Research Of Load Balance In WLAN Based On Software Defined Networking

With the rapid development of the Internet and the growing popularity of wireless intelligent terminals, the requirements of WLAN are increasingly high. Since traditional WLAN has many limitations,such as complicated network equipments, complex protocols, inflexible architectures and so on, it faces a variety of problems and becomes more and more difficult to meet people's needs. In recent years, an emerging technology called Software Defined Networking(SDN) provides a new scheme to solve those problems in traditional WLAN. Compared with traditional network architectures, SDN has many new characteristics, such as control and forwarding separation, programmable, centralized management, etc. Recently, how to apply SDN into WLAN has became a hot research topic.This thesis introduces WLAN technology which includes network architecture and common protocols, and analyses problems and shortcomings in traditional WLAN. Subsequently this thesis describes SDN technology and analyzes the key issues of it, such as architecture, OpenFlow, SDN controller and so on. Then, this thesis expounds several WLAN architectures based on SDN. After that, this thesis introduces some common load balancing schemes.This thesis proposes a new WLAN architecture based on Software Defined Networking. By the features of SDN, the wired backbone and Access Points can have a unified manage plane to achieve centralized management. And then, this thesis proposes a seamless handover mechanism which forwards the handover control from wireless terminals to SDN controller by using the characteristic of controller centralized management. After that, this thesis realizes the OpenFlow switches and APs in physical layer and management strategies in service layer. This thesis also develops a desktop application to manage the network more convenient. Compared with traditional WLAN, the architecture of this thesis has certain advantages in throughput, handover time delay.Then this thesis proposes two load balance algorithms in wired backbone network and wireless access layer, the main idea is to monitor the traffic of transmission links in wired backbone and APs in access layer by using the granular traffic control and global view of SDN, and discover the problems which lead to the load unbalance and adjust them timely, and take all factors which will affect network performance into account in the process of adjustment. This thesis accomplishs the two algorthms by programming and deploys them on SDN controller. Physical and simulate experiments show that the scheme proposed by this thesis effectively improves the performance of the network in throughput, and reduces transmission delay and packet loss rate.In the end, this thesis summarizes the work which already has been done, and gives the future work direction.