Autor: Safi, S. - Katalog OPAC zbiorów

Skocz do pozycji: 1.

Tytuł:: Compensation of Fading Channels Using Partial Combining Equalizer in MC-CDMA Systems
Autorzy:: Zidane, M.
Safi, S.
Sabri, M.
Powiązania:: https://bibliotekanauki.pl/articles/307612.pdf
Data publikacji:: 2017
Wydawca:: Instytut Łączności - Państwowy Instytut Badawczy
Tematy:: bit error rate
blind channel identiﬁcation
higher order cumulants
MC-CDMA systems
partial combining equalizer
Opis:: In this paper the performance of a partial combining equalizer for Multi-Carrier Code Division Multiple Access (MC-CDMA) systems is analytically and numerically evaluated. In the part of channel identification, authors propose a blind algorithm based on Higher Order Cumulants (HOC) for identifying the parameters representing the indoor scenario of Broadband Radio Access Networks (BRAN A) channel model normalized for MC-CDMA systems. Theoretical analysis and numerical simulation results, in noisy environment and for different Signal to Noise Ratio (SNR), are presented to illustrate the performance of the proposed algorithm in the one hand, and the other hand the impact of partial combining equalizer on the performance of MC-CDMA systems.
Źródło:: Journal of Telecommunications and Information Technology; 2017, 1; 5-11
1509-4553
1899-8852
Pojawia się w:: Journal of Telecommunications and Information Technology
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 2.

Tytuł:: Comparative Study between Several Direction of Arrival Estimation Methods
Autorzy:: Khmou, Y.
Safi, S.
Frikel, M.
Powiązania:: https://bibliotekanauki.pl/articles/308017.pdf
Data publikacji:: 2014
Wydawca:: Instytut Łączności - Państwowy Instytut Badawczy
Tematy:: array processing
Direction of Arrival
geolocalization
propagation
smart antenna
spectral analysis
Opis:: In this paper a comparative study, restricted to one-dimensional stationary case, between several Direction of Arrival (DOA) estimation algorithms of narrowband signals is presented. The informative signals are corrupted by an Additive White Gaussian Noise (AWGN), to show the performance of each method by applying directly the algorithms without pre-processing techniques such as forward-backward averaging or spatial smoothing.
Źródło:: Journal of Telecommunications and Information Technology; 2014, 1; 41-48
1509-4553
1899-8852
Pojawia się w:: Journal of Telecommunications and Information Technology
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 3.

Tytuł:: Focusing Operators and Tracking Moving Wideband Sources
Autorzy:: Frikel, M.
Safi, S.
Khmou, Y.
Powiązania:: https://bibliotekanauki.pl/articles/309477.pdf
Data publikacji:: 2016
Wydawca:: Instytut Łączności - Państwowy Instytut Badawczy
Tematy:: DoA
localization
tracking
wideband signal
Opis:: In this paper, the localization of wideband source with an algorithm to track a moving source is investigated. To locate the wideband source, the estimation of two directions of arrival (DOA) of this source from two different arrays of sensors is used, and then, a recursive algorithm is applied to predict the moving source’s position. The DOA is estimated by coherent subspace methods, which use the focusing operators. Practical methods of the estimation of the coherent signal subspace are given and compared. Once the initial position is estimated, an algorithm of tracking the moving source is presented to predict its trajectory.
Źródło:: Journal of Telecommunications and Information Technology; 2016, 4; 53-59
1509-4553
1899-8852
Pojawia się w:: Journal of Telecommunications and Information Technology
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 4.

Tytuł:: Lorentzian Operator for Angular Source Localization with Large Array
Autorzy:: Khmou, Y.
Safi, S.
Frikel, M.
Powiązania:: https://bibliotekanauki.pl/articles/308330.pdf
Data publikacji:: 2015
Wydawca:: Instytut Łączności - Państwowy Instytut Badawczy
Tematy:: array processing
Direction of Arrival
narrowband
operator
Opis:: Source localization problem consists of an ensemble of techniques that are used to obtain spatial information of present radiation in given medium of propagation, with a constraint of the antenna geometry and the characteristics of radiating sources. This condition gives multitude of cases to study, hence several methods were proposed in the literature. In this paper, a new algorithm for estimating the Direction of Arrival (DoA) of narrowband and far eld punctual sources is introduced. By exploiting the spectrum of covariance matrix of received data, the Lorentzian function on spectral matrix to lter the eigenvalues is applied. This ltering process eliminates the eigenvalues belonging to signal subspace. Parameters of Lorentz function are adjusted using rst and second statistics of eigenvalues. The algorithm requires the knowledge of minimum eigenvalue and is performing when the dimension of antenna is relatively large which is conrmed by several Monte Carlo simulations.
Źródło:: Journal of Telecommunications and Information Technology; 2015, 4; 98-105
1509-4553
1899-8852
Pojawia się w:: Journal of Telecommunications and Information Technology
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 5.

Tytuł:: Minimum Array Elements for Resolution of Several Direction of Arrival Estimation Methods in Various Noise-Level Environments
Autorzy:: El Ouargui, I.
Saﬁ, S.
Frikel, M.
Powiązania:: https://bibliotekanauki.pl/articles/956990.pdf
Data publikacji:: 2018
Wydawca:: Instytut Łączności - Państwowy Instytut Badawczy
Tematy:: covariance matrix
direction of arrival
geolocation
resolution
noise
smart antenna
Opis:: The resolution of a Direction of Arrival (DOA) estimation algorithm is determined based on its capability to resolve two closely spaced signals. In this paper, authors present and discuss the minimum number of array elements needed for the resolution of nearby sources in several DOA estimation methods. In the real world, the informative signals are corrupted by Additive White Gaussian Noise (AWGN). Thus, a higher signal-to-noise ratio (SNR) offers a better resolution. Therefore, we show the performance of each method by applying the algorithms in diﬀerent noise level environments.
Źródło:: Journal of Telecommunications and Information Technology; 2018, 2; 87-94
1509-4553
1899-8852
Pojawia się w:: Journal of Telecommunications and Information Technology
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 6.

Tytuł:: Using Least Mean p-Power Algorithm to Correct Channel Distortion in MC-CDMA Systems
Autorzy:: Zidane, M.
Safi, S.
Sabri, M.
Frikel, M.
Powiązania:: https://bibliotekanauki.pl/articles/308275.pdf
Data publikacji:: 2018
Wydawca:: Instytut Łączności - Państwowy Instytut Badawczy
Tematy:: adaptive equalization
adaptive identification
BER
BRAN C
LMP
MC-CDMA system
ZF
Opis:: This work focuses on adaptive Broadband Radio Access Network (BRAN) channel identiﬁcation and on downlink Multi-Carrier Code Division Multiple Access (MCCDMA) equalization. We use the normalized BRAN C channel model for 4G mobile communications, distinguishing between indoor and outdoor scenarios. On the one hand, BRAN C channel parameters are identiﬁed using the Least Mean p-Power (LMP) algorithm. On the other, we consider these coeﬃcients in the context of adaptive equalization. We provide an overview and a mathematic formulation of MC-CDMA systems. According to these fundamental concepts, the equalizer technique is investigated analytically to compensate for channel distortion in terms of the bit error rate (BER). The numerical simulation results, for various signal-to-noise ratios and diﬀerent p threshold, show that the presented algorithm is able to simulate the BRAN C channel measured with different accuracy levels. Furthermore, as far as the adaptive equalization problem is concerned, the results obtained using the zero-forcing equalizer demonstrate that the algorithm is adequate for some particular cases of threshold p.
Źródło:: Journal of Telecommunications and Information Technology; 2018, 3; 23-30
1509-4553
1899-8852
Pojawia się w:: Journal of Telecommunications and Information Technology
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 7.

Tytuł:: Channel Identification Using Chaos for an Uplink/Downlink Multicarrier Code Division Multiple Access System
Autorzy:: Frikel, M.
Safi, S.
Targui, B.
M'Saad, M.
Powiązania:: https://bibliotekanauki.pl/articles/308067.pdf
Data publikacji:: 2010
Wydawca:: Instytut Łączności - Państwowy Instytut Badawczy
Tematy:: channel identification
chaos code
equalization
MC-CDMA system
Opis:: A scheme of chaotic spreading sequence for multicarrier code division multiple access system (MC-CDMA) iproposed to estimate the transmission channel. This systespreads spectrum and identifies the channel, simultaneously. The proposed scheme uses a chaotic sequence generated by a logistic map as a training signal and estimate channel parameters according to dynamics of the chaotic sequence. Encoding data by chaotic sequences is first built and then the orthogonal codes are used to spread the encrypted data for multiusers scheme. At the reception, first the channel parameters are identified using a training chaotic sequence in order to equalize the received data, and then the encrypted information is decoded for the desired user. The studies reveal that the proposed system (chaos plus orthogonal codes) significantly outperforms the Walsh-Hadamard code spreading in MC-CDMA system. The performance of the system is considered in the multiuser case by means of simulation. The simulation result shows that the proposed chaotic code spreading approach for channel identification achieves significant improvement in the channel identification, comparing to using others training sequence or the least square method.
Źródło:: Journal of Telecommunications and Information Technology; 2010, 1; 48-54
1509-4553
1899-8852
Pojawia się w:: Journal of Telecommunications and Information Technology
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 8.

Tytuł:: Higher Order Cumulants for Identification and Equalization of Multicarrier Spreading Spectrum Systems
Autorzy:: Safi, S.
Frikel, M.
Zeroual, A.
M'Saad, M.
Powiązania:: https://bibliotekanauki.pl/articles/309082.pdf
Data publikacji:: 2011
Wydawca:: Instytut Łączności - Państwowy Instytut Badawczy
Tematy:: blind identification and equalization
communication channels
higher order cumulants
MC-CDMA systems
Opis:: This paper describes two blind algorithms for multicarrier code division multiple access (MC-CDMA) system equalization. In order to identify, blindly, the impulse response of two practical selective frequency fading channels called broadband radio access network (BRAN A and BRAN E) normalized for MC-CDMA systems, we have used higher order cumulants (HOC) to build our algorithms. For that, we have focussed on the experimental channels to develop our blind algorithms able to simulate the measured data with high accuracy. The simulation results in noisy environment and for different signal to noise ratio (SNR) demonstrate that the proposed algorithms are able to estimate the impulse response of these channels blindly (i.e., without any information about the input), except that the input excitation is i.i.d. (identically and independent distributed) and non-Gaussian. In the part of MC-CDMA, we use the zero forcing and the minimum mean square error equalizers to perform our algorithms. The simulation results demonstrate the effectiveness of the proposed algorithms.
Źródło:: Journal of Telecommunications and Information Technology; 2011, 2; 74-84
1509-4553
1899-8852
Pojawia się w:: Journal of Telecommunications and Information Technology
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 9.

Tytuł:: Adaptive Algorithms Versus Higher Order Cumulants for Identification and Equalization of MC-CDMA
Autorzy:: Zidane, M.
Safi, S.
Sabri, M.
Boumezzough, A.
Frikel, M.
Powiązania:: https://bibliotekanauki.pl/articles/307974.pdf
Data publikacji:: 2014
Wydawca:: Instytut Łączności - Państwowy Instytut Badawczy
Tematy:: blind identification and equalization
higher order cumulants
RLS
LMS
MC-CDMA systems
Opis:: In this paper, a comparative study between a blind algorithm, based on higher order cumulants, and adaptive algorithms, i.e. Recursive Least Squares (RLS) and Least Mean Squares (LMS) for MultiCarrier Code Division Multiple Access (MC-CDMA) systems equalization is presented. Two practical frequency-selective fading channels, called Broadband Radio Access Network (BRAN A, BRAN B) normalized for MC-CDMA systems are considered. In the part of MC-CDMA equalization, the Zero Forcing (ZF) and the Minimum Mean Square Error (MMSE) equalizer techniques were used. The simulation results in noisy environment and for different signal to noise ratio (SNR) demonstrate that the blind algorithm gives approximately the same results obtained by adaptive algorithms. However, the proposed algorithm presents the advantage to estimate the impulse response of these channels blindly except that the input excitation is non-Gaussian, with the low calculation cost, compared with the adaptive algorithms exploiting the information of input and output for the impulse response channel estimation.
Źródło:: Journal of Telecommunications and Information Technology; 2014, 3; 53-62
1509-4553
1899-8852
Pojawia się w:: Journal of Telecommunications and Information Technology
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 10.

Tytuł:: Crack growth diagnostic of ball bearing using vibration analysis
Autorzy:: Belaidi, S.
Lecheb, S.
Chellil, A.
Mechakra, H.
Safi, B.
Kebir, H.
Powiązania:: https://bibliotekanauki.pl/articles/2174182.pdf
Data publikacji:: 2022
Wydawca:: Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:: łożysko kulkowe
drgania
pękanie
zmęczenie
ball bearing
vibration analysis
frequency
cracking
diagnosis
fatigue life
Opis:: It is known that supported ball bearings have great effects on the vibrations of the gear transmission system, above in all the presence of local faults as well as the crack growths. For this purpose, this paper focuses on shock and vibration crack growth diagnostic of ball bearing using vibration analysis. Our work is devoted first to a study the static behaviour of the ball bearing by determining the stress, strain and displacement, then its dynamic behaviour by determining the first four natural frequencies. Secondly, a dynamic analysis study of the bearing was carried with defects as a function of crack size and location. The obtained results clearly show that the natural frequencies decrease in a non-linear way with the growth of the length of the crack, on the other hand the stress increases with the presence of the singular points of the crack. Finally, this residual decrease in natural frequencies can be used as an indicator of the state of failure, as well as a parameter used for the diagnosis and screening, and to highlight the fatigue life of the bearing.
Źródło:: International Journal of Applied Mechanics and Engineering; 2022, 27, 1; 35--45
1734-4492
2353-9003
Pojawia się w:: International Journal of Applied Mechanics and Engineering
Dostawca treści:: Biblioteka Nauki

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