On the impact of links characterization and power allocation in relay assisted communications

Relay assisted communications exploit cooperative diversity to efficiently extend area coverage or improve the performance in wireless channels. We propose a mathematical framework to analyze the frame error probability (FEP) at the destination depending on distributed coding, nodes spatial distribution, and power allocation among source and relay nodes. We evaluate the impact of cooperative links characterization on the overall FEP at the destination by considering simple approximations on the link FEP which depend on the signal-to-noise ratio and diversity. We consider a number of power allocation techniques such as uniform, ideal power control, outage-optimal, and FEP-optimal. Results are given for a case study in which pragmatic space-time codes are employed as distributed coding technique. Analytical results are confirmed by simulations that are given to serve as a benchmark for the considered cases. The framework enables the system designer to allocate power and individuate the best relay position to minimize the FEP.