Performance Analysis of Amplify-and-Forward Cooperative Communication with Adaptive M-QAM Modulation

This paper studies the performance of multiple relays amplify-and-forward (AF) cooperative communication system with adaptive M-QAM modulation in Rayleigh fading channel. The average spectral efficiency of the fixed and adaptive rate M-QAM scheme are both researched and analyzed. We come into the conclusion that under certain BER level, the adaptive M-QAM scheme achieves significant efficiency gains over the non-adaptive one. Besides, we obtain the spectral efficiency loss for the fixed rate M-QAM scheme resulting from the increase of the number of the relay nodes which are confirmed can in a great extent be compensated for in the adaptive one. In addition, the simulation of probability of outage for the rate-adaptive M-QAM modulation system exhibits that the adaptive scheme can acquire high successful transmission rate as well as guarantee the bit error rate.