自组网中动态拓扑的性能分析

Performance analysis of dynamic topology in ad hoc networks

研究了自组网中动态拓扑性能.通过选用最短路径和基于最短路径的最稳定路径作为路由度量,选用平均路径稳定时间和平均路径长度作为性能度量,考查节点密度、运动速度、暂停时间等因素对网络拓扑性能的影响.仿真结果表明,暂停时间对网络拓扑的影响较小,仅在高速情况下平均路径长度随暂停时间的增加而明显增加;移动速度的增大使平均路径稳定时间急剧下降,但平均路径长度基本不变;节点密度的增加对平均路径稳定时间影响较小,但会使平均路径长度明显下降.在设计路由协议时,将路径稳定性作为路由选择的依据可显著提高系统性能,维护现有活动路径比重新发现新路由更为重要,路径有效时间随路径长度和移动速度的增加而降低.

Differing form other networks, the rapid, frequent and unpredictable topopogy change is the key distinguishing feature of ad hod networks. The selected path according to different routing metrics has different rules of changes. The shortest-path and the most stable path based on the shortest-path are selected respectively as routing criteria and average path stability time, and average path length as performance metric to explore the effects of node density, mobility rate, and pause time on the network topology performance. The simulation showed the following results: the pause time slightly affects the network topology while only in high velocity case the average path length increase obviously as the pause time increases; the increased velocity make the average path stability time drop rapidly but does not affect the average path length. When the routing protocols are designed, selecting path stability as routing criterion will dramatically improve the system performance, maintaining the current active path is more important than rediscovering the new one and the path valid time will decrease as the path length and the node velocity increase.