SERBIAN JOURNAL OF ELECTRICAL ENGINEERING
Vol. 14, No. 3, October 2017
CONTENTS
| Guest editors: | , | Don State Technical University, Rostov-on-Don, Russia |
| , | Don State Technical University, Rostov-on-Don, Russia |
Adaptive Algorithm Based on Antenna Arrays for Radio Communication Systems
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DOI: https://doi.org/10.2298/SJEE1703301F
Abstract: Trends in the modern world increasingly lead to the growing popularity of wireless technologies. This is possible due to the rapid development of mobile communications, the Internet gaining high popularity, using wireless networks at enterprises, offices, buildings, etc. It requires advanced network technologies with high throughput capacity to meet the needs of users. To date, a popular destination is the development of spatial signal processing techniques allowing to increase spatial bandwidth of communication channels. The most popular method is spatial coding MIMO to increase data transmission speed which is carried out due to several spatial streams emitted by several antennas. Another advantage of this technology is the bandwidth increase to be achieved without expanding the specified frequency range. Spatial coding methods are even more attractive due to a limited frequency resource. Currently, there is an increasing use of wireless communications (for example, WiFi and WiMAX) in information transmission networks. One of the main problems of evolving wireless systems is the need to increase bandwidth and improve the quality of service (reducing the error probability). Bandwidth can be increased by expanding the bandwidth or increasing the radiated power. Nevertheless, the application of these methods has some drawbacks, due to the requirements of biological protection and electromagnetic compatibility, the increase of power and the expansion of the frequency band is limited. This problem is especially relevant in mobile (cellular) communication systems and wireless networks operating in difficult signal propagation conditions. One of the most effective ways to solve this problem is to use adaptive antenna arrays with weakly correlated antenna elements. Communication systems using such antennas are called MIMO systems (Multiple Input Multiple Output multiple input - multiple outputs). At the moment, existing MIMO-idea implementations do not always noticeably accelerate traffic at short distances from the access point, but, they are very effective at long distances. The MIMO principle allows reducing the number of errors in radio data interchange (BER) without reducing the transmission rate under conditions of multiple signal re-reflections. The work aims at developing an adaptive space-time signal algorithm for a wireless data transmission system designed to improve the efficiency of this system, as well as to study the efficiency of the algorithm to minimizing the error bit probability and maximizing the channel capacity.
Keywords: MIMO, OFDM, Channel, Adaptation, Channel capacity.
Steganography Method for the G.711 Channel
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DOI: https://doi.org/10.2298/SJEE1703313N
Abstract: This paper deals with an improved algorithm developed for the transmission of the hidden information in the G.711 channel [1]. The subject of the research is a method of improving characteristics of a steganography system by means of using specially developed codes. Also analysis of transmission characteristics of the hidden information depending on a number of bits of the original data replaced at a given threshold was conducted.
Keywords: Steganography, Hidden data transmit, Data rate, G.711.
Influence of Control Algorithms Parameters on an Electromechanical Converter with a Secondary Discrete Part
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DOI: https://doi.org/10.2298/SJEE1703323K
Abstract: An alternative configuration of a device with a secondary discrete part using a magnetic system of a similar multi-phase inductor machine and concen¬trated windings without an internal rotor is proposed. An algorithm of sensorless control of a motion process of a secondary discrete part is proposed. The analysis of the distribution nature of the magnetic field for various switching algorithms is carried out to reduce negative influence of the “dead” zones of the first and second order. The features of the movement process of the secondary discrete part in the working chamber of the device are considered. The results of in the electromagnetic force change affecting a ferromagnetic working element are presented, and recommendations for the application of switching algorithms are given.
Keywords: Electromechanical converter, Secondary discrete part, Sensorless control, Mathematical modeling, Switching algorithm.
Partition Optimization for a Random Process Realization to Estimate its Expected Value
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DOI: https://doi.org/10.2298/SJEE1703333M
Abstract: The paper provides an analytical proof the optimal number of partitions of a non-stationary random process realization, which is necessary for estimating its expected value when using “the estimation reproduction” method for signal processing. This method allows to process signal with a limited volume of priori information about the desired signal function and statistical characteristics of the additive noise component.
Keywords: Desired signal, Noise, Signal-to-noise ratio, Expected value, Estimation, Random process.
Space Monitoring of the Earth on the Presence of Solid Domestic Wastes Using a Discrete Orthogonal Transforms
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DOI: https://doi.org/10.2298/SJEE1703343K
Abstract: The paper investigates multivariate Wavelet Haar’s series. To study on the correctness is made by means of Tikhonov’s method. A theorem on stability and uniform convergence of a regularized summable function of the wavelet-Haar’s series functions in Lipschitz class with approximate coefficients is proved. An experiment confirms the validity of Tikhonov’s method using space monitoring of waste disposal facilities is conducted as an example. Namely, the decoding of space images-images using N-dimensional Haar’s wavelet transform is used.
Keywords: Fourier transform, N-dimensional discrete wavelet transform, Wavelet Haar’s series, N-dimensional discrete Fourier transform, Tikhonov’s method, Space monitoring of waste disposal sites.
Two Approaches to Solving the Problem of Smoothing Digital Signals Based on a Combined Criterion
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DOI: https://doi.org/10.2298/SJEE1703365S
Abstract: The paper presents a method for smoothing signals, represented by a single realization of a finite-length random process, under conditions of a limited amount of a priori information about the signal function and statistical characteristics the noise component. The recommendations on the use of parameters affecting the processing speed and the efficiency of smoothing are given. Two solutions are presented to obtain the result of smoothing the signals. The efficiency results are shown for the processing of digital signals. Examples of comparison of simple methods and suggested ones are given.
Keywords: Signal processing, Denoising, Two-criteria method, Smoothing.
Combination of Single Image Super Resolution and Digital Inpainting Algorithms Based on GANs for Robust Image Completion
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DOI: https://doi.org/10.2298/SJEE1703379H
Abstract: Image inpainting, a technique of completing missing or corrupted image regions in undetected form, is an open problem in digital image processing. Inpainting of large regions using Deep Convolutional Generative Adversarial Nets (DCGAN) is a new and powerful approach. In described approaches the size of generated image and size of input image should be the same. In this paper we propose a new method where the size of input image with corrupted region can be up to 4 times larger than generated image.
Keywords: Inpainting, Deep learning, Super-resolution.
Television Images Identification in the Vision System Basis on the Mathematical Apparatus of Cubic Normalized B-Splines
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DOI: https://doi.org/10.2298/SJEE1703387K
Abstract: The solution the task of television image identification is used in industry when creating autonomous robots and systems of technical vision. A similar problem also arises in the development of image analysis systems to function under the influence of various interfering factors in complex observation conditions complicated the registration process and existing when priori information is absent, in background noise type. One of the most important operators is the contour selection operator. Methods and algorithms of processing information from image sensors must take into account the different character of noise associated with images and signals registration. The solution of the task of isolating contours, and in fact of digital differentiation of two-dimensional signals registered against a different character of background noise, is far from trivial. This is due to the fact that such task is incorrect. In modern information systems, methods of numerical differentiation or masks are usually used to solve the task of isolating contours. The paper considers a new method of differentiating measurement results against a noise background using the modern mathematical apparatus of cubic smoothing B-splines. The new high-precision method of digital differentiation of signals using splines is proposed for the first time, without using standard numerical differentiation procedures, to calculate the values of the derivatives with high accuracy. In fact, a method has been developed for calculating the image gradient module using spline differentiation. The method, as proved by experimental studies, and computational experiments has higher noise immunity than algorithms based on standard differentiation procedures using masks.
Keywords: Denoising, Spline, Approximation, Segmentation, Contouring.
Medical Image Segmentation Using Modified Active Contour Method
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DOI: https://doi.org/10.2298/SJEE1703401V
Abstract: Image data is of major practical importance in medical informatics. Accurate segmentation of medical images largely determines the final result of image analysis, which provides significant information for 3D visualization, surgical planning and early detection of diseases. In this paper, a modified segmentation approach based on the active contour method is proposed to extract parts of bones from MRI data sets. The efficiency of the method is verified on real MRI slices. Good results are shown in comparison with existing approaches of segmentation of medical data.
Keywords: Magnetic Resonance Imaging (MRI), Segmentation, Anisotropic Gradient, Active Contour, Region-based Active Contour, Medical Images.
Fast Computation of the Iteration-Based Simulation Method - Case Study of Non-coherent ASK with Shadowing
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DOI: https://doi.org/10.2298/SJEE1703415M
Abstract: This article presents a new method of fast symbolic computations of very complex calculations, which are necessary for the analysis, simulation, and design of wireless communication systems using CAS (Computer Algebra System). CAS is applied to formulate hypotheses and define joint probability density functions of certain modulation technique. This is used to prepare for the semi-symbolic calculation to complete specify wireless system by using CAS. We have developed an iteration-based simulation method that aids to solve semi-symbolic expressions and gives closed form solutions (with some parameters specified as numbers and some as symbols). So far, they are solved by numerical methods. Students can perform performance analysis and understand the processes in the data transfer. Engineers and researchers may have a better insight into the impact of the important parameters necessary to properly transmit and detect information unlike traditional numerical methods. The main contribution is to obtain solutions for the probability density function, and outage probability where no solution can be obtained using numerical methods. A strong emphasis is placed on very fast calculations that significantly save the time of analysis, simulation, and design.
Keywords: Iteration-Based Simulation Method, Kummer’s transformation, Closed-form solution, Closed-form expression.