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Multi-packet FEC

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Multi-packet FEC

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  1. Multi-packet FEC Authors: Date: 2007-11-13 Alex Ashley, NDS Ltd

  2. Abstract This presentation describes an example of an end-to-end flow of video content in which a forward error correction code is applied. Alex Ashley, NDS Ltd

  3. Retransmissions outside the home disabled, to avoid overloading network. Example IPTV Deployment Content flows from VOD servers to the home via the core network. This flow has to provide end-to-end QoS. VOD Servers DSLAM Core Network DSL Modem Alex Ashley, NDS Ltd

  4. Multi-packet FEC • A side-channel is added at the VOD server, which provides ‘n’ error correction data packets • Ptotal = Pdata + Pprotection • Receiver can create perfect picture with loss of any ‘n’ packets Alex Ashley, NDS Ltd

  5. 0 1 2 3 4 5 6 7 8 9 Example IPTV Deployment VOD Servers 7 data packets + 3 FEC packets One packet is lost in the core network DSLAM Core Network X DSL Modem Alex Ashley, NDS Ltd

  6. 0 1 2 3 4 5 6 7 8 9 X Example IPTV Deployment VOD Servers One packet is lost over the DSL link One more packet can be lost, whilst still maintaining error-free video DSLAM Core Network DSL Modem X Alex Ashley, NDS Ltd

  7. Multi-packet FEC & 802.11 • Over 802.11, all unicast traffic gets re-transmitted until positive ACK received • Or MIB defined retry limit reached • If an application level FEC is already in place, 802.11 could be more intelligent in its retries • A STA could reduce its retries if it had knowledge of higher level recovery technique • Similar to puncture coding where bits are deliberately removed from the coded data to reduce over-the-air data Alex Ashley, NDS Ltd

  8. References Alex Ashley, NDS Ltd