802.11规定的切换过程十分耗时, 同时移动终端根据接收到的信号强度来选择AP往往不能满足通信带宽的需求, 这两点对于需要依靠不间断通信来进行作业的工业机器人十分不利. 本文面向工业机器人场景提出一种基于动态无线地图的带宽保证快速切换技术. 利用预先建立和下载的无线地图, 机器人不需扫描信道即可获得附近可用的AP基站, 同时利用服务器实时收集AP的工作负载并向机器人提供AP选择服务, 可同时满足低切换延时和带宽保证两个切换目标. 本文在网络仿真平台NS3上实现了所提出的快速切换框架, 并与已有的切换方案进行比较. 实验结果表明, 本文方案在任何情况下都优于已有的切换方案, 并且只要机器人附近存在带宽可满足的AP, 本文方案总是可以关联到最佳的AP.
The handoff process specified in 802.11 is time-consuming, and the strategy of choosing AP based on the received signal strength often fails to meet the mobile station’s bandwidth requirement. Therefore, 802.11 is unsuitable for industrial robots which have to rely on uninterrupted communication to work. This study proposes a fast handoff technology based on dynamic WiFi map that can provide bandwidth guarantee for mobile industrial robots. A prebuilt WiFi map is used to help the robots obtain their nearby Access Points (APs) without channel scanning, and at the same time, a server is used to collect the workloads of all APs periodically and provide robots with AP selection service that tries to meet both low handoff delay and bandwidth guarantee. This study implements the proposed fast handoff technology on a famous network simulation platform NS3 and compares it with some existing handoff schemes. The experimental results show that the proposed handoff scheme is superior to other handoff schemes in all cases, and can always choose the best APs with bandwidth satisfaction as long as there exists APs in the vicinity of the robot that have sufficient bandwidth.