Low Complexity Parameter Estimation Approach for OTFS-Based ISAC System

Given that Orthogonal time frequency space (OTFS) modulation provides high robustness to Doppler shifts, its integrated sensing and communications (ISAC) has attracted more attention. In this work, we investigate the fractional delay-Doppler (DD) estimation problem for the OTFS-based ISAC system. We establish a two-dimensional (2D) correlation structure with superimposed multiple frames and propose an efficient Maximum Likelihood algorithm based on multi-frame superposition (ML-MFS) that significantly reduces computational complexity. To further improve the estimation accuracy in multi-target scenarios, we develop an estimation method based on the whale optimization algorithm, named WOA-MFS. Simulation results demonstrate that both algorithms markedly reduce complexity, with the WOA-MFS demonstrating superior estimation accuracy.