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Video over Wireless : Performance Evaluation in the GSM Circuit-Switched Channel

Video over Wireless : Performance Evaluation in the GSM Circuit-Switched Channel. Almudena Konrad Amoolya Singh University of California, Berkeley December 7, 1999 www.cs.berkeley.edu/~agni/mm. Project Evolution. Understood the Matching Pursuits (MP) video codec

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Video over Wireless : Performance Evaluation in the GSM Circuit-Switched Channel

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  1. Video over Wireless: Performance Evaluation in the GSM Circuit-Switched Channel Almudena Konrad Amoolya Singh University of California, Berkeley December 7, 1999 www.cs.berkeley.edu/~agni/mm

  2. Project Evolution • Understood the Matching Pursuits (MP) video codec • Designed interface between MP and UDP (transport protocol) • packetization code: • packetized video stream • added RTP (Real Time Protocol) functionality • socket interface: send/receive data to/from UDP • Built testbed • putting all the pieces together • Sent video streams • collecting traces • Analyzed collected traces Application Packetization RTP Socket Interface UDP IP Data / Radio Link Physical

  3. Testbed & Tools MP Decoder MP Encoder UDP/IP/PPP RLP GSM Network PSTN Mobile Host Fixed Host GSM UNIX (BSDi 3.0) UNIX (BSDi 3.0) Base Station SocketDUMP SocketDUMP RLPDUMP MultiTracer Plotting & Analysis Tool MATLAB

  4. Decoder Encoded Video Stream Packet Reassembler Packetizer 512 2048 RTP seq, time RTP 12 Socket Socket UDP / IP / PPP / RLP Codec and Packetization Encoder frame rate: 10 Hz bit rate : 10.12 kbps

  5. ARQ protocol with a fixed frame size of 30 bytes (6 bytes header) Reliability at the cost of additional end-to-end delay User data rate of 9.6kbps, window size of 62 frames Error recovery mechanisms SREJ (initiated by receiver) Checkpointing (initiated by sender) A fr # 2 B 1 3 SREJ 2 4 5 timeout A P = 1 fr # 5 B 1 2 3 4 checkpointing 5 6 7 RLP: Radio Link Protocol

  6. Performance Analysis • Collect two sets of measurements • UDP/IP/PPP with RLP • UDP/IP/PPP without RLP • RLP: reliability vs. delay introduced • For each trace, we calculated • end-to-end delay of packets • throughput • loss rate • jitter (delay variation between packets) • For each metric, we calculated statistics • avg, std dev, min, and max values

  7. Measurements with RLP4000 Kbits of video traces ~ 7 min of connection - buffer overflow in sender’s kernel - packet loss rate < 1% - mobile signal strength (3-4)

  8. Measurements without RLP4000 Kbits of video traces ~ 7 min of connection - buffer overflow in sender’s kernel - packet loss rate 13.93 % - mobile signal strength (1-3) - mean interarrival time increases as packet loss rate increases

  9. Metrics Note: non-RLP measurements taken on worse radio environment

  10. Conclusions • Delay introduced by RLP degrades performance on delay-sensitive traffic • jitter increases • Packet loss increases without RLP • Low RLP data rate causes buffer overflow

  11. Ongoing Work • Collect measurements on environments with different error characteristics • Incorporate error resilience functionality • Implement UDP Lite, PPP Lite, RLP Lite • allows corrupted data to be used by error resilient codecs • compare performance statistics with existing data • Send video and audio on different channels

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