Optimal power allocation for parallel access multiuser scheduling

In this paper, we study the optimal power allocation for orthogonal parallel-access scheduling schemes. We propose and study a parallel access scheme called generalized selection multiuser diversity (GSMuD), which ranks the channels of a total of L users and selects the L-c users with the largest signal-to-noise ratios (SNRs) for channel access. Besides the equal power allocation (EPA), two optimal power allocation algorithms are designed for the selected users in the GSMuD, namely (i) one-dimensional (I-D) optimal waterfilling (WF) power allocation along the channels given a fixed total power at each time slot; and (ii) two-dimensional (2-D) optimal WF along both the time and the channels given a fixed average total power. Accurate performance analyses of the above schemes are provided. Numerical results show that the 2-D WF power allocation yields the largest sum rate, while the EPA is near-optimal for many cases of practical interest.