WLC42-4: OFDMA Optimality Analysis in MIMO Uplink Channels

This paper studies the optimality of OFDMA in MIMO enabled multi-user multicarrier uplink network. We present the necessary and sufficient conditions for OFDMA being optimal on any boundary point of the capacity region. In the low SNR case, we further derive the probabilities of these conditions. For the general MIMO case, we provide an example with which we quantify OFDMA optimality and show the probability of OFDMA being optimal is non-travial regardless of the SNR regions. To reach the the MISO sum capacity limit, our results show that the number of shared subchannels under the optimal solution should be less than the number of total users, thus the performance gap between the OFDMA scheme and the optimal solution is negligible when the number of subchannels is sufficiently large.