High Accurate Beam Tracking with Hybrid Antenna Array for OTFS-Based mmWave Air-to-Air ISAC

This paper investigates beam tracking in orthogonal time frequency space (OTFS)-based millimeter-wave (mmWave) air-to-air (A2A) integrated sensing and communication (ISAC) systems. The focus is on maintaining reliable links under high mobility, particularly between high-altitude small aircraft. To reduce hardware complexity and cost, we propose a high accurate beam tracking scheme based on a hybrid antenna array. The design enables both communication and sensing within the symbol domain, thereby eliminating the need for additional sensing receivers. It first estimates the angle-of-arrival (AoA), range, and radial velocity via a two-step parameter estimation, and then predicts the state using an unscented Kalman filter (UKF) integrated with a relative motion model. This scheme effectively mitigates beam misalignment while avoiding frequent beam training overhead. Simulation results verify that the proposed scheme achieves accurate and robust tracking performance under diverse operating conditions, while maintaining low hardware complexity.