Telecommunications science

20140910-03
Resource structure for smart metering systems supporting prepaid functionality
Ivaylo I. Atanasov

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Smart metering is one of the main application areas of Machine-to-Machine communications (M2M). Smart meters using M2M can automatically collect and send data about energy supply and usage for monitoring and billing by utilities ...  read more

20140910-02
Design and investigations of approximately linear phase Hilbert transformers
Kamelia Nikolova

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In this work a new design procedure of approximately linear phase (ALP) digital Hilbert transformers (HT) is proposed. First, the possible positions of the transfer function (TF) poles of such HTs realizations are studied ...  read more

20140910-01
Approaching risk management in IT by implementing it in ITIL
Mario Ivanov, Biser Stefanov

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The aim of this article is to suggest a way for adopting a strengthened risk management in the ITIL (Information Technology Infrastructure Library) framework which will be based on specific guidelines without changing the ...  read more

20141112-07
Research of miniaturized hexagonal resonators
Research of miniaturized hexagonal resonators

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Abstract: This paper presents and researches the application of miniaturized hexagonal resonators in microstrip bandpass filters in the mobile communication systems. There are investigated both basic topologies of miniaturized ...  read more

20141112-06
Application of high order APSK modulations in satellite digital video broadcasting
Lidia T. Jordanova, Lyubomir B. Laskov, Dobri M. Dobrev

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In this paper are presented the results of a study of the characteristics of the DVB-S2 channels when using 32APSK and 64APSK modulation. Expressions for determining the probability of bit error after APSK demodulator, LDPC ...  read more

20141112-05
DOA algorithms noise performance analysis for cognitive radio systems
Todor D. Tsvetkov, Ilia G. Iliev

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In this paper the precision of variety direction of arrival (DOA) algorithms used in cognitive radio systems are investigated. The researched algorithms are MUSIC, Capon (MVDR), ROOT MUSIC, ESPRIT-LS and ESPRIT-TLS. The goal ...  read more

20141112-04
Transmission quality assurance in the design of HFC television network
Lidia T. Jordanova, Dobri M. Dobrev

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The paper deals with signal degradation due to noise and nonlinear distortion in the forward channel of HFC television network. A mathematical model of the optical channel is presented that makes it possible for the following ...  read more

20141112-03
Optimal divergence of laser beam in optical wireless communication systems
Tsvetan A. Mitsev, Nikolay K. Kolev

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DОtОrmТnТng tСО optТmal dТvОrgОncО oП transmТttОr’s bОam Тn optТcal аТrОlОss communТcatТon systems (OWCS) can largely compensate for the negative impact of the change in the direction of propagation ...  read more

20141112-02
Computer simulation of distortions in optical fiber for CATV systems
Kalin L. Dimitrov, Lidia T. Jordanova, Tsvetan A. Mitsev

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A general overview of most problems appearing when signals are transmitted in the fiber optic part of a CATV system is made. Some basic theoretical dependencies, as well as numerical methods suitable for computer simulation, ...  read more

20141112-01
Synthesis of microstrip filters based on miniaturized hexagonal resonators
Marin V. Nedelchev, Ilia G. Iliev

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The paper proposes the application of the miniaturized hexagonal resonators in the microstrip filter design and their applicability in mobile communication systems. The main coupling topologies are researched and the coupling ...  read more