Performance analysis of adaptive modulation in cooperative networks

In cooperative networks, different single-antenna terminals cooperate in order to provide better signal quality over Rayleigh fading channels. The main drawback of cooperative diversity is the throughput loss due to the extra resources needed for relaying. Therefore, we propose to use adaptive modulation in cooperative networks in order to compensate the throughput loss due to the relaying. In this paper, we analyze the performance of different cooperative schemes using adaptive modulation. For cooperative schemes, we consider amplify and forward (AF) protocol with one relay, AF protocol with two relays and AF protocol based on the Alamouti space-time code. For the adaptive modulation, we propose a novel criterion for the determination of the decision table for the modulation choice. Simulation results show that, in bad channel conditions, these adaptive protocols have better performance compared with the classical system with direct transmission.