Research And Implementation Of Satellite Network-Links Emulation System

With the rapid development of satellite networks technology, many special network protocols and applications for satellite networks have emerged. Before being used in practice, the protocols and applications of the satellite networks must be debugged, tested and evaluated in detail. So it is important to build a reliable laboratorial environment for this purpose.Network emulation combines of the advantages of network simulation and live testbed. It can build a controlled and reproduced environment. It also can exchange network data with the outside in real time and using real implementations of network protocols. Network emulation can get the reliable experimental results with low costs, so it is very suitable for the requirement of satellite networks testing.This thesis focuses on the study of satellite network-links emulation. By analyzing and comparing the characteristics of the existing network emulation system, we discuss the solutions to the critical issues of dynamic update, packet capture, time synchronization and real-time scheduling. In order to get rid of the physical network-links effects to the emulation tests, we change the way of packet capture and introduce the time synchronization mechanism.Based on the characteristics of the satellite network, we have finished the design and implement of the prototype of the satellite networks-link emulation system. This system is fully implemented in user space, with distributed architecture and open interface. We make out the solutions to the critical issues, such as dynamic expansion, real-time updating and emulation of the characteristics of link.Real-time is one of the characters of the emulation system. We introduce the time synchronization idea to the distributed emulation system and establish a unified expression and conversion of time. Then the accurate emulation delay can be calculated easily. In addition, with the study on real-time schedule in user space, we use the way of error compensation to improve the accuracy of the emulation.Finally, we make some experiments for the function of delay control, error control and real-time update. The result can be used to verify the algorithms of time synchronization, real-time schedule in user space and error compensation.