Mokhtar Besseghier was born in 1987 in Mascara, Algeria. He received the Master degree in Telecommunications from MASCARA University in 2012, and the Ph.D. degree from Sidi Bel Abbes University, Algeria, in 2017. Currently, he was an Associate Professor at the University of Mascara in the department of Electronics, and does his research at the Telecommunication and Digital Signal Processing Laboratory in Sidi Bel Abbes University. His current research interests include wireless communications and signal processing.
La revue : IEEE Communications Letters
Domaine : Telecommunications
Mots Clés : OFDM/OQAM Estimation CFO
Auteur : Mokhtar Besseghier; Djebbar Ahmed Bouzidi
Issn : 1089-7798 Eissn : 1558-2558 vol : 24, Num : 7, pp : 1451 - 1454
Date de publication : 2020-04-02
Résume : To solve the performance degradation due to Carrier Frequency Offset (CFO) for OFDM/OQAM system, a new blind CFO estimation method is proposed in this letter. This method uses the header structure of the transmitted signal by considering that there is an OFDM/OQAM symbol of null-valued OQAM symbols before the first one and exploits the orthogonality among subcarriers as well as the orthogonality between synthesis and analysis filter banks to estimate the CFO. Therefore, without compromising the spectral efficiency of OFDM/OQAM system this method can estimate accurately the CFO. Simulation results illustrate the effectiveness of the proposed method.
Semi-Blind Estimation of CFO and Channels for STBC-OFDM System
La revue : International Journal of Computer Aided Engineering and Technology
Domaine : Telecommunications
Mots Clés : Estimation CFO
Auteur : Mokhtar Besseghier; Djebbar Ahmed Bouzidi
Issn : 1757-2665 Eissn : 1757-2657 vol : , Num : , pp :
Date de publication : 0000-00-00
Résume : Space Time Block Coding-Orthogonal Frequency Division Multiplexing (STBC-OFDM) based MIMO (Multi Input Multi Output) system has been shown to be robust against non ideal operating conditions such as antenna correlation, channel estimation errors, and Doppler effects. But, the later suffers from carrier frequency offset (CFO) which makes channels estimation more challenging.rnIn this paper, we propose joint semi-blind CFO and channels estimators based on modified- multiple signal classification (M-MUSIC) algorithm for STBC-OFDM system over MIMO channels. Channels state information can be estimated at the receiver using pilot symbols embedded in each transmission block. To this end, we propose to encode pilot symbols by a Specific Space-Time Block Coder (S-STBC) while information symbols are encoded by Alamouti based space-time block coding (A-STBC). MUSIC based estimation algorithms are characterized by a high computational complexity. To overcome this drawback, we derive an iterative algorithm which leads to low complexity, high performance CFO and channels estimation. The performance of our algorithms is compared with existing approach by simulations.
La revue : Wireless Personal Communications
Domaine : Telecommunications
Mots Clés : Joint Semi-Blind Estimation
Auteur : Mokhtar Besseghier; Djebbar Ahmed Bouzidi; Iyad Dayoub
Issn : 0929-6212 Eissn : 1572-834X vol : 81, Num : 2, pp : 473-487
Date de publication : 2014-11-01
Résume : The large number of subcarriers, used in OFDM systems, increases the sensivity to frequency offset which results from a Doppler shift, due to mobile movement, as well as from a mismatch between the carrier frequencies at the transmitter and receiver. The problem of channel estimation in a practical OFDM receiver that suffers from CFO has been addressed in this paper. We first derived the modified MUSIC based blind CFO estimator. Next, we propose new joint training-based and joint semi-blind CFO and channel estimation for OFDM systems. Whereas the training-based estimator only assumes knowledge of pilot tones, the semi-blind estimator assumes knowledge of the virtual subcarriers (VSCs). For both estimators we derive a maximum likelihood (ML) algorithm for block processing and LMS algorithm for adaptive processing. It is demonstrated that the CFO estimators are able to perform well with a very small number of OFDM blocks. The performance of our estimators was investigated by simulations.
La revue : AEU - International Journal of Electronics and Communications
Domaine : Telecommunications
Mots Clés : Joint Semi-Blind Estimation
Auteur : Mokhtar Besseghier; Djebbar Ahmed Bouzidi
Issn : 1434-8411 Eissn : 1434-8411 vol : 69, Num : 4, pp : 759-764
Date de publication : 2015-01-19
Résume : The greatest threat to the OFDM system is the loss of orthogonality between subcarriers due to the carrier frequency offset (CFO) which results in significant performance degradation. In addition to this last problem was the effect of propagation over multipath fading channel. Hence, both the channel and the CFO need to be estimated and corrected at the receiver for subsequent symbol detection. A new joint semi-blind CFO and channel estimation method for OFDM systems operating in multipath fading channels is investigated in this paper. The proposed algorithms are based on virtual subcarriers (VSC) in one hand and on a new design of pilot patterns in OFDM blocks in other hand. We propose to use Newton-Raphson algorithm for the estimation of CFO that has a faster convergence and a lower complexity compared to similar estimators that not employed this algorithm. Finally, we derive the Modified Cramer-Rao bounds (MCRB) for semi-blind CFO and channel estimation to evaluate the performance bounds of the proposed methods for commonly encountered scenarios. The simulation results are given to verify the validity of the proposed methods.
La revue : IET Communications
Domaine : Telecommunications
Mots Clés : STBC-OFDM
Auteur : Brahim Dehri; Mokhtar Besseghier; Djebbar Ahmed Bouzidi; Iyad Dayoub
Issn : 1751-8628 Eissn : 1751-8636 vol : 13, Num : 17, pp : 2827 - 2833
Date de publication : 2019-10-29
Résume : Here, the authors propose a robust blind digital modulation classification (BDMC) algorithm for space time block coding (STBC)-based MIMO-OFDM system in the presence of carrier frequency offset (CFO) and channel estimation errors. Previous papers published on the topic of modulation identification were limited to single-carrier systems operating over frequency-flat channels. The problem of joint channel and CFO estimation in conjunction with blind digital modulation classification for STBC-OFDM in frequency selective channel and in the presence of the impulsive noise has not been addressed before to the best of their knowledge. To cope with performance degradation of BDMC due to CFO and channels errors, they propose joint semi-blind CFO and channels estimation methods. Higher order statistics (HOS), used for feature extraction, are combined with pattern recognition methods to solve the modulation identification problem. The main contribution of their work is the development of estimators, the study of their impacts on the blind classification capability, and the use of simulations to demonstrate the superior performance of the proposed algorithms.
La revue : Telecommunication Systems
Domaine : Telecommunications
Mots Clés : Estimation
Auteur : Mokhtar Besseghier; Djebbar Ahmed Bouzidi; Zouggaret Abdelhak; Iyad Dayoub
Issn : 1018-4864 Eissn : 1572-9451 vol : , Num : , pp :
Date de publication : 2019-12-24
Résume : Orthogonal frequency division multiplexing based cooperative system using Alamouti space–time block coding at relay node represents an alternative solution to achieve better connectivity and significant enhancement to the data rate in wireless fading channels. But, these advantages cannot be achieved without an efficient estimation of the channels which becomes more challenging for cooperative communications. This paper addresses the joint channel estimation and data detection for cooperative communication systems. Indeed, equispaced pilot symbols are used by maximum likelihood (ML) algorithm to derive channels estimator, and then equalizers are calculated and applied to improve receiver data detection. The main contribution of our work is the development of the ML estimator, the corresponding Cramer–Rao lower bound, mean square error, signal to interference plus noise ratio, outage probability, bit error probability and the use of simulations to demonstrate the superior performances of the proposed methods.
