2003/4

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    Wireless LAN Network Design: Site Survey or Propagation Modeling?
    (Společnost pro radioelektronické inženýrství, 2003-12) Zvanovec, Stanislav; Pechac, Pavel; Klepal, Martin
    There are two basic ways to deploy wireless LAN access points in an indoor scenario: manual deployment using a site survey based on empirical measurements or planning using a software tool with built-in signal propagation models. In this paper advantages and disadvantages of both ways are discussed. The planning based on propagation modeling is recognized as a highly preferable approach for design of large WLANs. Experimental data in this paper were processed in MATLAB.
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    Utilization of MATLAB for Digital Image Transmission Simulation.,
    (Společnost pro radioelektronické inženýrství, 2003-12) Kratochvil, Tomas
    The paper deals with the utilization of Matlab for simulation and analysis of the digital image transmission and transmission distortions in DTV (Digital Television) and DVB (Digital Video Broadcasting) area. The simulation model that covers selected phenomena of DVB standard baseband signal processing applied in Matlab is presented and features of the protection against transmission errors are outlined. The practical results of FEC (Forward Error Correction) codes efficiency are presented and at the end the GUI application for experimental simulation and education is outlined with a simulation example.
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    A Computer Simulation of Ultrasound Thermal Bio-Effect in Embryonic Model
    (Společnost pro radioelektronické inženýrství, 2003-12) Orel, Daniel; Rozman, Jiri
    At the present time, the usage of ultrasound diagnostic equipment has become an inseparable part of diagnosis for a number of medical investigations. Several scientific studies published in the last years showed that when applying a diagnostic ultrasound system on animals it is possible to create negative changes in tissues. New ultrasound technologies and higher output acoustic powers have brought a possible risk connected to the usage of ultrasound in diagnostics. The knowledge of risk level and exploration of limiting factors is an important point for the assessment of marginal ultrasound exposure values of medical investigation during pregnancy, especially in the first trimester. The contribution presents a MATLABZ application for modeling of tissue heating in human embryos at the developmental age of seven and eight weeks. Recent calculations of US fields, which are generated by several types of various unfocused single transducers (rectangular, circular, and annular), represent maximum temperature elevation of 0.4 °C in embryonic model tissues for the exposure of 1 min. The models of embryonic tissue heating provide comparative studies of possible bio-effect with the purpose to explore limiting factors of ultrasound exposure.
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    Mobile Radio Channels Modeling in MATLAB
    (Společnost pro radioelektronické inženýrství, 2003-12) Kostov, Nikolay
    In this paper, a MATLAB based approach for mobile radio channels modeling is presented. Specifically, the paper introduces the basic concepts for modeling flat fading channels in MATLAB by means of user-defined m-files. Typical small-scale fading channel models are derived such as uncorrelated Rician fading channel and Rayleigh fading channel with Doppler shift. Further, simple and useful MATLAB constructions for approximation of cumulative distribution functions (CDFs) and probability density functions (PDFs) are also given. Finally, a MATLAB based Monte Carlo simulation example is presented, which comprises performance estimation of phase shift keying (PSK) signaling over a Rician fading channel.
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    Electronic Textbook of Electromagnetic Waves
    (Společnost pro radioelektronické inženýrství, 2003-12) Raida, Zbynek; Cernohorsky, Dusan; Froehling, Kenneth; Gona, Stanislav; Michalek, Vaclav; Navratil, Vlastimil; Novacek, Zdenek; Otevrel, Viktor; Pomenka, Petr; Sebesta, Jiri; Skvor, Zbynek; Urbanec, Tomas; Vanderstegen, Geert; Vandijck, Bart
    Teaching university courses, which deal with the phenomena of the electromagnetic (EM) substantiality and their applications, is rather difficult due to their abstract nature. Therefore, teaching has to be accompanied by clear explanations and by simulations illustrating the examined topics. This is why an electronic textbook (ET) of EM waves and applications was developed. The ET presents theoretical descriptions of selected EM phenomena on two levels - on a bachelor's one and a master's one. Descriptive parts of the ET are completed by computer programs, which enable the reader to simulate the studied phenomena. Moreover, the ET explains the practical implementation of simulation routines in MATLAB, which helps students to understand a relationship between rather complicated mathematics and a relatively simple source code of its software implementation. Since the ET is freely accessible on the web, students can use it whenever as a classical textbook, a handbook or a software package. This fact positively influences the students' knowledge and understanding as proven by our experience.