Opportunistic Relaying for Cooperative Small-Cell Systems with Unreliable Wireless Backhauls

초록

In this paper, we investigate the outage performance of opportunistic relaying for a cooperative small-cell system with M small-cell transmitters and N relays. To enable flexible deployment of ultra dense small-cells, wireless backhauls are applied for connecting a macro-cell base station and M smallcell transmitters. In each transmission block, the transmitterrelay pair achieving the highest end-to-end signal-to-noise ratio is selected to transmit the source signal to the destination. The backhaul reliability is considered for revealing the practical constraints on wireless backhaul-based opportunistic relaying, while cyclic pre-fixed single carrier transmission is employed for mitigating frequency-selective fading. The new closed-form outage probability and asymptotic outage performance limit are derived for the cooperative small-cell system with unreliable backhauls and under frequency-selective fading channels. It is shown that transmitter cooperation and a corresponding backhaul reliability levels exclusively determine asymptotic outage probability, while diversity gain is jointly determined by M, N, and the sum number of multi-path components of frequencyselective fading channels. Link-level simulations are conducted to verify the derived joint impact of backhaul reliability and transmitter-relay cooperation on the outage performance.