Improving communication reliability by use of an intermittent feedback channel

This paper describes and analyzes a feedback communication scheme where the feedback channel is used only to inform the transmitter, at specified times (prior to a final decision), which message the receiver considers most likely. The feedback information is used by the transmitter to modify its transmission according to a rule known also to the receiver. When orthogonal signals are used and only an average transmitter power constraint is imposed, the error probability can be made to decrease in anN-fold exponential manner with increasing