A Joint Time Delay-Angle Elliptic Localization Method for Dynamic Underwater Acoustic Integrated Sensing and Communications

ObjectivesTIn mobile underwater acoustic communications based on orthogonal chirp division multiplexing (OCDM), the coupling between multipath propagation and Doppler effects leads to significant degradation in localization accuracy. To address this issue and overcome the limitation of conventional methods that treat multipath as interference, a joint delay–angle elliptic localization method oriented to integrated sensing and communication (ISAC) is proposed. Methods First, a spatio-temporal receiving model for Fourier precoded OCDM (FT-OCDM) signals based on a transducer array is established, and a three-dimensional steering vector incorporating delay, angle, and Doppler frequency is derived. Doppler frequency is estimated and compensated in the Fresnel domain, and super-resolution joint delay–angle estimation is achieved using the multiple signal classification (MUSIC) algorithm. Then, parameter pairing is accomplished based on the uniqueness of Doppler frequency, and channel parameters (delay and angle) are transformed into localization parameters (range and bearing). Finally, an elliptic localization scheme is developed, which exploits the geometric relationship between the line-of-sight path and single-bounce reflection paths to simultaneously estimate the positions of the transmitter and reflectors at the receiver side.Results Simulation results under dense multipath and shallow-water scenarios demonstrate that, in the set high-speed conditions, i.e. v= 10, 13, 15 m/s), the proposed method achieves a reduction of approximately 16.28 dB in delay estimation relative root mean square error (RRMSE) compared with Orthogonal Frequency Division Multiplexing (OFDM). When the signal-to-noise ratio (SNR) is 0 dB, the localization resolution for both the transmitter and reflectors in shallow-water scenarios can reach approximately 1.00 m. Conclusions The proposed method enables high-precision joint delay–angle estimation and localization under significant Doppler effects. By effectively exploiting multipath information, it provides a new technical approach for ship underwater integrated sensing and communication (ISAC) systems.