Voice Over HSPA

WCDMA RAN

Voice over HSPA/HSPA+ Feature Parameter Description

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

WCDMA RAN Voice over HSPA/HSPA+ Contents

Issue 01 (2010-03-30) Huawei Proprietary and Confidential Copyright © Huawei Technologies Co., Ltd

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

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

2 Overview of Voice over HSPA/HSPA+/ ................................................................................2-1 2.1 Development of UMTS Voice Bearer Technologies ...................................................................... 2-1 2.2 Schemes of Voice over HSPA/HSPA+ .......................................................................................... 2-1

3 Technical Description ..............................................................................................................3-1 3.1 Bearer............................................................................................................................................ 3-1 3.2 Scheduling and Flow Control ........................................................................................................ 3-1 3.3 Mobility .......................................................................................................................................... 3-2 3.4 Functions of Increasing Air Interface Capacity.............................................................................. 3-3 3.5 Functions of Increasing Trasmission Efficiency on the Air Interface............................................. 3-3

4 Glossary ......................................................................................................................................4-1

5 Reference Documents .............................................................................................................5-1

WCDMA RAN Voice over HSPA/HSPA+ 1 Introduction


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1 Introduction 1.1 Scope This document describes the development of voice bearer technologies and the bearer schemes of voice over HSPA. It provides an overview of the key technologies used for HSPA to carry CS/PS voice.

1.2 Intended Audience This document is intended for:

Personnel who are familiar with WCDMA basics Personnel who need to understand voice over HSPA Personnel who work with Huawei products

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: refers to the change in the voice over HSPA feature. 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 (2010-03-30) Draft (2009-12-05)

01 (2010-03-30) This is the document for the first commercial release of RAN12.0.

Compared with issue Draft (2009-12-05) of RAN12.0, this issue optimizes the description.

Draft (2009-12-05) This is the draft of the document for RAN12.0.

This is a new document.

WCDMA RAN Voice over HSPA/HSPA+ 2 Overview of Voice over HSPA/HSPA+/


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2 Overview of Voice over HSPA/HSPA+/ 2.1 Development of UMTS Voice Bearer Technologies UMTS voice services consist of the AMR service (CS voice) and the VoIP service (PS voice). The traditional voice bearer scheme is voice over DCH. With the development of technologies and the enhancement of bearer efficiency, HSPA/HSPA+ is being increasingly used for voice bearer.

Table 2-1 describes the development process of UMTS voice bearer technologies.

Table 2-1 Development process of UMTS voice bearer technologies

Protocol Release CS Voice PS Voice

3GPP Release 99 AMR over DCH -

3GPP Release 4 TFO, TrFO, and soft switch -

3GPP Release 5 AMR-WB over DCH VoIP over DCH (IMS-based)

3GPP Release 6 - VoIP over HSPA

3GPP Release 7 - VoIP over HSPA+ (CPC)

3GPP Release 8 AMR over HSPA/HSPA+ -

Table 2-2 compares different voice bearer technologies.

Table 2-2 Comparison between voice bearer technologies

Item AMR over DCH AMR over HSPA/HSPA+

VoIP over HSPA/HSPA+

VoIP over DCH

Radio bearer R99 DCH HSPA/HSPA+ HSPA/HSPA+ DCH

RNC rate control AMRC AMRC None None

RLC TM UM UM UM

CN CS CS PS+IMS PS+IMS

Terminal Ordinary terminal Supports HSPA/HSPA+.

Supports AMR over HSPA/HSPA+.

Supports HSPA/HSPA+.

Supports the VoIP client.

Supports the VoIP client.

2.2 Schemes of Voice over HSPA/HSPA+ The traditional voice bearer scheme is AMR over DCH. In 3GPP R99, the VoIP over DCH technology is feasible, but it does not improve the capacity and performance to a great extent compared with AMR over DCH. The HSPA/HSPA+ technology, especially HSPA+ Continuous Packet Connectivity (CPC), can greatly increase the transmission efficiency of voice services (or small-volume services) and cell

2 Overview of Voice over HSPA/HSPA+/ WCDMA RAN

Voice over HSPA/HSPA+

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

Issue 01 (2010-03-30)

capacity and reduce UE battery consumption. Thus, the HSPA/HSPA+ technology is being increasingly used for transmitting voice services.

The voice over HSPA/HSPA+ schemes consist of VoIP over HSPA/HSPA+ (WRFD-010617 VoIP over HSPA/HSPA+) and AMR over HSPA/HSPA+ (WRFD-010619 CS voice over HSPA/HSPA+).

Figure 2-1 shows the data flow of VoIP over HSPA/HSPA+ and AMR over HSPA/HSPA+.

Figure 2-1 Data flow of VoIP over HSPA/HSPA+ and AMR over HSPA/HSPA+

The two voice bearer schemes are described as follows:

VoIP over HSPA/HSPA+ In the RAN, the VoIP service is carried on the HSPA/HSPA+ channel. In the CN, the VoIP service is carried on the PS domain and requires the support of the IMS. The IMS controls calls and connections by using the SIP protocol. Compared with voice data, TCP/IP headers are very large, which greatly reduces the transmission efficiency of the air interface. Therefore, the VoIP service requires the support of Robust Header Compression (RoHC) to reduce the overhead of TCP/IP headers.

AMR over HSPA/HSPA+ In the RAN, AMR over HSPA/HSPA+ enables the CS voice to be carried on the HSPA/HSPA+ channel instead of the DCH. In the CN, the AMR service is carried only on the CS domain. Thus, operators need not deploy the IMS for the VoIP service. Only RNCs need to update the related mapping to support AMR over HSPA/HSPA+. MSCs and NodeBs are not affected. The call process of AMR over HSPA/HSPA+ is the same as that of AMR over DCH. The PDCP capability and signaling are extended to same extent.

Voice services have a small traffic volume. When services with a small volume are carried on the HSPA/HSPA+ channel, the power and codes of downlink HS-SCCHs and the power of uplink DPCCHs account for a large proportion of the total resources. CPC (DTX, DRX, and HS-SCCH Less Operation) can greatly reduce the resource consumption of these channels and significantly increase the capacity of a single cell. Therefore, the scheme of voice over HSPA/HSPA+ becomes more logical after CPC is introduced.

WCDMA RAN Voice over HSPA/HSPA+ 3 Technical Description


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3 Technical Description This provides an overview of the key functions related to voice over HSPA/HSPA+ so that you can have a general understanding of these functions.

3.1 Bearer This section involves the feature "WRFD-01061701 RAB Mapping.”

For AMR over DCH, the CN transmits three sub-flows to the RNC, and then the RNC sets up three RBs by using TM RLC to carry the three sub-flows. For VoIP/AMR over HSPA/HSPA+, the CN transmits only 3 flows to the RNC, and then the RNC merges them into one flow and sets up one RB by using UM RLC to carry the flow. The difference between AMR over HSPA/HSPA+ and VoIP over HSPA/HSPA+ is that PDCP contains RTP/UDP for VoIP not for AMR.

Figure 3-1 shows the difference between these voice bearer schemes.

Figure 3-1 Difference between voice bearer schemes

CS and PS voice can be carried on the DCH, HS-DSCH, or E-DCH, depending on bearer policies and switching parameters. For details, see the Radio Bearers Feature Parameter Description.

The outer loop power control (OLPC) target of voice over HSUPA is RBLER. HSUPA OLPC adjusts the SIR target of DPCCH pilot based on the comparison between the RBLER target and the measured RBLER. For details, see the Power Control Feature Parameter Description.

3.2 Scheduling and Flow Control This section describes/involves the feature "WRFD-01061703 Optimized Scheduling for VoIP over HSPA.”

Voice services such as VoIP and AMR are delay-sensitive. The functions of scheduling and flow control need to meet the delay requirements of voice services.

HSDPA scheduling and flow control Before voice data is scheduled, it enters priority queues of MAC-hs/ehs and waits for scheduling. According to the waiting time in the queues, voice data is classified into urgent data and non-urgent data. If the voice data is urgent data, its scheduling priority is raised. Otherwise, the voice data is considered as ordinary data and waits in the queue. Thus, the voice data can meet the delay requirement and does not occupy too many resources. For details on scheduling, see the HSDPA Feature Parameter Description.

3 Technical Description WCDMA RAN



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Voice services have a small traffic volume, and they have a little impact on the Iub interface and require that the delay be as short as possible. Therefore, flow control is not required for voice services. For details, see the Transmission Resource Management Feature Parameter Description. If there is no flow control, admission control is required to ensure that sufficient resources are available for voice services to guarantee the QoS. The GBR admission control is used for the VoIP service, and the MBR admission control is used for the AMR service. For details, see the Call Admission Control Feature Parameter Description.

HSUPA scheduling and flow control Voice services have a high requirement for delay, and therefore flow control and scheduling are not performed so that voice data can be transmitted quickly. For details, see the HSUPA Feature Parameter Description and Transmission Resource Management Feature Parameter Description. If there is no flow control or scheduling, the QoS is guaranteed through admission control. Admission control ensures that sufficient resources are available for voice services. For details, see the Load Control Feature Parameter Description.

3.3 Mobility Mobility of VoIP over HSPA/HSPA+ For the handover of VoIP over HSPA/HSPA+, whether the target cell supports VoIP over HSPA/HSPA+ needs to be considered. The possible scenarios of handover are as follows:

Handover between the cells that support VoIP over HSPA/HSPA+ (intra- or inter-frequency handover): follows the normal handover procedure.

Handover between the cells that support VoIP over HSPA/HSPA+ and the cells that do not support VoIP over HSPA/HSPA+ (intra- or inter-frequency handover): VoIP over HSPA/HSPA+ needs to roll back to VoIP over DCH or AMR over DCH.

Handover between the cells that support VoIP over HSPA/HSPA+ and the GSM cells: VoIP over HSPA/HSPA+ needs to roll back to AMR over DCH before handover.

Mobility of AMR over HSPA/HSPA+ AMR over HSPA/HSPA+ enables AMR services to be carried on the HSPA/HSPA+ channel, which results in the change in the mobility management of AMR services.

In the case of static relocation or relocation due to hard handover, when the target RNC supports AMR over HSPA/HSPA+, the H2H relocation procedure is initiated. When the target RNC does not support AMR over HSPA/HSPA+, AMR over HSPA/HSPA+ needs to roll back to AMR over DCH and then the D2D relocation procedure is initiated.

The handover function of AMR over HSPA/HSPA+ is similar to that of AMR over DCH. AMR over HSPA/HSPA+ has no impact on decision and triggering of handovers. AMR over HSPA/HSPA+ does not support unilateral HSPA/HSPA+ bearer (UL HSUPA/DL DCH, or UL DCH/DL HSDPA). Therefore, there are new requirements for the mobility management of AMR over HSPA/HSPA+.

In the case of 1A/1C, there are no additional requirements for adding new cells. In the case of 1B/1C, if the cells to be removed are non-serving cells, there are no additional requirements. Otherwise, AMR over HSPA/HSPA+ needs to roll back to AMR over DCH before the handover.

In the case of 1D, if the new best cell supports HSPA/HSPA+, there are no additional requirements. Otherwise, AMR over HSPA/HSPA+ needs to roll back to AMR over DCH before the serving cell changes.

In the case of 1J, mobility management involves only the E-DCH active set and there are no additional requirements.

WCDMA RAN Voice over HSPA/HSPA+ 3 Technical Description


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For hard handover, if the target cell supports HSPA/HSPA+, the normal handover procedure is performed. If the target cell does not support HSUPA or HSDPA, AMR over HSPA/HSPA+ needs to roll back to AMR over DCH, along with a hard handover.

When a UE moves from the GSM cell to a 3G cell, the inter-RAT incoming handover procedure may be triggered. For voice over HSPA/HSPA+, associated parameters need to be configured. For voice over DCH, the normal handover procedure is performed. When a UE moves from the 3G cell to a GSM cell, the inter-RAT outgoing handover procedure may be triggered. It is a normal handover procedure.

3.4 Functions of Increasing Air Interface Capacity The fundamental method of increasing capacity is to minimize resource consumption and guarantee the QoS, that is, reducing uplink interference, downlink transmit power, and downlink codes.

Voice services generate and transmit voice packets every 20 ms. In the case of intermittent transmission, data on associated control channels need not be received or transmitted continuously. Voice services have a small traffic volume, but the resources used by control channels account for a large proportion of the total resources. This is the key factor that limits the cell capacity of voice over HSPA/HSPA+. To solve this problem, 3GPP has introduced the F-DPCH, HS-DPCCH preamble and postamble, and CPC (HS-SCCH Less Operation and DTX/DRX) to reduce the overhead of associated control channels.

F-DPCH Before the Fractional DPCH (F-DPCH) is introduced, each HSDPA user requires an associated DPCCH, which consumes the downlink power and codes.

The F-DPCH is introduced in 3GPP Release 6. The F-DPCH is a simplified DPCCH and has only a TPC field. One F-DPCH can be shared by up to 10 UEs. Therefore, F-DPCHs reduce the consumption of associated DPCCHs and save the codes and power of the cell.

HS-DPCCH Preamble and Postamble Preambles and postambles are introduced in 3GPP Release 6. The UE can send them before or after sending NAC/ACK to improve the possibility of demodulation of ACK/NACK. These preambles and postambles decrease the requirements for HS-DPCCH power and reduce the uplink interference.

For details on HS-DPCCH power control, see the Power Control Feature Parameter Description.

DTX/DRX For services such as VoIP and web browsing, UEs need to maintain uninterrupted connection and transmit data intermittently. When the number of UEs of this type increases, uplink DPCCHs greatly increase the uplink load of the cell. In the downlink, UEs need to listen to HS-SCCHs without interruption, thus wasting battery power.

DTX/DRX is introduced in 3GPP Release 7. Uplink DTX allows UEs to disable the uplink DPCCH transmission periodically to reduce interference caused by the uplink DPCCH and increase uplink capacity. Downlink DRX allows UEs to receive data on the HS-SCCH at the specified time periodically, thus reducing the power consumption of UEs.

For details on DTX/DRX, see the HSPA+ Feature Parameter Description.

3.5 Functions of Increasing Trasmission Efficiency on the Air Interface Encapsulating VoIP voice data into an IP packet results in a large overhead. IPv4 and IPv6 increase the packet size by 40 bytes and 60 bytes respectively, as shown in Figure 3-2. The IP header is larger than voice data, and thus the transmission efficiency of the air interface decreases to a great extent.

3 Technical Description WCDMA RAN



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Figure 3-2 An example of IPv6 encapsulation

Therefore, before transmission on the air interface, the IP header needs to be compressed. RoHC is introduced in the 3GPP PDCP. It is used to compress IP headers. After RoHC is performed, the redundant headers are reduced from 40–60 bytes to 3–5 bytes.

For details on RoHC, see the PDCP Header Compression Feature Parameter Description.

WCDMA RAN Voice over HSPA/HSPA+ 4 HGlossaryH


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

WCDMA RAN Voice over HSPA/HSPA+ 5 Reference Documents


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5 Reference Documents [1] HSDPA Feature Parameter Description

[2] HSUPA Feature Parameter Description

[3] Transmission Resource Management Feature Parameter Description

[4] Handover Feature Parameter Description

[5] Power Control Feature Parameter Description

[6] Load Control Feature Parameter Description

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