A Comparative Study on Phase Noise Model in Ultra-High Data-Rate Sub-THz Communications

PN and high Peak-to-Average Power Ratio (PAPR) are significant challenges for 6G communications over the subterahertz (sub-THz) band, affecting signal integrity and system reliability. While standardized phase noise (PN) models, such as those from Hexa-X and 3GPP, provide theoretical frameworks, their accuracy in real-world conditions remains uncertain, requiring hardware-specific tuning. This paper presents a comparative analysis of two PN models: a standardized Hexa-X model and a hardware-tuned 3GPP approach. The impact of PN on high-order modulation schemes is examined, revealing its influence on optimal subcarrier spacing and necessitating adjustments for high-order modulation, specifically in OFDM systems. The feasibility of DFT-s-OFDM for PAPR reduction under PN constraints is also investigated. Furthermore, PN mitigation via common phase error (CPE) estimation is evaluated, demonstrating distinct model-dependent performance variations. The findings provide critical insights into PN model selection and waveform optimization for robust 6G system design.