An integrated sensing and random access scheme for the aircraft-to-LEO satellite uplink

The Low-Altitude Economy (LAE) has become an important emerging industry and a key growth driver for leading economies worldwide. As a new generation of space-based information infrastructure, Low-Earth Orbit (LEO) satellites can provide wide-area, highly reliable, and low-latency communication support for LAE applications. However, the extensive coverage of a single LEO satellite may lead to contention for uplink resources among hundreds or even thousands of aerial nodes within its service area. In this context, achieving efficient collision avoidance alongside precise sensing of range and velocity is critical. This paper proposes an integrated sensing and random access scheme based on Contention Resolution Diversity Slotted ALOHA (CRDSA) for the aircraft-to-LEO satellite uplink. The proposed scheme establishes a unified transmission framework that facilitates simultaneous random access and independent sensing, while maintaining the standard frame structure and the inherent conflict resolution performance of CRDSA. Building upon this framework, we further develop range and velocity estimation algorithms that leverage both coherent and non-coherent integration, thereby providing an efficient integrated communication and sensing solution for low-altitude infrastructure. To benchmark the performance of the estimators, the Cramér-Rao Lower Bound for the estimation error is derived. Numerical results demonstrate that the proposed coherent integration-based sensing algorithm outperforms its non-coherent counterpart, and that the integrated design achieves a performance gain of approximately 3 dB compared to conventional separated approaches.