Effect of delay on uncertainty feedback systems (Corresp.)

Recent work on feedback communications systems is predicated on negligible delay in the forward and the feedback channels. The effect of delay on binary feedback systems of the type considered by Turin and Horstein is studied. Both sequential and nonsequential detection at the receiver are considered. It is shown that if the round-trip delay is small relative to the detection time at the receiver, uncertainty feedback offers considerable advantage. However, for the class of signals considered, the presence of delay precludes operation at channel capacity with zero probability of error.