Joint Source-Channel Coding for Cribbing Models

In this work we study problems of joint source-channel coding for the multiple access channel with cribbing encoders. These problems are motivated by modern communication scenarios such as an uplink channel for cellular users. Provided that the users are close enough to each other, they can causally crib to the output signals of their neighbours, thus obtaining some measure of cooperation. Three scenarios are considered in this work: (i) the symmetric model, where both encoders crib strictly causally at each other's output, (ii) the model where encoder 1 cribs strictly causally at the output of encoder 2, and encoder 2 cribs causally at the output of encoder 1, and (iii) the model where only one encoder cribs, in a causal or non-causal manner. For the symmetric case, model (i), sufficient conditions are derived for lossless transmission of a correlated pair source (U, V) via the multiple access channel (MAC). For the non-symmetric scenarios (ii) and (iii), necessary and sufficient conditions are derived, for transmissibilty of the pair source via the MAC. The main focus of this work is on lossless transmission, however, for case (iii) we allow distortion in one of the source components.