Zero-delay joint source-channel coding

In zero-delay joint source-channel coding each source sample is mapped to a channel input, and the samples are directly estimated at the receiver based on the corresponding channel output. Despite its simplicity, uncoded transmission achieves the optimal end-to-end distortion performance in some communication scenarios, significantly simplifying the encoding and decoding operations, and reducing the coding delay. Three different communication scenarios are considered here, for which uncoded transmission is shown to achieve either optimal or near-optimal performance. First, the problem of transmitting a Gaussian source over a block-fading channel with block-fading side information is considered. In this problem, uncoded linear transmission is shown to achieve the optimal performance for certain side information distributions, while separate source and channel coding fails to achieve the optimal performance. Then, uncoded transmission is shown to be optimal for transmitting correlated multivariate Gaussian sources over a multiple-input multiple-output (MIMO) channel in the low signal to noise ratio (SNR) regime. Finally, motivated by practical systems a peak-power constraint (PPC) is imposed on the transmitter's channel input. Since linear transmission is not possible in this case, nonlinear transmission schemes are proposed and shown to perform very close to the lower bound.