Waveform Characteristics of OTFS and OFDM Modulated with Zadoff–Chu Sequences

Integrated sensing and communications (ISAC) has emerged as a promising technology for future wireless networks, particularly for aerial platforms where efficient waveform designs are indispensable for joint communication and sensing. In this paper, we investigate the waveform characteristics of orthogonal time frequency space (OTFS) and orthogonal frequency division multiplexing (OFDM) signals modulated with Zadoff–Chu (ZC) sequences. We construct two-dimensional (2D) ZC sequence codewords for OTFS modulation and a truncated ZC sequence for OFDM, and analyze their delay–Doppler (DD) domain behavior using the ambiguity function. The analytical results show that both waveforms exhibit symmetric resolution properties in the delay and Doppler dimensions, while numerical evaluations demonstrate that ZC-modulated OTFS (ZC-OTFS) achieves a narrower mainlobe, a higher peak-to-sidelobe ratio (PSLR), and more stable sidelobes compared to ZC-modulated OFDM (ZC-OFDM), and simultaneously maintains a low peak-to-average power ratio (PAPR). In addition, the simulation results further confirm the DD symmetry of both waveforms.