The continuous evolution of wireless communication systems toward sixth-generation paradigms has intensified the exploration of new waveforms capable of supporting extreme data rates, ultra-reliable links, and high mobility in challenging propagation environments. Among the most critical operating regimes under consideration are millimeter-wave and sub-terahertz frequency bands, where hardware imperfections, propagation losses, and time-varying channels pose fundamental obstacles to reliable transmission. Orthogonal Time Frequency Space modulation has emerged as a promising alternative to conventional orthogonal frequency division multiplexing due to its inherent robustness in doubly dispersive channels and its ability to exploit the delay-Doppler domain representation of wireless channels. At the same time, phase noise originating from local oscillators becomes increasingly detrimental at high carrier frequencies, manifesting as inter-carrier interference, common phase error, and loss of orthogonality. This article presents an extensive theoretical investigation into phase noise effects on OTFS-based communication systems operating in sub-THz and high-mobility scenarios. Drawing strictly on established literature, the study synthesizes propagation modeling, waveform design, channel estimation, synchronization, and phase noise compensation strategies into a unified analytical narrative. Emphasis is placed on understanding how OTFS fundamentally reshapes the impact of phase noise compared to OFDM, particularly in sparse delay-Doppler channels and under fractional Doppler conditions. The methodology integrates descriptive modeling of oscillator impairments, pilot-aided synchronization techniques, coherence bandwidth exploitation, and non-iterative compensation approaches adapted from OFDM to OTFS frameworks. Results are discussed qualitatively in terms of robustness trends, interference mitigation capabilities, and system-level performance implications without reliance on mathematical formalism. The discussion further explores theoretical limitations, trade-offs between complexity and robustness, and the relevance of emerging machine learning-based transceiver designs. The article concludes by positioning phase noise aware OTFS as a foundational waveform concept for future sub-THz mobile systems while identifying open research challenges in practical implementation and standardization.

Orthogonal Time Frequency Space modulation, phase noise, high mobility channels

Bello, Y., Barnola, S., Demmer, D., and Doré, J.-B. (2022). OTFS waveform with phase noise in sub-THz. IEEE 96th Vehicular Technology Conference Fall.

Bhatti, J., and Moeneclaey, M. (2007). Pilot-aided carrier synchronization using an approximate DCT-based phase noise model. IEEE International Symposium on Signal Processing and Information Technology.

Bouras, D., Mathiopoulos, P., and Makrakis, D. (1993). Optimal detection of coded differentially encoded QAM and PSK signals with diversity reception in correlated fast Rician fading channels. IEEE Transactions on Vehicular Technology.

Casas, R., Biracree, S., and Youtz, A. (2002). Time domain phase noise correction for OFDM signals. IEEE Transactions on Broadcasting.

Chung, M., Liu, L., and Edfors, O. (2022). Phase-noise compensation for OFDM systems exploiting coherence bandwidth. IEEE Transactions on Wireless Communications.

Doré, J.-B., Berg, V., and Kténas, D. (2014). Channel estimation techniques for 5G cellular networks. Transactions on Emerging Telecommunications Technologies.

Ergen, M. (2009). Mobile broadband including WiMAX and LTE. Springer Science and Business Media.

Hadani, R., and Monk Cohere, A. (2018). OTFS a new generation of modulation addressing the challenges of 5G. arXiv preprint.

Hashimoto, N., Osawa, N., Yamazaki, K., and Ibi, S. (2021). Channel estimation and equalization for CP-OFDM-based OTFS in fractional Doppler channels. IEEE International Conference on Communications Workshops.

Leshem, A., and Yemini, M. (2017). Phase noise compensation for OFDM systems. IEEE Transactions on Signal Processing.

Naikoti, A., and Chockalingam, A. (2021). A DNN-based OTFS transceiver with delay-Doppler channel training and IQI compensation. IEEE International Symposium on Personal, Indoor and Mobile Radio Communications.

Pometcu, L., and D’Errico, R. (2020). An indoor channel model for high data-rate communications in D-band. IEEE Access.

Rabiei, P., Namgoong, W., and Al-Dhahir, N. (2010). A non-iterative technique for phase noise ICI mitigation in packet-based OFDM systems. IEEE Transactions on Signal Processing.

Wiffen, F., Sayer, L., Bocus, M. Z., Doufexi, A., and Nix, A. (2018). Comparison of OTFS and OFDM in ray launched sub-6 GHz and mmWave line-of-sight mobility channels. IEEE International Symposium on Personal, Indoor and Mobile Radio Communications.

Xing, Y., and Rappaport, T. S. (2021). Propagation measurements and path loss models for sub-THz in urban microcells. IEEE International Conference on Communications.