PRACH Signal Design and Detection for LEO Satellite Systems with Imperfect UE Positioning

This paper investigates a novel physical random access channel (PRACH) signal design and detection scheme tailored to low Earth orbit (LEO) satellite systems operating at the Ka band, particularly in presence of user positioning errors. The primary aim is to guarantee the initial access despite substantial time and carrier frequency offsets are experienced by the received preamble. To enable reliable detection, a well-suited preamble structure is crucial. To that end, one viable approach involves the use of a preamble crafted by concatenating a single root Zadoff Chu (ZC) sequence with different cyclic shifts. Building upon this notion, we propose an innovative preamble design that interleaves the redundancy blocks with the ZC sequences, thereby enhancing the performance of the detector. Numerical evaluations show that the proposed scheme has significantly lower missed detection probability (MDP) compared to existing solutions that transmit the whole cyclic prefix (CP) block ahead of the sequence.