Joint Doppler and Angle Tracking for LEO Satellite Communications Exploiting Orbit Characteristics

In high-dynamic low earth orbit (LEO) satellite communication (SATCOM) systems, frequent channel state information (CSI) acquisition consumes a large number of pilots, which is intolerable in resource-limited SATCOM systems. To tackle this problem, we propose to track the state-dependent parameters including Doppler shift and channel angles, by exploiting the physical and approximate orbit characteristics for LEO satellite and ground users (GUs), respectively. As a prerequisite for tracking, we formulate the state evolution models and measurement models. Then based on the tracking models, the proposed joint Doppler and angle tracking (JDAT) algorithm can be divided into four parts: rough Doppler estimation, rough angle estimation, measurement error prediction, along with the extended Kalman filter (EKF)-based state tracking and parameter update. Simulation results show that compared with the rough estimation methods, the proposed algorithm performs much better in estimating the state-dependent parameters.