Antenna Topology Optimization for Massive MIMO Near-Field Wireless Communications with Line-of-Sight Deterministic Channels

In this paper, we investigate the optimization of non-uniform planar array (NUPA) for massive multi-input multi-output (MIMO) near-field wireless communications with line-of-sight (LOS) channels. In particular, the NUPAs at both the transmitter and receiver are misaligned placed with certain placement angles. Our focus is on the maximization of the system channel capacity, by optimizing the antenna elements position in the transmit/receive NUPAs. With the near-field spherical wave channel modeling, and by taking into account the geometric structure relationship of the arrays, the mathematically expression of channel capacity with this NUPA deployment is derived. Then, the relationship between the eigenvalues and the misaligned angles is analyzed, which further reveals the effect of the misalignment angle on the channel capacity. We show that channel capacity under specific transmission distance is related to the offset angle but irrelevant to the placement angles. Numerical results demonstrate that our theoretical analysis are consistent with the simulation results and the superiority of our optimized NUPA topology in system capacity.