A coded multicarrier framework for the optimization of coherent multi-user communication systems over fading channels

We present a class of multicarrier systems for studying the effect of the method of diversity allocation on coherent multi-user communication system performance over fading channels. After demonstrating that a number of popular multi-user system alternatives are represented by systems in the class, optimization over this class of systems is considered for a fixed number of users in the system. For a system where there is only multiple-access interference and additive white Gaussian noise (AWGN), it is observed that either the exclusive allocation or completely shared allocation is optimal for any signal-to-noise ratio and user density. For reasonable signal-to-noise ratios and user densities, it is shown that the exclusive allocation scheme is optimal in a single-cell environment with perfect subchannel separation at the receiver. Next, we consider optimization in the presence of partial-band interference. Once again, the exclusive allocation or maximum sharing scheme is observed to be optimal. The presence of the partial-band interference enlarges the region where the maximum resource sharing scheme is optimal, especially when the probability of a particular time-frequency slot experiencing interference is high.