Resolving the high-dynamics vs. low-signaling dilemma: a PPS-aided, shared-sequence ALOHA framework for LEO direct-to-satellite burst access

Abstract

High-precision frequency compensation and high-throughput concurrent access constitute the core bottlenecks for burst access reliability in LEO satellite IoT. Conventional solutions, hampered by large open-loop residual errors, high closed-loop signaling overhead, and onboard multidimensional search and storage costs growing with the user population, cannot simultaneously accommodate high-dynamic conditions and low-signaling access. This paper proposes a PPS-aided, shared-sequence ALOHA burst access framework: on the terminal side, open-loop frequency pre-compensation is accomplished with zero uplink signaling by leveraging GNSS Pulse-Per-Second signals and downlink broadcasts; on the satellite side, a single 24-stage m-sequence is shared among all terminals, with code phase differences naturally induced by propagation delay used to distinguish users, thereby eliminating the multi-user storage bottleneck; a cascaded data-aided estimator and phase-locked loop then deliver fast, precise closed-loop tracking. Simulation results demonstrate: compensation error is reduced by approximately 97% relative to the BeiDou open-loop scheme, and by 80% and 40% relative to Iridium and GEO closed-loop schemes, respectively; total satellite-side synchronization latency is 85.8 ms; peak throughput improves by approximately 25% over spread-spectrum slotted ALOHA; single-beam access capacity reaches 1,317,100 messages per hour at 9.6 kbps; and steady-state zero uplink signaling is achieved.