Performance bounds on analog modulations over fading channels - Or - Analog modulation-where has it gone?

Analog modulation as a field of research has been dormant for about the past thirty years. This paper presents some new results on the theoretical bounds on the performance of analog communications over Rayleigh fading channels. We consider both single-diversity and dual-diversity receivers. One of the main purposes of this paper is to try to renew interest in the field of analog communications.