ARQ for network coding
Kumar Sundararajan, J.; Shah, D.; Medard, M.
Information Theory, 2008. ISIT 2008. IEEE International Symposium on
Volume , Issue , 6-11 July 2008 Page(s):1651 - 1655
Digital Object Identifier 10.1109/ISIT.2008.4595268
Summary:A new coding and queue management algorithm is proposed for communication networks that employ linear network coding. The algorithm has the feature that the encoding process is truly online, as opposed to a block-by-block approach. The setup assumes a packet erasure broadcast channel with stochastic arrivals and full feedback, but the proposed scheme is potentially applicable to more general lossy networks with link-by-link feedback. The algorithm guarantees that the physical queue size at the sender tracks the backlog in degrees of freedom (also called the virtual queue size). The new notion of a node ldquoseeingrdquo a packet is introduced. In terms of this idea, our algorithm may be viewed as a natural extension of ARQ schemes to coded networks. Our approach, known as the drop-when-seen algorithm, is compared with a baseline queuing approach called drop-when-decoded. It is shown that the expected queue size for our approach is O[(1)/(1-rho)] as opposed to Omega[(1)/(1-rho)2] for the baseline approach, where rho is the load factor.
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