SIGNAL DESIGN FOR FAST FADING CHANNELS

The design of signals for digital communication over fast fading channels is considered; the emphasis is on nonorthogonal signaling schemes. By using a discrete channel model, necessary and sufficient conditions on the transmitted signals are found that make the Bayes optimum receiver independent of the channel parameters. By using a geometric interpretation of the resultant receiver a hueristic design criterion is developed. Then union bounds for particular nonorthogonal signaling schemes are evaluated. Nonorthogonal schemes based on modulation similar to differential-phase-shift-keyed modulation are found to use substantially less bandwidth than equivalent schemes based on generalized frequency-shift-keyed modulation. (Author)