# Technical Program

## Paper Detail

 Paper ID I.2.4 Paper Title On the Broadcast Channel with Non-Distinct Message Demands and Symmetric Side Information Authors Mohamed Salman, Mahesh Varanasi, University of Colorado-Boulder, United States Session I.2: Broadcast Channel II Presentation Lecture Track Network Information Theory Manuscript Click here to download the manuscript Virtual Presentation Click here to watch in the Virtual Symposium Abstract In this paper, we consider the $K$-receiver discrete memoryless (DM) broadcast channel (BC) with non-distinct message demands; in particular, the $K$-receivers demand $N\leq K$ messages of the same rate $R$ with each message demanded by a (disjoint) subset of receivers. Moreover, each message consists of $2^K$ independent sub-messages, with each sub-message available at a distinct subset of receivers as side information. We assume symmetric side-information in that the sub-messages that are available at the same number of receivers as side information have the same rate. This model is akin to coded caching with non-distinct demands over the general BC (rather than a shared noiseless link) and also extends our recent work in which message demands were distinct. We propose a coding scheme that consists of (a) a new form of network coding in which the non-distinctness of the message demands and the side information are used to create $2^{K}{-}2^{K-N}$ groupcast messages \textemdash and these are not in general the same as for decentralized caching over a shared noiseless link in recent work by Yu {\it et al.} \textemdash (b) message merging where certain sets of those groupcast messages are bijectively mapped into a single message each (c) superposition coding to generate the codebooks for the merged messages and (d) successive decoding at each receiver to find its intended message with the aid of the side information. In particular, while each receiver decodes the codebooks of certain merged messages, some of the receivers must in addition also locally generate $2^{K-N-1}$ groupcast messages to find their respective intended messages. Although we do not provide proofs of converses, the proposed scheme is optimal for two stated categories herein of BCs and message demands.