2003/4

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    Clear-Air Propagation Modeling using Parabolic Equation Method
    (Společnost pro radioelektronické inženýrství, 2003-12) Grabner, Martin; Kvicera, Vaclav
    Propagation of radio waves under clear-air conditions is affected by the distribution of atmospheric refractivity between the transmitter and the receiver. The measurement of refractivity was carried out on the TV Tower Prague to access evolution of a refractivity profile. In this paper, the parabolic equation method is used in modeling propagation of microwaves when using the measured data. This paper briefly describes the method and shows some practical results of simulation of microwave propagation using real vertical profiles of atmospheric refractivity.
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    Comparative Evaluation of UMTS, WLAN, BWA, MBWA, and UWB Systems
    (Společnost pro radioelektronické inženýrství, 2003-12) Ledl, Petr; Pechač, Pavel
    UMTS, WLAN, BWA and UWB systems are compared in this paper. The comparative analysis covers system capacity, QoS, and radiowave propagation.
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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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    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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    Utilization of MATLAB in Simulation of Linear Hybrid Circuits
    (Společnost pro radioelektronické inženýrství, 2003-12) Brancik, Lubomir
    In the paper a MATLAB-based method for simulating transient phenomena in linear hybrid circuits containing parts with both lumped and distributed parameters is presented. Distributed parts of the circuit are multiconductor transmission lines, which can generally be nonuniform, with frequency-dependent parameters, and under nonzero initial voltage and/or current distributions. In principle a solution is formulated using the modified nodal analysis method in the frequency domain. Subsequently an improved fast method of the numerical inversion of Laplace transforms in the vector or matrix form is applied to obtain solution in the time domain.