Service Quality Optimization Of Wireless Networks In SDN

At present,webapplications have been migrated from the desktop to mobile phones.Various challenges have arisen and some of them are prioritized as the most important research topics.Among them,one critical question is how to improve the performance of an application in terms of effectiveness,security and intelligence.To achieve this,this research proposes three solutions to address them respectively: to provide an effective network with global network bandwidth optimization;to provide a secure network with preserving mobile usrs' privacy;to provide an intelligent network with a conte xt-aware user-oriented handover.Traditional nework lacks a centeral entity to manage all the networking resources from a global perspective,which usually leads to local optimal solutions.A novel architecture,software defined network(SDN),provides a new strategy to manage the network by separating the control plane from the data plane.Thus a network administrator can configure,manage,programe the network equipments without any changes in the infrastructure layer.This purpose of this research is to improve mobile user experiences with the help of the emerged software defined wireless network(SDWN)platform.The key challenges in SDWN such as resource scheduling,security and handover are fully analyzed and researched.The major contributions are as below: 1.To fully utilize the bandwidth in a software defined wireless mesh network,a helper node is selected to help other link to transmit packets.Based on this,a distributed cooperative routing algorithm is proposed with the help of cooperative routing.This algorithm provides an effective network in term of networking bandwith in which each link contains a routing path and a corresponding helper node.The results demonstrate that this algorithm can be easily applied in traditional network as well as SDN to improve the network performance significantly.2.In application layer,this research present a solution to the improvement of a hybrid network's total throughput o by means of the coordination between multiple devices.Unlike to the existing solutions which usually switch to mobile networks while ethernet broadband networks are unavailable,the algorithm proposed in this thesis maximizes the uplink bandwidth by redistributing the traffic to all available links based on their capabilities and real-time load.Two approaches are presented: distributed non-interactive model and SDN based interactive mode.The experiment results prove that this algorithm can be easily integrated into an existing network to improve total uplink bandwidth.3.With the widely adoption of SDN and social networking,mobile user's privacy and security issues are raised.A novel and practical solution is proposed in this thesis to provide the relative location of two mobile users based on their WiFi scanned results rather than on the additional sensors.Privacy concern has been eliminated in this solution because end users will not collect and send any sensitive information to the server.The feasibility is proved with the prototype of "Circle Your Friends" System(CYFS)on Android phone which allows a mobile user to query his/her friends' distance.4.A SDN controller has the capabilities to acquire and process large amount of information from all network layers,which provides the feasibility to design an intelligent handover algorithm.A multi-round fuzzy logic based context-aware handover algorithm is proposed in this research.The solution can make intelligent handover decision to align with the users' preference with the least interactions.