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.

The problem of broadcasting a pair of correlated Gaussian sources using optimal separate source and channel codes is studied. Considerable performance gains over previously known separate source-channel schemes are observed. Although source-channel separation yields suboptimal performance in general, it is shown that the proposed scheme is very competitive for any bandwidth compression/expansion scenarios. In particular, for a high channel SNR scenario, it can be shown to achieve optimal power-distortion tradeoff.

We propose a compression/transmission scheme that allows the quality of the reconstructed signal to gracefully degrade as the channel quality drops, as well as steadily improve with the channel improvement. The main idea is to partition the channel and/or network resources into m units (e.g., sub-bands, packets) and compress the source independently m times to perfectly match single unit resources, thus creating m independently distorted source versions. Consequently, we create a multiple-description, joint source-channel like architecture, that enables efficient reconstruction starting from a single received description with improvements onward. We further split the compression rate in two parts, allocating one to a rate-distortion optimal encoder, and the other to transmitting uncoded source symbols. We show how this architecture can easily leverage modularity in terms of adjustable rate-splitting ratio and the maximum number of descriptions, e.g., through software parameters, to simultaneously and robustly (i.e. avoiding the cliff effect) achieve operating points close to rate-distortion curve for many channel states. We demonstrate how statistical description of channel states (or performance statistics of content delivery network) can be used to set the two parameters constructively in terms of converging to optimal operation in the range of interest.

A new hybrid digital/analog scheme is proposed for lossy transmission of a Gaussian source over a bandwidth-matched Gaussian broadcast channel with source side information available at each receiver. The proposed scheme combines two schemes that were previously shown to achieve optimal point-to-point distortion/power tradeoff simultaneously at all receivers under two distinct conditions stated in terms of channel and side information quality parameters. For the two-receiver case, the combined scheme is shown to achieve the same kind of optimality for the entire region in the parameter space sandwiched between those two conditions. Crucial to this result is a new degree of freedom discovered in designing point-to-point hybrid digital/analog schemes with side information. When superimposed with analog transmission, the proposed scheme outperforms all previously known schemes even outside the optimality region in the parameter space.

A new hybrid digital/analog scheme is proposed for lossy transmission of a Gaussian source over a two-receiver bandwidth-matched Gaussian broadcast channel with source side information available at each receiver. The proposed scheme makes use of a new level of freedom for point-to-point transmission and combines two previously known schemes that are optimal under two different conditions regarding channel and side information quality parameters. It is shown that for the entire intermediate region in the parameter space sandwiched between those two conditions, the proposed scheme can achieve the same distortion-power tradeoff as in point-to-point transmission simultaneously for both channels, and is therefore optimal.

Two new schemes are proposed for transmitting a Gaussian source over a Gaussian channel. These schemes directly generalize previous results of Bross and Puri A scaled version of either the source itself or the quantization error is superimposed on the digital information, and thus serves as effective channel state information (CSI) unknown to the receiver. It is shown that for any power allocation between the coded and uncoded components of transmission, optimal distortion can be achieved by a continuum of auxiliary random variables (rather than only Costa's) if the decoded auxiliary codeword is properly used. This observation provides a new degree of freedom in point-to-point transmission. This freedom, in turn, can be utilized in multiterminal scenarios, as is demonstrated with an example.