Joint Relay Selection and Adaptive Modulation and Coding for Wireless Cooperative Communications

This paper considers a wireless cooperative communication system with the adaptive modulation and coding (AMC). We take the joint relay and AMC mode selection as two time-scales of optimization problems, which aim at maximizing the achievable data rate. We treat the best relay selection as a long-term objective and the best AMC mode selection as a short-term objective, to limit the signaling overhead for the wireless communication system. However, the evaluation of the achievable data rate for any of relay and AMC mode combinations needs the estimation of the wireless channel. To this end, we propose an online optimization-while-estimation algorithm based on discrete stochastic approximation to jointly solve both the relay and AMC selection problems. The algorithm requires only per-frame channel sampling and estimation in each algorithm iteration, and approaches the optimal achievable data rate asymptotically. Simulation results show that our proposed algorithm can quickly converge to the maximum achievable data rate.