KORENKO, B. — HLAVÁČ, M. — ČERVEŇOVÁ, J. — JASENEK, J.:
Excitation of Semiconductor Laser for OTDR Based on Photon Counting [full paper]
The main goal of the paper is to explain the design of the excitation circuit for the semiconductor laser diode used in OTDR reflectometer based on photon counting. The main criterion was to achieve a rather high space resolution of the device and simultaneously to maintain the maximum possible simplicity of the circuit. The key parts of the designed system are based on technology compatible with emitter coupled logic. The numerical simulation of our hierarchical model has proved that the excitation optical impulse with the minimal width of 300ps can be achieved. That kind of circuit makes possible to construct OTDR reflectometer with rather high space resolution approaching 3cm.
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BUTKA, P. — LUKÁČ, G. — MACH, M. — SABOL, T.:
Semantic-Based Groupware System for Collaborative Support in Public Administration Processes [full paper]
In the article, a survey of our research activities the goal of which is to develop a methodology allowing to design on-line checkers for digital components and communication protocols are described. First, our experiments with PSL language and FoCs tool are demonstrated for simple RT circuits and communication protocols. It is shown how PSL can be used to describe conditions to be checked by an on-line checker of a digital component. It is demonstrated that on-line checkers generated from PSL description demand more sources than the unit under check which is seen as unacceptable result. The principle of our methodology for generating VHDL descriptions of hardware checkers from the formal model is presented, too. The results and compare of both methodologies are described. The possibilities of utilizing these approaches in the design of Fault Tolerant Systems are described in conclusion.
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ZEGNINI, B. — MAHI, D. — CHAKER, A.:
Modeling Parameters Optimizations of 750kV Insulators Flashover Voltage under Pollution Conditions in High Altitude Areas Using RBF Artificial Neural Networks [full paper]
In this paper an attempt has been made to estimate the pollution flashover voltage under various meteorological factors using the radial basis function (RBF) neural network with orthogonal least squares(OLS) learning method in order to test the lines design ability against the pollution flashover of the high voltage post insulators. Based on experimental data taken from different types of typical high intensity, big diameter post insulators, the artificial contamination tests are carried out in different pressure cases corresponding to high altitudes and in typical kinds of equivalent salt deposit density (ESDD). The results show that RBF neural networks trained by the least orthogonal square have a better accuracy and performance to optimize flashover voltage of post insulator in high altitude areas.
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URBAN, J. — MARSALEK, R.:
The Combination of Clipping and Filtering with Selective Mapping Methods for Peak to Average Power Ratio Reduction in OFDM [full paper]
The high Peak to Average Power Ratio (PAPR) is a serious drawback of the Orthogonal Frequency Division Multiplex (OFDM). In this paper, the advantages of two different approaches to PAPR reduction are exploited in order to reduce the PAPR more significantly. The first approach is based on clipping and provides a high PAPR reduction at the cost of signal distortion. The second approach (selective mapping) results in no distortion, but it suffers from higher complexity. Two cases of simulation setup have been chosen for the evaluation – one with a lower number of subcarriers (Wimax-like signal), the other signal is similar to the future DVB-T2 32K mode. The performance of the combined method is evaluated on the PAPR distribution function and on the Bit Error Rate as a function of both Signal to Noise Ratio ( Additive Gaussian Noise Channel) and Input Back Off (Saleh model of nonlinear power amplifier).
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ŽELEZNÍK, O. — HAVLICE, Z.
MDA Approach in Embedded Systems with Strict Real-Time Response and On-the-Fly Modelling Requirements [full paper]
The paper presents a proposal of a method for MDA based “on-the-fly” modelling of Musical Real Time Applications. The method is based on use of the Executable and Translatable UML approach (xtUML) with regards to implementation on embedded systems. Since the goal is to implement a real-time application requiring certain real-time Quality of Service (QoS) properties, the real-time response requirement influence on modelling is discussed as well. To provide a solution for the main user requirement, which is a possibility for an application model modification in real-time (during execution), we discuss a method, which splits the application into two parts. The first part is the implementation environment – the programmer/provider system, which will provide for the runtime environment of the second part, the user model itself, modelled using xtUML on-the-fly. The advantage of such separation results in an increased modelling easiness and reasonable real-time performance on user modelling as well as low signal processing latency..
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AMARAL, A. M. R. — CARDOSO, A. J. M.:
Using Hybrid System Theory to Simulate the Behaviour of Step-Down DC-DC Converters [full paper]
This paper presents a simulation technique for step-down DC-DC converters based on the hybrid systems theory. The proposed technique is able to simulate the behaviour of the converter in both transient and steady state regimes. To show the applicability of the proposed technique a buck converter is considered. Both output voltage and inductor current are acquired with a digital oscilloscope and are compared with the ones obtained with the proposed technique during steady state regime to show its applicability. Besides, both transient and steady responses of the converter obtained from the proposed simulation technique are compared with ones computed from MATLAB/SIMULINK environment.
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KOTMANOVÁ, D.
Simulation and Verification of Digital Systems with NuSMV [full paper]
We explore, in this work, some possibilities of the new model checker NuSMV, based on model checking algorithms. We started out from the former model checker SMV by verifying a very simple digital device, a two-state MicroWave Oven we designed, and then submitted the same device to the NuSMV Simulator and Model Checker. All results we obtained in verification and simulation with NuSMV are presented in the paper.
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PLAVKA, J. — SZABÓ, P.:
The O(n2) Algorithm for the Eigenproblem of an ε-Triangular Toeplitz Matrices in max-plus Algebra [full paper]
Please find the abstract in the attached paper
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GAZDA, J. — DROTÁR, P. — KOCUR, D. — GALAJDA, P. —
BLICHA, R.:
Joint Evaluation of Nonlinear Distortion Effects and Signal Metrics in OFDM Based Transmission Systems [full paper]
In this contribution, we provide a theoretical characterisation of nonlinear distortion effects in orthogonal frequency division multiplex (OFDM) either in the downlink as well as in the uplink scenario. Previous papers presented on this topic considered OFDM signal as a Gaussian distributed mostly. It will be shown that the discussion must be strictly distinguished in case we observe the downlink or the uplink OFDM scenario. In the uplink scenario, where usually low number of subcarriers are employed for the transmission and Gaussianity does not hold, poorer performance results with than that of downlink scenario are achieved. This effect will be properly explained by theoretical framework and proved by the computer simulations. Moreover, the basic properties of commonly used signal metrics for the predictions of nonlinear distortion in OFDM are introduced.
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CHOCHOL, P.:
Qualitative Factors that Impact Real Implementing VoIP in Private Networks
[full paper]
Integrating enterprise voice services on a data network can offer significant capital and operational cost reductions, and can enable new competitive services. However, if these business values are to be realized, customers must be won and retained by meeting their expectations for service quality. In networking, quality can mean many things. In VoIP, quality simply means being able to listen and speak in a clear and continuous voice, without unwanted noise. Quality depends mainly on the following factors: data loss, consistent delay characteristics (called jitter) and latency, leading to echo. QoS (Quality of Service) is more in demand on corporate LANs, private networks and intranets (private networks interconnecting parts of organizations) than on the Internet and ISP networks. QoS, reliability and security are an important tools for VoIP success. Call quality testing has traditionally been subjective: picking up a telephone and listening to the quality of the voice. The leading subjective measurement of voice quality is the MOS (mean opinion score) as described in the ITU (International Telecommunications Union) recommendation P.800. Considerable progress has been made in establishing objective measurements of call quality on example the E-model (ITU G.107).
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