Intraditional WLANs

when a user with a station (STA) accesses the Internet through AP (Access Point)

due to the mobility of the user

the STA may move out of the coverage area of current AP and enter the coverage area of anotherAP. Thus

STA needs to handover between APs. In traditional WLANs

such a handover often incurs a sudden increase of the network delay

a sharp decrease of throughputs and even disconnection. This paper presents a new handover scheme based on the AP virtualization and OpenFlow technique. By developing an OpenFlow switch network

we can realize a fine-grained control on the traffic of STAs

and realize the roaming of STA among different APs. Furthermore

we build up a practical WLAN testbed and real experiments show that the proposed scheme will only lead to a handover delay of about 5ms

a throughput reduction of about 1s and delay of 16ms when a handover happens. Compared with other existing schemes

the proposed scheme has smoother handover process since it does not need re-authentication and re-routing.