A Study On Wireless Handover Based On Software-Defined Networking

In recent years, the coverage area of wireless networks expands greatly and the number of wireless users increases dramatically, resulting in sharp demands for highly efficient WLAN deployment and services. However, there are some problems in the traditional WLAN networking, e.g., when a user hands over, network services will be interrupted, due to the change of the user’s network address. This problem is caused by the TCP/IP protocol suite and limitations of traditional network devices, thus reduces the quality of experience of end users.To overcome the traditional WLAN handover problem, this thesis studies wireless handover based on Software-Defined Networking (SDN). SDN transfers the network from a distributed architecture to a centralized one by separating the control plane from the data plane. This innovative capability of SDN improves the forwarding capability of the devices and addresses issues related to user access. In the thesis, an SDN-based wireless handover scheme is presented where each mobile device is deployed with a single wireless network card. In this scheme, the SDN controller percepts the dynamic change of the network topology in time and generates flow table entries for switches. Switches deal with data flows according to their flow tables. By modifying the route of a flow so that it can be redirected to the new location of the user, wireless handover is achieved. However, due to the lack of buffering mechanism in the network, there inevitably exists a short period of time when data transfer is interrupted in the process of handover. To deal with this issue, this thesis proposes another handover scheme where each mobile device is deployed with two separate wireless network cards. This scheme enables simultaneous access to two Openflow-enabled access points, thus realizes seamless wireless network handover under some constraints.