Abstract :

Broadcast channel refers to a scenario in multi-user information theory where one sender wishes to simultaneously transmit independent pieces of information to different receivers or groups of receivers over a channel that introduces errors. The problem of computing the capacity region remains open even for the simplest case of two receivers requiring independent messages. However the optimal regions are known for lots of important and interesting special cases as well as good inner and outer bounds for the general 2-receiver case.

A natural question here is whether 3 or more receivers is a straightforward extension of the two receivers at least in special cases of interest.

In this talk I shall show, using an important special case, that such straightforward extensions are not optimal. We introduce a new technique, called indirect decoding, that can be combined with existing techniques to improve the capacity region. Further, combining this technique with the existing techniques a new coding technique emerges for a general broadcast channel with 3 or more receivers which adds to our understanding of even the 2-receiver case.

This is joint work with: Prof. Abbas El Gamal, Stanford The main results in this talk is quite new and can be found either from my webpage:

http://chandra.ie.cuhk.edu.hk/pub/publications.html or reference: http://arxiv.org/abs/0712.3327