1. 1 WiSE Video: using in-band wireless loss notification to improve rate- controlled video streaming A. Markopoulou, E. Setton, M. Kalman, J. Apostolopoulos To appear in IEEE ICME 2004

2. 2 Outline WiSE Mechanism WiSE Video Simulation Results

3. 3 Outline WiSE Mechanism WiSE Video Simulation Results

4. 4 M-ECN Network to higher layers signaling needed –E.g. signal congestion, announce available BW etc… –Ways to signal: ICMP, dedicated bits, … … M-ECN –opportunistic signaling, using bits of the IP header that are lightly utilized –Capacity of ECN “channel” –Stengths: no overhead, no dedicated packet fields, incrementally deployable –Limitations: low rate, delay

5. 5 WiSE: Wireless Signaling via ECN TCP over wireless –Should not backoff in case of wireless loss –Wireless loss notification for TCP Distinguish congestion from wireless losses Avoid backing off in case of wireless loss –Many approaches [ELN, ETEN, …] WiSE: Use M-ECN to signal corruption vs. congestion WiSE-Agent on router and WiSE-TCP to decode wirelesswired 123

6. 6 Outline WiSE Mechanism WiSE Video Simulation Results

7. 7 Video Streaming Characteristics: stream traffic, dependencies Require: low loss and low delay Rate-control –needed to react to congestion –rate-based vs. window-based I1P2P3 P10I11 P12 … time … GOP

8. 8 Rate Control Schemes considered HTTP streaming –One description stored, sent over TCP [TCP friendly] –Compute TCP friendly rate –Adjust parameters (Q,fps) to meet it –E.g. [RAP: Reja et.al], [Zakhor et.al], … Switch Stream (SSRC) –Receiver sends feedback –Sender switches (at GOP borders) to lower rate during congestion higher rate otherwise TCP friendliness Natural to Video

9. 9 Video over wireless Problems in wireless –High values of loss and delay –High variability in loss and delay –Corruption can be misinterpreted as congestion Solution: proxies, explicit messages WiSE can help: –To distinguish congestion from corruption –In rate control: to avoid unnecessary decreases –In error resilience: to retransmit fast

10. 10 Outline WiSE Mechanism WiSE Video Simulation Results –Topology –Streaming 1: SSRC –Streaming 2: HTTP

11. 11 Simulation Scenario Topology –Links: wired (10Mbps, 10ms), wireless (1.1 Mbps, 100ms) –Congestion Loss: due to interfering traffic (FTP and HTTP) –Wireless Loss: model (bernoulli, bursty), rates 0-10% WiSE Agent n0 n1 n2 n3 n5 n4 Wireless Link bottleneck Video stream Interfering traffic Video Source Playout buffer Video Rcvr

12. 12 Video Streaming Details Foreman sequence –10sec, 30fps, QCIF, H.264, GOP=15 (1I:14P), UDP/RTP Streams of various rates are pre-stored Switching among streams –only allowed at GOP borders –dictated by rate control scheme Stream number01234 Bitrate (kbps)5078116184346 Avg PSNR (dB)27.4 30.332.935.739.1

13. 13 Rate Control 1: Switch Stream (SSRC) SSRC Receiver –If sequence gap, then send a NACK Sender –If NACK received, then switch one stream lower –Otherwise (and no NACK or increase recently), switch one stream higher WiSE SSRC Receiver –If sequence gap, read WiSE message, send NACK + cause (congestion, corruption) Sender –If congestion NACK, then switch one stream lower –If corruption NACK, then retransmit + do not switch –Otherwise (and no NACK or increase recently), switch one stream higher

14. 14 SSRC vs. WiSE SSRC- an example

15. 15 Demo (1) : SSRC vs. WiSE-SSRC Scenario: No congestion, 4% bernoulli wireless loss Improvement: better quality pictures, less freezes, 8dB Quality metric: avg PSNR (dB)

16. 16 SSRC vs. WiSE SSRC – Bernoulli Wireless Loss

17. 17 SSRC vs. WiSE SSRC- Bursty Wireless Loss

18. 18 SSRC vs. WiSE SSRC - all (wireless, wired) losses SSRC: 31..22dB WiSE-SSRC: 36..28dB wirelesswired 123 wired loss % wireless loss %

19. 19 Rate Control 2: HTTP streaming TCP Receiver –send ACKs Sender –If congestion, then retransmit and half the window –Otherwise (no congestion for some time), then increase WiSE TCP Receiver –Send ACKs with echo set (WiSE marks) Sender –If drop, then decode WiSE If congestion, then retransmit + half the window If corruption, then retransmit but do not half the window –Otherwise (no congestion for sometime), then increase Video description #1 only. Viewed as a file to transfer No notion of video-specifics, GOP, etc

20. 20 TCP vs. WiSE TCP - an example Video description #1, 200sec wireless loss: 0.6% bursty congestion: interfering long FTPs

21. 21 TCP vs. WiSE TCP

22. 22 Demo (2): TCP vs. WiSE TCP With congestion, 2% wireless loss Improvement: (much) less freezes

23. 23 Conclusion WiSE improves the quality of rate-controlled video over wireless, for a wide range of conditions Further applications of network-to- application signaling ? –E.g. playout buffer, monitoring paths –Limitations How much info? How fast? (video: 30fps, WiSE: multiple packets for 1 bit, perceptible delays: ~150ms) Compared to e2e?