Gain Adaptation Policies for Dual-Hop Nonregenerative Relayed Systems

We examine the performance of a dual-hop nonregenerative system with adjustable relay gain, subject to power constraints. An optimization problem is formulated and solved algorithmically for the binary phase-shift keying bit-error rate utility. The model allows for arbitrary channel statistics. Emphasis is placed on the relation between the optimal solutions obtained when observing the channels of either the first or both hops, as well as the comparison with easily implementable heuristic policies. Numerical results indicate that simple heuristics perform well for a wide range of signal-to-noise ratio (SNR), except for certain high-SNR cases. Finally, the effect of independent channel assumption on system performance is evaluated.