2008/3

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    Joint Source-Channel CELP Coding
    (Společnost pro radioelektronické inženýrství, 2008-09) Pleshkova-Bekiarska, Snejana G.
    The method of speech coding CELP is extensively used in much voice communication-, multimedia-, video conference and other systems. There are a lot of papers related to CELP coding characteristics improvement for a better speech quality after decoding. Most of the papers are dedicated to lower the rate of CELP coded speech transmission. One problem related to low rate CELP speech transmission with a good speech decoding quality is noising in the channel for transmission. The goal of this paper is to combine the advantages and the possibilities of CELP speech coding to reduce the rate of transmission and the methods of channel coding to protect the most important CELP coding parameters in each speech frame such as line prediction coefficients, excitation indexes etc.
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    Dispersion and Pulse Interferences Investigation for UWB Signal Propagation
    (Společnost pro radioelektronické inženýrství, 2008-09) Urban, Robert; Zvanovec, Stanislav
    The Ultra WideBand (UWB) technology utilizing nanosecond pulses has been one of the main phenomena in communications and radar applications for several years. This paper discusses the basic measurement techniques of impulse systems, particularly focusing on the dispersion and pulse interferences of the UWB propagation channel. Propagation aspects of two-ray approach are investigated in depth, using both measurements and simulations.
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    Modeling of Microwave Semiconductor Diodes
    (Společnost pro radioelektronické inženýrství, 2008-09) Pokorny, Michal; Raida, Zbynek
    The paper deals with the multi-physical mode-ling of microwave diodes. The electrostatic, drift-diffusion and thermal phenomena are considered in the physical model of the components. The basic semiconductor equati-ons are summarized, and modeling issues are discussed. The simulations of the Gunn Effect in transferred electron devices and the carrier injection effect in PIN diodes are investigated and discussed. The analysis was performed in COMSOL Multiphysics using the finite element method.
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    Extraction of Facial Features from Color Images
    (Společnost pro radioelektronické inženýrství, 2008-09) Oravec, Milos; Kristof, Branislav; Kolarik, Michal; Pavlovicova, Jarmila
    In this paper, a method for localization and extraction of faces and characteristic facial features such as eyes, mouth and face boundaries from color image data is proposed. This approach exploits color properties of human skin to localize image regions – face candidates. The facial features extraction is performed only on preselected face-candidate regions. Likewise, for eyes and mouth localization color information and local contrast around eyes are used. The ellipse of face boundary is determined using gradient image and Hough transform. Algorithm was tested on image database Feret.
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    Performance of Advanced Hybrid Link Adaptation Algorithms in Mobile Radio Channel
    (Společnost pro radioelektronické inženýrství, 2008-09) Wieser, Vladimir; Psenak, Vladimir
    The fast power adaptation is essential for WCDMA based mobile radio networks, as 3G UMTS. Although the first version of UMTS has been released in 1999 (Release 99) evolution was not finished yet. Quality of Service (QoS) and user data rate (e.g. HSDPA and HSUPA) are continuously increasing from release to release. Even though link adaptation frequency (1500 times per second) seems to be enough to span accidental fadings of mobile radio channel, used link adaptation algorithm is based on non-actual information about mobile radio channel state, which causes transmitter reaction delay to the actual channel state. Usage of appropriate prediction method to estimate near future channel state seems to be a valuable step to improve hybrid link adaptation algorithm. In this article we have described and simulated the new SIR-slot based advanced link adaptation algorithms. Algorithms were designed to increase efficiency of data transmission among a user equipment and base stations (uplink) for different simulation environments (pedestrian channel with mobile subscriber speed 5 km/h, 15 km/h and vehicular channel with speed 45 km/h).