Cooperative relaying with side information

We study the problem of cooperative communication in the case that the assisting node (i.e. the relay) has access to correlated information about the source that needs to be reconstructed at the destination. Finding the relaying strategy that minimizes the reconstruction distortion at the destination, is one of the long standing open problems in information theory. In this paper, we propose a novel relaying strategy and show that, for Gaussian sources and additive Gaussian noise (AWGN) channels, this scheme always achieves within a factor of 6 of the least possible reconstruction distortion. Therefore, we find a uniformly near optimal strategy for Gaussian models, and approximate the minimum possible distortion in reconstructing the source within a factor of 6.