Sensing-Aided Hierarchical Beam Search in Low Earth Orbit Satellite Communications

Abstract

Low earth orbit (LEO) satellite communication which can provide global wireless service plays a critical role in the future wireless communication networks. However, due to the high speed of satellite motion, numerous narrow beams, and complex satellite-terrestrial channels, the initial access between the LEO satellites and user terminals (UEs) becomes more complicated. To establish a stable link, a beam search is required between the satellite and the UE. However, traditional beam search methods (e.g., exhaustive search) have high time complexity which is not suitable in high-speed scenarios. Therefore, in this paper, a sensing-aided hierarchical beam search method is proposed, which is performed in two stages. In the first stage, wide beam scanning is performed to find the optimal angular range. In the second stage, after determining the directions of narrow beams via sensing the direction of arrival (DOA) of satellite signals, the narrow beams generated at estimated directions are used to sweep the satellite beams. This method can help fast beam alignment and obtain high beam search accuracy, which is verified by simulation results. Moreover, we analyze the gain of beam alignment from the two-stage beam search method.

Keywords

low earth orbit satellite communication / beam search / initial access / sensing-aided communication