Performance of a differential modulation scheme with wireless relays in Rayleigh fading channels

We develop a new differential amplify-and-forward (DAF) scheme for cooperative wireless relay when the channel state information (CSI) is unknown to any node in the system. For a cooperative system with one source, one relay and one destination node, we derive closed-form expressions of the probability density function (PDF) of the signal-to-noise ratio (SNR) and the average bit error rate (BER) for the proposed DAF scheme. Numerical simulations validate our analytical results. The proposed DAF scheme offers cooperative diversity gain and outperforms the conventional noncooperative differential binary phase shift keying (BPSK) in Rayleigh fading channels.