TELFOR is the abbreviation for the Telecommunications Forum, a long lasting scientific, engineering and professional event which started in 1993 in Belgrade, Serbia. Initial idea was to establish a new modest national scientific conference in Telecommunications and related areas. During the years, that idea evolved in such a way that today TELFOR is a huge regional international conference, having also its several other parallel tracks, like special presentations of companies, presentations and papers of invited experts, exhibition of telecommunications hardware, software, systems and services, then seminars, tutorials, round tables, etc. During TELFOR’s existence several thousands of scientific papers were presented and published, quite a number of them being with a considerable quality and important results.
Having such resources at disposal, establishing a new scientific journal, the TELFOR Journal, was a very natural next step for several reasons:
- Authors with favourable TELFOR reviewers’ assessments would have additional chances to improve and expand their initial ideas;
- Editorial board would have a wide set of prospective invited authors;
- After some time of existence, one could expect that TELFOR Journal would attract independent authors to submit their papers to be considered for publishing.
The history of TELFOR Journal is not a long one. The first volume consisting of two issues was published during the TELFOR 2009 conference in November 2009. That first volume of the Journal was intended to present a selection of the improved and expanded versions of the best scientific papers presented at Telecommunications Forum 2008.
The second volume of the TELFOR Journal, again with two issues, was electronically published before the TELFOR 2010 conference, in November 2010. Printed copies were realized slightly later. This is the third volume, based on the selected, expanded and improved results from the TELFOR 2010 conference.
After three years of existence one can easily conclude that TELFOR Journal is already a recognizable scientific publication in the region of south-east Europe. The impressions of the scientific and research community were positive, both with respect to the Journal scientific quality and the very nice design.
The TELFOR Journal is published in the English language, with both electronic and printed versions, minimally with the two issues per year. Having in mind that recent studies have shown that freely available papers are cited more often, Editorial board decided that electronic version will be once again free of charge.
The TELFOR Journal is an IEEE co-supported publication and it is following all the IEEE rules, procedures, and consequently the scientific quality.
The large spectrum of TELFOR Journal topics accounts for the rapid convergence through telecommunications towards the information and knowledge society. The Journal provides a medium for exchanging research results and technological achievements accomplished by the scientific community from academia and industry.
Editor-in-Chief
Prof. Dr Đorđe Paunović
In this paper we present the basic characteristics of Orthogonal Frequency Division Multiplex (OFDM) systems with quadrature phase shift keying (QPSK) modulation and multi-bit differential detection (MBDD). In the simulation environment designed for this purpose, we analyze the effects of frequency offset on the performances of OFDM digital communications. We also analyze the influence of OFDM system parameters on system performances for various values of frequency offset, number of bits for multi-bit detection and the number of subcarriers. We have shown the advantages and disadvantages of using MBDD in the OFDM systems.
Keywords: orthogonal frequency division multiplexing, differential quadrature phase shift keying, multi-bit differential detection, frequency offset, frequency synchronization.
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Subject Category: Communication Theory
Page(s): 78-81
Modern networks are expecting fast and efficient setup procedures for their connections. Strict time limits are requested for signaling in the normal operational mode and also for the recovery/restoration mode. As a possible solution, I proposed a method for fast source routed connection setup that takes advantage of the existing distributed processing potential in order to minimize the dependency of setup time on the path length. Two alternatives for the parallel setup are presented: sequential synchronization in the intermediate nodes and final synchronization in the egress node. The expected time reduction is considerable. The proposal is in general terms, using abstract messages instead of a specific signaling protocol. In the meantime, RSVP is established as the state of the art signaling protocol. The research community is still looking for ways to increase its speed and efficiency. In this context, I'm proposing an implementation of the mentioned method based on the current RSVP standard and I'm comparing it with a recent similar proposal.
Keywords: component, GMPLS signaling, RSVP, Source routed connection setup.
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Subject Category: Communication Theory
Page(s): 82-85
The hybrid automatic repeat request technique (HARQ) represents the error control principle which combines an error correcting code and automatic repeat request procedure (ARQ), within the same transmission system. In this paper, using Monte Carlo simulation process, the characteristics of HARQ technique are determined, for the case of the Universal Mobile Telecommunication System (UMTS) turbo code.
Keywords: Automatic repeat request (ARQ), Hybrid automatic repeat request (HARQ), Monte Carlo simulation, UMTS Turbo code.
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Subject Category: Communication Theory
Page(s): 86-89
An approach to scattering parameter calculation for a wave digital model of elliptic structure is described. The z-domain scattering parameters are given via wave transfer parameters. The main purpose of this paper is to show that the resultant equations for a wave digital model of elliptic structure can be used in the analysis of the models of structures with open/short-circuited stubs. This possibility reduces the number of wave digital network types, and contributes to the generalization of applied analysis approach and its software implementation.
Keywords: Microstrip structure, wave digital networks, z -domain functions, scattering parameters, open and shortcircuited stubs.
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Subject Category: Signal Processing
Page(s): 90-95
This paper analyzes the models for switching scalar quantization of a source with the Laplacian and Gaussian distribution. We have analyzed the results of real telephone speech and proposed a model of switching scalar quantization, which, in addition to adaptation on the power of speech, includes the adaptation on the distribution of signals (Gaussian and Laplacian ), which resulted in a better quality of voice signal pronounced with Signal-to- Quantization-Noise Ratio.
Keywords: Quantization algorithms, speech signal processing, switched scalar quantization
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Subject Category: Signal Processing
Page(s): 96-99
This paper presents an experimental study on the impact of telephone channels on the accuracy of automatic speaker recognition. Speaker models and the design of the recognizer used in this study are based on Hidden Markov models. In order to simulate telephonequality speech signals, several experimental conditions were introduced taking two control factors into consideration: the type of the applied codec and the probability of transmission errors. In addition, the impact of echo signals – that are often present in Internet telephony – on the accuracy of automatic speaker recognition systems is considered. Finally, the paper provides a brief overview of several methodologies for the adaptation of the recognizer to the expected environmental conditions that may enhance the robustness of the speaker recognizer.
Keywords: Automatic speaker recognition, experimental study, telephone channel, echo in VoIP, adaptation.
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Subject Category: Signal Processing
Page(s): 100-104
Extracting video shots is an essential preprocessing step to almost all video analysis, indexing, and other content-based operations. This process is equivalent to detecting the shot boundaries in a video. In this paper we presents video Shot Boundary Detection (SBD) based on Multifractal Analysis (MA). Low-level features (color and texture features) are extracted from each frame in video sequence. Features are concatenated in feature vectors (FVs) and stored in feature matrix. Matrix rows correspond to FVs of frames from video sequence, while columns are time series of particular FV component. Multifractal analysis is applied to FV component time series, and shot boundaries are detected as high singularities of time series above pre defined treshold. Proposed SBD method is tested on real video sequence with 64 shots, with manually labeled shot boundaries. Detection accuracy depends on number FV components used. For only one FV component detection accuracy lies in the range 76-92% (depending on selected threshold), while by combining two FV components all shots are detected completely (accuracy of 100%).
Keywords: Shot boundary detection, multifractal analysis, threshold, feature vectors
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Subject Category: Multimedia
Page(s): 105-110
Community noise surveys, such as those carried out during the process of acoustical zoning of open space, sometimes require analyses which cannot be made using standard sound level meters. This can be overcome by implementing a dedicated research tool for noise measurement and analysis. This paper describes software designed as an integral part of such a tool. Its functions are listed and the use is demonstrated on some practical examples.
Keywords: community noise, equivalent sound level, noise measurement.
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Subject Category: Multimedia
Page(s): 111-115
The analysis of impulse response has a central place in room acoustics. The research presented in this paper was aimed at examining possibilities for applying multifractal theory in room acoustics focusing on the analysis of room impulse response. Observing an impulse response as a signal with multifractal features gives an opportunity for a new approach in determining the acoustic properties of a sound field in a room. Through the use of characteristic values, gained from multifractal spectra, authors have tried to quantify impulse responses of different rooms. The method used in this paper, together with achieved results, is displaying some of the directions which can be followed when applying multifractals in the field of room acoustics.
Keywords: impulse response, multifractals, multifractal spectrum, room acoustic.
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Subject Category: Multimedia
Page(s): 116-120
A novel higher order entire-domain finite element technique is presented for accurate and efficient fullwave three-dimensional analysis of electromagnetic structures with continuously inhomogeneous material regions, using large (up to about two wavelengths on a side) generalized curved hierarchical curl-conforming hexahedral vector finite elements (of arbitrary geometrical and fieldapproximation orders) that allow continuous change of medium parameters throughout their volumes. The results demonstrate considerable reductions in both number of unknowns and computation time of the entire-domain FEM modeling of continuously inhomogeneous materials over piecewise homogeneous models.
Keywords: Computer-aided analysis, electromagnetic analysis, electromagnetic scattering, finite element method, higher order elements, inhomogeneous media, method of moments.
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Subject Category: Applied Electronics
Page: 121-124
In the paper, the effective relative permittivity of a square coaxial line with anisotropic and isotropic dielectric layers of different heights is calculated by the use of the Galerkin formulation of the Finite Element Method (FEM). Special attention is devoted to the case when the line is half filled with dielectric. It was shown that, in this case, the effective relative permittivity is practically equal to the value obtained by a simple formula given in the paper.
Keywords: Anisotropic dielectric, FEM, weak formulation, quasi-static analysis, square coaxial line.
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Subject Category: Applied Electromagnetics
Page: 125-127