## 1 Introduction  
With the widespread adoption and advancement of low-power wide-area network technology, the deployment and connectivity demands for Internet of Things (IoT) devices have experienced an exponential surge. Challenges arise in regions such as oceans, deserts, and remote mountainous areas, where constructing terrestrial-based stations is impractical or cost-prohibitive. As a consequence, Narrowband Internet of Things (NB-IoT) terminals relying solely on terrestrial-based infrastructure exhibit notable deficiencies in service capacity, leading to a significant disparity between service capabilities and actual demands [1]. In response to these challenges, low Earth orbit (LEO) satellite-based IoT networks have emerged as a promising solution, serving as a complementary and extended alternative to terrestrial-based networks. LEO satellite-based IoT networks address the limitations associated with deploying terrestrial-based stations and establishing communication networks on the ground [2]. Iridium Communications announced Project Stardust which it describes as \"the evolution of its direct-to-device (D2D) strategy with 3 GPP 5G standards-based NB-IoT via non-terrestrial network (NTN) systems [3]. This approach boasts advantages such as global coverage and the ability to deploy terminals without substantial spatial constraints. Therefore, LEO satellite-based IoT networks have become a hot topic in the IoT research field. The application of NB-IoT as a public network IoT system in LEO satellite-based networks has been widely studied, with a primary focus on the adaptive modifications of NB-IoT in the context of high-dynamic and long-distance transmission links in LEO satellite channels, such as waveform, synchronization, protocol stack, etc. In [4], the authors focus on the impact of Doppler shift on NB-IoT waveforms and propose some possible solutions. In the literature [5], the authors not only take into account the adaptations at the NB-IoT physical layer but also include the higher layers, like Medium Access Control (MAC), Radio Link Control (RLC), Packet Data Convergence Protocol (PDCP), and Radio Resource Control (RRC) layers, in LEO satellite-based networks. The authors propose a resource allocation approach in order to reduce the high values of differential Doppler under the maximum value supported by the 3 GPP standard. They also demonstrate the link budgets of LEO satellite-based networks with different parameters, providing some simulation results as a benchmark for further study. To address the problem during the RA procedure, they investigate the effects of the differential Doppler and delay on the RA procedure and point out some solutions to overcome those challenges, such as the use of Global Navigation Satellite System (GNSS)-aided solutions and the removal of Hybrid Automatic Repeat Request (HARQ). In addition, they propose an RA technique which is robust to typical satellite channel impairments. Simulation results show that the proposed method can address the problem of long delay in an NTN scenario. In [6], the authors review the fundamentals of NB-IoT and explain how to support NB-IoT satellite communication through a minimal set of modifications. In [7], the authors select the suitable antenna and proper satellite parameters to ensure link reliability in LEO satellite-based IoT networks. In [8], the authors describe the NB-IoT uplink problem in LEO satellite-based networks and increase the compensation range of the NB-IoT receiver by adding the number of Demodulation Reference Signal (DMRS) symbols. Furthermore, the RA procedure is the main challenge of NB-IoT technology's application into the NTN scenario due to the presence of a long delay. Therefore, more researchers have focused on the problems during the RA procedure in LEO satellite-based IoT networks. To solve the problems, the authors in [9] analyze the challenges imposed by the increased delay in the communication link on the RA procedure and propose new solutions to overcome those challenges.