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Tunisia

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Tunisia
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Lahsini C.,SYSCOM Laboratory | Zaibi S.,SYSCOM Laboratory | Bouallegue A.,SYSCOM Laboratory
Proceedings - 2016 International Conference on Wireless Networks and Mobile Communications, WINCOM 2016: Green Communications and Networking | Year: 2016

Today's the paradigm for video compression has been significant development represented by the emergence of an important number of international standards efforts of ITU-TVCEG and ISO-IEC MPEG. The main objective of the current systems (such as the standards of MPEG-X and H-E6X) is to compress the original information in order to reduce the transmission rate. © 2016 IEEE.


Laouini N.,SYSCOM Laboratory | Ben Hadj Slama L.,INNOVCOM Laboratory | Bouallegue A.,SYSCOM Laboratory
International Conference on Multimedia Computing and Systems -Proceedings | Year: 2014

Layered decoding is well appreciated in Low-Density Parity-Check (LDPC) decoder implementation since it provides efficient and high-throughput implementation of LDPC decoders. Variable-Node Layered Belief Propagation (VL-BP) algorithm and their reduced-complexity derivatives for LDPC codes are presented. The VL-BP algorithm is a modification of Belief Propagation algorithm (BP), where the variable nodes are divided in subgroups called layers and each iteration is broken into multiple sub-iterations. Some simplifications can also be made to lower the complexity of both BP and CL-BP algorithms, and particularly the complexity of the check node update rule. In this paper, we consider Variable Node Layered BP (VL-BP) algorithm and propose an optimized min-sum VL-BP (MS VL-BP) algorithm for decoding LDPC code which has better performance not only from MS VL-BP algorithm but also from BP algorithm. In this decoding method, unlike other layered algorithms, we consider for the first layer a set of variable nodes that has a low value of the intrinsic information. Simulation results show that good performance can be achieved, and which can even be improved by the addition of either a normalization term or an additive offset term. © 2014 IEEE.


Laouini N.,SYSCOM Laboratory | Ben Hadj Slama L.,INNOVCOM Laboratory | Bouallegue A.,SYSCOM Laboratory
2012 9th International Conference on High Capacity Optical Networks and Enabling Technologies, HONET 2012 | Year: 2012

The Layered Belief Propagation L-BP algorithm is is a modified Belief Propagation BP algorithm, where the check nodes are divided in subgroups called layers and each iteration is broken into multiple sub-iterations. In this paper, we consider layered belief propagation decoding and propose an efficient variable node layering for decoding LDPC codes that performs well. We compare the performance of the first introduced LDPC decoding algorithm BP and Layered BP using check node layering with Layered BP using variable node layering in terms of bit error rate (BER). We show that the convergence for decoding LDPC codes is increasing by using a simple and efficient layering strategy. © 2012 IEEE.


Laouini N.,SYSCOM Laboratory | Ben Hadj Slama L.,INNOVCOM Laboratory | Bouallegue A.,SYSCOM Laboratory
4th International Conference on Communications and Networking, ComNet 2014 - Proceedings | Year: 2014

Shuffled decoding is known to provide efficient and high-throughput implementation of LDPC decoders. In this paper, a new grouping technique of variable nodes to accelerate the message-passing rate is presented. In this algorithm, unlike other group-shuffled decoding methods, we consider for the first sub-group a set of variable nodes that has a low value of the intrinsic information, where the variable nodes of the code graph are divided into sub-groups called layers to perform group-by-group message-passing decoding and each iteration is broken into multiple sub-iterations. This paper proposes a simplification of the Variable Node group-shuffled Belief Propagation (Optimized VN group-shuffled BP) to lower the complexity of the check node update rule. Simulation results, verify that the Optimized VN group-shuffled BP does yield a faster convergence rate than both Belief Propagation (BP) and Check Node group-shuffled Belief Propagation (CN group-shuffled BP) decoder. © 2014 IEEE.


Oueslati N.,SysCom Laboratory | Aguili T.,SysCom Laboratory
ICEIE 2010 - 2010 International Conference on Electronics and Information Engineering, Proceedings | Year: 2010

This paper proposes a solution to deal with the problem of the errors introduced by the presence of discontinuities in planar microstrip circuits in computing some physical quantities, like the distribution of the current, by the moment method. In this approach, we combine the Moment Method (MoM) with the method of generalized equivalent circuit (MCEG) [1] for analyzing step discontinuities in microstrip circuits. The interest of the method is the translation of an electromagnetic problem to an electric one and the use of a few number of subdomain trial functions in the base of entire domain trial functions in the moment method, generally one or two functions by interface to correct the mistake of the results at the discontinuities of the structure. Furthermore, the obtained results are conformed to theory with respect to the boundary conditions and they are reasonably in good agreement with previously published data. © 2010 IEEE.


Metya S.K.,Malaviya National Institute of Technology, Jaipur | Janyani V.,Malaviya National Institute of Technology, Jaipur | Modani S.G.,Malaviya National Institute of Technology, Jaipur | Najjar M.,SysCom Laboratory
Optical and Quantum Electronics | Year: 2013

Polarization mode dispersion (PMD) which is the time space varying nature of two parallel splitting rays polarized perpendicularly in single mode fiber, causes a serious problem in high bit rate transmission. We evaluated the PMD induced system penalty by means of simulations for Miller and Manchester signals under similar conditions and found that Miller is more tolerant to PMD than Manchester. © 2012 Springer Science+Business Media, LLC.


Mhamdi B.,Syscom Laboratory | Grayaa K.,Syscom Laboratory | Aguili T.,Syscom Laboratory
AEU - International Journal of Electronics and Communications | Year: 2011

The application of three techniques for the reconstruction of the permittivity profile of cylindrical objects from scattered field measurements is studied in the present paper. These approaches are applied to two-dimensional configurations. After an integral formulation, a discretization using the method of moments (MoM) is applied. Considering that the microwave imaging is recast as a nonlinear optimization problem, a cost functional is defined by the norm of a difference between the measured scattered electric field and that calculated for an estimated relative permittivity distribution. Thus, the permittivity profile can be obtained by minimizing the cost functional. In order to solve this inverse scattering problem, three techniques are employed. The first is based on a basic real coded genetic algorithms (GAs). The second is a hybrid technique (mGA-CG) which is based on a conjunction of a micro genetic algorithm (mGA) approach with the conjugate gradient based method (CG). The third is an application of an artificial neural network (ANN) having multilayered perceptrons architecture (MLPs). Three algorithms: conjugate gradient with PolakRibiere updates (CGP), LevenbergMarquardt (LM) and gradient descent (GD) are used to train the ANN. Computer simulations of these methods are performed for reconstruction of circular cylinders against laboratory-controlled microwave data. © 2010 Elsevier GmbH. All rights reserved.


Hakimi W.,Syscom Laboratory | Ammar M.,Syscom Laboratory
2011 3rd International Conference on Next Generation Networks and Services, NGNS'2011 | Year: 2011

It is well known that HARQ technique generates delays du to the retransmissions. Thus, the high speed real time services quality, in High Speed Downlink Packet Access (HSDPA), depends on the number of the retransmissions. Motivated by the important diversity that multiple transmitting antennas and multiple receiving antennas (MIMO) can provide, we study the possibility to avoid HARQ retransmissions by using evolved detector as Multipath Parallel Interference Canceller (MPIC) associated to MIMO. Based on generalized Alamouti codes, then, we demonstrate that MIMO 44 MPIC detector could give better performance than MIMO 22 Space-time Rake taking into account the HARQ context. © 2011 IEEE.


Nejla O.,SysCom Laboratory | Aguili T.,SysCom Laboratory
PIERS 2010 Cambridge - Progress in Electromagnetics Research Symposium, Proceedings | Year: 2010

In this work, we propose a solution to deal with the problem of the errors introduced by the presence of discontinuities in planar microstrip circuits in computing some physical quantities, like the distribution of the current, by the moment method (MoM). This approach combines the Moment Method with the generalized equivalent circuit method to analyze a planar circuit. The interest of the method is the use of the attachment functions in the base of trial functions in the moment method, generally one or two functions by interface. In order to assess its efficiency, the proposed method is developed for analyzing discontinuities in a rectangular microstrip antenna. To achieve this purpose, the current traveling on the feed line toward the patch edge is calculated and the coupling coefficient of a rectangular microstrip antenna array in H-plane configuration is investigated. The convergence study of the matrix in TE and TM mode is highlighted.


Mhamdi B.,Syscom Laboratory | Grayaa K.,Syscom Laboratory | Aguili T.,Syscom Laboratory
International Multi-Conference on Systems, Signals and Devices, SSD'11 - Summary Proceedings | Year: 2011

In this paper, a microwave imaging technique for reconstructing the shape of two-dimensional perfectly conducting scatterers by means of a stochastic optimization approach is investigated. Based on the boundary condition and the measured scattered field derived by transverse magnetic illuminations, a set of nonlinear integral equations is obtained and the imaging problem is reformulated in to an optimization problem. A hybrid approximation algorithm, called PSO-SA, is developed in this work to solve the scattering inverse problem. In the hybrid algorithm, particle swarm optimization (PSO) combines global search and local search for finding the optimal results assignment with reasonable time and simulated annealing (SA) uses certain probability to avoid being trapped in a local optimum. The hybrid approach elegantly combines the exploration ability of PSO with the exploitation ability of SA. Reconstruction results are compared with exact shapes of some conducting cylinders; and good agreements with the original shapes are observed. © 2011 IEEE.

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