-based cell reselection is initiated to redirect the MS to a neighboring cell with higher signal strength if the receive level of the serving cell is lower than the MINACCRXLEV parameter for a period of time.

The P/N criterion should be met before a coverage-based cell reselection is initiated. That is, in the period specified by the RESELWATCHPERIOD parameter, if the number of times that the receive level of the serving cell is lower than the value of the MINACCRXLEV reaches the value of the RESELWORSENLEVTHRSH, a coverage-based cell reselection is initiated.

In a coverage-based cell reselection, the EUTRAN neighboring cell with the highest NCELLPRI and the best signal quality is selected as the target cell. When the Service EUTRAN CCO Value part is set to 10 or 11, no EUTRAN cells can be selected as the target cell.


5 Inter-RAT Handover Between the GERAN and the EUTRAN


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5 Inter-RAT Handover Between the GERAN and the EUTRAN 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, and GBFD-511306 GSM/LTE Service Based PS Handover.

The inter-RAT handover between the GERAN and the EUTRAN involves inter-RAT handover from the GERAN to the EUTRAN and inter-RAT handover from the EUTRAN to the GERAN. The inter-RAT handover from the GERAN to the EUTRAN is a handover in which the mobile terminal is handed over from a GERAN cell to an EUTRAN cell, and the inter-RAT handover from the EUTRAN to the GERAN is a handover in which the mobile terminal is handed over from an EUTRAN cell to a GERAN cell.

When NCO is set to NC0 or NC1 and the handover is an NACC-based handover, NACCSPT needs to be set to YES.

When NCO is set to NC2, the handover may be a service-based handover, quality-based handover, load-based handover, coverage-based handover, priority-based handover, or blind handover. Blind handover is a special type of inter-RAT handover from the GERAN to the EUTRAN. The target EUTRAN cell for blind handover is determined by the GERAN configuration. That is, no algorithm is required to select the target EUTRAN cell.

If the PDU (DL-UNITDATA PDU, CREATE-BSS-PFC PDU, or PS-HANDOVER-REQUEST PDU) sent from the SGSN to the BSS indicates a suitable RAT for the current service, the MS performs a service-based PS handover. Otherwise, the MS performs a quality-based, load-based, or coverage-based PS handover. The target cell is the neighboring cell with the highest neighboring cell priority. Priority of a neighboring cell is determined by the setting of NCELLPRI in neighboring cell relationship. When the parameter is set to an invalid value (255), the priority of the neighboring cell depends on the setting of the parameter for neighboring cells of the same RAT, namely the setting of GERANPRI, UTRANPRI, or EUTRANPRI. For example, if NCELLPRI for a GERAN neighboring cell is set to an invalid value (255), the priority of the neighboring cell depends on the setting of the parameter for neighboring cells of the same RAT, namely the setting of GERANPRI.

The detailed PS handover schemes are as follows:

If the PDU sent from the SGSN to the BSS indicates that the most suitable RAT for the current service is EUTRAN, then the MS is triggered to perform a service-based PS handover and the target cell is an EUTRAN cell. If a suitable target cell is not found, then the MS performs a quality-based, load-based, or coverage-based PS handover and the target cell is the GERAN neighboring cell with the highest neighboring cell priority.

If the PDU sent from the SGSN to the BSS does not indicate any suitable RAT for the current service, then the MS performs a quality-based, load-based, or coverage-based PS handover and the target cell is the neighboring cell with the highest neighboring cell priority.

The principle of target cell selection in the service-based, quality-based, load-based, and coverage-based handover algorithms is the same as that of target cell selection in the service-based, quality-based, load-based, and coverage-based eNC2 cell reselection algorithms respectively. For details, see 4.6 eNC2. Note that the priority-based handover algorithm must be used together with the service-based, quality-based, load-based, or coverage-based handover algorithm. That is, the service-based, quality-based, load-based, or coverage based handover algorithm selects a target cell according to the value of Priority of Neighboring Cell.

The triggering conditions of an inter-RAT handover between the GERAN and the EUTRAN are as follows:

The MS supports the PS handover.




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

The BSC supports the PS handover. NC2SPT is set to YES, NCO is set to NC2, and PSHOSUP is set to YES. In the case of an inter-RAT handover from the GERAN to the EUTRAN, SPTLTEOUTBSCPSHO is set to YES. In the case of an inter-RAT handover from the EUTRAN to the GERAN, SPTLTEINBSCPSHO is set to YES. In the case of an inter-RAT blind handover from the GERAN to the EUTRAN, NACCSPT is set to NO, NCO is set to NC0 or NC1, PSHOSUP is set to YES, SPTBLINDHO is set to YES, and SPTLTEINBSCPSHO is set to YES.

The SGSN supports the PS handover. The Extended Feature Bitmap field is added to the BVC RESET and BVC RESET ACK messages transmitted over the Gb interface between the SGSN and the BSC. This field specifies whether the NSE supports the PS handover. − If the BVC RESET or BVC RESET ACK message sent from the SGSN does not contain the

Extended Feature Bitmap field or if the Extended Feature Bitmap field indicates that the PS handover is not supported, it is regarded that none of the cells under the NSE of the SGSN supports the PS handover. That is, the source cell does not support the PS handover.

− Otherwise, all the cells under the NSE of the SGSN support the PS handover, that is, the source cell supports the PS handover.

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

The BSC and the SGSN support the PFC procedure.

Inter-RAT Handover from the GERAN to the EUTRAN Inter-RAT handover from the GERAN to the EUTRAN involves NACC-based handover, service-based handover, quality-based handover, load-based handover, coverage-based handover, priority-based handover, and blind handover. Note that the priority-based handover algorithm must be used together with the quality-based, load-based, or coverage-based handover algorithm. The triggering conditions of these handovers are described as follows:

The triggering conditions of inter-RAT NACC-based handover from the GERAN to the EUTRAN are as follows: The PACKET CELL CHANGE NOTIFICATION message from the MS to the BSC contains the information about the target cell; the target cell is an EUTRAN cell, and the source cell is a GERAN cell; SPTLTEINBSCPSHO is set to YES. Otherwise, inter-RAT handover from the GERAN to the EUTRAN is not performed. The information about the target cell can be obtained according to the triggering conditions.

An inter-RAT service-based, quality-based, load-based, coverage-based, or priority-based handover from the GERAN to the EUTRAN is triggered when all the following conditions are met: The MS sends measurement reports to the BSC; the BSC obtains the information about the target cell of PS handover through the handover algorithm; the target cell is an EUTRAN cell, and the source cell is a GERAN cell; SPTLTEOUTBSCPSHO is set to YES. Otherwise, an inter-RAT handover from the GERAN to the EUTRAN is not triggered. The information about the target cell can be obtained according to the triggering conditions.

The target EUTRAN cell for blind handover is determined by the GERAN configuration. That is, no algorithm is required to select the target EUTRAN cell. An inter-RAT blind handover from the GERAN to the EUTRAN is triggered when any of the following conditions is met: − The DL-UNITDATA, CREATE-BSS-PFC, and PS-HANDOVER-REQUEST messages carry the Service UTRAN CCO IE, the value of Service UTRAN CCO Value part is not 000, and the value of Service EUTRAN CCO Value part is 01.




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− The channel multiplexing rate of the GERAN cell is higher than LOADRESELSTARTTHRSH, EUTRANPRI is higher than GERANPRI and UTRANPRI, and the value of the Service EUTRAN CCO Value part is 01.

Blind handover occurs only in the scenario where a GERAN cell and an EUTRAN cell are co-cited and provide coverage for the same area.

Inter-RAT Handover from the EUTRAN to the GERAN The time for triggering an inter-RAT handover from the EUTRAN to the GERAN is determined by the EUTRAN. The PS Handover Required message sent from the eNodeB to the BSS carries the information about the target cell.

GSM BSS GSM/LTE Interoperability 6 SRVCC


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

Overview In Single Radio Voice Call Continuity (SRVCC), speech services are implemented in EUTRAN packet 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 GERAN. A UE accesses the IMS to maintain the speech service through circuit switch in the GERAN or packet switch in the EUTRAN.

The SRVCC feature supports only handover of speech services from EUTRAN to GERAN. It is available only when the EUTRAN and the GERAN cover the same area.

Figure 6-1 shows the Network Elements (NEs) involved in SRVCC.

Figure 6-1 NEs involved in SRVCC

MS E-UTRAN

MME

MSC ServerTarget GERAN

Serving/PDNGW

IMS

MS Um A

S3

Sv

S11S1-MME

S1-UUu SGi

HSSS6aSGSN

Gb

Bearer path before HOBearer path after HOSIP signaling path before HO

As shown in Figure 6-1, 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 VoIP speech service routing, control, and triggering by the IMS and the handover control by the Mobile Management Entity (MME), the speech service in the EUTRAN network can be handed over to the GERAN/UTRAN smoothly.

Principles The SRVCC feature is enabled only when the SRVCCHOEN parameter is set to YES.

The principles for SRVCC are described as follows:

The serving MME splits speech data from non-speech data based on the QCI related to speech data and on SRVCC handover indication, and sends the SRVCC PS to CS Request message to the serving MSC server to initiate the PS to CS handover.

The serving MSC server (connected to the MME) considers the handover request to be an inter-MSC CS handover request and sends a Prepare Handover Request message to the target MSC. In this case, the MSC server uses a configured default Service Area Identifier (SAI) as the identifier of the serving cell. When GERAN, UTRAN, and EUTRAN cover the same area, this SAI must be different from the SAI

GSM BSS GSM/LTE Interoperability 6 SRVCC


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used by the UTRAN. Otherwise, the BSC cannot interpret the handover request as an SRVCC handover request.

The BSC receives and decodes the SRVCC handover request from the MSC. If the SAI of the serving cell is the same as the configured default SAI, the BSC interprets the handover request as an SRVCC handover request. If the SAI of the serving cell is different from the configured default SAI, the BSC interprets the handover request as a 3G-to-2G handover request and responds to the MSC accordingly.

GSM BSS GSM/LTE Interoperability 7 CS Fallback


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7 CS Fallback Overview CS Fallback (CSFB) is a feature through which the UE camping on the EUTRAN is moved to a GERAN cell through PS handover or PS cell reselection (on the basis of NACC or other cell reselection algorithms). In this case, the UE performs speech services or other CS services in the CS domain or PS domain of the GERAN.

The CSFB feature is available only when the EUTRAN and the GERAN cover the same area.

Figure 7-1 shows the NEs involved in CSFB.

Figure 7-1 NEs involved in SRVCC

MS MSC sever

GERAN

SGSN

E-UTRAN MME

A

S3

Gs

GbUm

LTE-Uu

S1-MMESGs

The SGs interface between the MSC server and the MME must be configured to implement CSFB.

Principles The CSFB feature can be enabled only when the BSC supports NACC or PS handover.

In MSC pool networking mode, when the BSC receives a response to the CSFB paging message,

The BSC obtains the signaling point of the MSC according to the Network Resource Identifier (NRI) carried in the Temporary Mobile Subscriber Identity (TMSI) and forwards the response to the MSC, if the response message carries the TMSI, that is, the CSFB paging message delivered from the eNodeB carries the S-TMSI.

The BSC selects a MSC from the MSC pool and forwards the response to the MSC, if the response message carries the International Mobile Subscriber Identity (IMSI), that is, the CSFB paging message delivered from the eNodeB carries the IMSI, and if the CSFBPAGRSPBCSWITCH parameter is set to YES, that is, the MSC supports Roaming Retry. If the CSFBPAGRSPBCSWITCH parameter is set to NO, the BSC discards the response message. This is because the paging message is not delivered from the BSC and the BSC does not buffer the correspondence between IMSI and the signaling point of the MSC.

The implementation of the CSFB feature on the calling party side differs from that of the CSFB feature on the called party side. For details, see the related description in "3GPP TS 23.272 Circuit Switched Fallback in Evolved Packet System"

GSM BSS GSM/LTE Interoperability 8 Engineering Guidelines


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8 Engineering Guidelines Related Parameters in the System Information The setting of the parameters related to system information affects the cell reselection between GERAN and EUTRAN. Assume that telecom operators require that an MS preferentially access EUTRAN when available, and the MS access GERAN when EUTRAN is not available. To enable the MS to measure the neighboring EUTRAN cells in the GERAN coverage, it is recommended that EUTRAN cell search be always performed, that is, THRPRISEARCH be set to 15.

Neighboring EUTRAN Cell Configuration To enable the GSM/LTE interoperability, neighboring EUTRAN cells must be configured. A GERAN cell can be configured with a maximum of 64 neighboring EUTRAN cells. These neighboring cells operate on a maximum of eight frequencies, with each frequency supports a maximum of 16 neighboring cells that do not support cell reselection.

If the parameter SPTRESEL is set to UNSUPPORT, it indicates that the EUTRAN cell is a barred neighboring cell of the GERAN cell. That is, cell reselection from the source GERAN cell to the target EUTRAN cell is not supported. You need to set the parameter SPTRESEL to UNSUPPORT for all the neighboring EUTRAN cells that do not support cell reselection.

If the parameter SPTRESEL is set to SUPPORT, it indicates that the EUTRAN cell is a neighboring cell of the GERAN cell, and cell reselection from the source GERAN cell to the target EUTRAN cell is supported. You need to set the parameter SPTRESEL to SUPPORT only once for all the EUTRAN cells that support cell reselection, because the EUTRAN cells that do not support cell reselection are filtered out.

GSM BSS GSM/LTE Interoperability 9 Parameters


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9 Parameters Table 9-1 Parameter description

Parameter ID NE MML Description

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

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

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

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 following decibel values: 0: -98 dBm, 1: -95 dBm, 2: -92 dBm, ..., 13: -59 dBm, 14: -56 dBm, 15: (always), that is, the MS always searches for neighboring cells in UTRAN or EUTRAN whose priority is lower than the GERAN priority. GUI Value Range: 0~15 Actual Value Range: 0~15 Unit: None Default Value: 15



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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, ..., 30: -80 dBm, 31: -78 dBm. GUI Value Range: 0~31 Actual Value Range: 0~31 Unit: None Default Value: 9

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 correspond to the following decibel values: 0: 0dB, 1: 2dB, 2: 4dB, 3: 6dB, ..., 30: 60dB, 31: 62dB. GUI Value Range: 0~31 Actual Value Range: 0~31 Unit: None Default Value: 20

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 parameter correspond to the following decibel values: 0: -100 dBm, 1: -98 dBm, 2: -96 dBm, ..., 13: -74 dBm, 14: -72 dBm, 15: (always), that is, the MS is always allowed to reselect a neighboring cell in



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UTRAN or EUTRAN whose priority is lower than the GERAN priority. GUI Value Range: 0~15 Actual Value Range: 0~15 Unit: None Default Value: 0

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 allowed to reselect a neighboring cell in EUTRAN whose priority is lower than the GERAN priority. The values of this parameter correspond to the following decibel values: 0: 0dB, 1: 2dB, 2: 4dB, 3: 6dB, ..., 30: 60dB, 31: 62dB. GUI Value Range: 0~31 Actual Value Range: 0~31 Unit: None Default Value: 20

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 about cell reselection, and the MS performs cell reselection immediately after channel release. GUI Value Range: UNSUPPORT(UNSUPPORT), SUPPORT(SUPPORT) Actual Value Range: UNSUPPORT, SUPPORT Unit: None Default Value: UNSUPPORT

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.



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GUI Value Range: NO(No Support), YES(Support) Actual Value Range: NO, YES Unit: None Default Value: NO

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

BSC6900 SET GCELLNC2PARA(Optional) 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 accumulatively. When the rate of the accumulated value to the number of received measurement reports on the downlink transmission quality (Packet Downlink Ack/Nack message) is greater than or equal to the value of this parameter, the emergency reselection is triggered. GUI Value Range: 0~100 Actual Value Range: 0~100 Unit: % Default Value: 30

LOADRESELALLOW

BSC6900 SET GCELLNC2PARA(Optional) 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

LOADRESELSTARTTHRSH

BSC6900 SET GCELLNC2PARA(Optional) Meaning: When the uplink load or downlink load of the cell exceeds this threshold, the load reselection decision is made.



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GUI Value Range: 0~100 Actual Value Range: 0~100 Unit: % Default Value: 85

LOADRESELRXTHRSH

BSC6900 SET GCELLNC2PARA(Optional) Meaning: When the uplink load or downlink load of the target cell is lower than this threshold, it can accept the MSs from the serving cell due to load reselection. GUI Value Range: 0~100 Actual Value Range: 0~100 Unit: % Default Value: 60

LOADRESELMAXRXLEV

BSC6900 SET GCELLNC2PARA(Optional) 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

NORMALRESELALLOW

BSC6900 SET GCELLNC2PARA(Optional) 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

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, the parameter value is used for the calculation of the times of the occurrence of bad normal cell reselection level. GUI Value Range: 0~63 Actual Value Range: 0~63 Unit: None Default Value: 15

RESELWATCHPERIOD

BSC6900 SET GCELLNC2PARA(Optional) Meaning: The number of received Packet Measurement Report messages on the



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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

RESELWORSENLEVTHRSH

BSC6900 SET GCELLNC2PARA(Optional) 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

NCO BSC6900 SET GCELLPSBASE(Optional) Meaning: Network control mode for cell reselection of the MS. There are three modes. NC0: normal MS control. The MS shall perform autonomous cell re-selection. NC1: MS control with measurement reports. The MS shall send measurement reports to the network and the MS shall perform autonomous cell re-selection. NC2: network control. The MS shall send measurement reports to the network. The MS shall only perform autonomous cell re-selection when the reselection is triggered by a downlink signaling failure or a random access failure. When this parameter is set to NC2 and "Support NC2" in "SET GCELLGPRS" is set to "YES", the network side can control the cell reselection for the MS. GUI Value Range: NC0(NC0), NC1(NC1), NC2(NC2) Actual Value Range: NC0, NC1, NC2 Unit: None Default Value: NC0

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 transmission state. In this way, the MS can reselect a cell in a



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shorter time. GUI Value Range: NO(No), YES(Yes) Actual Value Range: NO, YES Unit: None Default Value: NO

NC2SPT BSC6900 SET GCELLGPRS(Optional) Meaning: Whether to support the network control 2 (NC2). The NC2 enables the network side to control the cell reselection for the MS when the MS reports the measurement report of the local cell and the neighboring cell.When this parameter is set to "YES" and "Network Control Mode" in "SET GCELLPSBASE" is set to "NC2", the network side can control the cell reselection for the MS. GUI Value Range: NO(No), YES(Yes) Actual Value Range: NO, YES Unit: None Default Value: NO

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

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

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

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

Meaning: Whether to support the blind handover from the source GSM cell to the



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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 measuring the target LTE cell. GUI Value Range: UNSUPPORT(UNSUPPORT), SUPPORT(SUPPORT) Actual Value Range: UNSUPPORT, SUPPORT Unit: None Default Value: UNSUPPORT

UTRANPRI BSC6900 SET GCELLPRIEUTRANSYS(Optional)

Meaning: Priority of UTRAN. 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: 1

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

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 message to one MSC in the MSC pool. GUI Value Range: NO(No), YES(Yes) Actual Value Range: NO, YES Unit: None Default Value: NO

SPTRESEL BSC6900 ADD GLTENCELL(Optional) MOD GLTENCELL(Optional)

Meaning: Whether to support cell reselection from GSM to LTE. If this parameter is set to SUPPORT, it indicates that the frequency of the target LTE cell is a neighboring frequency of the source GSM cell and cell reselection from GSM to LTE is supported.



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If this parameter is set to UNSUPPORT, it indicates that the frequency of the target LTE cell is a neighboring frequency of the source GSM cell but the LTE cell is a barred neighboring cell of the GSM cell. That is, cell reselection from the source GSM cell to the target LTE cell is not supported. GUI Value Range: UNSUPPORT(UNSUPPORT), SUPPORT(SUPPORT) Actual Value Range: UNSUPPORT, SUPPORT Unit: None Default Value: SUPPORT

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 is invalid. GUI Value Range: 0~7, 255 Actual Value Range: 0~7, 255 Unit: None Default Value: 255

GSM BSS GSM/LTE Interoperability 10 Counters


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

GSM BSS GSM/LTE Interoperability 11 Glossary


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

GSM BSS GSM/LTE Interoperability 12 Reference Documents


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12 Reference Documents [1] 3GPP TS 45.008: "Radio subsystem link control" [2] 3GPP TS 44.060: "Radio Link Control (RLC) / Medium Access Control (MAC) protocol" [3] 3GPP TS 36.211: "Evolved Universal Terrestrial Radio Access (E-UTRA); Physical channels and

modulation" [4] 3GPP TS 44.018: "Mobile radio interface layer 3 specification; Radio Resource Control (RRC)

protocol" [5] BSC6900 Feature List [6] BSC6900 GSM Parameter Reference [7] BSC6900 GSM MML Command Reference [8] BSC6900 GSM Performance Counter Reference [9] BSC6900 Optional Feature Description [10] GBSS Reconfiguration Guide