Research On Stable Congestion Control Algorithm In Wireless Software Defined Networks

A large number of data transmission may lead to network congestion,even affect the decrement of the network performance.Stability control of network congestion in Wireless Software Defined Networks(WSDNs)is a solution for network congestion problem.The stability control of network congestion keeps the network performance stable by optimizing the network parameters in WSDNs with propagation delay and external interference.Based on the analysis of the distributed and centralized congestion control,this thesis researches the stable congestion control algorithm with propagation delay and the robust congestion control algorithm with propagation delay and external interference,respectively.The researches of the model establishment,control algorithm and the performance analysis are studied.The main contributions can be summarized as follows.(1)To solve the stable congestion control problem in WSDNs caused by a large number of data transmission,specifically,to stabilize the network parameter at the optimized state of maximizing global network throughput with propagation delay under the stable congestion control and keep the optimized state stable with propagation delay and external interference under the robust congestion control,a hierarchical distributed WSDN network architecture is proposed,which consists of the core WSDN(Core-WSDN)and the subnetwork Cluster Wireless Sensor Network(Sub-CWSN).By the means of this hierarchical architecture,the thesis researches the stable congestion control problems in the distributed Sub-CWSN and the centralized Core-WSDN respectively,in the presence of propagation delay and external interference.A corresponding stable congestion control algorithm is offered,and then the stability conditions is obtained by theoretical analysis when the network parameter is stabilized at the optimized state of maximizing the global network throughput;and the thesis proposes a corresponding robust congestion control algorithm,and obtains the stability conditions by theoretical analysis when the network parameter stays at the optimized value of stable state.It solves the global stability problem of the congestion control in Core-WSDNs.(2)For the optimization problem of the global network throughput performance under the stable congestion control in WSDNs,this thesis proposes corresponding scheduling algorithms to maximize the global network throughput.Based on the network parameter in WSDNs,the resource allocation is analyzed on the nodes processing the data flow.This algorithm is an optimization algorithm of network resource fair allocation,which provides the ideal goal of control for the stable congestion control algorithm,and implements the stable congestion control algorithm.(3)Considering the global stability of the congestion control in the distributed SubCWSN,by analyzing the network parameter and the detection adjustment technology requirement,the thesis proposes an algorithm based on the Additive-Increase MultipleDecrease(AIMD)scheme,the Random Early Detection(RED)algorithm and the channel competition from neighbor nodes.The concept of cluster synchronization is introduced,which means that the sending rates on all the nodes have the same variations(increasement or decreasement).And then a global stable congestion control algorithm is proposed in Sub-CWSNs.The thesis adopts the stability analysis method in the control theory,and combines the congestion control scheme in the wireless network and the stability analysis method in the control theory.By employing the Lyapunov-Krasovskii functionals,the global congestion control algorithm is converted to the global cluster synchronization algorithm,and then obtains the sufficient conditions.Simulation results show that the network parameter can be kept at the optimized value of maximizing the global network throughput,when the algorithm that is implemented to achieve the stable congestion control satisfies the sufficient conditions.Compared with the traditional RED algorithm,it shows the advantage on the network performance.(4)To solve the increment of network cost and unstabilization problems in SubCWSNs and Core-WSDNs with propagation delay and external interference,the thesis constructs corresponding congestion control models with propagation delay and external interference,and proposes corresponding robust congestion control algorithms to implement the models.The algorithms can buffer the impact of propagation delay and external interference on the aforementioned stabilized network,and obtain the sufficient conditions of the robust congestion control algorithms by theoretical analysis by means of the Lyapunov-Krasovskii functionals.Simulation results show that the network parameter can be kept at the optimized value of maximizing the global network throughput for a long time,when the algorithms that are implemented to achieve the robust congestion control satisfy the sufficient conditions.It solves the robustness problem of the congestion control in Sub-CWSNs and Core-WSDNs with propagation delay and external interference.Compared with the traditional congestion control algorithms,these show the advantage on the network performance.(5)To simplify the algorithm procedure,this thesis gives the concept of padding waiting time,which can be arranged on the network nodes by centralized control with the help of global congestion information.A congestion control model is constructed with propagation delay and external interference,and a discrete robust congestion control algorithm is proposed in centralized Core-WSDNs,and then the stability conditions is obtained by theoretical analysis.Simulation results show that the network parameter can be kept at the optimized value of maximizing the global network throughput for a long time,when the algorithm that is implemented to achieve the robust congestion control satisfies the sufficient conditions.It solves the robustness problem of the congestion control in centralized Core-WSDNs with propagation delay and external interference.Compared with previous algorithms,the algorithm procedure of the congestion control is simplified,which realizes the robust congestion control algorithm.