Performance of differential modulation with wireless relays in Rayleigh fading channels

We propose a new amplify-and-forward scheme amenable to differential modulation for cooperative systems with wireless relays. We derive closed-form expressions of the probability density function (PDF) of the signal-to-noise ratio (SNR) and average bit-error rate (BER) for the proposed scheme, and the analytical results are confirmed with numerical simulations. An asymptotic analysis reveals that the proposed cooperative scheme with one relay offers a diversity order approaching two in Rayleigh fading channels as the average SNR increases.