Η επέκταση και η αύξηση της κυκλοφορίας του Διαδικτύου, έχουν καθιερώσει τον έλεγχο συμφόρησης ως ιδιαίτερα σημαντική μονάδα της σχεδίασης της λειτουργίας των δικτύων. Οι μηχανισμοί ελέγχου συμφόρησης, αποτελούνται από έναν αλγόριθμο ελέγχου, ο οποίος εκτελείται στην πηγή καound in where local stability around an equilibrium is addressed, since linearized versions of the fluid flow model and queue dynamics are considered. Furthermore, owing to their implementation on the links, the total number of computations performed due to congestion control, should be kept to a minimum. The practical assumption that link algorithms are unavailable to the designer, lead alternatively to the design of congestion controllers operating in the source. However, certain key questions need to be carefully addressed, prior to implementation. Specifically: a) a model for the plant has to be devised, otherwise stability analysis is impossible; b) determining a desired and feasible system performance is a non-trivial task, owing to the highly uncertain and dynamically varying nature of the Internet; c) the controlled system should not be only stable, but additionally robustly stable against modeling imperfections, exogenous disturbances, delays and errors in interpreting the network produced congestion signals; d) the output of any proposed control scheme should be saturated. Fortunately, in the source control theoretic approaches, the simplicity constraint is relaxed. The thesis proposes a Neural Network Rate Control theoretic framework, addressing all four aforementioned key questions. It was comprised: i) an on-line desired round trip estimator, whose main objective was to output reliable, piecewise constant predictions of feasible round trip times; ii) an adaptive and saturated transmission rate controller, capable of robustly tracking the desired round trip time; iii) an adaptive and saturated number of communication channels controller, capable of achieving fairness in allocating network resources among competing sources at equilibrium; iv) a future path congestion level estimator. The notion of parallel operating communication channels was introduced in order to improve the throughput of the network. It was clearly shown that regulating round trip time to follow a piecewise constant profile, is equivalent to queueing delay and queue length regulation around a piecewise constant profile. Moreover, the resulted scheme still achieves small enough queues at equilibrium, to prevent large queueing delays and congestion collapse, though not zero to avoid link starvation.
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