On Competitive Zero-Delay Joint Source-Channel Coding

We consider zero-delay joint source-channel coding of individual source sequences for a general known channel. Given an arbitrary finite set of schemes with finite-memory (not necessarily time-invariant) decoders, a scheme is devised that does essentially as well as the best in the set on all individual source sequences. For the case where the channel is a DMC we construct an implementable scheme guaranteed to asymptotically attain the performance of (or strictly beat) the best in the set of all schemes with “symbol-by-symbol” decoders (and arbitrary encoders), on every individual sequence. Decoding in the latter construction employs a recently derived discrete universal filter.