Date Added: Aug 2009
The authors consider the problem of communicating over a channel for which no mathematical model is specified. They present achievable rates as a function of the channel input and output sequences known a-posteriori for discrete and continuous channels. Furthermore they present a rate-adaptive scheme employing feedback which achieves these rates asymptotically without prior knowledge of the channel behavior. The problem of communicating over a channel with an individual, predetermined noise sequence which is not known to the sender and receiver was addressed by Shayevitz and Feder and Eswaran et. al.