Opportunistic feedback with adaptive modulation over multiuser diversity systems

In this paper, we propose an opportunistic feedback protocol with adaptive modulation. The proposed feedback protocol is divided into two stages. During first stage, the proposed scheme uses feedback collision information in order to find the signal-to-noise ratio region where the user with the best channel quality belongs to. In second stage, based on random access protocol, the users in that signal-to-noise ratio region compete to send a feedback message. We analyze and evaluate the proposed feedback protocol in terms of the average transmission capacity and the outage probability. Simulation results show that the proposed scheme lowers the outage probability. Thus, it achieves the high average transmission capacity with limited feedback information.