NC2(GBSS13.0_02)

NC2 GBSS13.0

Feature Parameter Description

Issue 02

Date 2012-06-30

HUAWEI TECHNOLOGIES CO., LTD.

Copyright © Huawei Technologies Co., Ltd. 2012. 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 contract made between Huawei and

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

within the purchase scope or the usage scope. Unless otherwise specified in 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 Technologies Co., Ltd.

Address: Huawei Industrial Base

Bantian, Longgang

Shenzhen 518129

People's Republic of China

Website: http://www.huawei.com

Email: [email protected]

http://www.huawei.com/

mailto:[email protected]

GSM BSS

NC2 Contents

Issue 02 (2012-06-30) Huawei Proprietary and Confidential

Copyright © Huawei Technologies Co., Ltd.

i

Contents

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

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

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

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

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

3 Technical Description.......................................................................................................... 3-1

3.1 Procedure ................................................................................................................................ 3-1

3.2 Cell Reselection Algorithms ...................................................................................................... 3-2

3.3 Cell Reselection Type ............................................................................................................... 3-6

4 Related Features .................................................................................................................. 4-1

5 Impact on the Network ........................................................................................................ 5-1

5.1 Impact on System Capacity ...................................................................................................... 5-1

5.2 Impact on Network Performance .............................................................................................. 5-1

6 Engineering Guidelines ...................................................................................................... 6-1

6.1 When to Use NC2 .................................................................................................................... 6-1

6.2 Information to Be Collected ...................................................................................................... 6-1

6.3 Network Planning ..................................................................................................................... 6-1

6.4 Overall Deployment Procedure ................................................................................................. 6-1

6.5 Deploying Network-Controlled Cell Reselection (NC2) .............................................................. 6-1

6.6 Troubleshooting ....................................................................................................................... 6-1

7 Parameters ............................................................................................................................ 7-1

8 Counters ................................................................................................................................ 8-1

9 Glossary ................................................................................................................................. 9-1

10 Reference Documents..................................................................................................... 10-1

GSM BSS

NC2 1 Introduction



1-1

1 Introduction

1.1 Scope

This document describes network control mode 2 (NC2) procedure, cell reselection algorithms, and cell reselection type in the NC2 feature.

The feature involved is GBFD-116201 Network-Controlled Cell Reselection (NC2).

1.2 Intended Audience

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 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 NC2 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:

02 (2012-06-30)

01 (2011-03-31)

Draft A (2011-01-15)

02 (2012-06-30)

This is the second commercial release of GBSS13.0.

Compared with issue 01 (2011-03-31) of GBSS13.0, issue 02 (2012-06-30) of GBSS13.0 incorporates the changes described in the following table.

Change Type Change Description Parameter Change

Feature change None. None.

Editorial change Added the following chapters:

Chapter 4 “Related Features”

Chapter 5 “Impact on the Network”

Chapter 6 “Engineering Guidelines"

None.

01 (2011-03-31)

This is the commercial release of GBSS13.0.

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NC2 1 Introduction



1-2

Compared with issue Draft A (2011-01-15) of GBSS13.0, this issue incorporates no change.

Draft A (2011-01-15)

This is the draft release of GBSS13.0.

Compared with issue 01 (2010-06-30) of GBSS12.0, issue Draft A (2011-01-15) of GBSS13.0 has no change.

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NC2 2 Overview



2-1

2 Overview

NC2 indicates network-controlled cell reselection. In the NC2 mode and GPRS Mobility Management (GMM) Ready state, the MS periodically sends packet measurement reports to the BSC. The BSC determines whether to perform cell reselection according to the packet measurement report from the MS, the current load in the serving cell and in the neighboring cells. If a cell reselection is required, the BSC sends a Packet Cell Change Order message to instruct the MS to reselect the target cell. 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 in the neighboring cell so that the MS can reselect a proper cell. In this way, the loads in the cells can be balanced.

In NC2 mode, any of the following events triggers a network-controlled cell reselection.

The MS signal strength keeps falling, and a neighboring cell with stronger signal strength exists.

The MS signal quality keeps deteriorating, and a neighboring cell with better signal quality exists.

The serving cell of the MS is overloaded, and a neighboring cell with lighter load and stronger signal strength exists.

The SGSN indicates that the Radio Access Technology (RAT, such as, GSM/EDGE Radio Access Network (GERAN), Universal Terrestrial Radio Access Network (UTRAN), or Evolved Universal Terrestrial Radio Access Network (EUTRAN)) most suitable for the MS is different from the current RAT.

In NC2 mode, any of the following events triggers an autonomous cell reselection rather than a network-controlled cell reselection.

Downlink signaling reception fails.

Attempts to access the network fail.

Visits to the serving cell are prohibited.

The path loss criterion C1 indicates that the path loss of the serving cell is too high, that is, the value of the path loss criterion C1 is smaller than 0. Path loss criterion C1 is used to indicate the amount of path loss in a cell reselection decision.

In the GMM Standby state, the MS is attached to the GPRS network and an MM context is established between the MS and the SGSN. The MS can receive paging messages and downlink signaling but cannot transmit or receive packet data. In this case, the MS initiates autonomous cell reselection regardless of the NC mode. In Dual Transfer Mode (DTM), the MS does not perform any autonomous cell reselection or network-controlled cell reselection. Cell reselection is controlled by the CS domain handover procedure on the network side.

An MS can perform the NC2 procedure in packet idle mode and in packet transfer mode.

NC2 in packet idle mode

After an MS in packet idle mode completes the packet/immediate assignment procedure on the PCCCH/CCCH, it periodically sends packet measurement reports to the BSC through the PCCCH/CCCH. The interval at which the MS sends packet measurement reports is determined by the RPTPERIODI parameter. Through the PCCCH/CCCH, the BSC sends the Packet Cell Change Order message to the MS to instruct the MS to implement cell reselection and perform an NC2 procedure in packet idle mode.

NC2 in packet transfer mode

An MS in packet transfer mode periodically sends packet measurement reports to the BSC through the PACCH. The interval at which the MS sends packet measurement reports is determined by the RPTPERIODT parameter. Through the PACCH, the BSC sends the Packet Cell Change Order message to the MS to instruct the MS to implement cell reselection and perform an NC2 procedure in packet transfer mode.

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NC2 2 Overview



2-2

Currently, Huawei BSC supports only NC2 in packet transfer mode.

The NC2 feature supports intra-BSC cell reselection, inter-BSC cell reselection, GERAN-to-UTRAN cell reselection, and GERAN-to-EUTRAN cell reselection.

GSM BSS

NC2 3 Technical Description



3-1

3 Technical Description

3.1 Procedure

If the cell configuration parameter NC2SPT is set to YES(Yes) and NCO is set to nc2(nc2), NC2 is enabled. If the NACCSPT parameter is set to YES(Yes), the cell reselection procedure in NC2 is accelerated.

If the cell configuration parameter NC2SPT is set to YES(Yes) and NCO is set to nc2(nc2), the NC2 feature is enabled. If the INTERRATCELLRESELEN parameter is set to YES(Yes), GERAN-to-UTRAN cell reselection is enabled. If the LTECELLRESELEN parameter is set to YES(Yes), GERAN-to-EUTRAN cell reselection is enabled. If the NACCSPT parameter is set to YES(Yes), the cell reselection procedure in NC2 is accelerated.

Figure 3-1 shows the cell reselection in NC2.

Figure 3-1 Cell reselection in NC2

1. An MS in the GMM Ready state periodically sends Packet Measurement Report messages to the BSC.

2. After receiving the packet measurement report, the BSC processes the measurement results. According to the NC2 cell reselection algorithm, the BSC determines whether to perform a cell reselection and determines the target cell for reselection.

3. If the BSC determines to initiate a cell reselection, it sends a Packet Cell Change Order message to the MS to instruct the MS to reselect the specified target cell. When the NACCSPT parameter is set to YES(Yes), the BSC sends a Packet Neighbor Cell Data message to the MS before sending the

Packet Cell Change Order message if the specified target cell is a GERAN cell or if the target cell is an external GERAN cell and the Gb interface supports the RAN Information Management (RIM) procedure. The Packet Neighbor Cell Data message carries the system information of the target cell to accelerate the cell reselection procedure.

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3-2

4. If a cell reselection fails, the MS sends a Packet Cell Change Failure message to the BSC. After receiving this message, the BSC subtracts the value of the PENALTYRXLEV parameter from the receive level of the target cell.

3.2 Cell Reselection Algorithms

The NC2 cell reselection algorithms are the service-based cell reselection algorithm, quality-based cell reselection algorithm, load-based cell reselection algorithm, and coverage-based cell reselection algorithm.

The PDU (DL-UNITDATA PDU, CREATE-BSS-PFC PDU, or PS-HANDOVER-REQUEST PDU) sent from the SGSN to the BSS may indicate the most suitable RAT for the current service. If so, the MS performs a service-based cell reselection. Otherwise, the MS performs a quality-based, load-based, or 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 the 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 performs 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 indicates that the most suitable RATs for the current service are UTRAN and EUTRAN, then the MS performs a service-based cell reselection and the target cell is the neighboring cell with the highest neighboring cell priority. If the suitable target cell is not found, then the MS performs a quality-based, load-based, or coverage-based cell reselection.

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.

When the NC2LoadResel parameter is set to Support, the load of the GERAN candidate cells under

the same BSC is considered during cell reselection. When the NC2LoadResel parameter is set to NotSupport, the load of the GERAN candidate cells under the same BSC is not considered during cell reselection. The LOADBROADCASTPERIOD parameter specifies the interval at which a cell broadcasts its current load to its neighboring cells under the same BSC.

Service-Based Cell Reselection Algorithm

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 takes the last received Service UTRAN CCO IE as the criterion. The Service UTRAN CCO IE, consisting of the Service UTRAN CCO Value part and Service E-UTRAN CCO Value part, indicates the most suitable RAT for the current service. Table 3-1 and Table 3-2 describe the Service UTRAN CCO Value part and Service E-UTRAN CCO Value part respectively.

Table 3-1 Service UTRAN CCO Value part

Coding Bit Semantic

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

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3-3

Coding Bit Semantic

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 information not available (bits 4-5 valid)

Other values If received, shall be interpreted as information not available

Table 3-2 Service EUTRAN CCO Value part

Coding Bit 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 information not available

When the Service UTRAN CCO Value part is set to 000 or when the Service E-UTRAN CCO Value part is set to 01, a service-based cell reselection is initiated. The details about the service-based cell reselection algorithm are as follows:

When the Service UTRAN CCO Value part is set to 000 and the Service E-UTRAN CCO Value part is not set to 01, the cell with the highest received signal level is selected as the target cell from the neighboring UTRAN cells.

When the Service UTRAN CCO Value part is set to 000 and the Service E-UTRAN CCO Value part is set to 01, NCELLPRI for UTRAN and NCELLPRI for E-UTRAN neighboring cells in neighboring cell relationship is compared and the neighboring cell with the highest neighboring cell priority is reselected.

When the Service UTRAN CCO Value part is not set to 000 and the Service E-UTRAN CCO Value part is set to 01, the cell with the highest received signal level is selected as the target cell from the neighboring EUTRAN cells.

If a UTRAN or EUTRAN target cell is not found, then the MS performs a quality-based, load-based, or coverage-based cell reselection.

When the Service UTRAN CCO Value part is not set to 000 and the Service E-UTRAN CCO Value part is not set to 01, then the MS performs a quality-based, load-based, or coverage-based cell reselection.

Quality-Based Cell Reselection Algorithm

The URGENTRESELALLOW parameter specifies whether to enable the quality-based cell reselection algorithm. When the conditions for initiating a service-based cell reselection are not met, the BSC determines whether to initiate a cell reselection based on the measurement reports (MRs) regarding the radio link on the Um interface. The MRs or bit error rate (BER) indicates the receive quality on the radio


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3-4

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 value of 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 MRs.

In a quality-based cell reselection, the cell with the highest priority is selected as the target cell from the list of GERAN candidate cells if GERAN is of the highest priority. The priority of a cell is determined by the received signal level and the characteristics information such as cell type, cell priority, and support of EDGE, about the cell. If UTRAN or EUTRAN is of the highest priority, the cell with the highest received signal level is selected as the target cell from the UTRAN or EUTRAN candidate cells. When the NC2LoadResel parameter is set to Support, the characteristics information about a cell also includes

the load of the GERAN candidate cells under the same BSC. A neighboring candidate cell must meet any of the following conditions:

Receive level of the neighboring GERAN candidate cell > Max(Receive level of the serving cell, MINACCRXLEV) + RESELHYST.

Measured ratio of energy per modulating bit to the noise spectral density (Ec/No) of the neighboring Frequency Division Duplex (FDD) cell > FDDECQUALTHRSH, or measured Received Signal Code Power (RSCP) of the neighboring FDD cell > FDDRSCPQUALTHRSH.

Measured RSCP of the neighboring Time Division Duplex (TDD) cell > TDDRSCPQUALTHRSH.

When the NC2LoadResel parameter is set to Support, the neighboring GERAN candidate cells under the same BSC are not congested.

When the Service UTRAN CCO Value part is set to 010 or 001, none of the neighboring UTRAN cells (TDD cells and FDD cells) can be selected as the target cell.

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

Load-Based Cell Reselection Algorithm

The LOADRESELALLOW parameter specifies whether to enable the load-based cell reselection algorithm. 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 reselection procedure, some MSs in heavily-loaded cells are reselected to light-loaded cells. In addition, the MSs in neighboring cells should not be reselected to heavily-loaded cells. Figure 3-2 shows the cell load reselection mode.

Figure 3-2 Load reselection

Cell with

heavy load

Cell with

heavy load

Cell with

heavy load

Cell with light

load

Cell with light

load

Cell with light

load

Cell with light

load

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3-5

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 the value of the LOADRESELSTARTTHRSH parameter, the load in the cell is heavy, and therefore the load-based cell reselection should be enabled.

If the average channel multiplexing rate of a cell is lower than the value of the LOADRESELRXTHRSH parameter, the 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 a 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 value of 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 received signal level in this cell is lower than the value of the LOADRESELMAXRXLEV parameter.

In a load-based cell reselection, the cell with the highest priority is selected as the target cell from the GERAN candidate cells if GERAN is of the highest priority. The priority of a cell is determined by the received signal level and the characteristics information such as cell type, cell priority, and support of EDGE, about the cell. If UTRAN or EUTRAN is of the highest priority, the cell with the highest received signal level is selected as the target cell from the UTRAN or EUTRAN candidate cells. When the NC2LoadResel parameter is set to Support, the characteristics information about a cell also includes the load of the GERAN candidate cells under the same BSC. A neighboring candidate cell must meet any of the following conditions:


Measured Ec/No of the neighboring FDD cell > FDDECQUALTHRSH, or Measured RSCP of the neighboring FDD cell > FDDRSCPQUALTHRSH.

Measured RSCP of the neighboring TDD cell > TDDRSCPQUALTHRSH.




Coverage-Based Cell Reselection Algorithm

The NORMALRESELALLOW parameter specifies whether to enable the coverage-based cell reselection algorithm. When the conditions for initiating a service-based cell reselection, the conditions for initiating a quality-based cell reselection, and the conditions for initiating a load-based cell reselection are not met, a coverage-based cell reselection is initiated to redirect the MS to a neighboring cell with stronger signal strength if the received signal 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 received signal level of the serving cell is lower than the value of the MINACCRXLEV parameter reaches the value of the RESELWORSENLEVTHRSH parameter, a coverage-based cell reselection is initiated.

In a coverage-based cell reselection, the cell with the highest priority is selected as the target cell from the list of GERAN candidate cells if GERAN is of the highest priority. The priority of a cell is determined by the received signal level and the characteristics information such as cell type, cell priority, and support of EDGE, about the cell. If UTRAN or EUTRAN is of the highest priority, the cell with the highest received signal level is selected as the target cell from the UTRAN or EUTRAN candidate cells. When the

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NC2LoadResel parameter is set to Support, the characteristics information about a cell also includes

the load of the GERAN candidate cells under the same BSC. A neighboring candidate cell must meet any of the following conditions:


Measured Ec/No of the neighboring FDD cell > FDDECQUALTHRSH, or Measured RSCP of the neighboring FDD cell > FDDRSCPQUALTHRSH.

Measured RSCP of the neighboring TDD cell > TDDRSCPQUALTHRSH.




3.3 Cell Reselection Type

Based on the reselected target cell, the NC2 cell reselection algorithm is designed for four NC2 cell reselections: intra-BSC cell reselection, inter-BSC cell reselection, GERAN-to-UTRAN cell reselection, and GERAN-to-EUTRAN cell reselection.

Intra-BSC Cell Reselection

In an intra-BSC cell reselection, the serving cell and the target cell are controlled by the same BSC. In the list of candidate cells, the target cell is selected depending on the priority of the cell. The selected target cell is the one whose priority is the highest in the list.

When a cell reselection fails, a penalty must be imposed on the target cell. If the time of the penalty imposed on the target cell is shorter than the value of the PENALTYLASTTM parameter, the value of the PENALTYRXLEV parameter is subtracted from the received signal level of the target cell. If the received signal level of the target cell is smaller than the value of the PENALTYRXLEV parameter, the received signal level of the target cell is set to 0.

Inter-BSC Cell Reselection

In an inter-BSC cell reselection, the serving cell and the target cell are both GERAN cells but are controlled by different BSCs. For the inter-BSC cell reselection, the priority of the external neighboring GERAN cells should be lowered so that it is lower than that of the internal neighboring GERAN cells. The priority of the internal GERAN cells equals the received signal level of the external neighboring GERAN cell minus an external cell reselection offset. This external cell reselection offset equals Max(2, RESELHYST/2).


A BSC is not allowed to obtain the information about the load in an external neighboring GERAN cell. This means that the load in an external neighboring GERAN cell is unknown during a load-based cell reselection. Therefore, all external neighboring GERAN cells are treated as cells without congestion.








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GERAN-to-UTRAN Cell Reselection

A GERAN-to-UTRAN cell reselection is an NC2 cell reselection in which the serving cell is a GERAN cell, and the target cell is a UTRAN cell. The target cell can be either a WCDMA cell or a TD-SCDMA cell. For the GERAN-to-UTRAN cell reselection, the UTRAN MRs should be processed.

A neighboring UTRAN cell can be selected as a candidate cell only when the quality of the MRs from the neighboring UTRAN cell is greater than the UTRAN cell reselection quality threshold. During the cell reselection, a cell with the highest received signal level is selected from the list of candidate cells and is considered as the target cell. For a neighboring FDD cell, both the RSCP measurement quality type and the Ec/No measurement quality type are supported. For a neighboring TDD cell, the RSCP measurement quality type is supported.


A BSC is not allowed to obtain the information about the load in an external neighboring UTRAN cell. This means that the load in an external neighboring UTRAN cell is unknown during a load-based cell reselection. Therefore, all external neighboring UTRAN cells are treated as cells without congestion.

GERAN-to-EUTRAN Cell Reselection

A GERAN-to-EUTRAN cell reselection is an NC2 cell reselection in which the serving cell is a GERAN cell, and the target cell is a EUTRAN cell. For the GERAN-to-EUTRAN cell reselection, the EUTRAN MRs should be processed.

During the cell reselection, a cell with the highest received signal level is selected from the list of candidate cells and is considered as the target cell.


A BSC is not allowed to obtain the information about the load in an external neighboring EUTRAN cell. This means that the load in an external neighboring EUTRAN cell is unknown during a load-based cell reselection. Therefore, all external neighboring EUTRAN cells are treated as cells without congestion.







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NC2 4 Related Features



4-1

4 Related Features

Feature/Function Prerequisite Feature Mutually Exclusive Feature

Affected Feature

Network-Controlled Cell Reselection (NC2)

GBFD-114101 GPRS GBFD-114151 DTM None

GSM-to-WCDMA Network-Controlled Cell Reselection

GBFD-114101 GPRS

GBFD-114301 GSM/WCDMA Interoperability

None None

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NC2 5 Impact on the Network



5-1

5 Impact on the Network

5.1 Impact on System Capacity

The Network-Controlled Cell Reselection (NC2) feature enables an MS to reselect a cell in view of the receive levels, service conditions, and loads in the serving cell and its neighboring cells. This ensures load balancing among cells and improves network capacity.

5.2 Impact on Network Performance

The Network-Controlled Cell Reselection (NC2) feature improves user experience by selecting a target cell with a higher receive level, higher spectral efficiency, or lower traffic load.

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NC2 6 Engineering Guidelines



6-1

6 Engineering Guidelines

6.1 When to Use NC2

It is recommended that this feature be used when traffic loads among cells are imbalanced.

6.2 Information to Be Collected

Before deploying this feature, collect the channel usage of the current GSM cell and its neighboring cells.

6.3 Network Planning

RF Planning

N/A

Network Topology

N/A

Hardware Planning

The DPUd or DPUg board has been configured.

6.4 Overall Deployment Procedure

None

6.5 Deploying Network-Controlled Cell Reselection (NC2)

For details about how to activate, verify, and deactivate this feature, see Configuring NC2.

6.6 Troubleshooting

None

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NC2 7 Parameters



7-1

7 Parameters

Table 7-1 Parameter description

Parameter ID NE MML Command Feature ID

Feature Name

Description

CELLRXQUALWORSENRATIOTHRSH

BSC6900

SET GCELLNC2PARA(Optional)

GBFD-116201

GBFD-511303


PS Handover Between GSM and LTE Based on Quality

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



../RNCParaHtml/mbsc/m-mml/set-gcellnc2para.html



GSM BSS

NC2 7 Parameters



7-2


Feature Name

Description

Range: 0~100

Default Value: 30

Unit: %

EUTRANPRI BSC6900

SET GCELLPRIEUTRANSYS(Optional)

GBFD-511301

GBFD-511312

Cell Reselection Between GSM and LTE

Fast LTE Reselection at 2G CS Call Release

Meaning: Priority of EUTRAN. Value 0 indicates the lowest priority, and value 7 indicates the highest priority.


Actual Value Range: 0~7

Default Value: 0

Unit: None

FDDECQUALTHRSH BSC6900

ADD GEXT3GCELL(Optional)

MOD GEXT3GCELL(Optional)

GBFD-114301

GSM/WCDMA Interoperability

Meaning: Minimum Ec/No of the 3G FDD cell candidate



Default Value: 10

Unit: dB

FDDRSCPQUALTHRSH BSC6900

ADD GEXT3GCELL(Optional)


GBFD-114301


Meaning: Minimum RSCP of the 3G FDD cell candidate



Default Value: 10

Unit: None

../RNCParaHtml/mbsc/m-para/gcellprieutransys_eutranpri.html

../RNCParaHtml/mbsc/m-mml/set-gcellprieutransys.html




../RNCParaHtml/mbsc/m-mml/add-gext3gcell.html


../RNCParaHtml/mbsc/m-mml/mod-gext3gcell.html







GSM BSS

NC2 7 Parameters



7-3


Feature Name

Description

GERANPRI BSC6900


GBFD-511301


Meaning: Priority of GERAN. Value 0 indicates the lowest priority, and value 7 indicates the highest priority.



Default Value: 7

Unit: None

INTERRATCELLRESELEN BSC6900

SET GCELLHOBASIC(Optional)

GBFD-511104

GBFD-114302

GSM and WCDMA Traffic Steering Based on Iur-g

GSM/TD-SCDMA Interoperability

Meaning: This parameter specifies whether the reselection from 2G cells to 3G cells is allowed.

GUI Value Range: NO(No), YES(Yes)

Actual Value Range: NO, YES

Default Value: NO

Unit: None

LOADBROADCASTPERIOD

BSC6900

SET BSCPSSOFTPARA(Optional)

GBFD-116201


Meaning: Intervals that the BSC broadcasts a cell's traffic load to its neighbor cells. The uplink load and downlink load indicate the traffic situation of a cell. The





../RNCParaHtml/mbsc/m-para/gcellhobasic_interratcellreselen.html

../RNCParaHtml/mbsc/m-mml/set-gcellhobasic.html




../RNCParaHtml/mbsc/m-mml/set-bscpssoftpara.html



GSM BSS

NC2 7 Parameters



7-4


Feature Name

Description

uplink load = number of uplink TBFs carried on all PDCHs in a cell / total number of PDCHs in a cell x ("PDCH Uplink Multiplex Threshold"/10) x 100%. The downlink load = number of downlink TBFs carried on all PDCHs in a cell / total number of PDCHs in a cell x ("PDCH Downlink Multiplex Threshold"/10) x 100%.



Default Value: 4

Unit: s

LOADRESELALLOW BSC6900


GBFD-116201

GBFD-511304

GBFD-511307


PS Handover Between GSM and LTE Based on Cell Load

eNC2 Between GSM and LTE

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

../RNCParaHtml/mbsc/m-para/gcellnc2para_loadreselallow.html




GSM BSS

NC2 7 Parameters



7-5


Feature Name

Description

reselection.

GUI Value Range: FORBID(Forbid), PERMIT(Permit)

Actual Value Range: FORBID, PERMIT

Default Value: PERMIT

Unit: None

LOADRESELMAXRXLEV BSC6900


GBFD-116201

GBFD-511304



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.



Default Value: 40

Unit: None

LOADRESELRXTHRSH BSC6900


GBFD-116201

GBFD-114301

GBFD-114322

GBFD-511304

GBFD-511310



GSM/WCDMA Load Based

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





../RNCParaHtml/mbsc/m-para/gcellnc2para_loadreselrxthrsh.html




GSM BSS

NC2 7 Parameters



7-6


Feature Name

Description

Handover


Multi Technology Neighbour Cell Based Handover

due to load reselection.



Default Value: 60

Unit: %

LOADRESELSTARTTHRSH

BSC6900


GBFD-116201

GBFD-511304



Meaning: When the uplink load or downlink load of the cell exceeds this threshold, the load reselection decision is made.



Default Value: 85

Unit: %

LTECELLRESELEN BSC6900

SET GCELLHOBASIC(Optional)

GBFD-511301

GBFD-511312


Fast LTE Reselection at 2G CS Call Release

Meaning: Whether to allow cell reselection from GSM to LTE.



Default Value: NO

Unit: None

MINACCRXLEV BSC6 SET GCELLNC2PARA(Optional

GBFD-11 Network-Controlled Cell

Meaning: Minimum






../RNCParaHtml/mbsc/m-para/gcellhobasic_ltecellreselen.html






GSM BSS

NC2 7 Parameters



7-7


Feature Name

Description

900 ) 6201

GBFD-511302

GBFD-511303

GBFD-511304

GBFD-511306

Reselection (NC2)

PS Handover Between GSM and LTE Based on Coverage



GSM/LTE Service Based PS Handover

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.



Default Value: 15

Unit: None

NACCSPT BSC6900

SET GCELLGPRS(Optional)

GBFD-116301

GBFD-119502

Network Assisted Cell Change (NACC)

PS Handover

Meaning: Whether to support Network Assisted Cell Change (NACC). NACC is used in the network control mode NC0, NC1 or NC2. When an MS is in packet


../RNCParaHtml/mbsc/m-mml/set-gcellgprs.html


GSM BSS

NC2 7 Parameters



7-8


Feature Name

Description

transfer mode, the NACC enables the network to notify the MS in advance of the system information about neighboring cells, accelerating cell reselection for MSs.



Default Value: NO

Unit: None

NC2LoadResel BSC6900

SET BSCPSSOFTPARA(Optional)

GBFD-116201


Meaning: Whether to involve the load of the target cell in the algorithm for NC2 cell reselection. If this parameter is set to Support, the load of the target cell is involved in the algorithm for NC2 cell reselection.

GUI Value Range: NotSupport(Not Support), Support(Support)

Actual Value Range:





GSM BSS

NC2 7 Parameters



7-9


Feature Name

Description

NOTSUPPORT, SUPPORT

Default Value: NOTSUPPORT

Unit: None

NC2SPT BSC6900

SET GCELLGPRS(Optional)

GBFD-116201

GBFD-119502

GBFD-511307

GBFD-511310


PS Handover



Meaning: Whether to support network control 2 (NC2). In NC2 mode, an MS sends the BSC measurement reports containing information about the serving cell and neighboring cells, and the network controls cell reselection for the MS.



Default Value: NO

Unit: None

NCELLPRI BSC6900

ADD GLTENCELL(Optional)

MOD GLTENCELL(Optional)

GBFD-511301


Meaning: Priority of the neighboring cell. Value 0 indicates the lowest priority, and value 7 indicates the highest priority. Value 255 is invalid.




../RNCParaHtml/mbsc/m-para/gltencell_ncellpri.html

../RNCParaHtml/mbsc/m-mml/add-gltencell.html

../RNCParaHtml/mbsc/m-mml/add-gltencell.html

../RNCParaHtml/mbsc/m-mml/mod-gltencell.html

../RNCParaHtml/mbsc/m-mml/mod-gltencell.html

GSM BSS

NC2 7 Parameters



7-10


Feature Name

Description

GUI Value Range: 0~7, 255

Actual Value Range: 0~7, 255

Default Value: 255

Unit: None

NCELLPRI BSC6900

ADD G2GNCELL(Optional)

MOD G2GNCELL(Optional)

GBFD-110402

Basic Cell Re-selection




Default Value: 255

Unit: None

NCELLPRI BSC6900

ADD G3GNCELL(Optional)

MOD G3GNCELL(Optional)

GBFD-114301

GBFD-114302






Default Value:


../RNCParaHtml/mbsc/m-mml/add-g2gncell.html

../RNCParaHtml/mbsc/m-mml/mod-g2gncell.html



../RNCParaHtml/mbsc/m-mml/add-g3gncell.html



GSM BSS

NC2 7 Parameters



7-11


Feature Name

Description

255

Unit: None

NCO BSC6900

SET GCELLPSBASE(Optional)

GBFD-119107

GBFD-114302

GBFD-119502

GBFD-111101

GBFD-511307

GBFD-511310

Networking Control Mode


PS Handover

System Information Sending



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


../RNCParaHtml/mbsc/m-mml/set-gcellpsbase.html

../RNCParaHtml/mbsc/m-mml/set-gcellpsbase.html

GSM BSS

NC2 7 Parameters



7-12


Feature Name

Description

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

Default Value: NC0

Unit: None

NORMALRESELALLOW BSC6900


GBFD-116201

GBFD-511302

GBFD-511307




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.


Actual Value Range: FORBID,

../RNCParaHtml/mbsc/m-para/gcellnc2para_normalreselallow.html




GSM BSS

NC2 7 Parameters



7-13


Feature Name

Description

PERMIT


Unit: None

PENALTYLASTTM BSC6900


GBFD-116201

GBFD-511302

GBFD-511303

GBFD-511304

GBFD-511306

GBFD-511310







Meaning: Penalty duration for cell reselection. Cell penalty can be performed only in this duration. When this parameter is set to a greater value, the MS cannot reselect a cell for a longer time in the case of reselection failure or reselection due to load. The penalty timer is shorter when this parameter is set to a smaller value.



Default Value: 10

Unit: s

PENALTYRXLEV BSC6900


GBFD-116201

GBFD-511302

GBFD-511303

GBFD-511304


PS Handover Between GSM and LTE Based

Meaning: When the cell reselection failure message is received or the load cell reselection is initiated, the









GSM BSS

NC2 7 Parameters



7-14


Feature Name

Description

GBFD-511306

GBFD-511310

on Coverage





"Cell Penalty Level" is subtracted from the receive level of the target cell to avoid that cell reselection failure occurs repeatedly or that multiple MSs are reselected to the same target cell. This parameter is valid only within "Cell Penalty Duration".



Default Value: 30

Unit: None

RESELHYST BSC6900


GBFD-116201

GBFD-511302

GBFD-511303

GBFD-511304

GBFD-511306

GBFD-511310





GSM/LTE

Meaning: Indicating that during cell reselection, the level of the target cell should meet the following condition: Level of target cell > [MAX (level of serving cell, "Cell Reselection Level Threshold") + "Cell Reselection Hysteresis"]. In this way,





GSM BSS

NC2 7 Parameters



7-15


Feature Name

Description

Service Based PS Handover


ping-pong handovers do not occur.



Default Value: 6

Unit: None

RESELWATCHPERIOD BSC6900


GBFD-116201

GBFD-511302



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.



Default Value: 10

Unit: None

RESELWORSENLEVTHRSH

BSC6900


GBFD-116201

GBFD-511302


PS Handover Between GSM and LTE Based

Meaning: If the number of times when the receive level of the serving cell within "Normal Cell

../RNCParaHtml/mbsc/m-para/gcellnc2para_reselwatchperiod.html









GSM BSS

NC2 7 Parameters



7-16


Feature Name

Description

on Coverage Reselection Watch Period" is lower than "Cell Reselection Level Threshold" is greater than the value of this parameter, the normal cell reselection is triggered.



Default Value: 1

Unit: None

RPTPERIODI BSC6900

SET GCELLNWCTRLMSRPARA(Optional)

GBFD-119107


Meaning: Cell reselection measurement report period in packet idle mode

GUI Value Range: 0.48sec(0.48sec), 0.96sec(0.96sec), 1.92sec(1.92sec), 3.84sec(3.84sec), 7.68sec(7.68sec), 15.36sec(15.36sec), 30.72sec(30.72sec), 61.44sec(61.44sec)

Actual Value Range: 0.48sec, 0.96sec, 1.92sec,

../RNCParaHtml/mbsc/m-para/gcellnwctrlmsrpara_rptperiodi.html

../RNCParaHtml/mbsc/m-mml/set-gcellnwctrlmsrpara.html



GSM BSS

NC2 7 Parameters



7-17


Feature Name

Description

3.84sec, 7.68sec, 15.36sec, 30.72sec, 61.44sec

Default Value: 15.36sec

Unit: s

RPTPERIODT BSC6900

SET GCELLNWCTRLMSRPARA(Optional)

GBFD-119107

GBFD-114302



Meaning: Interval at which an MS in packet transfer mode sends measurement reports for cell reselection.

GUI Value Range: 0.48sec(0.48sec), 0.96sec(0.96sec), 1.92sec(1.92sec), 3.84sec(3.84sec), 7.68sec(7.68sec), 15.36sec(15.36sec), 30.72sec(30.72sec), 61.44sec(61.44sec)

Actual Value Range: 0.48sec, 0.96sec, 1.92sec, 3.84sec, 7.68sec, 15.36sec, 30.72sec, 61.44sec

Default Value: 0.96sec

Unit: s

TDDRSCPQUALTHRSH BSC6 ADD GBFD-11 GSM/TD-SC Meaning:

../RNCParaHtml/mbsc/m-para/gcellnwctrlmsrpara_rptperiodt.html






GSM BSS

NC2 7 Parameters



7-18


Feature Name

Description

900 GEXT3GCELL(Optional)


4302 DMA Interoperability

Minimum RSCP quality threshold that the TDD 3G candidate cell must reach



Default Value: 10

Unit: None

URGENTRESELALLOW BSC6900


GBFD-116201

GBFD-511303

GBFD-511307




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.


Actual Value Range: FORBID, PERMIT


Unit: None

UTRANPRI BSC6900


GBFD-511301

Cell Reselection Between GSM and

Meaning: Priority of UTRAN. Value 0 indicates the



../RNCParaHtml/mbsc/m-para/gcellnc2para_urgentreselallow.html




../RNCParaHtml/mbsc/m-para/gcellprieutransys_utranpri.html




GSM BSS

NC2 7 Parameters



7-19


Feature Name

Description

LTE lowest priority, and value 7 indicates the highest priority.



Default Value: 1

Unit: None

GSM BSS

NC2 8 Counters



8-1

8 Counters

Table 8-1 Counter description

Counter ID Counter Name Counter Description

Feature ID Feature Name

1279172426

NC.CELL.RESELECT.ATMPT H9010:Number of Network-Controlled Cell Reselection Attempts

GBFD-116201


1279172427

NC.CELL.URG.RESELECT.ATMPT H9011:Number of Network-Controlled Cell Reselection Attempts Due to Downlink Quality

GBFD-116201


1279172428

NC.CELL.LOAD.RESELECT.ATMPT H9012:Number of Network-Controlled Cell Reselection Attempts due to Traffic Load

GBFD-116201


1279172429

NC.CELL.GENERAL.RESELECT.ATMPT

H9013:Number of Network-Controlled Cell Reselection Attempts for Better Cell

GBFD-116201


1279172430

NC.CELL.RESELECT.FAIL.ATMPT H9014:Number of Failed Network-Controlled Cell Reselections

GBFD-116201


1279172431

NC.CELL.INTRABSC.RESELECT.ATMPT

H9015:Number of Intra-BSC Network-Controlled Cell Reselection Attempts

GBFD-116201


1279172432

NC.CELL.INTERBSC.RESELECT.ATMPT

H9016:Number of Inter-BSC Network-Controlled Cell Reselection Attempts

GBFD-116201


1279172433

NC.CELL.INTERRAN.RESELECT.ATMPT

H9017:Number of Inter-RAT Network-Controlled Cell Reselection Attempts

GBFD-116201


1279172434

NC.CELL.2G.TO.3G.RESELECT.ATMPT

H9018:Number of Network-Controlled 2G to 3G Cell

GBFD-116201


../RNCCounterHtml/mbsc/m-perf/Mt-2638.html


















GSM BSS

NC2 8 Counters



8-2

Counter ID Counter Name Counter Description

Feature ID Feature Name

Reselection Attempts

1279172435

NC.CELL.2G.TO.3G.RESELECT.FAIL H9019:Number of Failed Network-Controlled 2G to 3G Cell Reselections

GBFD-116201


1282429613

NC.CELL.2G.TO.4G.RESELECT.ATMPT

H9701:Number of Network-Controlled 2G to 4G Cell Reselection Attempts

GBFD-116201

GBFD-511307



1282429614

NC.CELL.2G.TO.4G.RESELECT.FAIL H9721:Number of Failed Network-Controlled 2G to 4G Cell Reselections

GBFD-116201

GBFD-511307









GSM BSS

NC2 9 Glossary



9-1

9 Glossary

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

Glossary.htm

GSM BSS

NC2 10 Reference Documents



10-1

10 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 43.064: "Overall description of the GPRS Radio Interface; Stage 2"

[4] 3GPP TS 43.022: "Functions related to Mobile Station (MS) in idle mode and group receive mod"

[5] BSC6900 Feature List

[6] BSC6900 Optional Feature Description

[7] BSC6900 GSM Parameter Reference

[8] BSC6900 GSM MML Command Reference

[9] BSC6900 Performance Counter Reference

NC2(GBSS13.0_02)

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