ps handover

PS Handover Feature Parameter Description

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Issue 02 (2009-09-30) Huawei Proprietary and Confidential Copyright Huawei Technologies Co., Ltd. i

BSS PS Handover Contents

Issue 02 (2009-09-30) Huawei Proprietary and Confidential Copyright Huawei Technologies Co., Ltd.

iii

Contents 1 Introduction to This Document .............................................................................................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 Handover Decision........................................................................................................................ 3-1 3.2 Common Intra-BSC Inter-Cell Handover ...................................................................................... 3-1 3.3 Inter-BSC Inter-Cell Handover ...................................................................................................... 3-4 3.4 2G/3G Inter-RAT Handover........................................................................................................... 3-4

4 Parameters .................................................................................................................................4-1

5 Counters......................................................................................................................................5-1

6 Glossary ......................................................................................................................................6-1

7 Reference Documents .............................................................................................................7-1

BSS PS Handover 1 Introduction to This Document


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1 Introduction to This Document 1.1 Scope This document describes the common intra-BSC inter-cell handover procedure, inter-BSC inter-cell handover procedure, and 2G/3G inter-RAT handover procedure.

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:

z Personnel working on Huawei GPRS products or systems z 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:

z Feature change Feature change refers to the change in the PS handover feature of a specific product version.

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

Document Issues The document issues are as follows:

z 02 (2009-09-30) z 01 (2009-06-30)

02 (2009-09-30) This is the second commercial release of GBSS9.0.

Compared with issue 01 (2009-06-30) of GBSS9.0, the following changes are incorporated:

Change Type

Change Description Parameter Change

Feature change

None. None.

Editorial change

3.4 2G/3G Inter-RAT Handover is added.

None.

01 (2009-06-30) This is the first commercial release of GBSS9.0.

1 Introduction to This Document BSS

PS Handover

1-2 Huawei Proprietary and Confidential Copyright Huawei Technologies Co., Ltd.

Issue 02 (2009-09-30)

Compared with issue 01 (2009-04-30) of GBSS8.1, issue 01 (2009-06-30) of GBSS9.0 has no change.

BSS PS Handover 2 Overview


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2 Overview The IP-based services, such as VoIP, PoC, and Gaming, have high requirements for time delay in the case of cell reselection. As there is an ever increasing number of subscribers to the IP-based services, a solution for minimizing time delay is in great demand. To achieve the minimum possible time delay, Huawei introduces the PS Handover feature that can allocate radio resources to the MS in the target cell before the cell reselection is performed. Thus, the delay is shortened to no more than 150 ms. In addition, the PS Handover feature considers factors such as signal level and load of the neighboring cells before cell reselection is performed. This ensures a high success rate of the PS handover and great data throughput in the target cell, thus improving the QoS.

A PS handover is triggered by the Packet Cell Change Notification message sent by the MS or by the NC2 cell reselection algorithm. If the triggering conditions of the PS handover are not met, cell reselection is performed. After reselecting the target cell, the MS initiates a cell update procedure. If the triggering conditions of the PS handover are met, a PS handover is performed. In this case, radio resources are allocated in the target cell before the MS initiates a cell update procedure in the source cell. The BSC delivers the MS data in the source cell and target cell simultaneously, thus ensuring that services are not disrupted during cell update.

Currently, DTM handover is not supported. In DTM, the BSC makes handover decisions according to CS services. For details, see Handover Feature Parameter Description. CS handovers may disrupt PS services.

With respect to the BSC, PS handovers can be classified into the following types:

z Common intra-BSC inter-cell handover The source cell and the target cell belong to the same BSC but to different RAs or NSEs. For details, see Packet-switched handover for GERAN A/Gb mode; Stage 2

z Inter-BSC inter-cell handover The source cell and the target cell belong to different BSCs. Inter-BSC inter-cell handovers include 2G/3G inter-RAT handovers. Inter-RAT handover means that the source cell and target cell belong to the systems of different radio access technologies, for example, the 2G network and the 3G network.

Both the common intra-BSC inter-cell handover and the inter-BSC inter-cell handover involve three procedures: handover decision, handover preparation, and handover execution. The handover decision conditions of a common intra-BSC inter-cell handover are the same as those of an inter-BSC inter-cell handover.

BSS PS Handover 3 Technical Description


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3 Technical Description 3.1 Handover Decision The following conditions must be met before a PS handover is performed:

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

z The license of the BSC supports the PS handover. z The BSC supports the PS handover.

The settings of the parameters should meet any of the following requirements: Support NACC is set to YES, Network Control Mode is set to NC0 or NC1, and PS Handover

Support is set to YES. Support NC2 is set to YES, Network Control Mode is set to NC2, and PS Handover Support is

set to YES. z 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 received 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.

z Both the BSC and the SGSN support the Packet Flow Context (PFC) procedure. z Any of the following handover triggering conditions is met:

The MS operating in NC0 or NC1 mode sends the BSC a Packet Cell Change Notification message, which contains the information on the target cell. If the target cell is a neighboring 2G cell, a PS handover procedure is initiated. If the target cell is a neighboring 3G FDD cell and Support Out Inter-RAT Inter-Cell PS Handover is set to SUPPORT, a PS handover procedure is also initiated. Currently, a PS handover to a neighboring 3G TDD cell is not supported. The MS operating in NC2 mode sends MRs to the BSC. The BSC selects the target cell of the PS

handover according to the NC2 cell reselection algorithm. If the target cell is a neighboring 2G cell, a PS handover procedure is initiated. If the target cell is a neighboring 3G FDD cell and Support Out Inter-RAT Inter-Cell PS Handover is set to SUPPORT, a PS handover procedure is also initiated. Currently, a PS handover to a neighboring 3G TDD cell is not supported.

3.2 Common Intra-BSC Inter-Cell Handover Handover Preparation Figure 3-1 shows the procedure for the preparation of a common intra-BSC inter-cell handover.

3 Technical Description BSS

PS Handover


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Figure 3-1 Procedure for the preparation of a common intra-BSC inter-cell handover

1. The MS in the source cell sends a PS Handover Required message to the SGSN. The message contains the following information elements (IEs): old TLLI, handover cause, source cell identifier, target cell identifier, transparent container (containing the radio access capability of the MS, paging mode, global TFI, whether to request the system information of the target cell) from the source BSC to the target BSC, and active PFC list (containing the PFI of each PFC).

2. After receiving the PS Handover Required message, the SGSN determines the handover type (intra-SGSN handover, inter-SGSN handover, or inter-RAT handover) according to the target cell identifier and checks whether the routing area is changed. If the routing area remains unchanged, the SGSN sends the target BSC a PS Handover Request message. The message contains the following IEs: TLLI, IMSI, handover cause, source cell identifier, target cell identifier, transparent container from the source cell to the target cell, and PFC list to be created. If the routing area changes, the SGSN allocates a new P-TMSI to the MS and generates a new TLLI based on the P-TMSI before sending a PS Handover Request message to the target cell.

3. After receiving the PS Handover Request message, the target cell creates the MS context and requests the uplink channel resources. In addition, the target cell obtains its own system information and creates the transparent container from the target BSC to the source BSC.

4. The BSC sends the SGSN a PS Handover Request Acknowledge message. The message contains the following IEs: TLLI, successfully created PFC list, and transparent container (including the PS handover command and the system information of the target cell) from the target cell to the source cell. Then, the BSC prepares to receive downlink LLC PDUs. When the SGSN receives the PS Handover Request Acknowledge message, the resource allocation for the MS in the target cell is complete. At this time, the PS handover preparation phase ends and the PS handover execution phase begins.

Handover Execution Figure 3-2 shows the procedure for the execution of a common intra-BSC inter-cell handover.



3-3

Figure 3-2 Procedure for the execution of a common intra-BSC inter-cell handover

1. The SGSN sends downlink LLC PDUs to the MS through the source cell. 2. After receiving the PS Handover Request Acknowledge message, the SGSN sends subsequent

LLC PDUs to the target cell according to the QoS. The BSC sends downlink data to the MS on the allocated radio channels. At this time, the MS still camps on the source cell.

3. The SGSN sends a PS Handover Required Acknowledge message to the BSC. The message contains the following information elements: TLLI, successfully created PFC list, and transparent container (including the handover command and the system information of the target cell) from the target BSC to the source BSC. Before sending the PS Handover Required Acknowledge message to the BSC, the SGSN can suspend the downlink data transmission of any PDP context according to the QoS.

4. The BSC suspends the downlink data transmission and then sends a PS Handover Command message to the MS. After sending the message, the BSC resumes the downlink data transmission until no LLC PDU needs to be transmitted or the PFC is released. After receiving the PS Handover Command message, the MS stops data reception in the source cell and meanwhile suspends the uplink data transmission. After receiving the PS Handover Command message, the MS processes the uplink data as follows:

In the case of a PFC with an ongoing handover, all the uplink data packets that are not transmitted are buffered according to the QoS levels. Subsequent uplink data packets are buffered according to the QoS levels. The MS can discard uplink data packets during the link disruption period to meet the real-time

requirements.

3 Technical Description BSS

PS Handover


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5. On the radio channels allocated in the handover preparation phase, the MS sends the BSC a PS Handover Access message through four access bursts. The message contains the reference information on the handover.

6. Based on the reference information in the PS Handover Access message from the MS, the BSC determines whether to send the MS a Packet Physical information message. If the PS Handover Command message does not contain the TA, the BSC sends a Packet Physical information message containing the TA to the MS. If the PS Handover Command message contains the TA, the BSC does not send a Packet Physical information message to the MS.

7. The MS determines whether the routing areas of the source cell and target cell are the same. If they are the same, the MS sends a Cell Update message to the SGSN. If they are different, the MS sends a Routing Area Update Request message to the SGSN.

8. After the target cell successfully receives the first uplink data block, the BSC sends the SGSN a PS Handover Complete (containing the TLLI and IMSI) message, notifying the SGSN that the MS is handed over to the target cell.

9. The MS starts to send uplink data packets. 10. After receiving the PS Handover Complete message, the SGSN instructs the BSC to delete the

PFC corresponding to the source cell. After receiving the Delete BSC PFC message from the SGSN, the BSC deletes the corresponding PFC and TBF and releases the radio resources. Then, the BSC starts to receive data from the MS in the target cell.

3.3 Inter-BSC Inter-Cell Handover On the BSC side, the procedures for handover preparation and handover execution in an inter-BSC inter-cell handover are the same as those in a common intra-BSC inter-cell handover. The procedures on the core network (CN) side, however, are different. For details about the procedures on the BSC side, see 3.2 Common Intra-BSC Inter-Cell Handover. For details about the procedures on the CN side, see 3GPP TS 43.129 Packet-switched handover for GERAN A/Gb mode; Stage 2.

3.4 2G/3G Inter-RAT Handover 2G/3G inter-RAT handovers can be classified into inter-RAT handovers from GSM to UMTS and inter-RAT handovers from UMTS to GSM. Inter-RAT handover from GSM to UMTS is a handover in which the mobile terminal is handed over from a GSM cell to a UMTS cell. Inter-RAT handover from UMTS to GSM is a handover in which the mobile terminal is handed over from a UMTS cell to a GSM cell.

If a PS handover from a GSM cell to a UMTS cell is required, Support Out Inter-RAT Inter-Cell PS Handover should be set to SUPPORT. If a PS handover from a UMTS cell to a GSM cell is required, Support In Inter-RAT Inter-cell PS Handover should be set to SUPPORT.

On the BSC side, the preparation procedure for an inter-RAT handover from GSM to UMTS is the same as that for a common intra-BSC inter-cell handover. The difference is that the PS Handover Required message in an inter-RAT handover from GSM to UMTS contains the transparent container from the source BSC to the target RNC. The execution procedure for an inter-RAT handover from GSM to UMTS is the same as that for a common intra-BSC inter-cell handover. The difference is that the PS Handover Required Acknowledge message in an inter-RAT handover from GSM to UMTS contains the transparent container from the target RNC to the source BSC. For details, see 3.2 Common Intra-BSC Inter-Cell Handover.

On the BSC side, the preparation and execution procedures for an inter-RAT handover from UMTS to GSM is the same as those for a common intra-BSC inter-cell handover. For details, see 3.2 Common Intra-BSC Inter-Cell Handover.



3-5

On the CN side, the procedures for a 2G/3G inter-RAT handover are different from those for a common intra-BSC inter-cell handover. For details, see 3GPP TS 43.129 Packet-switched handover for GERAN A/Gb mode; Stage 2.

For details about 2G/3G inter-RAT handover, see 2G/3G Inter-RAT Handover of 2G/3G Interoperability Feature Parameter Description.

BSS PS Handover 4 Parameters


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4 Parameters The following describes the parameters related to PS handover.

For the meaning of each parameter, see Table 4-1. For the default value, value range, and related MML commands of each parameter, see Table 4-2.

Table 4-1 Parameter description (1)

Parameter Description

Support NACC

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 shorter time.

Network Control Mode

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 signalling failure or a random access failure.

PS Handover Support

Whether to support PS Handover(PS HO). The PS HO is used to reduce the interval of the cell reselection of the MS.

Support NC2

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.

Support Out Inter-RAT Inter-Cell PS Handover

Whether support Out Inter-RAT Inter-Cell PS Handover. The MS in the BSC local cell can be handed over to the UMTS cell through PS handover algorithm.

Support In Inter-RAT Inter-cell PS Handover

Whether to support In Inter-RAT Inter-cell PS Handover. The MS in the UMTS cell can be handed over to the BSC local cell through PS handover algorithm.

Table 4-2 Parameter description (2)

Parameter

Default Value

GUI Value Range

Actual Value Range

Unit MML Command

Impact

Support NACC NO

NO(No), YES(Yes) NO, YES None

SET GCELLGPRS(Optional) Cell

4 Parameters BSS

PS Handover


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GUI Actual MML Paramet Default er Value Value Range

Value Unit Range

Comman Impact d

Network Control Mode NC0

NC0(NC0), NC1(NC1), NC2(NC2)

NC0, NC1, NC2 None

SET GCELLPSBASE(Optional) Cell

PS Handover Support NO

NO(No Support), YES(Support) NO, YES None

ADD NSE(Optional) NSE

Support NC2 NO

NO(No), YES(Yes) NO, YES None


Support Out Inter-RAT Inter-Cell PS Handover

UNSUPPORT

UNSUPPORT(Not Support), SUPPORT(Support)

UNSUPPORT, SUPPORT None


Support In Inter-RAT Inter-cell PS Handover

UNSUPPORT

UNSUPPORT(Not Support), SUPPORT(Support)

UNSUPPORT, SUPPORT None


BSS PS Handover 5 Counters


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

BSS PS Handover 6 Glossary


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

BSS PS Handover 7 Reference Documents


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7 Reference Documents z 3GPP TS 43.129: Packet-switched handover for GERAN A/Gb mode; Stage 2 z 3GPP TS 48.018: BSC GPRS Protocol (BSCGP) z 3GPP TS 44.060: Radio Link Control/Medium Access Control (RLC/MAC) protocol z BSC6900 Feature List z BSC6900 Optional Feature Description z GBSS Reconfiguration Guide z BSC6900 GSM Parameter Reference z BSC6900 GSM MML Command Reference z BSC6900 Performance Counter Reference

1 Introduction to This Document 1.1 Scope 1.2 Intended Audience 1.3 Change History 2 Overview 3 Technical Description 3.1 Handover Decision 3.2 Common Intra-BSC Inter-Cell Handover 3.3 Inter-BSC Inter-Cell Handover 3.4 2G/3G Inter-RAT Handover

4 Parameters 5 Counters 6 Glossary 7 Reference Documents

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