Institute of Electron Technology
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Pilot Design for Sparse Channel Estimation in Orthogonal Frequency Division Multiplexing Systems, Journal of Telecommunications and Information Technology, 2018, nr 2
Get PDFOrthogonal Frequency Division Multiplexing (OFDM) is a well-known technique used in modern wide band wireless communication systems. Coherent OFDM systems achieve its advantages over a multipath fading channel, if channel impulse response is estimated precisely at the receiver. Pilot-aided channel estimation in wide band OFDM systems adopts the recently explored compressive sensing technique to decrease the transmission overhead of pilot subcarriers, since it exploits the inherent sparsity of the wireless fading channel. The accuracy of compressive sensing techniques in sparse channel estimation is based on the location of pilots among OFDM subcarriers. A sufficient condition for the optimal pilot selection from Sylow subgroups is derived. A Sylow subgroup does not exist for most practical OFDM systems. Therefore, a deterministic pilot search algorithm is described to select pilot locations based on minimizing coherence, along with minimum variance. Simulation results reveal the effectiveness of the proposed algorithm in terms of bit error rate, compared to the existing solutions
Genetic Algorithm for Combined Speaker and Speech Recognition using Deep Neural Networks, Journal of Telecommunications and Information Technology, 2018, nr 2
Get PDFHuge growth is observed in the speech and speaker recognition field due to many artificial intelligence algorithms being applied. Speech is used to convey messages via the language being spoken, emotions, gender and speaker identity. Many real applications in healthcare are based upon speech and speaker recognition, e.g. a voice-controlled wheelchair helps control the chair. In this paper, we use a genetic algorithm (GA) for combined speaker and speech recognition, relying on optimized Mel Frequency Cepstral Coefficient (MFCC) speech features, and classification is performed using a Deep Neural Network (DNN). In the first phase, feature extraction using MFCC is executed. Then, feature optimization is performed using GA. In the second phase training is conducted using DNN. Evaluation and validation of the proposed work model is done by setting a real environment, and efficiency is calculated on the basis of such parameters as accuracy, precision rate, recall rate, sensitivity, and specificity. Also, this paper presents an evaluation of such feature extraction methods as linear predictive coding coefficient (LPCC), perceptual linear prediction (PLP), mel frequency cepstral coefficients (MFCC) and relative spectra filtering (RASTA), with all of them used for combined speaker and speech recognition systems. A comparison of different methods based on existing techniques for both clean and noisy environments is made as well
Enhancement of Air-groundMatching by Means of a Chirped MultilayerStructure: Electromagnetic Modelingwith the Method of Single Expression, Journal of Telecommunications and Information Technology, 2017, nr 3
Get PDFThe enhancement of air-ground electromagneticmatching by means of a chirped multilayer structure is inves-tigated. The modeling and simulation of the considered struc-ture are performed by using the method of single expression(MSE), which is a convenient and accurate tool for wavelength-scale simulations of multilayers comprising lossy, amplifyingor nonlinear (Kerr-type) materials. Numerical results showthat a suitable chirped multilayer structure can reduce the re- ection from the ground. Different values of the number oflayers and of the layer thicknesses are considered. The distributions of the electric eld components and the power owdensity within the modelled structures are calculated
A Photonic-Crystal Selective Filter, Journal of Telecommunications and Information Technology, 2017, nr 3
Get PDFA highly selective filter is designed, working at 1.55 μm and having a 3-dB bandwidth narrower than 0.4 nm, as is required in Dense Wavelength Division Multiplexed systems. Different solutions are proposed, involving photonic crystals made rectangular- or circular-section dielectric rods, or else of holes drilled in a dielectric bulk. The polarization and frequency selective properties are achieved by introducing a defect in the periodic structure. The device is studied by using in-house codes implementing the full-wave Fourier Modal Method. Practical guidelines about advantages and limits of the investigated solutions are given
Sharing Spectrum UE LTE and Air-Traffic Control Radars in 800 MHz Band, Journal of Telecommunications and Information Technology, 2017, nr 2
Get PDFThe need to ensure LTE network coverage in sparsely populated and rural areas of Europe (ITU Region 1) has led to a massive use of 800 MHz band (band 20) with its good characteristics of radio wave propagation in LTE networks. However, the frequency band of 800 MHz called “digital dividend” in Region 1 is used on a primary basis not only by the terrestrial mobile service but also by air-traffic control radars (ATCR) that can lead to the creation of harmful interferences at the receivers’ input of ATCR. Such scenarios of mutual interferences became possible after granting licenses for LTE-800 frequencies to operators in such countries as Azerbaijan, Kazakhstan, Russia and other CIS countries, so this problem should be solved by operators at the deployment of LTE-800 networks in airports and areas close to them. So far, for such scenarios the ITU and CEPT have not formulated criteria for interference protection. The proposed protection criteria for receivers of ATCR from user devices’ interferences of LTE-800 networks were tested by experimental studies and can provide a solution to the electromagnetic compatibility (EMC) problem in a complex electromagnetic environment of modern airports and cross-order coordination of 800 MHz frequency bands in Region 1
Analytical Investigation on a New Approach for Achieving Deep Penetration in a Lossy Medium: The Lossy Prism, Journal of Telecommunications and Information Technology, 2017, nr 3
Get PDFRecent studies highlighted deep-penetration prop-erties of inhomogeneous waves at the interface between a loss-less and a lossy medium. Such waves can be generated bymeans of radiating structures known as Leaky-Wave Anten-nas (LWAs). Here, a different approach is proposed basedon the use of a lossy prism capable to generate an inhomo-geneous wave when illuminated by a homogeneous wave. Thelossy prism is conceived and designed thinking of Ground-Penetrating Radar (GPR). The results achieved by the lossyprism will be compared with those obtained by means of a pre-viously designed LWA that was created with the identical ob-jective. The approach of this paper is purely theoretical, andit aims at providing basic ideas and preliminary results usefulfor an innovative LWA design
A New Efficient Authenticated and Key Agreement Scheme for SIP Using Digital Signature Algorithm on Elliptic Curves, Journal of Telecommunications and Information Technology, 2017, nr 2
Get PDFVoice over Internet Protocol (VoIP) has been recently one of the more popular applications in Internet technology. It benefits lower cost of equipment, operation, and better integration with data applications than voice communications over telephone networks. However, the voice packets delivered over the Internet are not protected. The session initiation protocol (SIP) is widely used signaling protocol that controls communications on the Internet, typically using hypertext transport protocol (HTTP) digest authentication, which is vulnerable to many forms of attacks. This paper proposes a new secure authentication and key agreement scheme based on Digital Signature Algorithm (DSA) and Elliptic Curve Cryptography (ECC) named (ECDSA). Security analysis demonstrates that the proposed scheme can resist various attacks and it can be applied to authenticate the users with different SIP domains
Evolution of Measurement of the Single Piece Mail Transit Time, Journal of Telecommunications and Information Technology, 2017, nr 4
Get PDFThe article presents the evolution of measurement of the transit time of priority mail methodology used for postal services quality assessment from the point of view of home and small business senders based on European postal standards. The paper also considers the possibility of test cost reduction by further changes in the measurements methodology
