  In this paper, we study the optimal transmission of a multi-quality tiled 360
virtual reality (VR) video from a multi-antenna server (e.g., access point or
base station) to multiple single-antenna users in a multiple-input
multiple-output (MIMO)-orthogonal frequency division multiple access (OFDMA)
system. We minimize the total transmission power with respect to the subcarrier
allocation constraints, rate allocation constraints, and successful
transmission constraints, by optimizing the beamforming vector and subcarrier,
transmission power and rate allocation. The formulated resource allocation
problem is a challenging mixed discrete-continuous optimization problem. We
obtain an asymptotically optimal solution in the case of a large antenna array,
and a suboptimal solution in the general case. As far as we know, this is the
first work providing optimization-based design for 360 VR video transmission in
MIMO-OFDMA systems. Finally, by numerical results, we show that the proposed
solutions achieve significant improvement in performance compared to the
existing solutions.
