Analysis of Communication Schemes Using an Intermittent Feedback Link
Department of Electrical Engineering, Stanford University., 1967 - Feedback (Electronics) - 86 pages
Given any set of signals for use with a one-way communication channel, a feedback channel can be used to decrease the average power used by the transmitter while keeping the error probability the same, or equivalently, decreasing the error probability for the same average transmitter power. The case of orthogonal transmitter signals is analyzed in detail. The feedback channel is used only to tell the transmitter at certain specified times (prior to a final decision) which signal the receiver believes is being sent. The feedback information is used by the transmitter to modify its transmission according to a rule known also at the receiver. The feedback communication scheme is analyzed for both a noiseless and a noisy feedback link. In the case of noiseless feedback if only an average transmitter power constraint is imposed and orthogonal signals are used, it is possible to have the error probability go down in an N-fold exponential manner with increasing signal duration, where N-1 corresponds to the number of feedback iterations per message. This is in contrast to only a double exponential form for the error probability with some previously proposed feedback schemes. If a peak transmitter power constraint is also imposed, neither the N-fold exponential nor the double exponential behavior can be obtained. The peak power constraint limits the error probability expression to only a single-exponential form. (Author).
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