A coding theorem for a class of unknown channels

We consider the problem of communication over a channel which is selected 1) in a fashion unknown to the communicator, 2) as a function of past history, 3) from a given set of discrete memoryless channels, and 4) for the purpose of maximizing the degradation in performance. An upperbound on error probability insurable with block coding is obtained which exponentially approaches zero with block length for rates less than capacity. Techniques for the communicator to achieve these results are considered. The design of relatively simple communication techniques for channels with memory and jammed channels are discussed.