Parameter estimation of range-migrating targets using OTFS signals from LEO satellites

This study investigates a communication-centric integrated sensing and communication system that utilizes orthogonal time-frequency space (OTFS) modulated signals emitted by low Earth orbit satellites to estimate the parameters of space targets experiencing range migration, hereinafter referred to as high-speed targets. Leveraging the signal samples produced by off-the-shelf OTFS demodulators, we derive a novel input-output model for the echo generated by a high-speed target when ideal and rectangular shaping filters are employed. Our findings reveal that the target response exhibits a sparse structure in the delay-Doppler domain, whose support is determined by the target initial-range and range-rate. Range migration induces a structured spread of this response, which is explicitly characterized in the paper and differs from that in previous models. We propose an approximate implementation of the maximum likelihood estimator for the target initial-range, range-rate, and amplitude. The estimation process first obtains coarse information on the target response using a block orthogonal matching pursuit algorithm, followed by a refinement step based on a bank of matched filters focused on a smaller initial-range/range-rate region. The proposed single-target procedure is extended to multiple targets via iterative estimation, reconstruction, and cancellation of dominant echoes. Finally, numerical examples are provided to evaluate the estimation performance.