Research On Load Balancing Mechanism In Wlans Based On SDN Architecture And Power Control

Nowadays,WLANs are widely deployed in enterprises,campuses,homes and public locations,and have become a promising technology for ubiquitous Internet access.In a WLAN,users are usually not evenly distributed with non-uniform traffic demands.Since the users would connect to a nearby AP that provides the strongest received signal strength,the load is unevenly distributed across the APs in the WLAN.As a consequence,the overloaded APs cannot provide enough bandwidth for their associated users while the resources of the lightly-loaded APs are wasted.Therefore,it is of great importance to balance the load among the APs so as to improve network performance and resource utilization in WLANs.To achieve load balancing,several approaches have been proposed,such as power control,user association management,and admission control.However,their performance is limited due to issues such as coverage hole and frequent handovers.In addition,SDN is a new promising architecture for the centralized management and control of switches.Nevertheless,SDN is mostly developed for the wired network.To apply this architecture for load balancing in WLANs,the OpenFlow protocol needs to be extended to dynamically control the APs.To address these issues,the load balancing mechanism in WLANs based on power control and SDN architecture is studied.Specifically,the main work includes the following three aspects.Firstly,the problem of load balancing based on power control in multi-rate WLANs is investigated.This thesis formulates the problem as a mixed integer linear programming model(MILP)and proposes a heuristic algorithm,which aims to minimize the AP utilization of the most congested AP while satisfying users' traffic demands.On this basis,the problem of load balancing optimization based on user association is investigated.The problem is formulated as an MILP model and a heuristic algorithm is proposed so as to get a better performance.Simulation experiments are conducted to evaluate the performance of the proposed algorithms.The results show the effectiveness and efficiency of the proposed algorithms.Secondly,dynamic control mechanism of APs' transmission power based on OpenFlow protocol is developed.To achieve this objective,this thesis analyzes the mechanism of the OpenFlow protocol.On this basis,the sets of OpenFlow messages and statistics are extended to control the WLAN via OpenFlow protocol.Moreover,this thesis designs the interactive process between the centralized controller and the APs,so that the controller can dynamically adjust APs' transmission power.Finally,integrating the WLAN load balancing algorithm with the dynamic control mechanism of APs' transmission power based on OpenFlow protocol,this thesis designs and implements an SDN WLAN load balancing prototype system,and the system testing is conducted.The experiment results not only validate the effectiveness of the dynamic control mechanism of APs' transmission power,but also show the load balancing function of the system.In summary,this thesis investigates the load balancing mechanism in WLANs based on SDN architecture and power control so as to improve the network throughput and resource utilization.For one thing,the AP coverage adjustment heuristic algorithm and user association optimization heuristic algorithm are proposed.For another,the dynamic control mechanism of APs' transmission power based on OpenFlow protocol is developed.And on this basis,the SDN WLAN load balancing prototype system is implemented.