SDN-based Routing Technologies Over Wireless Mesh Networks

Compared to the wireless access network,wireless mesh networks is more flexible,each node can work both as an access point and as a router.This structure makes the common problems in wireless networks,such as local congestion and local link failures,can be solved through routing technologies by allocating traffic more flexibly,which can achieve better network performance with limited network resources.Therefore,routing is one of the most important and indispensable issues in wireless mesh networks.However,in multi-hop wireless mesh networks,the traditional distributed control architecture may cause too much overhead or low efficiency of control signaling transmission.Using centralized control structure,SDN controller takes advantage of the reported information from the forwarder to obtain the network structure accurately instead of the multi-hop flooding operation in the distributed control structure.This centralized control structure and the corresponding control information transmission method are suitable for more efficient routing algorithms,which makes higher resource utilization of wireless mesh network becomes possible.Firstly,the SDN-based wireless mesh networks simulation platform is built up based on mininet and Opendaylight,and the corresponding scenarios are designed to test the proposed routing algorithm and routing loop eliminating mechanism.On this basis,this paper proposes a new approach of SDN-based multipath routing algorithm.The proposed protocol takes load as an important factor and makes use of the SDN centralized control structure to judges whether a link is congested according to the load parameters reported by nodes.If the link is congested,the controller can select the alternative route for the subsequent flow and bypass the local congestion link on the basis of keeping the original data flow constant which achieves the goal of load balancing.This paper introduces link saturation to SDN,which SDN controller uses to define the link as congested.Moreover,this paper proposes the corresponding link quality evaluation model to define the optimal path.In addition,how to eliminate the routing loop in the wireless mesh network to avoid the broadcast storm is another key problem.In traditional distributed control architecture,spanning tree protocol is usually used to solve this problem,but a large number of multi-hop flooding operations and the whole network reconstruction operations seriously affect the performance and the efficiency of the networks.Based on the topology learning process the SDN architecture,this paper proposes a method to eliminate the loop based on the source node ID,the port number and the destination node ID sequence.The controller can calculate the possible routing loops according to the above sequences reported by forwarders and block the redundant ports by the unified centralized command.