On dynamic channel emulation in sector MPAC for over-the-air testing of beamformed massive MIMO devices

In this article, novel emulation strategies for the sectored multiple probe anechoic chamber (SMPAC) are proposed to enable the reliable evaluation of the massive multiple-input multiple-output (MIMO) device operating at beamforming mode, which requires a realistic non-stationary channel environment. For the dynamic propagation emulation, an efficient closed-form probe weighting strategy minimizing the power angular spectrum (PAS) emulation errors is derived, substantially reducing the associated computational complexity. On the other hand, a novel probe selection algorithm is proposed to reproduce a more accurate fading environment. Various standard channel models and setup configurations are comprehensively simulated to validate the capacity of the proposed methods. The simulation results show that more competent active probes are selected with the proposed method compared to the conventional algorithms. Furthermore, the derived closed-form probe weighting strategy offers identical accuracy to that obtained with complicated numerical optimization. Moreover, a realistic dynamic channel measured in an indoor environment is reconstructed with the developed methodologies, and 95.6% PAS similarity can be achieved with 6 active probes. The satisfactory results demonstrate that the proposed algorithms are suitable for arbitrary channel emulation.