Preamble Structure and Timing Advance Method for Satellite IoT

Satellite-based networks have emerged as a promising solution for global Internet-of-Things (IoT) to bridge the coverage gaps of terrestrial networks (TNs). However, due to the wider coverage and rapid movement, satellite-based communication has two distinct characteristics from the terrestrial one, notably longer propagation delay and larger Doppler shift. These distinctions pose significant technical challenges to implementing efficient random access (RA) schemes in satellite-based networks. In this letter, we propose an efficient RA scheme tailored for satellite IoT. Firstly, the preamble structure is designed based on two types of LoRa chirps, which facilitates the joint estimation of timing advance (TA) and carrier frequency offset (CFO). Secondly, a frequency-domain TA method is proposed for multipath channels, whose accuracy is improved with reduced computational complexity. Numerical results manifest that the timing accuracy is enhanced in the low and medium SNR areas, and the estimation range of CFO can be up to half the signal bandwidth.