Dual-hop wireless communications with combined gain relays

A dual-hop relayed wireless communication system is presented where the gain of the relay, called combined gain relay (CGR), is produced after combining the channel state information from both hops, depending on the mean hop´s signal-to-noise ratio (SNR). The proposed scheme can be efficiently applied in dual-hop transmissions with unbalanced mean SNRs due to the long-term fading effects produced by the movement of the user in the area served by the wireless network. The overall system performance is studied in Rayleigh fading channels. Closed-form expressions are derived for important system performance metrics, such as average end-to-end SNR, average error probability and outage probability. The CGR´s average power consumption is investigated which in certain cases is lower compared with existed relays. Numerical results and simulations show an improvement in the end-to-end system performance.