In this thesis we provide a model for a bufferless optical burst switching (OBS) and an optical packet switching (OPS) network. The thesis is divided in three parts. <p><p>In the first part we introduce the basic functionality and structure of OBS and OPS networks. We identify the blocking probability as the main performance parameter of interest. <p><p>In the second part we study the statistical properties of the traffic that will likely run through these networks. We use for this purpose a set of traffic traces obtained from the Universidad Politécnica de Catalunya. Our conclusion is that traffic entering the optical domain in future OBS/OPS networks will be long-range dependent (LRD). <p><p>In the third part we present the model for bufferless OBS/OPS networks. This model takes into account the results from the second part of the thesis concerning the LRD nature of traffic. It also takes into account specific issues concerning the functionality of a typical bufferless packet-switching network. The resulting model presents scalability problems, so we propose an approximative method to compute the blocking probability from it. We empirically evaluate the accuracy of this method, as well as its scalability. / Doctorat en Sciences de l'ingénieur / info:eu-repo/semantics/nonPublished

This thesis treats of QoS (Quality of Service) in UMTS system. The term quality of service is frequently used, recently, however not only in computer networks, but also more and more in mobile networks also. Present system of 2nd generation (2G) GSM enables only limited exploitation of QoS function. System UMTS is a system of 3rd generation (3G) already and contains quality of service in greater measure which is ensured with number of algorithms and functions. Individual QoS functions enable effective utilization of radio interface, support maintenance of planned coverage and offer high spectral efficiency. Functions that cater to quality of service are called RRM functions (Radio Resource Management). There exist five basic functions in UMTS system that are Admission control (AC), Power control (PC), Load control (LC), Handover control (HC) and Packet scheduler (PS). These functions are responsible for control of network access, control of power, control of network load, control of handover and packet (bit rate) scheduling. Last three functions are usually collectively designated as Congestion control, control of network overload. UMTS layer model, differentiation of services, traffic classes and 3GPP concept are also discussed. In thesis the attention is piad to Admission control algorithm – control of network access – in the uplink direction and to different ways of load (in the cell) modeling. Individual approaches are simulated in MATLAB. A possibility of using algorithm in the real system is discussed in conclusion.