Achieving Exponential Diversity in Wireless Multihop Systems with Regenerative Relays

We present and analyze two different power allocation strategies for considerably improving the average bit error rate (BER) performance of wireless multihop systems with an arbitrary number of regenerative relay stations. In both cases, the power allocation is done based on instantaneous channel state information subject to an overall sum power constraint as well as possible additional per-node power constraints and it is optimal in terms of minimizing an upper bound on the average end-to-end BER. It is shown that for a general class of fading distributions with both schemes exponential diversity can be achieved and we express the corresponding upper bounds on the average BER in closed-form for the important case of Nakagami-m fading on all hops. Finally, the performance of our approach is illustrated and evaluated by means of both numerical and simulation results.