On the Optimality of OFDMA MIMO Channels

This paper studies the optimality of OFDMA in MIMO enabled multiuser multicarrier uplink (UL) and downlink (DL) dual system. In the special low SNR and SIMO cases, we prove that OFDMA is actually DL sum rate optimal. For the general MIMO case, we modify the algorithms in [1] and [2] to compute the optimal sum capacity of multiuser multicarrier UL/DL system. Our numerical results show the probability of OFDMA being sum-rate optimal is non-travial regardless of the SNR regions. Finally, we evaluate a set of computation efficient sum-rate approaches for OFDMA.