Telfor Journal Vol.3 No.2 (2011)

Content

Editorial HyperLink
Editor-in-Chief: Prof. Dr Đorđe Paunović

Influence of frequency offset on the reception of OFDM/QPSK signal using MBDD algorithm

B. Dimitrijević, S. Stošović, N. Milošević, and Z. Nikolić
Topic:
Communication Theory
Abstract
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.
Full Text
HyperLink Influence of frequency offset on the reception of OFDM/QPSK signal using MBDD algorithm
Page(s)
78-81

Fast Source Routed Connection Setup - Proposal for a RSVP Implementation

F. J. Lataretu and C. Toma
Topic:
Communication Theory
Abstract
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.
Full Text
HyperLink Fast Source Routed Connection Setup - Proposal for a RSVP Implementation
Page(s)
82-85

Performance Evaluation of HARQ Technique with UMTS Turbo Code

S. S. Brkić and P. N. Ivaniš
Topic:
Communication Theory
Abstract
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.
Full Text
HyperLink Performance Evaluation of HARQ Technique with UMTS Turbo Code
Page(s)
86-89

Application of the Equations for Elliptic Structure Digital Model to Models of Structures utilizing Open/Short-circuited Stubs

B. Stošić
Topic:
Signal Processing
Abstract
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.
Full Text
HyperLink Application of the Equations for Elliptic Structure Digital Model to Models of Structures utilizing Open/Short-circuited Stubs
Page(s)
90-95

Switched Scalar Quantization with Adaptation Performed on both the Power and the Distribution of Speech Signal

G. M. Petković, Z. H. Perić, and L. V. Stoimenov
Topic:
Signal Processing
Abstract
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.
Full Text
HyperLink Switched Scalar Quantization with Adaptation Performed on both the Power and the Distribution of Speech Signal
Page(s)
96-99

The Impact of Telephone Channels on the Accuracy of Automatic Speaker Recognition

I. Jokić, S. Jokić, M. Gnjatović, M. Sečujski, and V. Delić
Topic:
Signal Processing
Abstract
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.
Full Text
HyperLink The Impact of Telephone Channels on the Accuracy of Automatic Speaker Recognition
Page(s)
100-104

Video Shot Boundary Detection based on Multifractal Analisys

G. J. Zajić, I. S. Reljin, and B. D. Reljin
Topic:
Multimedia
Abstract
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.
Full Text
HyperLink Video Shot Boundary Detection based on Multifractal Analisys
Page(s)
105-110

Software Tool for Community Noise Surveys

D. Mašović, M. Mijić, and J. Ćertić
Topic:
Multimedia
Abstract
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.
Full Text
HyperLink Software Tool for Community Noise Surveys
Page(s)
111-115

Applications of Multifractals in the Analysis of Room Impulse Response - Initial Research

M. Pavlović and D. M. Ristić
Topic:
Multimedia
Abstract
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.
Full Text
HyperLink Applications of Multifractals in the Analysis of Room Impulse Response - Initial Research
Page(s)
116-120

Hybrid Higher Order FEM-MoM Analysis of Continuously Inhomogeneous Electromagnetic Scatterers

M. M. Ilić, S. V. Savić, A. Ž. Ilić, and B. M. Notaroš
Topic:
Applied Electromagnetics
Abstract
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.
Full Text
HyperLink Hybrid Higher Order FEM-MoM Analysis of Continuously Inhomogeneous Electromagnetic Scatterers
Page(s)
121-124

Analysis of Square Coaxial Line with Anisotropic Dielectric by Finite Element Method

Ž. J. Mančić and V. V. Petrovic
Topic:
Applied Electromagnetics
Abstract
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.
Full Text
HyperLink Analysis of Square Coaxial Line with Anisotropic Dielectric by Finite Element Method
Page(s)
125-127