Implementation of OFDM-Based Downlink and Monostatic ISAC Testbed

Integrated sensing and communication (ISAC) refers to the integration of communication and radar sensing, which have been considered independent areas. One of efficient way to realize ISAC is to add sensing functionality to existing communication systems. Therefore, this paper describes the implementation of an ISAC testbed with radar-imaging functionality added to an OFDM-based communication system. A downlink communication and monostatic sensing situation is assumed, where the user equipment receives data transmitted by the base station, and the base station detects the surrounding environment by receiving the reflected downlink signals. The testbed consists of an RF front-end part, which includes an mmWave up/down converter and RF switch for TDM MIMO radar implementation, an IF/baseband signal processing part that performs wideband OFDM communication/radar signal processing, and a digital control part that controls the phase-locked loop, mixer, and switch. In the IF/baseband signal processing part, basic CP-OFDM signal processing, channel estimation, and synchronization are performed, and two-dimensional radar imaging based on the back-projection algorithm is also performed. It is implemented on an FPGA for high-speed processing and is designed using the NI LabVIEW program. Using this testbed, the communication and radar-imaging performance were confirmed through experiments in the 28 GHz band.