Abstract: How to realize the rapid inter-AP hard handoff has become one of the key technologies for WiFi based onboard Internet applications，because the communicating link is always disrupted suddenly with the current AP by the obstacles and etc in the fast moving scenario.This problem may be resolved by a multi-radio based inter-AP handoff approach which bonds two wireless NICs to the virtual one, and switches the active link to slave when the master link is detected to be disconnected.To validate the feasibility of the approach，a hard inter-AP handoff testbed is built up and serials of experiments are carried out with the hard inter-AP handoff process triggered by changing the status of the current AP.Experimental results show that the handoff approach can decrease the hard handoff latency to 300~400 ms，and the negative influence on the throughput can almost be ignored during the hard handoff process.

摘要： 在车载Internet等快速移动应用环境下，由于障碍物遮挡等原因，当前通信链路可能突然与当前AP失去连接，如何实现快速的AP间硬切换成为基于WiFi的车-地互联系统的关键技术之一。为此，可采用一种基于多无线模块的方法将主从两块无线网卡捆绑为一块虚拟网卡，当检测到主链路失去连接后迅速切换到从链路以实现快速的AP间硬切换。为验证该方法的有效性，建立了AP间硬切换实验床，通过改变当前AP的工作状态以触发主从无线模块的硬切换进程，从而系统地研究和分析AP间硬切换导致的网络延迟和带宽变化。实验结果表明，该方法的AP间硬切换延迟仅为300~400 ms，网络带宽基本不受影响。