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Performance Modeling of Database Systems: a Survey, Journal of Telecommunications and Information Technology, 2018, nr 4
Get PDFThis paper presents a systematic survey of the existing database system performance evaluation models based on the queueing theory. The continuous evolution of the methodologies developed is classified according to the mathematical modeling language used. This survey covers formal models – from queueing systems and queueing networks to queueing Petri nets. Some fundamentals of the queueing system theory are presented and queueing system models are classified according to service time distribution. The paper introduces queueing networks and considers several classification criteria applicable to such models. This survey distinguishes methodologies, which evaluate database performance at the integrated system level. Finally, queueing Petri nets are introduced, which combine modeling power of queueing networks and Petri nets. Two performance models within this formalism are investigated. We find that an insufficient amount of research effort is directed into the area of NoSQL data stores. Vast majority of models developed focus on traditional relational models. These models should be adapted to evaluate performance of non-relational data stores
An Optimized Propagation Model based on Measurement Data for Indoor Environments, Journal of Telecommunications and Information Technology, 2018, nr 2
Get PDFPropagation is an essential factor ensuring good coverage of wireless communications systems. Propagation models are used to predict losses in the path between transmitter and receiver nodes. They are usually defined for general conditions. Therefore, their results are not always adapted to the behavior of real signals in a specific environment. The main goal of this work is to propose a new model adjusting the loss coefficients based on empirical data, which can be applied in an indoor university campus environment. The Oneslope, Log-distance and ITU models are described to provide a mathematical base. An extensive measurement campaign is performed based on a strict methodology considering different cases in typical indoor scenarios. New loss parameter values are defined to adjust the mathematical model to the behavior of real signals in the campus environment. The experimental results show that the model proposed offers an attenuation average error of 2.5% with respect to the losses measured. In addition, comparison of the proposed model with existing solutions shows that it decreases the average error significantly for all scenarios under evaluation
Journal of Telecommunications and Information Technology, 2018, nr 1
Get PDFThe rearreangeable conditions for the 2×2 three-stage switching fabric of a W-S-W architecture for elastic optical switches are considered in this paper. Analogies between the switching fabric considered and the three-stage Clos network are shown. On the other hand, differences are also shown, which presented the modifications required in the control algorithm used in rearrangeable networks. The rearrangeable conditions and the control algorithm are presented and proved. Operation of the proposed control algorithm is shown based on a few examples. The required number of frequency slot units in interstage links of rearrangeable switching fabrics is much lower than in the strict-sense non-blocking switching fabrics characterized by the same parameters
Numerical Evaluation of Electromagnetic-wave Penetration at Normal Incidence through an Inhomogeneous-wave Approach, Journal of Telecommunications and Information Technology, 2018, nr 2
Get PDFThis paper presents numerical scenarios concerning penetration in a lossy medium that can be obtained by radiating inhomogeneous electromagnetic waves. Former papers approached this problem, both analytically and numerically, finding requirements and limits of the so-called “deeppenetration” condition, which consists of a wave transmitted in a lossy medium having an attenuation vector whose direction forms the angle of ninety degrees with the normal to the separation surface. The deep-penetration condition always requires an oblique incidence, therefore is not practical in many applications. For this reason, we are interested here in finding whether an inhomogeneous wave guarantees larger penetration than the one obtainable with homogeneous waves, even when the incident wave is normal to the separation surface between two media, i.e. when the deep-penetration condition is not satisfied. We are also interested in verifying numerically whether the lossy-prism structure may achieve larger penetration than the one obtainable through traditional leakywave antennas, and we also wish to propose a lossy-prism design more realistic than the one previously presented in the literature
Observation of WiMAX Radio Parameters to Enhance Spectrum Utilization in Mixed Environment, Journal of Telecommunications and Information Technology, 2018, nr 1
Get PDFIt is believed that 5G networks will provide 1000 times more capacity than current solutions. One of the keys to achieve that goal is not only the utilization of additional radio bands, but also and foremost, the dynamic and efficient spectrum sharing. To successfully implement it such feature statistical observation and analysis of currently operational legacy systems are required. Comprehensive data on the signal parameters will allow then to determine and tune the approach to simultaneous bandwidth usage by existing and new systems. Therefore, to define and introduce the problem this paper presents a conceptual analysis of IEEE 802.16e based WiMAX network operating in the 3.6--3.8 GHz band on the eve of spectrum sharing introduction
Stereoscopic 3DTV Video Quality Metric: the Compressed Average Image Intensity, Journal of Telecommunications and Information Technology, 2018, nr 2
Get PDFThis paper presents a newly designed stereoscopic video quality metric. Overall insights towards the creation of mechanisms utilized within the genuine metric are presented herein. Delivery of the core information and motivation behind the features implemented, as well as functionality of the Compressed Average Image Intensity (CAII) quality metric are of utmost importance. The mechanisms created might be characterized as an objective, reliable and versatile quality evaluation tool for advanced analysis of the content delivery chain within stereoscopic video services
Profesor na trudne czasy, Telekomunikacja i Techniki Informacyjne, 2018, nr 1-2
Get PDFArtykuł poświęcony działalności prof. Janusza Groszkowskiego i jego uczniów
Interference Aware Routing Game for Cognitive Radio Ad-hoc Networks, Journal of Telecommunications and Information Technology, 2018, nr 3
Get PDFCognitive radio is a new communication paradigm that is able to solve the problem of spectrum scarcity in wireless networks. In this paper, interference aware routing game, (IRG), is proposed that connects the flow initiators to the destinations. A network formation game among secondary users (SUs) is formulated in which each secondary user aims to maximize its utility, while it reduces the aggregate interference on the primary users (PUs) and the end-to-end delay. In order to reduce the end-to-end delay and the accumulated interference, the IRG algorithm selects upstream neighbors in a view point of the sender. To model the interference between SUs, IRG uses the signal-to-interference-plus noise (SINR) model. The effectiveness of the proposed algorithm is validated by evaluating the aggregate interference from SUs to the PUs and end-to-end delay. A comprehensive numerical evaluation is performed, which shows that the performance of the proposed algorithm is significantly better than the Interference Aware Routing (IAR) using network formation game in cognitive radio mesh networks
Energy Aware Data Centers and Networks: a Survey, Journal of Telecommunications and Information Technology, 2018, nr 4
Get PDFThe past years have brought about a great variety of clusters and clouds. This, combined with their increasing size and complexity, has resulted in an obvious need for power-saving control mechanisms. Upon presenting a basis on which such solutions - namely low-level power control interfaces, CPU governors and network topologies – are constructed, the paper summarizes network and cluster resources control algorithms. Finally, the need for integrated, hierarchical control is expressed, and specific examples are provided