Performance Analysis and Joint Receiver Design for an OTFS-Based ISAC System in Time-Varying Channels

In this paper, we consider an integrated sensing and communication (ISAC) system using orthogonal time frequency space (OTFS) modulation in time varying channels. For such an system, we tackle the joint receiver design, where a communication signal from an uplink user and the sensing echos from target(s) are simultaneously received and processed for reliable sensing and communication. In particular, we devise a four-stage joint sensing and detection method, where the first two stages are dedicated for coarse sensing and detection and the last two stages are for fine sensing and detection via pilot aided channel estimation and a modified low complexity maximum ration combining (MRC) detection. To study the interaction between both functionalities, we analyze the error performance of the system in terms of pairwise error probability (PEP), then derive an upper bound on PEP and the diversity gain of the system. Finally, simulation results validate the effectiveness of the proposed system.