Performance analysis of dual hop relaying over Rayleigh fading channels

Transmit diversity is created in the regular cooperative diversity (RCD) networks when the selected nodes assist the source by relaying its information signal to the destination using orthogonal channels to avoid co-channel interference. This decomposition is necessary because practical limitations in radio implementation prevent the relay from simultaneously transmitting and receiving on the same channel. K relays in RCD require K+1 channels which shows that as the number of relays increases the number of required channels increases linearly. This increase in channels gives fundamental drawback in all cooperative diversity networks. So if this problem is not addressed the cooperative diversity networks will lose attractiveness for high data rate, high efficiency communications. In this paper this problem is addressed tried to find a solution. The performance of the best-relay selection scheme will be examined in which only the “best” relay takes part in relaying, therefore only two channels take part in transmission regardless of the number of relays. The relay node that gives the highest signal-to-noise ratio (SNR) at the destination node is considered to be the best relay. A general mathematic probability model is presented and examined the performance of best-relay selection using amplify and forward (AF) scheme.