Модель превентивного обмеження швидкості передачі низхідного каналу зв’язку технології WIMAX в умовах перевантажень

Abstract

To meet the put forward contradictory technical and economic demands to the structure of transmission networks it is necessary to use multi-criteria optimization methods when planning them. During our planning of a transmission network we design such a topology that has to provide high quality and sufficient reserve capacity at least costs. In practice it means that the designer must balance three transmission network quality factors, which characterize the cost, the quality and the capacity. In this paper we are going to discuss mostly the features of performing the nominal stage of the transmission network planning with the aid of multi-criteria optimization methods. We substantiate our choice of the set of quality factors which can be used to find the optimal topology of a transmission network with respect to them. The optimization procedure includes the next steps: 1) forming a set of valid network topology variants; 2) extracting from the obtained set the Pareto-optimal variants followed by selection of a single variant. The main method to protect against unavailability factor increase is to build a ring topology. However this strategy requires the use of additional equipment and trunks which will lead to a considerable increase in the cost of our network. The cost of the network should be calculated in accordance with the required number of connections and of cross-connectors. That is why it is advisable to carry out the optimization of a mobile communications transmission network with respect to these two conflicting parameters, namely, unavailability factor and cost. Analysis of stages and tasks of mobile communication transmission networks has been done. Initial data, technical characteristics and quality factors that are taken into account during transmission networks planning have been determined. A feature of such networks is that their quality factors are not only related and contradictory to each other, but the values of them depend on the selected specific network topology. That is why to select optimal topologies of a transmission network taking into account the set of quality factors we have to use general provisions of multi-criteria optimization. The paper presents results of solution to the problem of discrete choice of transmission network optimal topologies. The choice takes into account the set of quality factors, namely, unavailability factor and network cost. The set of valid topologies is constructed. The values of contradictory quality factors are estimated and the subset of Paretooptimal variants of network topology over the criterion space of estimates of quality factors is found. By using the conditional preference criterion we extracted a single variant of transmission network topology from the Pareto subset. Рассмотрены особенности оптимизации транспортной сети и приведены результаты решения задачи выбора оптимальной топологии транспортной сети с учетом совокупности показателей качества на основе методов многокритериальной оптимизации.