Performance Evaluation of Dual Strategies for Enhancing NB-IoT Access in NTN

As the number of Internet of Things (IoT) devices continues to surge, particularly in remote areas, ensuring efficient and reliable connectivity has become a critical challenge. The integration of Narrowband IoT (NB-IoT) with Non-Terrestrial Networks (NTN) offers a promising solution. However, in Low Earth Orbit (LEO) satellite environments, existing random access (RA) procedures face significant issues, especially with high user density, leading to increased collisions and reduced access efficiency. While progress has been made in areas like delay compensation and Doppler effect management, challenges in collision mitigation remain. This paper proposes two innovative strategies to enhance RA performance in NB-IoT NTN systems: a non-orthogonal frequency hopping pattern for the narrowband physical random access channel (NPRACH) preamble, which increases the number of available preambles by allowing controlled overlap in frequency hopping sequences, thus reducing collision rates; and an adaptive access mechanism, which dynamically adjusts access parameters like backoff intervals and access barring factors based on network conditions to improve access success rates. Simulation results demonstrate the effectiveness of these improvements, especially in high-traffic environments, providing a more efficient and reliable solution for future NB-IoT deployments in NTN.