A cooperative diversity transmission scheme by superposition coding relaying for a wireless system with multiple relays
This paper proposes a cooperative diversity transmission scheme by superposition coding relaying (SC-relaying) for a wireless system with multiple relays. In this scheme, two layer signals, i.e., signal \({x_1}\) and \({x_2}\), are transmitted from a base station (BS) in the first and the second time slot, while signal \({x_1}\) is also forwarded from multiple relays to a user in the second time slot. The two layer signals (\({x_1}\) and \({x_2}\)) meet and superimpose with each other in the air in the second time slot. Then successive interference cancellation (SIC) is used for decoding at the user. In this paper, the optimal power allocation that maximizes the sum throughput of \({x_1}\) and \({x_2}\) is first studied. Then the optimal number of selected relays and optimal transmission rate at the BS is derived. Finally the outage probability and diversity gain of the transmission of \({x_1}\) and \({x_2}\) is evaluated for system robustness. Simulation results show that the proposed scheme realizes the goal of increasing spectral efficiency and enhancing system robustness.
cooperative diversity superposition coding relay power allocation rate