Communications - Scientific Letters of the University of Zilina, 2000 (vol. 2), issue 2
Articles
Intermodal interference in optical fibres
Ivan Martincek, Ivan Turek, Milan Dado, Karol Grondzak, Slavomir Cernicky
Communications - Scientific Letters of the University of Zilina 2000, 2(2):4-9 | DOI: 10.26552/com.C.2000.2.4-9 
In this paper the results of a theoretical analysis and practical investigation of mode interference in single mode optical fibres are described. It is shown that inter-modal interference is a sensitive parameter depending on the quality of an index profile or geometrical parameters of optical fibre. The comparison of experimental and theoretical values of mode interference indicates that the measurement of interference could be used for testing how the real refractive index profile of investigated fibre corresponds with the refractive index profile assumed at the calculation (step-index profile).
Playout buffer control for cbr traffic
Martin Klimo
Communications - Scientific Letters of the University of Zilina 2000, 2(2):10-15 | DOI: 10.26552/com.C.2000.2.10-15
Networks based on the packet switching principle introduce a new type of the continuous signal distortion which is caused by a random delay of packets. To eliminate this distortion, playout buffers are introduced. The paper presents a method how to evaluate the rest of this distortion in terms of Signal-to-Noise Ratio, when static policy is used for sample rate control in the case of CBR traffic.
Salt & pepper noise impact on image coding based on image splitting
Milan Karpf, Boris Simak
Communications - Scientific Letters of the University of Zilina 2000, 2(2):16-20 | DOI: 10.26552/com.C.2000.2.16-20
The paper deals with the influence of noise and two control parameters on a segmentation method for image coding. Dynamic min_max criterion and variance criterion were used as segmentation control parameters. For the segmentation of images we have used the method of image splitting. The influence of the value of variance and dynamic criterion on the quality of the segmentation coded image is demonstrated. We have evaluated the objective criterion of the quality of the image (peak signal-to-noise ratio) and number of regions in the image for different values of segmentation control parameters and noise density.
Parts of model of information and safety systems
Pavol Tomasov, Karol Rastocny, Jiri Zahradnik
Communications - Scientific Letters of the University of Zilina 2000, 2(2):21-29 | DOI: 10.26552/com.C.2000.2.21-29
Modelling techniques for large and composite systems are chosen with regard to the expected result of modelling. For routine procedure of synthesis the empirical method is sufficient in most cases. System model with exact description of its attributes demands application of some theoretical conclusions. For information and safety systems a model derived from Information theory is selected. This model can then be specified with the help of the system and, eventually, circuit theory. In the presented paper two tools of Information theory apparatus for model system processing are described. They express information processing inequality and quantification...
A study of a dynamic scheduling mechanism to guarantee QoS
Rachid Laalaoua, Tulin Atmaca
Communications - Scientific Letters of the University of Zilina 2000, 2(2):30-37 | DOI: 10.26552/com.C.2000.2.30-37
Packet scheduling is one of the key mechanisms that will be used in network elements (switches and routers) for supporting real-time applications in broadband networks. Provision of Quality-of-Service (QoS) guarantees is an important and challenging issue in the design of integrated service packet networks. Scheduling disciplines are an integral part of the problem and are closely related to other aspects of network modeling such as traffic charaterization and QoS specification. In this paper we discuss two priority scheduling mechanisms: Head of Line (HoL) and preemptive discipline; for both, we propose an analytical description and present numerical...
Intelligent adaptable systems: First order approach
Peter Geczy, Shiro Usui
Communications - Scientific Letters of the University of Zilina 2000, 2(2):38-55 | DOI: 10.26552/com.C.2000.2.38-55
Future of communications inevitably calls for technologies that feature high-level flexibility, adaptability, and intelligence. Intelligent adaptable systems are particularly suitable for this mission. Majority of adaptable systems utilize neural networks. Artificial neural networks are systems with huge network-like interconnectivity. They are not programmed. Neural Networks gain valuable properties through the process of adaptation called learning. Presented intelligent adaptable system utilizes neural network technology. The system incorporates internal adaptability at several levels. It autonomously adapts its parameters and structure to the presented...
The digital conception of sigma - delta D/A converter implemented into FPGA
Oldrich Kovar, Juraj Micek
Communications - Scientific Letters of the University of Zilina 2000, 2(2):56-60 | DOI: 10.26552/com.C.2000.2.56-60
D/A converters are technical means which allow mutual communication between discrete and analog systems. Then base function is accurately comprehended in the statement "D/A converters create bridge between digital and analog world". D/A converter transforms the discrete signal, progression of the binary numbers to the analog equivalent. Nowadays it is difficult to imagine realization of the digital control systems and some applications of the digital signal processing without using them. The authors of the article describe the digital conception of the Sigma - Delta D/Aconverter which is completely implemented into aprogrammable logical device FPGA,...
Two new best [27,10,9 ] codes
Peter Farkas, Sergio Herrera-Garcia
Communications - Scientific Letters of the University of Zilina 2000, 2(2):61-63 | DOI: 10.26552/com.C.2000.2.61-63
This paper presents two new [27,10,9] binary linear block codes which reach the upper bound in [1] for best known codes. They have different spectra as the known [27,10,9] codes constructed by Piret [2], Farkaš and Juling [5].
Processor for impulsive noise suppression in telecommunication channels
Csaba Stupak, Rastislav Lukac, Stanislav Marchevsky
Communications - Scientific Letters of the University of Zilina 2000, 2(2):64-70 | DOI: 10.26552/com.C.2000.2.64-70
In recent years, many linear filters have been replaced by nonlinear filters, especially in case of impulse noise distorting. Stack filters, the class of non-linear filters are very interesting for easy hardware realisation and threshold decomposition property. The development of digital HDTV gives technological push in this area. Various of very efficient order-statistics filters such as median or LUM smoother are useful in many applications. In addition, these filters can be realised as stack filters. This paper gives a short review of the stack filter class.