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Comparison of Raptor Codes with ARQ for Video Streaming on Peer-to-Peer Networks

Comparison of Raptor Codes with ARQ for Video Streaming on Peer-to-Peer Networks. Rohit Watve Deepan Gandhi. Outline. Overview of Raptor codes Overview of SPPM Modeling for Raptor Code Scheme Modeling for ARQ Scheme Model evaluations Experimental results Conclusion.

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Comparison of Raptor Codes with ARQ for Video Streaming on Peer-to-Peer Networks

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  1. Comparison of Raptor Codes with ARQ for Video Streaming on Peer-to-Peer Networks Rohit Watve Deepan Gandhi

  2. Outline • Overview of Raptor codes • Overview of SPPM • Modeling for Raptor Code Scheme • Modeling for ARQ Scheme • Model evaluations • Experimental results • Conclusion

  3. A Type of Fountain Codes Suitable for Erasure Channels Rateless Code – Variable Redundancy Systematic Coding is possible Overview of Raptor Codes

  4. Stanford P2P Multicast Protocol (SPPM) • Multiple Tree-based protocol • Losses can occur due to ungraceful disconnection • Raptor Codes can be beneficial if simultaneous tree disconnections are limited

  5. Source node T : total trees 1 T 2 … Tree 1 1 f 1 f 1 f ... ... ... 1 … … … … … … Model Parameters • Homogenous Peers • Balanced Trees

  6. Modeling for Raptor Code Scheme • A node is an interior node of only one tree • N: Total Number of nodes • T: Total Number of trees • d: depth of tree • f: fanout (number of children per peer)

  7. Modeling for Raptor Code Scheme • B: Uplink Bandwidth • r: Data rate on each tree • R: Total Video Rate • rt: Maximum number of tree losses supported

  8. Modeling for Raptor Code Scheme • p: Probability of node leaving ungracefully • Pd: Probability of getting disconnected from a tree • Ploss: Probability of losing a packet

  9. Source node T : total trees 1 T 2 … 1 f 1 f 1 f ... ... ... 1 f ... Modeling for Raptor Code Scheme • Worst Case Delay

  10. Modeling for ARQ scheme • High uplink bandwidth is required for raptor codes • Same Bandwidth assumed here for fair comparison • Losses due to congestion caused by retransmission are very small – verified by model • Model without considering congestion described here

  11. Modeling for ARQ scheme • Initially, let us consider only one tree disconnection • probability that a node will be disconnected from a tree because of a node at the level ‘m’ = p·(1-p)m-1 • Total number of other leaf nodes disconnected from this tree = • Total number of leaf nodes =

  12. Modeling for ARQ scheme • Probability of loss for this particular case • RetransNum: the number of times retransmission requests are allowed

  13. Modeling for ARQ scheme • Probability that a packet will be lost: • Worst case delay: additional waiting time

  14. Model evaluation • Uplink bandwidth = 800kbps, Video rate = 490kbps, Total nodes = 10000, Number of trees varied from 5 to 20, Node disconnection probability = 0.05

  15. Model evaluation: More Analysis • Uplink bandwidth = 800kbps, Video rate = 490kbps, Total nodes = 10000, Number of trees varied from 5 to 20, Node disconnection probability = 0.05

  16. Model evaluation: More Analysis • Uplink bandwidth = 800kbps, Video rate = 490kbps, Total nodes = 10000, Number of trees varied from 5 to 20, Node disconnection probability = 0.05

  17. Model evaluation: More Analysis • Uplink bandwidth = 800kbps, Video rate = 490kbps, Total nodes = 10000, Number of trees varied from 5 to 20, Node disconnection probability = 0.05

  18. Model evaluation • Number of retransmissions = 2 (other parameters same as before).

  19. Model evaluation • Uplink bandwidth = 800kbps, Video rate = 490kbps, Total nodes = 10000, Number of trees varied from 5 to 20, Node disconnection probability = 0.1

  20. Experimental results • Uplink bandwidth = 800kbps, Video rate = 490kbps, Total nodes = 80, Number of trees = 8, Node disconnection probability = 0.01

  21. Experimental results • Uplink bandwidth = 800kbps, Video rate = 490kbps, Total nodes = 80, Number of trees = 8, Node disconnection probability = 0.1

  22. Experimental results • Uplink bandwidth = 800kbps, Video rate = 490kbps, Total nodes = 80, Node disconnection probability = 0.01, delay = 1000ms

  23. Conclusion • Loss probability can be decreased if more delay is acceptable • More number of trees result into more delay but less loss probability • Raptor codes more suitable for tight delay constraint and less disconnection probability • Scheme with more than one retransmission is superior in terms of loss probability

  24. Thank You

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