Peak-to-Average Power Ratio Reduction of OTFS Based on Precoding DFT-Spread

Orthogonal time frequency space (OTFS) modulation can effectively combat the multipath and Doppler effects in doubly-selective channels, making it suitable for high-speed mobility scenarios. However, conventional OTFS modulation suffers from a high peak-to-average power ratio (PAPR), hindering its practical implementation in ground mobile terminals. To address this challenge, this paper proposes a PAPR reduction method based on precoding discrete Fourier transform spread (DFT-spread) technique. First, the information symbols are precoded, followed by DFT-spread, and finally inverse discrete Zak transform (IDZT) is applied to achieve OTFS modulation. The precoding DFT-spread ensures that the OTFS modulation output approximates a repetition of the input, thereby achieving the PAPR performance comparable to single-carrier modulation. Furthermore, the proposed method simplifies the modulation architecture by replacing conventional inverse symplectic finite Fourier transform (ISFFT) and Heisenberg transform (HT) with IDZT, effectively reducing implementation complexity. Simulation results demonstrate that this method reduces the PAPR of OTFS signal by up to 4.0 dB, outperforming traditional DFT-spread techniques by approximately 1.4 dB.