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Simple LDPC-Staircase FEC Scheme for FECFRAME draft-roca-fecframe-ldpc-01

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Simple LDPC-Staircase FEC Scheme for FECFRAME draft-roca-fecframe-ldpc-01. IETF 79 – Beijing, November 2010 V. Roca – M. Cunche (INRIA) J. Lacan (ISAE). Goals. specifies how to use LDPC-staircase codes in FECFRAME complements our RFC 5170 (RMT WG) - PowerPoint PPT Presentation
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PowerPoint Presentation - Security and Reliable Multicast Transport Protocols: Discussions and Guidelines

Simple LDPC-Staircase FEC Scheme for FECFRAME draft-roca-fecframe-ldpc-01IETF 79 Beijing, November 2010

V. Roca M. Cunche (INRIA)J. Lacan (ISAE)

11 Goalsspecifies how to use LDPC-staircase codes in FECFRAMEcomplements our RFC 5170 (RMT WG)provides a single scheme: LDPC-Staircase for arbitrary packet flows

DOES NOT consider RTP framing of FEC repair packetsleft to future works if the need arises22Modifications since -00 versioninitial -00 version in July 2009get stuck by Qualcomm's patent on FECFRAMEsame situation as that of Reed-Solomonforced to wait until the situation is clarified

00 versus 01 modifications:take draft-roca-fecframe-simple-rs-01 and replace reference to "Reed-Solomon" by "LDPC-Staircase"RS and LDPC I-D are now almost the sameonly minor modifications to address LDPC specificities (e.g. FSSI)same philosophy : K.I.S.S.restrict to the case where G==1 in RFC 5170see: http://www.ietf.org/mail-archive/web/rmt/current/msg01384.html3Why yet another FEC scheme?well suited to certain FECFRAME applicationswith high bitrate flowswhen a large number of flows must be globally protectedwhen low complexity software decoding is a MUST

complements (but does not replace) Reed-Solomon and 2D parity schemesAn example of use:K. Matsuzono, J. Detchart, M. Cunche, V. Roca, H. Asaeda"Performance Analysis of a High-Performance Real-Time Application with Several AL-FEC Schemes"IEEE Local Computer Networks (LCN'10), October 2010

4DVTS/FECFRAME results (from LCN'10)DVTS: a high-performance/high-throughput real-time/interactive video application over IPDigital Video Transport System (DVTS)support DV/HDV formatsCBR flows: 30 Mbps (DV format)widespread use (symposium, e-learning, telemedicine)see: http://www.sfc.wide.ad.jp/DVTS/ http://www.internet2.edu/communities/dvts/senderDVTSfecframe lib.DVTSfecframe lib.

IP networks(congestion, fading, etc)

5Experimental Setup3 performance metrics:recovery capabilitiesframe delay above FECFRAMECPU loadFEC CodesSymbol Length (Bytes)Code RateSource Block Length (k)N12D Codes13752/316noneRSE Codes13752/3170noneLDPC Codes13752/3170500100075566Experimental SetupSENDER: Pentium4 / 2.4 GHz512 MB RAM / 32-bit LinuxRECEIVER: Core2 / 1.66GHz512 MB RAM / 32-bit Linux

packet loss proba. (0% ~ 51%)77

2D codes2D codes unrecovered data loss continuously happens RS, LDPC codes no data loss until 30% packet loss probabilityRS codesLDPC codes(k=170)LDPC codes(k=500, 1000)Results: recovery capabilities882D codes: usually lower than 50msec RS: over 100msec around 12% loss rateover 500msec around 30% loss rate LDPC codes When k=170, 50msec until 24% loss rate, 89msec above When k= 500,1000, greater especially in high loss rates

RS codesLDPC codes(k=500, 1000)Results: frame delay after FECFRAME proc.992D codesRS codesLDPC codesk161701705001000Ave. CPU load (%)14.174.312.011.012.6

RS codes2D codesLDPC codes(k=170)LDPC codes(k=500, 1000)Results: CPU loadsender:

receiver:1010Resultsin summary:for this target environment, LDPC-staircase codes (k=170) were the best choicesee paper for additional details

additionallyif several DVTS flows were to be carried between the same locations, globally FECFRAME protected, LDPC-staircase codes (with higher k) would be even more beneficial 11More fundamentally, LDPC-staircase codeshave excellent recovery capabilitiese.g. k=256 symbols, N1=7: average overhead=0.68%(i.e. 1.74 symbols in addition to k)while keeping very high decoding speedse.g. k=256, N1=7: 1.39-2.46 Gbps(Xeon 5120/1.86GHz, 64-bit Linux)12.6 to 28.2 times faster than RS over GF(28)

RS over GF(28)RS over GF(24)LDPC (N1=5 & 7)

RS over GF(24)RS over GF(28)LDPC (N1=7)Erasure recovery testsDecoding speed tests12RS over GF(28): 0.10-0.11 GbpsRS over GF(24): 0.90-0.94 Gbps12To concludeLDPC-staircase codessimple, easy to understand and implementclose to ideal recovery performanceshigh performance codec developed in an open source projectan interesting alternative to proprietary codesconsidered in standards

current I-D is considered as finishedready for WGLC if accepted as WG Item13To conclude, next steps will consist in:1-

This is our roadmap!

Last but not least, WG Item?13

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Simple LDPC-Staircase FEC Scheme for FECFRAME draft-roca-fecframe-ldpc-01 IETF 79 – Beijing, November 2010 V. Roca – M. Cunche (INRIA) J. Lacan (ISAE) 1
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