Efficient Ray-Tracing Simulation for Near-Field Spatial Non-Stationary mmWave Massive MIMO Channel and Its Experimental Validation

Massive Multiple Input Multiple Output (MIMO) at millimeter-Wave (mmWave) frequencies is envisioned as a key technology for beyond 5G communication. Accurate channel modeling is crucial for the design and evaluation of such systems. Ray-Tracing (RT) can be used to accurately simulate the propagation channel. However, state-of-the-art RT for multi-antenna systems typically employs plane-wave extension under far-field conditions, failing to capture Near-Field (NF) and Spatial non-Stationary (SnS) properties that are observed in real-world mmWave massive MIMO channel measurements. This work aims at accurate and efficient RT simulations for massive MIMO systems, with a proposed coarse-refinement strategy capable of capturing NF and SnS. The channel is simulated using RT on a few sparsely located array elements and then interpolated onto other elements using spherical/astigmatic-wave approximation and the Uniform Theory of Diffraction, thus significantly reducing simulation complexity while maintaining accuracy. The proposed strategy is demonstrated to offer almost the same simulation accuracy as the brute-force method, with a dramatic reduction in complexity through experimental validation. The significance, novelty, effectiveness, and simplicity of the proposed framework make it highly valuable for massive MIMO channel research.