Expanded Golay Complementary Sequences-Based Grant-Free Random Access Preamble Design for Satellite-Assisted Low-Altitude IoT Networks

Integrating satellite communication into low-altitude economy networks can provide ubiquitous coverage and comprehensive support for diverse emerging Internet of Things (IoT) services. Due to the unique characteristics of satellite environment, one of the significant challenges in this integrated network is to accommodate massive random access requests of IoT devices. Considering the traffic characteristics and low-cost requirements of access devices, we propose a novel preamble design scheme based on the expanded binary Golay complementary sequences for supporting massive grant-free random access in satellite-assisted low-altitude IoT. By means of the Kronecker transformation and sequence concatenation, the proposed length-flexible preamble sequence is capable of having a notably enlarged preamble capacity and reduced coherence, while maintaining a low peak-to-average power ratio (PAPR). Furthermore, the closed-form expressions of the upper bounds on PAPR and coherence are derived, which theoretically guarantee the effectiveness of the proposed preamble sequences. Simulation results demonstrate that the proposed preamble sequences enable compressed sensing-based joint activity detection and channel estimation to achieve more reliable performance in typical satellite scenarios, compared to the existing schemes.