Differential Modulation for Cooperative Wireless Systems

This paper examines differential binary modulation for wireless networks that utilize wireless relays to seek cooperative diversity and improved performance. Two differential cooperative transmission schemes, referred to as differential amplify-and-forward (DAF) and differential decode-and-forward (DDF), respectively, are introduced. These schemes require no channel state information at any node in the system. A set of analytical results pertaining to the probability density function of the instantaneous signal-to-noise ratio, average bit error rate, outage probability, and diversity order of the proposed schemes in Rayleigh fading channels are obtained. The analytical results are confirmed by numerical simulations. It is shown that the differential cooperative DAF and DDF schemes achieve cooperative diversity and outperform the conventional noncooperative differential modulation