针对低轨( LEO)卫星网络切换中切换点受限、切换频繁等问题，提出一种基于平面扇形角定理的任意点切换定位算法，并设计上下文传递模式下基于性能优化策略的安全切换方案。应用平面扇形角定理求解切换点经纬度坐标，从而避免应用球面三角形内角和定理的局限性，计算得到临近空间中任意切换点的位置坐标。从两方面对切换协议进行性能优化：选择与飞行器当前巡航速度契合度最高的卫星作为下一跳切换卫星，从而减少网络平均切换次数；通过引入历史信息，从会话密钥保护、指令消息完整性和新鲜性保护等方面增强协议的安全性。切换协议采用上下文传递模式，与其他采用预认证模式的典型切换协议相比，减少了通信和运算开销。仿真实验结果表明，该方案具有通信与计算开销低、切换次数少、协议安全性高等特点，适用于LEO卫星网络切换。%To solve the problems just like limited cut point and handoff frequently when switching in low earth orbit,an algorithm that is used to orientate the handoff point based on the theorem called flat fan angle and the security cutting protocol related which is based on optimization strategy is proposed. Firstly,the flat sectorial angle theorem is applied to fix the latitude and longitude coordinates of the switch point,using this method avoided the limitations of the application of spherical triangle theorem;Therefore the new algorithm can calculate any cutting point in space. Secondly,it optimizes the performance of switching protocol from two aspects:Choosing the satellite which is most fit for the aircraft in speed to be next-hop satellite when switching,doing like that can shrunk the cut frequency;The new protocol is enhanced security by drawing into historical record which can reflect the past secret key and the integrity of orders. Finally,the new protocol is designed under the context transmission mode, which can decrease the communication and computing costs when compared with protocols under other authentication mode. Simulation experimental results show that the low communication and computing costs, less switching frequency and high security features makes the protocol be more suitable for LEO satellite network.
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