Optimal Diversity Allocation in Multi - UserCommunication Systems - Part II : Optimization 1

In Part I 1] of this paper, a class of multicarrier systems was proposed to study the eeect of the method of diversity allocation on the performance of coherent multiuser communication systems operating over fading channels. In this part of the paper, optimization over the proposed class of systems is considered for a xed number of users per unit bandwidth. The rst case studied is a system where the only noise not attributable to users in the system is additive white Gaussian noise. It is observed that either a system employing exclusive allocation, where users are allocated time-bandwidth resources that are not simultaneously shared with other users, or a system employing maximum resource sharing, where all users simultaneously share time-bandwidth resources, is optimal. Next, the preferable of these two extreme forms of resource allocation is determined. For any reasonable signal-to-noise ratio and user density, it is shown that the system employing exclusive resource allocation is optimal in a single-cell environment with perfect subchannel separation at the receiver. Finally, the optimization is repeated in the presence of partial-band interference. Once again, either a system employing exclusive resource allocation or a system employing a maximum resource sharing scheme is observed to be optimal. The presence of the partial-band interference increases the range of user densities and signal-to-noise ratios where a system employing a maximum resource sharing scheme is optimal, particularly when the probability of a particular time-bandwidth slot experiencing interference is high.