Search On Hybrid Control In Internet Congestion Control System

With the rapid development of communication and information technologies, the applications of Internet become more popular, which have profound impact on people’s daily work and life. Because of the constantly expanding of the network scope, and the number of network users are also increasing year by year, which make network congestion has become increasingly harsh. The direct result of network congestion conditions is to reduce the network performance, mainly displays in: bandwidth utilization dropped significantly in network; packets of loss; even causing the collapse of the whole network in extreme conditions. So taking effective control strategy for the network congestion problem, optimizing performance of the network and enabling the network to work efficiently are taken many researchers’attention.Hybrid control method is one of classical control theory, which adding a compensating structure (parameter perturbations) on the basis of the feedback controller to achieve controlling tasks of improving precision or interference ability. The advantage of hybrid control method is that when the system parameters are uncertain, it can delay Hopf bifurcation effectively to ensure the stable dynamical behavior of the system, which has a strong applicability. In recent years, the research on the dynamic models of network congestion control system becomes very active, Main work and innovations of this paper are shown as follows:1. In order to increase the application scope of hybrid control algorithm in network congestion control system, hybrid control method is applied to the fluid flow model (Fluid-Flow Model) of Internet congestion control system in this paper, employing the idea of delaying or eliminating bifurcations, thereby expanding the stability range of the system. By selecting the appropriate control parameters, we can control the occurrence of Hopf bifurcation. Using the center manifold theorem and the normal form theory, it can get the direction of Hopf bifurcation and the stability of the bifurcation periodic solutions.2. Meanwhile, to control the Hopf bifurcation of the high bandwidth delay product networks XCP (eXplicit Control Protocol) protocol, hybrid control algorithm is adopted. According to Routh-Hurwitz stability criterion to judge the stability of the controlled system, and using Hopf bifurcation theorem to solve the equilibrium point of the controlled system, theoretical analysis to the stability of the controlled system. In order to verify the effectiveness of the proposed algorithm in this paper, the Matlab is employed to numerical simulations, further we verify the correctness of the algorithm theoretical derivation. Conclusions show that the bifurcation can be well controlled by adjusting the parameter in the algorithm, improving performance and resource utilization of the system, while ensuring to utilize network bandwidth availably and network works normally.