中文摘要：

典型的切换过程包括扫描、认证和重关联3个阶段,其中扫描阶段占切换时延的90%以上,因此解决切换时延问题主要是降低扫描阶段的时延。文章对传统邻居图切换机制进行了介绍,提出了基于改进邻居图的WLAN快速切换机制。该机制综合考虑接入点（access point,AP）的信号强度、负载以及移动站点（station,STA）的运动方向,计算出每个AP的权值,确定候选AP的优先级;根据优先级STA依次选择候选AP进行认证重关联,直至成功,从而减少扫描信道数量,达到降低扫描时延的目的。仿真结果表明,该切换机制有效降低了切换时延,减少了乒乓切换的发生,满足实时性应用的需求,实现了快速切换。

英文摘要：

The typical handoff process consists of three phases,namely scan,authentication and re-association.More than 90%of handoff delay is caused by scan phase,and therefore reducing the delay in scan phase is the key to solve the handoff problem.In this paper,the traditional neighbor graph handoff mechanism is introduced,and a fast handoff mechanism based on improved neighbor graph for wireless local area network（WLAN）is presented.In the mechanism,the signal strength of access points（AP）,loading of access points and the movement direction of the mobile stations（STA）are considered comprehensively,the weight of every access point is calculated so as to determine the priority of the candidate access points.The mobile stations select the access point according to the priority to handoff until they succeed.The mechanism reduces the number of scanning channels,thus reducing the scanning delay.The simulation results show that the mechanism reduces the handoff delay and the occurrence of ping-pong handoff,meets the requirements of real-time applications and achieves the goal of fast handoff.