Broadcasting of a common source : information-theoretic results and system challenges

We consider the problem of sending a common source to several users simultaneously at possibly different level of distortion. In this paper we review the classical information theoretic results on Broadcast Channels, then we examine the optimality of analog communication (single-letter coding) and we review the Hybrid Digital Analog (HDA) approach. Finally we motivate the need of all digital transmission and outline a joint source-channel coding approach based on layering.