## 5 Regional Division and Analysis
### Regional Division  
In LEO satellite networks, the existing regional division method is used to improve the efficiency of switching authentication within each region. [PERSON] et al. proposed a division method, taking the satellite in the middle position as the main node and establishing links between two adjacent satellites in the same orbit and two adjacent satellites in the adjacent orbit so that the five satellites can be divided into a region [25]. However, given the potential of reverse slits in the satellite network, as well as the instability or disconnection of links between different orbits as the satellite moves to high latitudes, the region will not work properly. In addition, it is more difficult to ensure that there are links between adjacent areas and the normal operation of areas in cross- regional switching authentication. In terms of storage mode, the method proposed by [PERSON] et al. uses the distributed hash table technology, which reduces data redundancy. However, when switching authentication, user authentication information needs to be transmitted through intersatellite communication, resulting in an increased delay of switching authentication.  
Aiming at the above problems, we propose a stable regional division method. This method can avoid the situation that a region fails to work properly due to the disconnection of links between satellites. At the same time, each node in the region has a complete blockchain ledger, which can avoid the response delay caused by excessive intersatellite communication when switching authentication. In addition, due to the limited onboard computing capacity, the regional partition method proposed in this paper can reduce the computing burden of the master node and reduce the network load. When dividing the region, considering that the adjacent satellite links in the same orbit are stable and the adjacent satellite links between orbits may change, the five satellites with a relatively close distance in the same orbit are divided into a region. In this region, satellites at both ends can send data to the main satellite in the middle of the region with only one or two hops. When weighing the size of the region, the number of blocks generated per unit time should be reduced as much as possible to reduce the number of broadcasts to reduce the load of inter-satellite links. Therefore, the region should be set larger. However, when generating blocks, the region should be set smaller to ensure the speed of transaction transmission within the region. Therefore, in the network topology of a satellite system, the above two factors are taken into account when dividing regions into appropriate sizes. For example, in the Iridium system, five satellites in the same orbit are divided into one region, as shown in Figure 7. Since the Iridium satellite system has six orbits with \(11\) satellites in each orbit, it is divided into \(12\) regions with two regions in each orbit. The purpose of this division is to ensure a low transmission delay in the region as much as possible and to let all nodes in the region share the computing overhead of the entire region without requiring a single node to undertake all computing. At the same time, transactions are verified by each receiving node, avoiding repeated broadcast of transactions and reducing the load of the entire network.