Artyushchyk O. Models and methods of active queue management of traffic in telecommunication networks

The object of research is the processes of active management of package queues. The subject of the study is models of active traffic queue management and methods of combating congestion in telecommunication networks. Methods of research. Researches of the thesis work were carried out using the theory of queuing systems, the teletraffic theory, probability theory and the theory of automatic regulation of control systems, with the help of which mathematical models and methods of active queue management were developed. To assess the adequacy of the proposed solutions, mathematical modeling and methods of simulation based on the MATLAB interactive system using mathematical statistics methods were applied. Theoretical and practical results: For the first time, a method for researching AQM-systems with regulators of the aggregate rate of incoming traffic based on log phase-frequency characteristics was proposed. This allows to establish the ability of the AQM-system of the TCP/IP network to maintain stability when changing network and traffic parameters and determine the stability margin by amplitude and phase; The mathematical model of the AQM-system was improved by replacing the transfer function of the pure-delay unit of the AQM-system by the complex n-th order Pade transfer function that already with 2-th order provides the accuracy of approximation of the pure delay link with an error of less than 1%, which simplifies the analysis of the AQM-systems; The stochastic model of the AQM-system, corrected by the PI-regulator as a closed automatic control system with feedback and time-variable parameters, has been improved, which allows to take into account the variable character of traffic intensity; The model of the fuzzy regulator of the AQM-system with triangular input and output functions is improved, which allows to increase the system performance when setting the queue length, as close as possible to the required one.