Relay selection in distributed alamouti space-time block coded networks

Alamouti distributed orthogonal space-time block coding has emerged as a diversity scheme that can achieve high spectral efficiency over a wireless networks. This paper employs the relay selection to maximize the received signal-to-noise ratio of Alamouti distributed orthogonal space-time block coding (Al-DSTC) in a two-relay networks. It makes collective use of the Alamouti distributed orthogonal space-time block coding and relay selection to implement an effective scheme. It is shown in this work that the proposed scheme obtains full diversity order and provides an additional array gain compared to conventional Al-DSTC and cooperative beamforming. The receiver can always find the optimal selected relay by exhaustive search where the number of relays is only two. Our results show that the proposed scheme preserves full diversity order and provide additional array gain by less transmit power when compared with other cooperative protocols. Also, the proposed scheme increases life time of the relay since 50% of the time the relay is off.