Outage based power allocation for a lossy-forwarding relaying system

In this paper, an optimal power allocation scheme for a simple lossy-forwarding relaying system is provided. Here, we extend our previous work of optimal power allocation of Slepian-Wolf relay system with constant source-relay error probability, to such that block Rayleigh fading is assumed for all transmission channel and lossy transmission is assumed in source-relay channel. Since data sequences transmitted from source and relay nodes are sent from one original source, they are correlated. At destination node, by exploiting the correlation knowledge between the two data sequences in joint decoding, the performance of the whole system can be significantly enhanced. This is because the network can be seen as a distributed Turbo code. A closed-form expression of the outage probability is derived at high signal-to-noisy ratios regime. It is shown that the outage curves calculated from the closed-form expression are sufficiently close to that obtained by the numerical calculation. Then, the optimum power allocation to the nodes for the system can be formulated as a convex optimization problem. Specifically, we minimize the outage probability while assuming the total transmit power is fixed, and also to minimize the total power under an given outage requirement. It is found that the system performance with the proposed optimum power allocation scheme outperform that with equal power allocation.