Joint Phase Noise Estimation and Data Detection in Millimeter-Wave OTFS Systems

The orthogonal time frequency space (OTFS), a recently introduced two-dimensional modulation in the delayDoppler domain, holds great promise for high-mobility communications. OTFS-based millimeter-wave systems are gaining attraction due to their ability to offer a larger bandwidth and increased robustness against Doppler spread. However, the presence of phase noise (PHN) from high-frequency oscillators can lead to severe inter-carrier interference in OTFS. In this paper, we present a new approach that addresses the challenge of PHN in millimeter-wave OTFS systems by introducing a joint design of data detection and PHN estimation, which are performed iteratively to facilitate the exchange of the posterior information between the two components. Specifically, a lowcomplexity expectation propagation algorithm is developed for data detection, where the posterior information is updated in an inverse-free way based on the minorization-maximization method. As for the PHN estimation, a belief propagation algorithm is applied for message passing on a factor graph. Simulation results demonstrate the superior performance of our proposed design, showcasing faster convergence and substantial gains compared to existing OTFS detectors. Moreover, our approach also exhibits robustness against PHN, highlighting its effectiveness in practical scenarios.