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This paper proposes an over-the-air (OTA) testing setup for millimeter-wave (mmWave) massive multiple-input multiple-output (MIMO) equipment using cascaded amplitude and phase modulation (APM) network and channel emulator. Compared with the existing test setup with mechanical switch, the proposed testing setup enables more accurate reconstruction of the radio channel environment under the multiprobe anechoic chamber (MPAC) setup without increasing the number of channel emulators (CEs) to control the system cost. The constructed MPAC testing setup for mmWave and massive MIMO equipment is composed of an anechoic chamber, a sectored probe wall containing a number of probes, an APM network, a fading channel emulator, and a user emulator (UE). In this paper, the structural model and the performance advantages of the proposed radiated testing setup are described, and a fully connected APM network for radiated testing is more prominent than the existing switch. Moreover, the angular spectrum is selected as the performance metric for the reconstructed channel. The ability of the proposed system to reconstruct the power angular spectrum (PAS) of the target channel is studied under both static and dynamic channel models, which can reflect the performance of beamforming procedures of the massive MIMO antenna arrays, e.g., beam acquisition, tracking, and refinement. The simulation results for angular spectrum support the superiority of the proposed OTA testing setup. Furthermore, the simulations for average channel capacity also show that radiated testing setup using cascaded APM network and channel emulator is valid. [ABSTRACT FROM AUTHOR]

Over-the-air (OTA) radiated testing for massive multiple-input–multiple-output (MIMO) base stations (BSs) poses an urgent challenge for the extended development and deployment of the fifth-generation mobile communication systems. Conventionally, MIMO OTA uses the spatial correlation-based metric for channel emulation to evaluate the fourth-generation user terminals. However, it does not provide sufficient accuracy due to the larger dimension of massive MIMO BSs. In this letter, we propose a new criterion based on angular spectrum similarity for channel emulation in OTA testing of massive MIMO BSs. As antenna array control is critical for the performances of massive MIMO BSs, the proposed metric can reconstruct power distribution more accurately in the angular domain, thus increasing channel emulation accuracy, which will affect notable performances, such as array gain, sidelobe interference, and direction-of-arrival estimation, for massive MIMO BS OTA testing. [ABSTRACT FROM AUTHOR]