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Cross-layer Two-stage FEC Scheme for Scalable Video Transmission over Wireless Networks

Cross-layer Two-stage FEC Scheme for Scalable Video Transmission over Wireless Networks. Yufeng Shan, Su Yi, Shivkumar Kalyanaraman and John W. Woods Rensselaer Polytechnic Institute. Google “Shiv RPI”. Outline. Problems Our proposed schemes Enhanced wireless MAC/PHY layer Two-stage FEC

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Cross-layer Two-stage FEC Scheme for Scalable Video Transmission over Wireless Networks

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  1. Cross-layer Two-stage FEC Scheme for Scalable Video Transmission over Wireless Networks Yufeng Shan, Su Yi, Shivkumar Kalyanaraman and John W. Woods Rensselaer Polytechnic Institute Google “Shiv RPI”

  2. Outline • Problems • Our proposed schemes • Enhanced wireless MAC/PHY layer • Two-stage FEC • Simulations • Conclusions

  3. Problems – 802.11 LANs • Any bit error can cause a whole packet being dropped • No cooperation between layers • 802.11 MAC ARQ is not efficient for packet bit error

  4. Our proposed two schemes • Enhanced MAC/PHY layer using Header CRC/FEC • helps to pass packet with errors to application and to forward more packets to next node • Two-stage FEC scheme at application layer • to cooperative with enhanced MAC/PHY layer for error recovery, both packet drop and bit error.

  5. System Diagram Video Encoder Stage1 FEC Encoder Stage2 FEC Encoder Application UDP-lite Enhanced Protocol Stack IP MAC PHY Video Decoder Stage1 FEC Decoder Stage2 FEC Decoder Enhanced MAC/PHY layer using header CRC/FEC increases application layer throughput Stage 1: Packet level Stage 2: Bit level

  6. Enhanced MAC/PHY layer Enhance MAC/PHY layer for multimedia: • Header CRC: only CRC the header part • Header FEC: add small bit level FEC to protect header part from bit errors Only header CRC/FEC HeaderFEC Headers FEC IP Packet payload APP UDP MAC

  7. Enhanced MAC/PHY layer 802.11 physical bandwidth 2 Mbps Packet payload 1000 bytes • Packet CRC checks whole packet • Header CRC checks only headers • Header FEC protect headers with BCH(511,502,1) Single hop application throughput Packet may have errors inside

  8. Two-stage FEC • FECs are processed only at application layer • Can recover both packet losses and bit errors inside packet • Cooperate with enhanced MAC/PHY layer to improve the application layer throughput.

  9. Two-stage FEC Error free throughput Effective application throughput increased Two-stage FEC: payload is protected by BCH(8191,8000,14)

  10. ns-2 simulations • ns-2 802.11b wireless module, PHY layer bandwidth is set to 2Mbps; • MAC layer retransmission 2; Channel model: Gilbert (burst length: 2) • Two-stage FEC: RS code + BCH code • Two scenarios: • Single hop: from sender to receiver1, CBR traffic is set to 2Mbps • Multi-hop: from sender to recever2, receiver 1 is relay node, CBR traffic is set to 1.2Mbps

  11. ns-2 simulations - throughput Single hop Multi-hop Header FEC: BCH(8191,8000,14) for payload, BCH(510,480,3) for header Packet CRC: 802.11b Header CRC: BCH(8191,9000,14) for payload

  12. ns-2 simulations – video • Monochrome Foreman, CIF, 30fps, 16 frame/GOP, source coder: MC-EZBC • Bitstream is pre-encoded with MD-FEC at 1 Mbps, 10% loss rate • Two kinds of simulations: • Single hop fixed FEC, CBR 1Mbps • Multi-hop w/ adaptive FEC, bitstream and FEC protection adapts based on network conditions

  13. ns-2 simulations - video Video PSNR of the first 7 GOPs PSNR = 0 if no enough bandwidth for base layer Multi-hop Single hop

  14. Conclusions • Two-stage FEC with enhanced MAC/PHY layer using header CRC/FEC increases application layer throughput • Efficient in wireless multimedia error protection. • Cooperation between layers can increase performance for multimedia over wireless networks.

  15. Thanks

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