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In this paper, we are interested in the design and performance of unequal error protection (UEP) rateless codes. These codes have interesting properties in the deployment of mobile peer to peer (MP2P) and mobile broadcast systems. As our main contribution, we propose a new UEP rateless code structure that is composed of a bank of precoders and a common rateless code. Through the bank of precoders, information layers are first expanded into encoded layers with a diminishing coding rate as the priority of the layer increases. The output of precoders are then concatenated and fed into a rateless encoder. The output of the rateless encoder naturally constitutes UEP encoding blocks carrying disproportionately more information on the higher priority layers. The decoder at the receiver end performs the inverse operations to recover each layer separately. We evaluate our proposed scheme comparing against the alternative solutions. Results show that over a broad class of rateless code structures the proposed scheme can substantially reduce the time required to recover higher priority layers while minimally impacting the time required to recover the lower priority layers.
Date of Conference: 6-12 May 2007