Low-PAPR OFDM-ISAC Waveform Design Based on Frequency-Domain Phase Differences

Low peak-to-average power ratio (PAPR) orthogonal frequency division multiplexing (OFDM) waveform design is a crucial issue in integrated sensing and communication (ISAC). This article introduces an OFDM-ISAC waveform design that utilizes the entire spectrum simultaneously for both communication and sensing by leveraging a novel degree of freedom (DoF): the frequency-domain phase difference (PD). Based on this concept, we develop a novel PD-based OFDM-ISAC waveform structure and utilize it to design a PD-based low-PAPR OFDM-ISAC (PLPOI) waveform. The design is formulated as an optimization problem incorporating four key constraints: 1) the time-frequency relationship equation; 2) frequency-domain unimodular constraints; 3) PD constraints; and 4) time-domain low PAPR requirements. To solve this challenging nonconvex problem, we develop an efficient algorithm, alternating direction method of multipliers (ADMM)-PLPOI, based on the ADMM framework. Extensive simulation results demonstrate that the proposed PLPOI waveform achieves significant improvements in both PAPR and bit error rate (BER) performance compared to conventional OFDM-ISAC waveforms.