1. Yi Liang Aug. 2, 01 Low-latency Internet media streaming using packet path diversity - prior and future work

2. HP Labs Project Meeting Yi Liang Outline What we have done UDP with path diversity for real-time voice Path diversity augmented TCP for file transfer and streaming multimedia Proposed work and open problems Source/channel coding adapted to channel conditions Retransmission on the transport layer

3. HP Labs Project Meeting Yi Liang Outline What we have done UDP with path diversity for real-time voice Path diversity augmented TCP for file transfer and streaming multimedia Proposed work and open problems Source/channel coding adapted to channel conditions Retransmission on the transport layer

4. HP Labs Project Meeting Yi Liang Real-time Voice Communication Best-effort services vs. strict QoS requirements of real-time speech communication. Low data rate of the voice stream Why alternative path/multi-path? Exists a superior alt. path in 30- 80% cases [Savage, 99’] Path diversity – network behavior averaged; burst loss converted to isolated loss; outage probability decreased [Apostolopoulos, 01’] Multi-path – independent delay jitter characteristics Realization: explicitly path selection using relay servers D S Relay 1 2 Data traffic Data traffic The bottleneck Voice traffic [Liang, Steinbach, Girod, ACM MM 01’]

5. HP Labs Project Meeting Yi Liang Delay Traces Measured over the Internet Playout of packets from multiple streams

6. HP Labs Project Meeting Yi Liang Multi-stream with MDC Stream 1: Even samples: quantized in finer resolution (PCM, 8-bit) Odd/even samples: quantized in coarser resolution (ADPCM, 2- bit) Stream 2: the opposite way [Jiang, 00’] MDC over Multiple Streams E s1 s2 O-E O E-O  Packets in multi-streams Multiple description coding (MDC): generates multiple descriptions of equal importance for the same source signal E O-E E E O E-O O

7. HP Labs Project Meeting Yi Liang Adaptive Playout Scheduling for Multiple Streams To minimize the Lagrange cost function C = delay + 1  p (packet from both streams lost) + 2  p (one packet lost) = d + 1  lp 1 lp 2 + 2  [lp 1 (1- lp 2 )+lp 2 (1- lp 1 )] Stream 1 d s1 lp 1 lp 2 d Freq Maintaining history for both streams; loss probability determined by delay and past history (order statistics) Stream 2 d s2

8. HP Labs Project Meeting Yi Liang Experiments over the Internet Path 1 (direct): Netergy – MIT Path 2 (alternative): Netergy – Harvard – MIT Direct path: 30ms UDP packets sent from source to dest.; routes determined by routing algorithm Alt. path: packets sent from source to relay server, then forwarded to dest. Exodu s Comm. BBN Planet Qwest Netergy networks 192.84.16.176 MIT 18.184.0.50 Harvard 140.247.62.110 (5) (45) (40)(5)

9. HP Labs Project Meeting Yi Liang Results – Improved Delay-loss Tradeoff Delay – loss curve obtained by varying 1 while keeping 2 small and fixed. Observed significant reduction in delay and loss rate by using multiple streams. Total/burst loss rate greatly reduced since jitter averaged. Path 1 (direct): Netergy – MIT Path 2 (alt): Netergy – Harvard - MIT

10. HP Labs Project Meeting Yi Liang Results – Improved Speech Quality PESQ (perceptual evaluation of speech quality): an objective measure in ITU-T P.862 Results obtained by varying 2 and 1 while keeping ratio fixed With higher delay: better chances to play both descriptions and lower erasure rate

11. HP Labs Project Meeting Yi Liang Outline What we have done UDP with path diversity for real-time voice Path diversity augmented TCP for file transfer and streaming multimedia Proposed work and open problems Source/channel coding adapted to channel conditions Retransmission on the transport layer

12. HP Labs Project Meeting Yi Liang TCP File Transfer and Media Transport [Steinbach, Liang, Girod, submitted to INFOCOM 02’] Packet path diversified TCP (PPD-TCP) DS PPD nodeTCP client Path 1 … PPD nodeTCP server … Path 2

13. HP Labs Project Meeting Yi Liang PPD-TCP Variants Studied PPD-TCP1 PPD-TCP2 PPD-TCP3

14. HP Labs Project Meeting Yi Liang Simulation Topology H8H6H5 H4H2H1 TCP server H3 H7 PPD node TCP client/ PPD node Simulation parameters 20 TCP/UDP sources attached to each intermediate hop as background traffic; avg load is varied All links 10Mbps Transfer 1000 bytes x 100 packet

15. HP Labs Project Meeting Yi Liang Results – Transmission time Identical avg load on two paths One path has avg load 20% lower

16. HP Labs Project Meeting Yi Liang Results – Media Throughput Identical avg load on two paths Load = 0.94 One path has lower avg load Load = 0.94/0.85

17. HP Labs Project Meeting Yi Liang Outline What we have done UDP with path diversity for real-time voice Path diversity augmented TCP for file transfer and streaming multimedia Proposed work and open problems Source/channel coding adapted to channel conditions Retransmission on the transport layer

18. HP Labs Project Meeting Yi Liang Multiple Description Video Coding 1 3 0 2 5 4 7 6 9 8 [Apostolopoulos, Wee, ICIP 01’] 1 3 0 5 4 79 8 Balanced coding Unbalanced coding

19. HP Labs Project Meeting Yi Liang Layered Coding Priority encoding transmission (PET) with FEC [Albanese et al. 96’] Prioritized coding -> non- prioritized coding: L0L0 L1L1 L2L2 LmLm FEC … MR layers r0r0 r1r1 r2r2 rmrm Packet MD k n RS(n,k)

20. HP Labs Project Meeting Yi Liang Scalable Video Codec Spatial/temporal scalability [Girod et al. VCIP 99’] Temporal scalability [Leicher et al. 94’] Progressive texture coding [Stockhammer et al.] [Puri, Ramchandran et al.] Optimal rate allocation for different priority layers – adapted to varying conditions of multiple channels Selection of the appropriate video codec: rate must be adjustable with enough flexibility BLEL FEC MR layers r0r0 r1r1 Packet k n RS(n,k) IP FEC r0r0 r1r1 Packet k n RS(n,k) B r2r2

21. HP Labs Project Meeting Yi Liang The Channel Model Channel loss rate (with memory) The Gilbert model for one network path [Girod et al. VCIP 99’] Two network paths: 4 states Other (unbalanced) channel conditions: Delay BW G B p GB p BG GG GB BG BB

22. HP Labs Project Meeting Yi Liang Communication with the Transport Layer Conditions of multiple paths can be estimated and recorded on transport layer: delay, BW, loss rate The selection of channel/bit allocation can be based on recorded history of channel conditions Optimize FEC vs. retransmission Need to model ARQ The cost function: Delay (on the order of rtt) Distortion Rate (constrained) L0L0 L1L1 L2L2 LmLm FEC … MR layers r0r0 r1r1 r2r2 rmrm Packet k n RS(n,k)

23. HP Labs Project Meeting Yi Liang Work Plan Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Video codec Transport layer; channel modeling Optimization Simulation & experiment