2010/3

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    Critical Comparison of Multi-objective Optimization Methods: Genetic Algorithms versus Swarm Intelligence
    (Společnost pro radioelektronické inženýrství, 2010-09) Sedenka, Vladimir; Raida, Zbynek
    The paper deals with efficiency comparison of two global evolutionary optimization methods implemented in MATLAB. Attention is turned to an elitist Non-dominated Sorting Genetic Algorithm (NSGA-II) and a novel multi-objective Particle Swarm Optimization (PSO). The performance of optimizers is compared on three different test functions and on a cavity resonator synthesis. The microwave resonator is modeled using the Finite Element Method (FEM). The hit rate and the quality of the Pareto front distribution are classified.
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    Evolution Strategies in the Multipoint Connections Routing
    (Společnost pro radioelektronické inženýrství, 2010-09) Krulikovska, Lenka; Filanova, Jana; Pavlovic, Juraj
    Routing of multipoint connections plays an important role in final cost and quality of a found connection. New algorithms with better results are still searched. In this paper, a possibility of using the evolution strategies (ES) for routing is presented. Quality of found connection is evaluated from the view of final cost and time spent on a searching procedure. First, parametrical analysis of results of the ES are discussed and compared with the Prim’s algorithm, which was chosen as a representative of the deterministic routing algorithms. Second, ways for improving the ES are suggested and implemented. The obtained results are reviewed. The main improvements are specified and discussed in conclusion.
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    A Complete Video Coding Chain Based on Multi-Dimensional Discrete Cosine Transform
    (Společnost pro radioelektronické inženýrství, 2010-09) Fryza, Tomas
    The paper deals with a video compression method based on the multi-dimensional discrete cosine transform. In the text, the encoder and decoder architectures including the definitions of all mathematical operations like the forward and inverse 3-D DCT, quantization and thresholding are presented. According to the particular number of currently processed pictures, the new quantization tables and entropy code dictionaries are proposed in the paper. The practical properties of the 3-D DCT coding chain compared with the modern video compression methods (such as H.264 and WebM) and the computing complexity are presented as well. It will be proved the best compress properties could be achieved by complex H.264 codec. On the other hand the computing complexity - especially on the encoding side - is lower for the 3-D DCT method.
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    Probabilistic Model for Free-Space Optical Links Under Continental Fog Conditions
    (Společnost pro radioelektronické inženýrství, 2010-09) Khan, Muhammad Saeed; Awan, Muhammad Saleem; Muhammad, Sajid Sheikh; Faisal, Muhammad; Marzuki; Nadeem, Farukh; Leitgeb, Erich
    The error characteristics of a free-space optical (FSO) channel are significantly different from the fiber based optical links and thus require a deep physical understanding of the propagation channel. In particular different fog conditions greatly influence the optical transmissions and thus a channel model is required to estimate the detrimental fog effects. In this paper we shall present the probabilistic model for radiation fog from the measured data over a 80 m FSO link installed at Graz, Austria. The fog events are classified into thick fog, moderate fog, light fog and general fog based on the international code of visibility range. We applied some probability distribution functions (PDFs) such as Kumaraswamy, Johnson SB and Logistic distribution, to the actual measured optical attenuations. The performance of each distribution is evaluated by Q-Q and P-P plots. It is found that Kumaraswamy distribution is the best fit for general fog, while Logistic distribution is the optimum choice for thick fog. On the other hand, Johnson SB distribution best fits the moderate and light fog related measured attenuation data. The difference in these probabilistic models and the resultant variation in the received signal strength under different fog types needs to be considered in designing an efficient FSO system.
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    A Novel Current-Mode Full-Wave Rectifier Based on One CDTA and Two Diodes
    (Společnost pro radioelektronické inženýrství, 2010-09) Khateb, Fabian; Vavra, Jiri; Biolek, Dalibor
    Precision rectifiers are important building blocks for analog signal processing. The traditional approach based on diodes and operational amplifiers (OpAmps) exhibits undesirable effects caused by limited OpAmp slew rate and diode commutations. In the paper, a full-wave rectifier based on one CDTA and two Schottky diodes is presented. The PSpice simulation results are included.