Communications - Scientific Letters of the University of Zilina, 2004 (vol. 6), issue 4
Articles
Mobility performance of a new traffic decentralization qos admission strategy
Georgios S. Paschos, Efstathios Vagenas, Stavros A. Kotsopoulos
Communications - Scientific Letters of the University of Zilina 2004, 6(4):5-12 | DOI: 10.26552/com.C.2004.4.5-12 
This paper proposes a new Admission Control strategy with Quality of Service (QoS) preservation for GSM networks. System initiated handover calls are used in the central cell in order to decentralize the traffic and redistribute it throughout the whole cluster. Although the channels and the cell size are fixed, the system behaves as if it had the 3G feature called soft capacity. The mobility characteristics of the users are investigated. Low speed and high speed moving users are used as input in the system and the effect of mobility on the proposed algorithm is extracted. Simulation results show that the proposed Admission Strategy is flexible, efficient...
Traffic savings through a cac procedure incorporating a fair bandwidth allocation policy for elastic services
Michael D. Logothetis, Ioannis D. Moscholios, George K. Kokkinakis
Communications - Scientific Letters of the University of Zilina 2004, 6(4):13-16 | DOI: 10.26552/com.C.2004.4.13-16
We apply the max-min fairness policy (MMF) for elastic services with min and max bandwidth requirements (approximated MMF) not to a single link but to a whole connection-oriented network. To achieve it we propose a Call Admission Control (CAC) procedure consisting of several scenarios dependent on the number of paths between the origin-destination (O-D) network nodes. We evaluate the global network performance at the call level by comparing the maximum Call Blocking Probability (CBP) of the proposed scheme with that of a no fair bandwidth allocation policy scheme. Simulation results show significant traffic savings in the case of the approximated MMF policy.
Speech recognition using hidden markov model with low redundancy in the observation space
Roman Jarina, Michal Kuba
Communications - Scientific Letters of the University of Zilina 2004, 6(4):17-21 | DOI: 10.26552/com.C.2004.4.17-21
Current speech recognition systems usually model a speech signal as a finite-state stochastic process, in which acoustic observations are obtained through short-term spectral analysis. The model has to deal with several thousands of speech parameters during one second of utterance. A great redundancy in the parameters makes processing computationally very expensive. We propose a combination of 2-D cepstral analysis and continuous Hidden Markov Model with a small, optimally designed, number of states and acoustic observations. 2-D cepstrum efficiently preserves spectral variations of speech and yields uncorrelated parameters in both time and frequency....
An eugenetic algorithm for delay-constrained minimum-cost routing of multipoint connections
Peter Kortis, Vladimir Olej, Karol Blunar
Communications - Scientific Letters of the University of Zilina 2004, 6(4):22-27 | DOI: 10.26552/com.C.2004.4.22-27
A special kind of genetic algorithm - eugenic algorithm is presented for constructing minimum-cost tree with delay constraints. Telecommunication network is represented by an undirected graph, which uses three independent metrics: cost, delay and capacity. The efficiency of two different bit representations of individuals (adjacent matrix, list of vertices) is compared.
SD L-filter for filtration of images corrupted by mixed noise in frequency domain
Robert Hudec
Communications - Scientific Letters of the University of Zilina 2004, 6(4):28-33 | DOI: 10.26552/com.C.2004.4.28-33
Slower filter coefficients adaptation of adaptive LMS (Least Mean Square) filters in time domain can be improved by their constrained or unconstrained modifications, but not rapidly. Other alternative is its realisation in frequency domain, where filtered signal is de-correlated and adaptation algorithm converges faster. Based on idea of adaptation in frequency domain there was developed L-filter in frequency domain.To the group of adaptive non-linear digital filters belong adaptive L-filters (L-F), whose outputs are linear combination of order statistics. They have a simple design and they know how to adapt own coefficients to various noise types....
Fast analytical design of maximally flat notch fir filters
Pavel Zahradnik, Miroslav Vlcek
Communications - Scientific Letters of the University of Zilina 2004, 6(4):34-38 | DOI: 10.26552/com.C.2004.4.34-38
A novel fast analytical design procedure for the maximally flat notch FIR filters is introduced. The closed form solution provides recursive evaluation of the impulse response coefficients of the filter. The discrete nature of the notch frequency is emphasized. One design example is included to demonstrate the efficiency of the presented approach.
Allpass based on a generalized divider principle
Dasa Ticha
Communications - Scientific Letters of the University of Zilina 2004, 6(4):39-47 | DOI: 10.26552/com.C.2004.4.39-47
This paper deals with a new allpass structure based on a generalized divider principle. An efficient modification of the basic general divider structure using Antoniou's GICs is presented and the corresponding 1st- and 2nd-order allpass circuits are derived. A detail discussion is devoted to the optimized design of the 2nd-order allpass, taking minimization of the active elements nonidealities and dynamics optimization into account. An original design procedure is described and documented on numerical examples.
Optimal location of service centres under uncertain costs
Vladimir Klapita, Zuzana Svecova
Communications - Scientific Letters of the University of Zilina 2004, 6(4):48-52 | DOI: 10.26552/com.C.2004.4.48-52
It is fairly questionable to estimate future costs in the problems of strategic decision. The uncertainty may cause that a resulting solution could be very inefficient considering current costs. In this report we try to find an approach, which enables to determine a unique solution of a location problem under uncertain costs so that the solution be resistant to future changes. We deal with a sensitivity analysis and with a connection of an exact mathematical programming method and the theory of fuzzy sets.
Techno-economic evaluation of broadband access alternatives for ip services
Robert Jankovsky, Radoslav Odrobinak
Communications - Scientific Letters of the University of Zilina 2004, 6(4):53-57 | DOI: 10.26552/com.C.2004.4.53-57
This paper deals with a techno - economic evaluation of broadband upgrade strategy for IP services. This scenario is focused on the FTTcab/VDSL architecture with ATM versus Ethernet approaches. Target market is residential customers and small business customers in urban and dense urban areas. Installed First Cost (IFC) and Net present Value (NPV) as main techno - economic results are discussed regarding common assumptions. The results show that the choice of technology (Ethernet or ATM) has almost no effect on the cost level and profitability of the cases.
UMTS uplink simulator
Vladimir Wieser, Tomas Marek
Communications - Scientific Letters of the University of Zilina 2004, 6(4):58-62 | DOI: 10.26552/com.C.2004.4.58-62
This paper presents the link level simulator developed at the Telecommunication Department of the University of Žilina. The simulator was developed as part of the project VEGA No. 1/0140/03 "Effective radio resources management methods in next generations of mobile communication networks" and it will be used in the more complex radio interface simulator of the next generation of mobile communication network built at our department. Students studying some problems about spread spectrum methods will also use the simulation model in some subjects, e.g. Digital communications, Mobile Radio Networks.The simulator was developed in MATLAB Simulink and is...
Selected issues of IP telephony
Martin Klimo, Tatiana Kovacikova, Pavol Segec
Communications - Scientific Letters of the University of Zilina 2004, 6(4):63-70 | DOI: 10.26552/com.C.2004.4.63-70
Technologies for transporting voice over networks based on IP protocol, known under various names, e.g., Voice Over IP (VoIP), Voice on the Net (VoN), IP telephony (below IP telephony), made a great progress in the last decade. IP telephony has become one of the most important and the most rapidly developing Internet technologies that is offering a technical as well as economical alternative to the existing telecommunication networks. The paper points three issues that from the authors' point of view seem to be crucial for a wide deployment of IP telephony in European networks: Development and implementation of new IP telephony services based on the...
The microcomputer converter of the telex signal
Vladimir Hottmar, Michal Kuba
Communications - Scientific Letters of the University of Zilina 2004, 6(4):71-73 | DOI: 10.26552/com.C.2004.4.71-73
This paper deals with a structure and a description of the microcomputer converter of the telex signal (MCTS) that we developed for the Slovak Telecom. The microcomputer converter was developed within the International contract between Hungary Telecommunication Association Matav, Slovak Telecom in Bratislava, and Department of Telecommunications at the University of Zilina. We made the following tasks: design, debugging and testing of the resident program of the converter. After evaluation of the prototype by the company Matav 150 pieces of the converters, were manufactured and then successfully implemented in the TELEX exchange in Slovak Telecom in...
Hyperexponential model of token bucket system
Juraj Smiesko
Communications - Scientific Letters of the University of Zilina 2004, 6(4):74-79 | DOI: 10.26552/com.C.2004.4.74-79
In the present paper we apply the Theory of Markov Chains for a formal description of a hyperexponential model of Token Bucket System (TBS). This paper extends the topic covered in [3] by replacing Exponential model of human speech by a more precise hyperexponential model. In the first section we deal with analysis of the Hyperexponential model of On-Off Source of human speech. In the second section we deal with steady-state analysis of Token Bucket system and we solve the balance equations for probabilities of states. In the third section we use real parameters of VoIP and we calculate characteristic of TBS and in the last section the values of probability...
Submission to CAC
Peter Kvackaj, Ivan Baronak
Communications - Scientific Letters of the University of Zilina 2004, 6(4):80-83 | DOI: 10.26552/com.C.2004.4.80-83
Asynchronous transfer mode (ATM) is the base for future telecommunication network. The greatly variable requirements for different applications, especially in video and data traffic, make high demands on the development of traffic control in ATM networks. Speaking about Quality of Service (QoS), in ATM there is a traffic control mechanism, which ensures the standard requested by a new application or service. In the following paper an introduction to traffic control mechanism in ATM known as a connection admission control (CAC) and appropriate CAC method are presented.
A wavelength-preserving all-optical 3r regenerator
J. Slovak, C. Bornholdt, B. Sartorius
Communications - Scientific Letters of the University of Zilina 2004, 6(4):84-88 | DOI: 10.26552/com.C.2004.4.84-88
A novel all-optical 3R regenerator operated in the optically clocked scheme (OC-3R) is presented. The regenerator basically comprises two semiconductor components: an ultra-long semiconductor optical amplifier (UL-SOA) for effective use of fast nonlinearities and a self-pulsating PhaseCOMB-laser for all-optical clock recovery. The dynamic behaviour of the key devices is investigated theoretically and experimentally. An excellent regenerative performance of the assembled OC-3R is demonstrated by eye analysis and by bit error rate (BER) measurements at 40 Gbit/s.
Extent of services supported by Q-signaling over IP
Miroslav Voznak
Communications - Scientific Letters of the University of Zilina 2004, 6(4):89-93 | DOI: 10.26552/com.C.2004.4.89-93
QSIG is a signaling protocol used for interconnection of various telecommunication systems in corporate networks. These networks are composed of homogeneous or heterogeneous elements. Basic procedures of connection and supplementary services are transferred through messages, which are defined in recommendations ETSI or ISO. QSIG can be used for transport proprietary signaling between the same PBXs and is supported in voice gateway of solution of Voice over IP too and environment of IP network is often chosen for interconnection between PBXs. The main aim of this paper is to acquaint specialists with the result of the QSIG compatibility test between...
ETSI activities on next generation networks
Christian Julien
Communications - Scientific Letters of the University of Zilina 2004, 6(4):94-97 | DOI: 10.26552/com.C.2004.4.94-97
The contribution deals with the current activities in ETSI (European Telecommunications Standards Institute) on Next Generation Networks (NGN). The first part includes the general information on ETSI and the creation of the new Technical Committee TISPAN (Telecommunications and Internet converged Services and Protocols for Advanced Networks) which is responsible for all aspects of the wired networks like signalling protocols or systems interworking and which is currently moving towards definition and specification of the NGN. The next part is aimed at the current structure of the TC TISPAN and finally, the key objectives within the TISPAN Releases...
The wavelength conversion in WDM networks
Miroslav Bahleda, Karol Blunar
Communications - Scientific Letters of the University of Zilina 2004, 6(4):98-102 | DOI: 10.26552/com.C.2004.4.98-102
In this paper we deal with the problem of wavelength conversion in WDM (wavelength division multiplex) networks. In all-optical networks the data are transmitted through optical networks transparently. It means that the data still remain in the optical domain between the source and end node. The data transmission between two nodes can be without wavelength conversion or with wavelength conversion (with full wavelength conversion or limited wavelength conversion). We want to give a comprehensive paper about recent and new forms of wavelength conversion.
Solution of some technical problems in marker and marker locator development
Peter Vestenicky
Communications - Scientific Letters of the University of Zilina 2004, 6(4):103-106 | DOI: 10.26552/com.C.2004.4.103-106
This paper gives a short description of selected technical problems and their solutions in development of a marker locator. The principle of underground engineering network equipment marking by markers and principle of marker location is explained. Next, mathematical analysis of signal intensity received from an excited marker and its dependence on distance is described. Moreover, influence of over current induced by lightning into a marker is analyzed and practically measured. These facts were used to increase reliability and lifetime of markers.
Optical SOA-based switching
Radoslav Odrobinak, Milan Dado, Robert Jankovsky
Communications - Scientific Letters of the University of Zilina 2004, 6(4):107-109 | DOI: 10.26552/com.C.2004.4.107-109
All-optical switches are fundamental building blocks for high-speed optical networks and basic blocks towards all-optical networks for future communications that utilize Optical Time Division Multiplexing (OTDM) techniques of signal with single channel data rate of hundreds Gbps. It seems that the most promising technology will be based on Semiconductor Optical Amplifiers (SOA). We can arrange these components to some interferometric architectures in which SOAs achieve efficient optical switching rate with low control energy and big optical sampling bandwidth. The interferometric optical switch geometries are presented and characterized in this paper....
Speech compression algorithm based on non-equidistant sampling
Igor Mihalik
Communications - Scientific Letters of the University of Zilina 2004, 6(4):110-112 | DOI: 10.26552/com.C.2004.4.110-112
The method presented here is one of the methods of time domain compression. The technique uses non-equidistant sampling. Human voice and voice conversation are characterized by transitions. During the speech frequency charactericstics change so that viariable sampling can be applied. The nonuniform sampling method which is implemented is described in this paper; its usage in speech synthesis software which is being developed at the Department of Info-Com Networks is shown.