An extended SDN controller for handover in heterogeneous wireless network

In software defined networks, a centralized control is commonly used to provide a global view of the network and to simplify the network operation as well as network programmability. However, in the centralized model, the control path between the network devices and the controller can be a single point of failure or a potential bottleneck. Therefore, in this paper, the traditional SDN controller has been extended and then being embedded in every node, aiming to reduce the risk of losing the connection to the controller and the delay in passing commands from the controller to the devices. This model also enables the benefit of SDN to be utilized in wireless environment. For example, the system resilience has been improved by switching an ongoing connection from a physical interface to another one. The performance of the system was evaluated in a real testbed and the experiment results show that the system which was equipped with the extended SDN controller was a promising solution for handover in heterogeneous wireless network. Specifically, there were a few packet loss when switching an ICMP flow, which has the packet interval of 1ms, between two Wi-Fi interfaces. The packet loss rate was increased up to 37.2% when a handover between Bluetooth and Wi-Fi interface occurred. However, the rate was reduced to below 2.4% when the packet interval was increased from 10ms to 100ms.