Browsing by Author "Суліма, С. В."
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Item Метод вибору мережі доступу в мобільній системі SDR при вертикальному хендовері(Видавництво Львівської політехніки, 2014) Глоба, Л. С.; Суліма, С. В.; Курдеча, В. В.Запропоновано метод вибору мережі призначення процедури вертикального хендоверу в гетерогенних мобільних радіосистемах зі здатністю реконфігуруватися, побудованих на основі технології Software Defined Radio: сформульовано задачу вибору мережі та представлено процедуру вертикального хендоверу в таких системах. Змодельовано і проаналізовано процес розв’язання оптимізаційної задачі прийняття рішення про вертикальний хендовер за допомогою системи Mathcad. In order to satisfy emerging user requirements in advanced services/applications, provided seamlessly, operators have to deploy complex network topologies of heterogeneous nature, where different Radio Access Technologies (RATs) co-exist in single composite network with shared resources. Network operator will have assign the appropriate RAT to perform the respective task, so as to achieve the required quality of service, cost-effectively. In such circumstances, there is a need in vertical handover – mechanism of transferring current connections from one radio access network to another. Furthermore, reconfigurable (adjustable) depending on the telecommunication environment devices should be used as user terminals. Software Defined Radio (SDR) technology has been identified as a key enabler of such equipment and networks. This paper is devoted to the vertical handover problem solving. Vertical handover decision problem is very important, because it has strong influence on the network performance and the quality of service of nodes. There are two main aspects of this problem: how to define “best” and how to determine the best access bearer. In the article the access selection method of vertical handover process in heterogeneous reconfigurable mobile radio systems based on SDR technology is proposed: access selection problem is formulated and vertical handover algorithm in such systems is described. To perform an accurate decision the proposed decision process rely on multiple attributes decision-making, while providing a small delay due to the sequential filtration and reduction of the set of possible alternatives. The method allows optimizing network and radio resources utilization and quality of service in heterogeneous network and also provides dynamic adaptation of the access selection decisionmaking rules according to the different telecommunication conditions and network policies. The proposed selection criteria, on the one hand, is simple and well-formalized, and therefore does not require significant computational and time costs, but on the other – provides adaptability. Vertical handover algorithm takes into account peculiarities of SDR devices and therefore can be used in SDR networks. To evaluate the method Mathcad system was used. The effectiveness of the method is confirmed by simulation example for UMTS, GPRS and WLAN networks, which is based on proposed decision-making process where decision is made not on the basis of the absolute advantage of alternative but on the basis of difference between the current and alternative modes parameters, therefore minimizing the amount of intersystem handovers causing additional load on the system. Simulation confirmed that linear aggregation function in multiple attributes decision-making process is the most appropriate because it provides almost the same results as the other methods but in a much simpler way.Item Організація управління в багатоетапних системах масового обслуговування(Видавництво Львівської політехніки, 2015) Скулиш, М. А.; Суліма, С. В.Розглянуто проблеми систем з кількома етапами, кількома типами ресурсів, кількома типами сервісів. Представлено метод динамічного управління ресурсами для багатоетапних систем, що використовує гнучку аналітичну модель для визначення кількості ресурсів, яку необхідно виділити для кожного етапу системи. The problem of growth of the mobile data traffic and the number of services becomes global, moreover, volume and frequency of control traffic transmitted through the network are increasing, and therefore there is a need for its effective management to ensure the quality of service required by users and optimal use of mobile network resources. In such circumstances, the load on the server that is created in the process of establishing the connection and its serving has its considerations. Wide range of modern information communication systems implies stagewise processing of incoming requests. In response to a request such systems perform a sequence of data processing actions, including, in general, number of steps. Likewise the billing system of mobile telecommunication operator involves performing succession of operations. Each service provided by the operator or service provider to the customers is charged using a distinct scheme, thus a billing system is a bottleneck in the service provisioning. This paper is devoted to the problems of multiple stage multiple resource multiple service systems. Dynamic resource provisioning in multi-stage systems is a useful technique for handling the variations seen in communication systems workloads. Virtualization technology allows to implement this approach. It is non-trivial to extend provisioning mechanisms designed for single-stage scenarios to multi-stage scenarios. Classical approaches may merely shift the bottleneck to another downstream stage. For another thing, in the networks various stages may be located on the same physical machine, and thus it is necessary to consider a common pool of the resources. An analytic model of a system would be attractive as it would be able to evaluate system characteristics under a wide range of conditions, and to be computed comparatively easily. It is also can incorporate numerical optimization techniques for system design. Moreover, there is a need in formulation and solving of the multi-criteria problem of resource allocation among different nodes with consideration for beside the failure probability other criteria – such as the cost of utilization of additional amount of resources (i.e. cost of activation of the additional server) or benefit from the certain service provisioning and so on. In this paper we argue that dynamic provisioning of multi-stage information communication systems raises new challenges not addressed by prior work on provisioning single-stage systems. An extended dynamic provisioning technique for multi-stage multi-resource multi-service systems that employs a flexible queuing model to determine how much resources to allocate to each stage of the system is proposed. The whole system is modelled as sequence of multidimensional Markov chains. Since the numerical evaluation of the closed-form failure probability in such system will become numerically intractable for a large number of traffic classes, a simpler approximate method of calculation for the state probabilities of the traffic model described is used. To evaluate the proposed technique Mathcad system is used. The effectiveness of the method is confirmed by simulation example for the system with two service types, two resource types and three stages. The proposed model is very general and can be used for analysis of different systems.