Performance regimes of uncoded linear communications over AWGN channels

Streaming degradable content (such as video or audio) over a wireless channel presents new challenges to modern digital design, which was founded on the separation theorem of Shannon theory. Joint source-channel coding (JSCC) has recently received increasing interest to address the varying nature of the wireless channel conditions (under mobility or multicast). The conventional approach to JSCC which combines successive refinement with superposition coding is still digital and separable. However, for a white Gaussian source on a white Gaussian channel, it is outperformed by uncoded, linear scaling, which achieves Shannon's distortion limit. Practical degradable content sources are not white, but better approximated by multivariate / non-white Gaussian models. We investigate the performance of a linear, uncoded communication scheme for such sources. We find that there exist regimes where the uncoded scheme is near-optimal for point-to-point communication and provides significant gains over the conventional digital design for broadcast.