Joint Uplink and Downlink Probe Selection for Bi-directional Channel Emulation in OTA Testing

Over-the-air (OTA) testing technology is widely utilized for performance testing of massive multiple-input multiple-output (MIMO) devices, particularly fifth-generation (5G) massive MIMO base stations (BSs), due to its simplicity and flexibility. The current multiprobe anechoic chamber (MPAC) OTA testing setup only considers uni-directional channel emulation, which can be well applied to time division duplexing (TDD) systems with the aid of uplink (UL) and downlink (DL) switches. In contrast, frequency division duplexing (FDD) systems, where both the UL and DL operate simultaneously, require bi-directional channel emulation. Furthermore, in beyond fifth-generation (B5G) systems, the introduction of emerging technologies such as integrated sensing and communication (ISAC) and co-frequency co-time full duplex has made the accurate simultaneous emulation of bi-directional channels even more urgent. In this paper, we propose a novel joint UL and DL probe selection algorithm based on the coordinated hunting method for the emulation of bi-directional channels. Simulation results demonstrate that the proposed algorithm can select appropriate probe positions for both UL and DL channels, respectively, ensuring that their positions are non-overlapping and achieving precise channel emulation of both target UL and DL channels.