Phase-Noise-Resisting Modulation and Demodulation for Sub-Terahertz Communications

Sub-terahertz (sub-THz) communications have promising prospects for future beyond-5G or 6G applications due to the sufficient spectrum resources. However, the bit-error-rate (BER) performance of sub-THz is seriously deteriorated by phase noise because of the defective high-frequency oscillators. In this paper, a novel modulation and demodulation method with low peak-to-average power ratio (PAPR) is proposed to resist phase noise, where the signal waveform is generated in the form of Gray-mapping amplitude and differential phase shift keying (Gray-ADPSK). As phase noise varies slowly in time, the amplitude and differential phase between adjacent symbols almost remain after transmission with Gray-ADPSK, and hence the BER performance is barely affected by phase noise. In order to support decoding effectively, a soft-decision demodulation method with low complexity is also put forward. Numerical simulations demonstrate that the proposed Gray-ADPSK can resist phase noise significantly, and the high-spectral-efficiency transmission even in the order of 4096 is feasible under high-intensity phase noise.