MIMO Precoding at the Speed of Wireless: Precoder Prediction for MIMO-OTFS Systems

As the development of 6G technologies progresses, there is a focused effort by international bodies and regulatory agencies to enhance worldwide connectivity, paying special attention to the needs of high-mobility users and networks, such as Mobile Ad-Hoc Networks (MANETs) and Vehicular Ad-Hoc Networks(VANETS) . These advanced systems face significant challenges, particularly the increased demand for rapid channel state information (CSI) feedback due to the fast-changing nature of channel conditions. In environments where traditional time-frequency domain approaches struggle, the adoption of delay-Doppler domain representations, like those used in OTFS (Orthogonal Time Frequency Space) modulation, shows promise for improved stability in mobile scenarios. This paper introduces a novel expression for predicting OTFS channel variations over time and proposes an efficient technique for dynamically updating MIMO (Multiple Input Multiple Output) precoders, enhancing the utility of outdated CSI while minimized signaling overhead and computational complexity. Subsequently, we conduct Monte Carlo simulations to evaluate the performance of OFDM and OTFS MIMO systems within high-mobility environments. These simulations aim to rigorously assess the robustness and efficiency of both modulation techniques under scenarios characterized by rapid user movement and fluctuating channel conditions.