Key issues and algorithms of multiple-input-multiple-output over-the-air testing in the multi-probe anechoic chamber setup

Multiple-input-multiple-output (MIMO) over-the-air (OTA) testing plays a key role in the research and development of wireless devices. MIMO OTA testing is necessary for the fifth generation (5G) wireless products, in which conventional radio frequency ports may be inaccessible. The performances of the test device can be evaluated in a repeatable and reliable way under laboratory conditions in OTA tests, which might not be feasible in conducted tests. Many efforts have been devoted to OTA test research and some achievements have been made. This paper mainly summarizes the channel emulation algorithms for two-dimensional user equipment and three-dimensional base station OTA testing in the anechoic chamber setup. In addition, the requirements of the test system design are also discussed in this paper, including the selection of the number of OTA probes, the size of the test zone, the physical dimension of the setup, and the flexible probe selection algorithm of the three-dimensional base station OTA setup. In addition, some novel test methods for 5G radio devices are also discussed.