Achieving Wireless Cable Testing for MIMO Terminals Based on Maximum RSRP Measurement

It is essential to perform end-to-end performance testing of multiple-input-multiple-output (MIMO) systems under realistic propagation channel conditions. However, due to the highly integrated and compact radio frequency (RF) system design, the traditional conducted cable testing method is getting more and more problematic. The wireless cable solution, which can achieve the equivalent functionality of the conducted cable testing without actual RF coaxial cables, has attracted huge attention from the industry and standardization for over-the-air (OTA) testing in recent years. However, the state-of-the-art solutions to achieve wireless cable testing necessitate at least reference signal received power (RSRP) reporting per device under test (DUT) antenna port for MIMO capable terminals, which is demanding and might not be accessible for commercial DUTs. In this work, a novel wireless cable solution based only on the maximum RSRP measurement of all DUT antenna ports is proposed, which can significantly alleviate the requirement of DUT RSRP reporting. To achieve the wireless cable testing, a novel calibration procedure is proposed to determine the transfer matrix between the probe antenna ports and the DUT antenna ports based on the DUT maximum reported RSRP measurement. The proposed algorithm is theoretically derived and experimentally validated for a 2x2 MIMO system, where the isolation of above 25 dB is achieved for the measurement setup. The numerical simulation and experimental validation demonstrate the efficiency and robustness of the proposed algorithm.