Time Synchronization-Aided Signal Detection for LEO Satellite Communications With Reduced Doppler and Delay Searching Ranges

Low Earth Orbit (LEO) satellite communications provide uninterrupted coverage and seamless services, which are becoming a crucial element in the Sixth-Generation of wireless communications. However, LEO communications are subject to high path loss and Doppler frequency shift, which presents significant challenges for such large-distance and time-changeable satellite-terrestrial transmission links. Direct Sequence Spread Spectrum (DSSS) has been widely adopted as a robust modulation technique in LEO satellite systems. Traditional DSSS signal detection methods, which rely on 2D searching, fail to effectively acquire the weak uplink signals due to the extremely low signal-to-noise ratio and pronounced channel dynamics. In light of these considerations, this study proposes an algorithm designated as time synchronization-aided signal detection, with the objective of enhancing the signal detection probability in low signal-to-noise ratio and high-mobility communication scenarios. Furthermore, we develop a novel transmission system based on time synchronization, with the objective of reducing the signal detection threshold by minimizing the impact of the Doppler frequency shift and time delay searching ranges. We theoretically analyze performance at varying time synchronization precision, numerical simulations and hardware experiments under diverse conditions demonstrate that, in comparison to the conventional algorithm, time synchronization can enhance the probability of signal detection.