基于QualNet的低轨卫星网络半实物仿真

Low-Earth-Orbit (LEO) satellite constellation, such as the Iridium constellation, has the advantage of ultra-low latency, global coverage as well as the capability of conducting dynamic routing and on-demand traffic engineering. Although LEO satellite networks have been researched for a quite long time, due to the cost issues and operation limitations, it is nearly impossible for researchers to validate their innovative protocol design ideas on the in-orbit LEO satellite platform. A workaround way is to evaluate their design entirely on softwarebased network simulators, such as NS2. However, the softwarebased network simulation also has its limitation when the physical satellite router has been developed and the evaluation of the network protocols as well as the system performance is required. Generally, to address this issue, closed-loop semi-physical simulation is a must. In this work, we propose the design and implementation of a QualNet-based semi-physical simulation for LEO satellite networks. The highlighted features of our system include: (1) for cost-effective system implementation, we adopt the network virtualization technique to virtualize one physical network interface into multiple virtual network interfaces to correspond with satellite’s multiple network interfaces; (2) we use the Linux netfilter to differentiate the protocol packets from the data packets at the ingress; (3) to satisfy the needs of dynamic routing and IP address reconfiguration for some space-dedicated network protocols, we use the Linux command route and ifconfig for the physical machine; (4) during the semiphysical simulation, we pinpoint a synchronization issue between the physical machine and the simulation machine, and solve this problem by synchronizing the cycle time of both machines. We believe our work is valuable for the large-scale satellite networks validation before launching these satellites into space.