Adaptive digital communication for a slowly varying channel

A theoretical analysis of variable-energy adaptive digital communication is given for a slowly-varying channel. The adaptation is accomplished by providing the receiver with the capability of measuring signal-to-noise ratio, and controlling the transmitted signal energy by means of a feedback loop. Theoretical gains achievable with adaptation are calculated in terms of reductions in required mean transmitter energy as a function of a signal-fading parameter for different probabilities of unsatisfactory operation.