Adaptive Modulation for Wireless Multihop Systems with Regenerative Relays

We present and analyze several adaptive modulation schemes for wireless multihop systems with regenerative relays. In particular, we consider both rate adaptation based on perfect channel state information (csi) of all hops as well as suboptimal strategies based on partial csi, which require only a very limited amount of feedback information and hence represent attractive approaches for practical systems. We thoroughly investigate the performance of all proposed schemes in terms of the average spectral efficiency as well as the average bit error rate, considering the important case of a Rayleigh-fading environment and M-ary quadrature amplitude modulation as a concrete example. Numerical results are shown to be in perfect agreement with simulation results-thus verifying the accuracy of our analysis-and illustrate the performance of our schemes in various situations.