基于可重构 OTA 装置的非平稳多维无线信道重构模型与应用性能分析

Massive multiple input multiple output(MIMO) is regarded as the crucial enabling technology of the fifth generation(5G) mobile communication. Reliable, feasible, and reconfigurable indoor multi-dimensional performance testing and verification are significant to boost basic theoretical research, key technology breakthrough, and commercial deployment for the massive MIMO system. To implement the technique validation, scenario completeness test, and defect assessment for the massive MIMO device, developing reliable and realistic indoor emulated performance testing methodology is essential. The key challenge is how to reconstruct the rich and complete target propagation environment for the device under test(DUT). Based on early research, i.e., efficient virtual probe position determination method and closed-form probe weighting strategy, which realize accurate multi-dimensional emulation for various channel scenarios, this paper proposes a multi-dimensional channel emulation methodology for non-stationary wireless propagation with reconfigurable over the air (OTA) setup. The proposed channel emulation mechanism effectively tackles the challenge of the conventional OTA techniques, i.e., multi-probe anechoic chamber(MPAC), radiated two stage(RTS), and reverberation chamber(RC), to test the realistic performance of the beam-steerable massive MIMO device typically operating in dynamic channel. By employing the phase shifters with various bit numbers, this paper investigates the emulation results of the reconstructed channel spatial profiles in terms of maximum spatial correlation, weightes root mean square correlation error, power angular spectrum(PAS) similarity, and fixes beam power loss. According to the complete scenario and multi-dimensional channel emulation in this paper, it is concluded that the 4 bit phase shifter can cost-effectively provide an accurate phase matrix for indoor realistic propagation channel reconstruction. It also provides the theoretical basis and technical approach for quantifying the impact of phase shifter errors on the virtual OTA method. This paper introduces the phase shifter resolution factor, which has not been reported so far, to the phase-matrix-based virtual OTA test setup for the performance testing of the massive MIMO wireless devices in the realistic complex electromagnetic propagation environment with the reconstructed communication link. Specifically, it mimics the propagation of the waves radiated from probe antennas by adjusting the phase responses among the DUT elements in the phase matrix to enable the emulation of the target channel scenario where the key performance indicators of the adaptive massive MIMO DUT are validated. In addition, the 3 bit phase shifter could also provide satisfying emulation performance using sufficient virtual probes, leading to meaningful guidance for the phase shifter selection and low-complexity phase matrix construction. On the other hand, one can select the 5 bit phase shifter for safety redundancy to ensure emulation accuracy. Furthermore, this paper emulates a more realistic dynamic channel environment based on the ray tracing model to further validate the effectiveness of the derived conclusion on the non-standard measured channel scenario. The accurate ray-tracing channel emulation on multiple positions experimentally demonstrates the applicability and feasibility of the obtained conclusion.