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. 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 RTP UDP IP Data / Radio Link Physical Socket Interface Packetization Application Project Evolution

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

4. Codec and Packetization 512 Encoded Video Stream Packetizer RTP Socket Decoder Packet Reassembler RTP Socket 2048 UDP / IP / PPP / RLP seq, time 12 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 B 1 3 SREJ 2 4 5 fr # 2 A B timeout 1 2 3 4 checkpointing 5 6 7 P = 1 fr # 5 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. - buffer overflow in sender’s kernel - packet loss rate < 1% - mobile signal strength (3-4) Measurements with RLP 4000 Kbits of video traces ~ 7 min of connection

8. - 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 Measurements without RLP 4000 Kbits of video traces ~ 7 min of connection

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