## 5 Simulation and Performance Analysis  
### Performance Evaluation  
The digital satellite-borne base station system's validation environment was constructed as depicted in Figure 4. A high-performance X86 server and a TAC accelerator card with a high-performance FPGA made up the hardware component for simulating the single satellite function, with the X86 server handling the simulation of the satellite-borne protocol processing unit and the TAC accelerator card handling the simulation of the satellite-borne baseband processing unit. The verification environment was composed of the process resource for four satellites and one global resource control center that was imitated by a server and one core network that was simulated by a PC. Each processing unit had a high-orbit satellite communication system communication protocol and baseband software loaded through the global resource control center. The high-orbit satellite communication system was composed of communication protocol software and baseband software, which was developed according to the standard GMR-1 3G from ETSI. The protocol software performed the L2-L3 layer's functions according to the standard, and the baseband software performed the high-PHY functions, which included only the control flow in PHY but not the signal processing. The RF path and feeder link components were streamlined and realized through an Ethernet connection in order to simplify the environment building task. To virtualize the functions of baseband software processing and protocol software processing, the virtualization platform software had to first be loaded on each server. For better virtualization, the protocol software was split into three parts, which were distributed protocol processing unit software, centralized signaling processing unit software and centralized data processing unit software. Then, through the global resource control center, a high-orbit satellite communication system virtualized baseband processing function unit software program was loaded on a virtualization platform of four servers, a high-orbit satellite communication system virtualized distributed protocol processing unit software program was loaded on the virtualization platform of four servers, and a high-orbit satellite communication system virtualized centralized signaling processing unit was loaded on the virtualization platform of one of the servers according to the functional requirements. The centralized signaling processing unit was loaded on the virtualization platform of one server, and the virtualized centralized data processing unit of a high-orbit satellite communication system was loaded on the virtualization platform of one server. These four servers were identical in terms of their hardware configuration, but the dynamic reconfiguration and flexible networking of each satellite protocol function were achieved by simulating the scheduling management, dynamic loading, and configuration management of baseband resources and protocol processing resources in the global resource control center. Since there was no precedent for a base station on a satellite, this validation system was compared with the deployment of an existing high-orbit satellite mobile communication system in terms of performance. The existing high-orbit satellite mobile communication system was composed of dedicated equipment that met the ATCA standard with a different functional hardware board. In order to compare the performance between the digital satellite-borne base station system and the existing high-orbit satellite base station system, four experiments were performed. First of all, the single functional unit deployment time was considered. The single functional unit deployment time was defined as the time for adding only one functional unit when the system is running (e.g., protocol processing unit), and the steps for the two systems were as below. For the traditional ground base station:  
1. Picking a dedicated protocol hardware board. 2. Uploading the protocol software and performing some configuration on the board.