# Digital Twin Technology-Based Networking Solution in Low Earth Orbit Satellite Constellations
## 6 Simulation and Analysis
### Twin Scenario Construction and Test Verification for \"Phase 1\"  
Pre-construction focuses on the constellation-wide ground verification of networking protocols for undeployed LEO constellation networks. The performance of the networking protocol is tested and judged by collecting simulation data in a twin verification environment that is similar to the actual system.  
To address the verification requirements of Phase 1, the pre-construction phase of the low Earth orbit constellation network protocol, a fully digital twin verification environment is constructed based on the research findings presented in Section 4. This verification environment simulates 50 low Earth orbit satellites, one gateway station, and several broadband terminals. Each low Earth orbit satellite is equipped with an onboard routing and switching node that runs inter-satellite routing protocols to enable data forwarding within and between satellites. The satellite terminals simulate the network layer and above functions of real user terminal devices. By running user-to-satellite routing protocols, they provide functionalities such as user access, service access, and inter-satellite handovers. The gateway station deploys a boundary gateway node that runs feederlink-to-ground routing protocols to handle the conversion and processing of low Earth feederlink layer protocols and ground-side protocols.  
As shown in Figure 8, the satellite terminal 0106 is connected to the low Earth orbit satellite L0106, and the satellite terminal 0107 is connected to the low Earth orbit satellite L0107. The satellite terminals 0106 and 0107 achieve inter-constellation communication by accessing the low Earth orbit satellites L0106 and L0107, respectively. Ping packet connectivity testing is performed between the satellite terminals.  
Figure 8: Verification of the environment of the fully digital low-orbit constellation twins in a virtual simulation.  
Based on the fully digital twin verification environment depicted in Figure 8, two testing and validation tasks were conducted.  
1. Testing and validating the performance of the low Earth orbit constellation network protocol when the inter-satellite topology undergoes predictable dynamic changes. Satellite terminal 0106 sends ping packets to satellite terminal 0107, with the IP address of 171.1.27.10. During ping packet transmission, the inter-satellite topology changes periodically based on the ephemeris data. Utilizing the functional model deployed in the low Earth orbit constellation twin verification environment, the ping packet display indicates normal business connectivity without packet loss. Additionally, the latency varies dynamically with the relative positions of the satellites, ranging from 31.17 to 39.86 milliseconds, as shown in Figures 9 and 10.
2. Testing and validating the adaptability of the designed low Earth orbit constellation network protocol when unpredictable abnormal disruptions occur in the inter-satellite links. Satellite terminal 0106 sends ping packets to satellite terminal 0107, with the IP address of 171.1.27.10. During ping packet transmission, a link abnormality interruption occurs between the low Earth orbit satellites L0106 and L0107. The routing convergence and business transmission conditions are illustrated in Figure 11. After conducting five repeated tests, the average business recovery time is determined to be 7.43 s.  
The protocol testing results based on this environment demonstrate that by constructing a twin verification environment that closely resembles the actual system, various typical application scenarios can be created to conduct network architecture and protocol validation before satellite deployment.  
Figure 9: Service interworking (simulated by virtual scenario).