Double opportunistic transmit relaying system with GSC for power saving in Rayleigh fading channel

Conventional opportunistic transmit (COT) relaying system does not consider the received SNR between R-D path. For that reason, it can´t guarantee all the received SNRs exceed the threshold at destination. In this paper, we propose double opportunistic transmission relay (DOT) system which considers the received SNR both from S-R and R-D paths. It is noticed that the proposed system can be reduced to 6.9, 20.9, 32.4, and 41.4 % of power saving to that of COT relay system for K = 3, 5, 7, and 9, respectively at a given condition of P_out =1×10^-3 and γ̅_SR/Γ = 30 dB. And the performance of DOT system is superior than that of COT system for the identical number of active transmit relays under the same condition of γ̅_RD/Γ_RD.