Ariana, Tunisia
Ariana, Tunisia

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Massaoudi A.,SupCom | Sellami N.,University of Sfax | Siala M.,SupCom
IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC | Year: 2013

Cognitive radio is a promising technique for efficient spectrum utilization in wireless systems. In this paper, we consider an underlay cognitive radio system where a large number of secondary users (SUs) can share the spectrum with a primary user (PU). We assume that M antennas are used at the cognitive base station (CBS) and the CBS does not have the full channel state information (CSI) from secondary users. We propose to study the problem of secondary users scheduling under the assumption of imperfect CSI of the interference channel between the CBS and the primary receiver. In order to minimize the interference to the PU, we propose to generate orthogonal beams to the estimate of the channel between the CBS and the PU. Then, to reduce the amount of required feedback, we propose a scheduling algorithm based on opportunistic beamforming. To further reduce the amount of feedback, a threshold is applied to the signal to interference and noise ratio (SINR) feedback. For the proposed scheme, we develop a statistical analysis for the interference caused to the PU as well as the throughput of the secondary system. © 2013 IEEE.

Ayadi R.,Supcom | Kammoun I.,University of Sfax | Siala M.,Supcom
IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC | Year: 2013

This paper investigates space-frequency (SF) coding for non-coherent (NC) Multiple Input Multiple Output (MIMO)-Orthogonal Frequency Division Multiplexing (OFDM) fading links, where neither the transmitter nor the receiver knows the channel. Our strategy consists in distributing the convolutional encoded and interleaved bits over the different transmit antennas, OFDM tones and OFDM symbols. The combination of the convolutional coding and bit interleaving with the SF coding can exploit the maximum spatial/frequency diversity over frequency-selective channels. In order to reduce the decoding complexity, we divide the OFDM symbol into several groups and apply differential encoding and decoding between adjacent groups. The proposed NC SF matrix is designed as a combination of a differential Cayley code and a systematic NC SF code, which leads to a simple decoding rule over the multipath channel. We show through asymptotic Pairwise Error Probability (PEP) analysis and simulation results that our encoding strategy can provide full diversity gain and achieves better performance in terms of spectrum efficiency and symbol error rate than all three the systematic NC-SF coding, the Cayley differential SF coding and our proposed SF coding without convolutional encoding and bit interleaving. © 2013 IEEE.

Massaoudi A.,SupCom | Sellami N.,University of Sfax | Siala M.,SupCom
2014 1st International Conference on Advanced Technologies for Signal and Image Processing, ATSIP 2014 | Year: 2014

Cognitive radio holds tremendous promise for increasing spectral efficiency in wireless systems. In this paper, we consider an underlay cognitive radio system where a large number of secondary users (SUs) can share the spectrum with a primary user (PU). We assume that M antennas are used at the cognitive base station (CBS) and the CBS does not have the full channel state information (CSI) from users. We propose to study the problem of secondary users scheduling under the constraint of interference to the PU while maximizing the throughput of the secondary system. In order to reduce the amount of required feedback, our scheduling algorithm is based on opportunistic beamforming. It consists of two steps. In the first step, the cognitive base station constructs N matrices of (M-m) nonorthogonal beams, 0 ≤ m ≤ M-1. The primary user selects the one which minimizes the interference to itself and sends the index of selected beamforming matrix to the CBS. In the second step, the (M-m) cognitive users having the highest signal to interference and noise ratios (SINRs) are selected for transmission, which can be done with little feedback. Simulation results show that our algorithm achieves a good tradeoff between interference to the PU and secondary system throughput. © 2014 IEEE.

Belmabrouk H.,University of Monastir | Bouallegue R.,SupCom
STA 2014 - 15th International Conference on Sciences and Techniques of Automatic Control and Computer Engineering | Year: 2014

In this paper, we aim at presenting a detailed classification of the most known authentication protocols using quantum means with calculation of quantum communication complexity. The Quantum Key Distribution protocols were basically proposed to establish secret keys that will be used later for encrypting and decrypting messages. Practically, QKD protocols are vulnerable against the men-in-middle attack. Thereby, in order to prevent masquerading any legitimate user and tampering with the communication, QKD schemes need authentication prior to communication. Many quantum authentication protocols have been proposed in the literature. Each one has a particular approach to authenticate the communicators. We attempt in the present work to introduce the various ways of quantum authentication and to classify them according to some specific criteria with a calculation of the quantum communication complexity. © 2014 IEEE.

Kaaniche M.,Telecom ParisTech | Pesquet J.-C.,University Paris Est Creteil | Benazza-Benyahia A.,SupCom | Pesquet-Popescu B.,Telecom ParisTech
ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings | Year: 2010

Many existing works related to lossy-to-lossless image compression are based on the lifting concept. However, it has been observed that the separable lifting scheme structure presents some limitations because of the separable processing performed along the image lines and columns. In this paper, we propose to use a 2D non separable lifting scheme decomposition that enables progressive reconstruction and exact decoding of images. More precisely, we focus on the optimization of all the involved decomposition operators. In this respect, we design the prediction filters by minimizing the variance of the detail signals. Concerning the update filters, we propose a new optimization criterion which aims at reducing the inherent aliasing artefacts. Simulations carried out on still and stereo images show the benefits which can be drawn from the proposed optimization of the lifting operators. ©2010 IEEE.

Abdelmoumen M.,SupCom | Frikha M.,SupCom | Chahed T.,Orange S.A.
2015 International Symposium on Networks, Computers and Communications, ISNCC 2015 | Year: 2015

The performance of Delay Tolerant Mobile Networks (DTMNs) depends on the mobility pattern through the nodes encounter process which constitutes opportunities for exchange of information between nodes. However, the exchange of information itself depends also on the routing/replication protocol and the network ressources as the node buffer capacity and which determines the effective network performance. We focus in this work on those two concepts: encounter and exchange, and evaluate them along with resulting network performance for different mobility patterns and routing protocols as well as under the limited buffer space constraint. We also propose the use of additional, mobile, dedicated relays so as to enhance the performance of the DTMN in cases of ill-behaved mobility schemes. © 2015 IEEE.

Jabeur T.B.,University of Paris Descartes | Abed-Meraim K.,Telecom ParisTech | Boujemaa H.,SupCom
Physical Communication | Year: 2012

In OFDM systems, the Inter-Symbol Interference (ISI) and the Inter-Block Interference (IBI) are mitigated by using Null-Tones (NTs) and the Guard Interval (GI) redundancy of length higher than the channel size. To preserve a high bit rate, channel shortening is required to reduce the GI length. We propose here a new adaptive method for the blind estimation of the Time domain EQualizer (TEQ) for time varying communication channels. Our contribution is three-fold. First, we exploit the knowledge of the first emitted symbol in a differential encoded OFDM system to derive the initial estimate of the TEQ. Then, we update the TEQ coefficients according to the channel variation by optimizing a criterion exploiting both the GI and NT redundancies and using a fast Generalized Eigen Value (GEV) tracking algorithm. Finally, the optimization of the previous criterion is achieved in such a way we control the Target Impulse Response (TIR) quality and we improve the overall system performance. Simulation results are provided to illustrate the performance of our method and assess our theoretical derivations. © 2011 Elsevier B.V.

Ben Jebara S.,SupCom | Besbes H.,Concordia University at Montréal | Jaidane M.,Campus University
European Signal Processing Conference | Year: 2015

This paper deals with the use of adaptive predictive algorithms in order to improve tracking performances of classical identification scheme. The performances of coupled structure depend on the prediction device. In this paper, we present a new robust algorithm for the predictive scheme. The robustness deals with insensibility of proposed algorithm to the input statistics variations, namely the power and fourth order statistics. We illustrate our contribution by performances evaluation of the proposed structure in double non stationary context: on tracking random walk channel with speech input signal. © 2000 EUSIPCO.

Ayadi M.,SupCom | Zineb A.B.,SupCom
IEEE Transactions on Wireless Communications | Year: 2014

Generally empirical models are developed on the basis of measurements achieved in empty buildings. But in practice human bodies and furniture presence induce a considerable fluctuation leading to huge differences between predictions and real measurements. In this paper a new indoor large scale path loss empirical model is presented. The model design, in addition to the considered phenomena in conventional empirical formulation, integrates additional suggestions recommended by electromagnetic techniques such as body shadowing and furniture effects. To achieve this work, a large number of experimental measurements have been carried on and saved in consequently voluminous databases. Their management and exploitation have considered data mining and especially neural networks to perform the new model called neural model. To prove model enhancement and accuracy we compare the 'neural model' predictions with measurements. Obtained results show that the mean error is close to zero, the standard deviation is about 4.47 dB with a correlation factor of 97%. © 2002-2012 IEEE.

Rejichi S.,Supcom | Chaabane F.,Supcom
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2011

This paper proposes a new HR spatio-temporal vegetation classification approach based on SVM. A multi-band SVM approach is first applied on satellite images time series then a graph based SVM algorithm is used for temporal analysis. © 2011 SPIE.

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