Adaptive modulation technique for amplify & forward cooperative diversity and fairness analysis

In recent years, cooperative diversity techniques have gained increased attention as a new method to combat degrading channel effects. Cooperation among two or more single antenna users generates a virtual diverse multiple-antenna transmission system in the wireless network. In this paper, we propose a scheme to improve the spectral efficiency of the amplify and forward system and investigate the application of adaptive modulation concept to the performance of cooperative techniques. We consider the adaptation of rate and power allocation with M-QAM modulation and study the performance of amplify & forward scenarios in Rayleigh fading channels. We compare this system with its comparable adaptive non-cooperative scenario and evaluate the energy saving achieved through cooperation. We introduce and analyze the concept of fairness in cooperation among two users. We propose a mechanism to increase the fairness in the cooperation algorithm and demonstrate the improvement achieved by using it.