CDG Technology ForumCDG Technology Forum

CDMA PoC:CDMA PoC:Interoperability & Interoperability &

Global PoC StandardsGlobal PoC Standards

Kalle Ahmavaara, Nokia, CDMA2000 Standardization

kalle.ahmavaara@nokia.com

San Diego, June 30th, 20041 © NOKIA

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Interoperability between PoC Clients

Example consumer PoC use cases:• Family in the shopping mall or theme parks

communicating plans• Group searching a person or a location • Discussing the game in a sports event• A group coordinating where to meet for an evening out• Teenagers organizing a party or calling friends during the

party• PoC chat groups

The service acceptance and the resulting market size for all of the above is completely different with a globally interoperable solution!

Anybody needs to be able to initiate PoC Session with anybody!

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Two Methods for PoC Interoperability1. Usage of a Common Global system

• Off-the-self, interoperable products from several vendors with competitive prices

• Lightest possible Network Functionality with no network media processing

• Backwards & forwards compatibility is taken care by the standard

• New features easy to introduce• Poc with data, pictures, video...• All interoperable immediately without

any network changes

• Optimal quality of service

GW1

GW1GW1

2. Signalling gateways & Media Transcoders

• Decreased quality of service

• Burden of specifying, implementing, operating and updating several PoC systems.

• No benefit from features that are not interoperable

• Complex and costly network with all the time increasing complexity

• Media packet processing in Nw• Difficult introduction of new features

• Gateway may become a bottleneck & control point

Usage of gateways & transcoders should be avoided whenever possible!

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OMA PoC Standardization

• Wide commitment in Industry to OMA PoC work.

• PoC WG is chaired by T-Mobile and co-chaired by Sprint & Vodafone. • Strong drive from carriers!

• OMA is committed to complete OMA PoC standard by the end of 2004

OMA produces following POC Specifications:

OMA PoC Requirements Document (OMA PoC RD): Approved, Editor: Siemens

OMA PoC Architecture Document (OMA PoC RD) : Final Review: Editor: Nokia

OMA PoC Control Plane Specifications: Draft (~50% completed), Editor: RIM• Specifies the usage of SIP signalling for OMA PoC

OMA PoC User Plane specification: Draft (~50% completed), Editor: Ericsson• Specifies the user plane (media, floor control, etc) for OMA PoC

Full set of PoC specifications available December 2004 from OMA!

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OMA Service Enablers and IMS/MMD

• OMA SIP based service enablers (like PoC) are to be specified on top of a common IMS/MMD platform

• IMS/MMD platform provides e.g. following features:

• Routing and reachability• Authentication and transitive trust• Signaling compression• Privacy • User profile storage• Charging, accounting• Interface to the access network

• These wheels do not need to be invented for each new service!

Service EnablersService Enablers

IMS/MMD Service IMS/MMD Service CCoreore

DynamicSubscriptionManagement

SessionControl

IntelligentChargingControl

OtherEnablers

Downloading, Streaming,

Messaging,...PoC

IP Connectivity

ISC

IMS Platform approach greatly reduces the OMA PoC Specification effort!

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End-to-End PoC Codec: Impact to System Efficiency

Different ways to optimize system capacity for different services:

1) Optimization for Traditional Conversational Speech:• Optimized codecs for each radio interface. • Each radio system has its own speech codecs optimized for the radio frame sizes

2) Optimization for PoC • Traffic model is different from conversational speech• Key optimization for PoC is the efficient packet based channel allocation

- System capability to fast packet based channel allocation for each talk burst- System capability to allocate reverse and forward links separately

Packet switchedCircuit switched

User action timerexpiry

0 Time (s)10 20 30 40 50

PTT button pressed / released / Reverse link resource reservedForward Link resource reserved

PoC should be kept as a generic IP service decoupled from air interfaces

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End-to-End PoC Codec: User Point of View

• EVRC Half Rate and AMR 5,15 are typical PoC speech codecs for CDMA and GSM

• Listening Test Arranged to test the quality of end to end speech coding versus transcoding:

• With end-to-end speech coding (no transcoding) the speech quality scores are above MOS 3.

• Transcoded EVRC-HR - AMR515 PoC sessions will have a very low quality

• MOS around 2 • The quality level may be unacceptable for

end users

1

1.5

2

2.5

3

3.5

4

4.5

5

Direct AMR 5.15 EVRC -HR AMR ->EVRC

EVRC->AMR

• It is clear that users will notice the QoS difference between End-to-End and transcoded connections

It may be that transcoded speech is not considered as a proper PoC service

Mean Opinion Score (MOS) results fora few narrowband speech samples

4,0

3,43,0

2,21,8

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AMR in CDMA PoC?: Feasibility Point of View

• Example AMR usage for PoC in GPRS: AMR 5,15mode, 8 frames encapsulated in one AMR RTP payload according to RFC 3267.

• How this fits to CDMA?

AMR RTP Payload packet, 110 octets

RTP packet, 122 octets

UDP packet, 130 octets

IP packet, 150 octets

5.15

ToC AMR payload = 8 x 20 ms = 824 bits = 103 octetsH

5.15 5.15 5.15 5.15 5.15 5.15 5.15

ToC AMR payloadHRTP

ToC AMR payloadHRTPUDP

ToC AMR payloadHRTPUDPIPv4

ToC AMR payloadHRTPUDPIPv4PPP PPP, 155 octets

8 AMR 5.15 frames, 160 ms of speech, 103 octets

Up to 160 octets

-Usage of basic ROHC header compression would improve the capacity and reduce delay variation

No issues in using AMR for PoC even in current 1X SO 33 over RS I channel

CDMA Case: Service option 33, without header compression. Fundamental RateSet -I channel.

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Summary

PoC requires wide interoperability for its success • Carrier specific PoC systems with advanced features don't add value

OMA PoC specifications to be available by end of year 2004• OMA PoC specifications are as compatible for CDMA as for GSM/GPRS• With OMA PoC a carrier has widest selection of handsets and PoC servers• OMA compliance ensures the future proofness of the solution

The application level issues (both media and signalling) should be kept decoupled from the underlying radios • Maximum flexibility for service evolution• No special CDMA transport solutions should be tailored for PoC• Generic packet channel based transport will greatly increase PoC capacity

An end-to-end media codec should be used when possible• Transcoder based solution could produce non acceptable speech quality• There is no technical reason why AMR could not be used also in CDMA PoC

PoC SIP signalling includes dynamic codec negotiation • CDMA packet transport (1X SO33, 1xEV-DO, 1xEV-DV) is suitable for any codec• No need to hard code specific PoC media codecs to 3GPP or 3GPP2