无线局域网下一种基于预处理的切换模式*

针对移动节点（mobile node，MN）在无线局域网中切换时，产生的切换延迟会严重影响实时应用的性能和丢包率问题，提出了一种基于预处理的切换模式。该模式是在满足预处理条件下，启动一种预先信道扫描算法，实施数据包的预转移和预恢复操作。这种切换模式不仅消除了切换过程中的信道扫描，而且实现了提前将发往MN的数据包转发到目的AP，从而解决了MN与对端主机建立路径所造成的丢包率过大的问题。实验结果表明，该切换模式降低了对实时应用的影响，达到了降低丢包率、减小切换延迟的目的。

Pre-disposal for handoff in wireless LAN

In order to solve the problem of huge handoff latency which had greatly influenced real-time applications and packets dropping during the handoff procedure which was implemented by MN,this paper proposed a new handoff mode, i.e. pre-disposal for handoff.In this handoff mode,pre-divert and pre-recover packets would be implemented based on channels scanning when the pre-disposal condition appeared before handoff. Thus, not only the scanning phase was eliminated during handoff, but also the packets destined for MN were pre-transferred to destination AP from current AP, and then the problem of packet loss rate caused during the route set up between MN and communication nation (CN) was solved. The experiment result shows that this handoff mode reduces the influence on real-time applications, and achieves the goal of lower packets dropping and smaller handoff latency.