| Space is another new area for activity and development of the mankind after land, sea and air. As the bridge connecting land-sea-space-aeronautics integration information systems, space information networks are strategic infrastructure. Since space information networks are often located in harsh or hostile environments, they are easily interfered or destructed. In order to ensure the network security, reliability and survivability, they must have strong self-protection and system recovery capabilities. Therefore, the demand of network reconfiguration technology in space information networks becomes increasingly urgent.A topology reconfiguration algorithm based on node mobility control was proposed for space information networks, with considering characteristics of locally asymmetry topology, node mobility, redundant links and node resources. The algorithm has four phases, which are judgment of redundant nodes, selection of repairing nodes, mobility control of repairing nodes and optimization of reconfigured area. The aim of the first phase is to judge the redundancy of a node locally through comparing the node connectivity with neighbor nodes. In the second phase, HELP-ACCEPT-SELECT mechanism is designed for partition nodes to collect around topology information and thus select proper repairing nodes based on the principle of rapid reconfiguration. In the third phase, virtual force is introduced. On an important assumption that repairing nodes are acted upon by four forces, including gravitation of partition node, repulsion of neighbor nodes and barriers, and random dithering force, repairing nodes move a step in the direction of net force. After finishing a step moving, repairing nodes compute current virtual net force and keep moving step by step until they arrive at the target area. In the fourth phase, aiming at minimizing local communication cost, repairing nodes cooperatively adjust their locations to form an optimized local topology with high coverage and strong connectivity, and thus improve integrated network performances.The network simulation software NS2was used to evaluate the proposed topology reconfiguration algorithm. Comparing the initial topology with the topology reconfigured in the respect of validity, scalability and invulnerability, simulation results demonstrate the algorithm can avoid the existing of the partition nodes effectively, increase network capacity and communication efficiency, and thus optimize network performances. |
