# Intelligent Beam-Hopping-Based Grant-Free Random Access in Secure IoT-Oriented Satellite Networks
## 1 Introduction  
As satellite communication technology continues to advance, it is now capable of serving users in various environments such as air, sky, earth, and sea. This has led to an increased demand for satellite communication in different scenarios, with users expecting higher communication quality. Currently, the international organization responsible for standardizing communication and prominent research institutions has prioritized global seamless high-speed coverage as a key area of study for the sixth-generation mobile communication technology (6G) [1, 2]. This research focuses on addressing high-speed communication challenges in various scenarios such as satellite connections, seismic communications, military communication, ocean communication, desert environments, and other situations where there are limitations on the number of users. The advancement of satellite communications and the secure Internet of Things (IoT) has positioned satellite IoT networks as a critical application scenario in both the present and future [3]. However, they face challenges in providing the same level of network service performance as terrestrial Fifth-Generation Mobile Communication Technology (5G) in special scenarios [4, 5, 6]. These challenges include dealing with significant transmission delays, limited communication resources, and an uneven distribution of covered users [7]. Given the current performanceof network services, it is imperative to investigate the communication issues in the satellite end scene to achieve worldwide uninterrupted, fast, intelligent and highly dependable communication [8]. In considering the terrestrial mMTC scenario, it becomes evident that traditional grant-based random access is afflicted by two significant shortcomings [9; 10; 11]. Firstly, the probability of failure for grant-based random access at a large scale will be high, resulting in a significant delay in access [12]. Secondly, large-scale grant-based random access is characterized by a significant signal overhead, which ultimately reduces the efficiency with which wireless resources are utilized [13]. In this context, the design of a large-scale random access system with low latency and high reliability is necessary to accommodate the specific characteristics of satellite Internet of Things. To address the challenges posed by large-scale random access, the academic community has put forth a grant-free random access (GFRA) technology [14]. The fundamental concept of grant-free random access is that, following the transmission of the preamble by an active device, the data signal can be sent directly without awaiting authorization from the satellite. This approach markedly reduces the access delay and signaling overhead associated with large-scale access. It is therefore widely considered that large-scale unlicensed random access may represent a potential technology for 6G wireless networks [15]. The sporadic nature of IoT services means that the satellite is unable to determine which devices have sent data [13]. However, the key to large-scale unlicensed random access is to detect activated devices based on the received preamble. In traditional multi-beam communication systems, each beam is fixedly allocated a certain amount of power. This results in a waste of power due to the uneven distribution of ground users. The amplifier aggregates the total power and facilitates the flexible transfer of power distribution. The phased array antenna is capable of modifying the antenna pattern through the manipulation of the phase of the feed, thereby enabling the flexible configuration of the coverage area size, coverage area position, and number of beams. This allows for the achievement of beam scanning and the attainment of comprehensive on-demand coverage of terrestrial beam positions [16]. Hence, it is imperative to address the issue of user communication interference in satellite scenarios in order to establish effective communication and maximize efficiency for achieving low-latency and dependable access.