Doppler Ambiguity-Resolving Waveform Design Based on Ziv–Zakai Bound Optimization

Motion state sensing is crucial in wireless communication systems employing Integrated Sensing and Communication (ISAC), with accurate target velocity estimation being central to its effectiveness. While waveform design for ISAC signals can enhance the sensing capability, most existing studies focus on single-target scenarios, with limited discussion on multi-target scenarios. This paper proposes a novel waveform design approach aiming for enhancing the multi-target sensing performance, under the prior knowledge that the Doppler difference between two hardly resolvable targets lies in a certain interval. In particular, we use the Ziv-Zakai Bound (ZZB) of Doppler difference to design the waveform for multi-target sensing, which effectively captures the ambiguity phenomenon. We first derive the expression of the Doppler difference ZZB, which reveals the connection between ZZB and the widely-used ambiguity function. Based on this expression, we propose an SNR-adaptive pulse modulation strategy that significantly improves the velocity estimation accuracy for multi-target scenarios. Numerical results demonstrate that the Doppler difference ZZB effectively reflects the multi-target Doppler frequency estimation performance of maximum aposterioriestimators.