Separate Source–Channel Coding for Transmitting Correlated Gaussian Sources Over Degraded Broadcast Channels

The problem of transmitting a pair of correlated Gaussian sources over degraded broadcast channels using optimal separate source and channel codes is studied. Upper bounds are derived for the rate penalty (in terms of channel uses per source symbol) and the power loss endured by separate coding compared to joint coding. Although source-channel separation is suboptimal in general, it is demonstrated that the performance of separate coding comes close to that of optimal joint coding, especially for low distortion pairs. In fact, in some cases, separate coding performs better than the best known joint schemes so far. It is also shown analytically that separate coding is optimal when either of the sources is to be reconstructed in a near-lossless fashion.