Joint Target Localization and Channel Estimation for ODDM-ISAC Systems

In pursuit of reliable performance for high-mobility integrated sensing and communication (ISAC) scenarios, the orthogonal delay-Doppler division multiplexing (ODDM) modulation can be leveraged to exploit the inherent channel sparsity in the delay-Doppler (DD) domain. In this letter, we propose a joint target localization and channel estimation method for ODDM-ISAC systems that employs a multi-pilot training frame to enhance parameter estimation with accumulated signal energy. By exploiting the block-circulant-like structure of the equivalent sampled DD domain (ESDD) channel matrix, multiple pilots are strategically arranged within a training frame. To facilitate effective energy accumulation from different pilots, a phase compensation strategy is devised, which improves the accuracy of parameter estimation for target localization and channel reconstruction. Moreover, the feasibility of the proposed method is theoretically analyzed when the actual delay and Doppler shift are on or off the quantized DD grid, respectively. Simulation results validate the effectiveness of the proposed method for both target localization and channel estimation.

I. Introduction

Joint target localization and channel estimation has become an essential technology in integrated sensing and communication (ISAC) systems [1], [2], [3]. In particular, channel estimation performance can be improved by leveraging the location parameters of the sensing targets as supplementary spatial information [4], [5], [6], [7]. As one of the representative modulation techniques in ISAC, orthogonal frequency-division multiplexing (OFDM) provides reliable target localization and channel estimation in low-velocity scenarios [8], [9]. However, in high-mobility scenarios such as the Internet of vehicles and unmanned aerial vehicle (UAV) swarms, Doppler spread caused by moving targets disrupts subcarrier orthogonality [10], [11], making it challenging to accurately capture the channel response in OFDM-based ISAC systems.