Performance analysis of decode-and-forward dual-hop opportunistic relaying with power control

Although cooperative relaying is generally considered as an attractive technique to improve system performances, the additional power consumption of a relaying link becomes a consistent concern. In order to characterize the power consumption of the dual-hop opportunistic relaying with power control, an exact expression for the cumulative distribution function of the total required transmission power is derived in this paper. Our analysis is based on the scenario that the best relay is selected among a set of decode-and-forward relays with homogeneous spatial Poisson distribution, such that the source-plus-relay power consumption is minimized. The required transmission power is evaluated by including the randomness of both path loss related to the locations of relays and the channel fading caused by multipath propagation. The analytical solution is verified by computer simulations and is used to compare the required power of relaying and direct links under different channel conditions. The results show that the dual-hop relaying is advantageous in long-term power saving by requiring a bounded average transmission power, while the power for the direct link communication is unbounded in some fading environments. Moreover, the required transmission power for the opportunistic relaying is less than that of the direct link with a reasonable relay density, therefore the cooperative communications can provide the power efficient transmission when the relay network is not sparse.