Optimal Spatial Power Allocation for Rayleigh Fading Relay Channels

In this paper, we derive an optimal spatial power allocation strategy that maximizes the achievable rate of the decode-and-forward (DF) relay channels in a Rayleigh fading environment. Different from prior work, the derived strategy only requires the knowledge of the variances of the channels at the transmitters, which does not require frequent updates. Furthermore, we demonstrate that the optimal spatial power allocation strategy leads considerable performance improvements over the equal power allocation one.