A Signalling Scheme for Frequency-Shift-Keying Channels With Noiseless Feedback

Stochastic approximation is applied to the design of a frequency-shift-keying (FSK) feedback scheme. FSK signals are transmitted over a channel with additive white Gaussian noise (AWGN) and the frequency estimate is fed back to the transmitter. A signaling scheme similar to the Schalkwijk-Kailath amplitude-shift-keying (ASK) scheme is derived and performance curves are presented. The scheme performs much better than ASK or FSK without feedback; however, under the average-power limitation, its performance is, in general, inferior to that of ASK feedback schemes.