SER performance analysis and optimal relay location of cooperative communications with distributed Alamouti code

Cooperative diversity enables single antenna transmitter in a multi-user or relay environment to share the antennas so as to achieve diversity gain. In this work, the cooperative communication system with distributed Alamouti code is investigated, where amplify-and-forward (AF), adaptive decode-and-forward (DF) or hybrid AF/DF are used at the relay, with both Rayleigh fading and path loss effect introduced into channel model. The following results are derived by utilizing the moment generating function (MGF) of end-to-end output signal- to-noise ratio (SNR). For AF protocol, when the relay is near the destination, the approximative closed-form symbol error rate (SER) of M-ary phase shift keying (M-PSK) and M-ary quadrature amplitude modulation (M-QAM) are derived, and approximative analytical SER expression is given for binary phase shift keying (BPSK) as an example. For adaptive DF protocol, the closed-form SER of M-PSK and M-QAM are derived, and analytical SER expression is presented for BPSK. Furthermore, the optimal relay location of adaptive DF protocol with BPSK signal is derived through analytical analysis. Finally, the Monte-Carlo simulations are performed to get the optimal relay location of other scenarios and verify all the analytical results.