Delay-Doppler Space Division-Based Multiple-Access Solves Multiple-Target Detection

Non-coherent signal with unknown delay and Doppler is recovered by Gabor Division/Spread Spectrum System (GD/S). A transmitted signal in GD/S is expressed by a Gabor expansion whose expansion coefficient is a product of time domain (TD) and frequency domain (FD) spread spectrum (SS) codes. A receiver in GD/S employs multiple TD integrators with TD SS codes and a prescribed delay and FD integrators with FD SS codes and a prescribed Doppler. These integrators estimate and update Doppler and delay cooperatively and individually. The receiver of GD/S is applicable to a multiple-target problem by borrowing an idea from code division multiple access (CDMA) philosophy. Namely, a delay-Doppler space is partitioned into four sub-spaces and their associated two-dimensional (2D) SS codes are assigned. Four delay-Doppler targets can be resolved and detected by four pairs of TD and FD correlators using the assigned SS codes.