Bistatic THz Sensing With MIMO-OFDM: A Two-Stage Transmission Approach With Maximum Likelihood Estimation

The extensive bandwidth available at THz frequencies offers unprecedented opportunities for high-resolution sensing in next-generation integrated sensing and communications (ISAC) systems. This paper proposes a novel ultra-wideband bistatic MIMO-OFDM ISAC framework tailored for extended target tracking in cluttered indoor environments. To overcome the range ambiguity introduced by the increased subcarrier spacingy—used to expand bandwidth without a proportional increase in complexity—we introduce a two-stage transmission scheme coupled with a GLRT-based detection and estimation approach. In the first stage, a narrow sub-band is employed to obtain a coarse, ambiguity-free target estimate; in the second stage, the full system bandwidth is exploited to achieve refined super-resolution localization. To complement the detection and estimation process, we develop a low-complexity technique for static clutter removal based on coarse Doppler estimation and propose an extended target tracking approach enhanced with a properly designed dynamic clutter suppression scheme. Finally, extensive numerical results demonstrate that the proposed ISAC system effectively mitigates range ambiguities and clutter, achieving accurate extended target detection, localization, and tracking with negligible utilization of the resources.