A hybrid transmission scheme employing opportunistic transmission and multiuser diversity

In this paper, we present a novel transmission scheme, which consists of a hybrid transmission method combining opportunistic transmission and multiuser diversity. The proposed scheme considers a multiuser scenario, where only one of the users transmits based on their channel quality. Specifically, the proposed scheme considers that users transmit only when the fading amplitude is above a threshold and in case of conflict the user with the best channel transmits. For this scheme, exact expressions to evaluate the mean bit error rate (BER) by employing BPSK, QPSK and M-QAM modulations are obtained. The channel model considers the presence of additive white Gaussian noise (AWGN) and flat slow Rayleigh fading. For better understanding, we firstly consider the presence of two users in the system and later we generalize the results for any number of users. Also, the mean spectral efficiency of the hybrid system is evaluated. Simulation results show that the BER expressions to evaluate the performance of those systems are accurate. The results also show that the hybrid scheme has better performance when compared with the opportunistic transmission or multiuser diversity separately.