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Wide band speech introduction into VoIP solutions9th June 2004

Gilbert DERVAL, Yannick MAHIEUX, D. DELEAMFrance Télécom - R&D Division

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VoIP : an opportunity for Wide band

s Packets switching networks offer bit rate versatility

s Wide bandwith links are available, even in access

networks

s IP services integration enables heterogeneous

solutions

s IP terminals become more and more intelligent

QEmbedded codecs and signal processing

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What are the success conditions?

s Limited impact on installed infrastructureQNetworkQServices platformsQTerminals

s Interoperability with existing solutions

s Short term availability

s Clear IPR situationQSimplicityQLow cost

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Limited impact on network infastructure

s Low bit rate increase

s No need of additionnal signalling channels

s Adaptability to traffic conditions

s Versatility when faced with different access

networks

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Low impact on service platformsWide band / narrow band interoperability

s No additionnal function in the call control equipment : VoIP protocols implement codec negotiation

s No additionnal transcoder in gateways

s Wide band messages on voice mail equally available from a wide band or a narrow band terminal

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Limited impact on terminals (1)

s The simplest case : reuse of POTSQTransducers (earpiece, open listening speaker) weak bandwith frequency compensation for low frequencies (<300 Hz) and high frequencies (>3400 Hz)QNeed of an external box such as a Home Gateway including the software (codec, VoIP protocols, RTP/UDP/IP stack, …)

s Softphones in PC : no problemQMultimedia equipment provides wide bandwithQPowerfull processors allow software implementation of complex algorithms (codecs, echo cancellation, …)

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Limited impact on terminals (2)

s Wide band IPphones :a specific design

QTransducers need to be chosen with care (bandwith, dimensions,…)

QAcoustic design has to be careful, specially for handsfree features (mechanic vibrations, acoustic coupling, echo cancellation)

s One example : France Telecom / ADTech SI-171

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Limited impact on terminals (3)s Wireless terminals

QThe same issues as the IPphones (tranducers, acoustics, …), –but made more difficult by the small terminal size

QAdditionnal issues due to the wireless link bitrate–WiFi : OK, no bandwith problem–Bluetooth : still under investigation (no defined codec)–DECT : not impossible but difficult (no R&D investment)

s Mobile phonesQWide band available in UMTS Release 5 in packet mode as in circuit modeQFirst wide band mobile phones available Q4 2004 / Q1 2005QSame bit rate as nowadays mobile phones : 12.65 kbps

s CPU issuesQSingle processor architectureQEmbedded applications (video, data)QWide band must have memory and CPU reasonable requirements

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IPR : keep it simple and low cost

s Short time to market Qsimple IPR licensing

–if possible, a single negotiating partnerQno long and costly negotiations

s Cost reductionQas few additionnal licences as possibleQIf possible, pay only the extra charge due to the changeover from narrow band to wide band

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A structuring component : the codecs The codec choice impacts the whole of the above issues

QBit rate in the network QVersatility when faced with different access networksQVersatility in case of network traffic problemsQWide band / narrow band interoperabilityQTranscoder need on VoIP services platform (Gateway, voice mail server, …)QTerminals (memory, CPU)QIPRQAudio quality

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One solution : a scalable codec

s Two parts in the bitstream :QA narrow band core compliant to G.729QA wide band additionnal part

s A wide bit rate range QByte level granularity for packets filling optimizationQWide band minimum bit rate at least from 14 kbpsQSame audio quality as G.722 for higher bit rates

s Dynamic bit rate variation without additionnal signalling

s A standardized narrow band core G.729 codecQLower cost and simplified IPR situationQWide band G.729 extension

s An ITU-T action is currently under discussion

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Conclusion : let's do it ASAP

s VoIP is currently in a phase of fast expansion

s Wide band can increase VoIP attactiveness

s Once the deployed terminal base too large, it will be more difficult to integrate evolutions

s So, it's necessary to be fast