High-Order MIMO Terminal Testing with the Reduced-Order Wireless Cable Method

Due to the large demand of high data rate and massive communication in mobile service, 5G network has been commercially deployed in several countries around the world. To obtain better mobile service, it is essential to complete the terminal performance test in a controllable channel environment. The conventional conducted method has been widely used in performance testing schemes for multiple-input multiple-output (MIMO) mobile terminals. With the commercialization of 5G, the terminal antenna design is becoming more complex and the connection of antenna ports via radio frequency (RF) cables will bring many practical problems. The wireless cable method is a promising alternative, which can achieve cable connection functionality without actual RF cable connections. However, the applicability of the method for higher-order MIMO terminals is mainly limited by the measurement complexity of the spatial transmission matrix. To solve this problem, a novel general reduced-order wireless cable (RWC) method is proposed in this paper, which can reduce the measurement complexity from exponential to linear without performance loss. Finally, a $4 \times 4$ MIMO 5G terminal is tested under a commercial base station (BS) and compared with the conducted method-based testing results. The result comparison demonstrates the effectiveness of the proposed RWC method.