Sofiane Cherif
Carthage University
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Publication
Featured researches published by Sofiane Cherif.
The Scientific World Journal | 2013
Mohamed Maalej; Sofiane Cherif; Hichem Besbes
Wireless sensor networks (WSN) are presented as proper solution for wildfire monitoring. However, this application requires a design of WSN taking into account the network lifetime and the shadowing effect generated by the trees in the forest environment. Cooperative communication is a promising solution for WSN which uses, at each hop, the resources of multiple nodes to transmit its data. Thus, by sharing resources between nodes, the transmission quality is enhanced. In this paper, we use the technique of reinforcement learning by opponent modeling, optimizing a cooperative communication protocol based on RSSI and node energy consumption in a competitive context (RSSI/energy-CC), that is, an energy and quality-of-service aware-based cooperative communication routing protocol. Simulation results show that the proposed algorithm performs well in terms of network lifetime, packet delay, and energy consumption.
Signal Processing | 2010
Rim Elasmi-Ksibi; Hichem Besbes; Roberto López-Valcarce; Sofiane Cherif
The problem of frequency estimation of a real-valued sinusoid in colored noise is addressed. A new estimator using higher-order lags of the sample autocorrelation is proposed, and a statistical analysis is provided. Computer simulations are included to validate the theoretical development and to demonstrate that the proposed approach outperforms several existing frequency estimators in terms of estimation accuracy.
international conference on acoustics, speech, and signal processing | 1995
Sylvie Marcos; Sofiane Cherif; Meriem Jaidane
High speed data transmission over bandlimited and/or dispersive channels require equalization to remove the intersymbol interference (ISI) between the successive transmitted data. This paper presents the cancellation of intersymbol interferences (ISI) as a criterion for the blind adaptation of decision feedback equalizers (DFE). We show that this criterion is an alternative to the decision directed (DD) algorithm. This paper also proposes to replace the hard limiter in the decision device of the DFE by a soft decision implemented by a hyperbolic tangent function in order to escape from local minima during the initialization of the blind algorithms. As the theoretical investigation of these criteria and algorithms is difficult, we analyse some simple examples to illustrate the interest of the proposed solutions.
personal, indoor and mobile radio communications | 2011
Safa Essassi; Mohamed Siala; Sofiane Cherif
Recently, the 3rd Generation Partnership Project has standardized a power control mechanism for the uplink of the Long Term Evolution system. This mechanism is based on the fractional compensation of the pathloss, also known as fractional power control. This approach decreases inter-cell interference but may impact the throughput. In this paper, a novel approach power control will be proposed to avoid such throughput loss. This method still uses fractional power control principle, but differentiates between users generating high interference and users generating low interference. Our simulations indicate that the proposed power control has better performance than the fractional power control.
IEEE Transactions on Signal Processing | 2016
Imen Nasr; Benoit Geller; Leila Najjar Atallah; Sofiane Cherif
In this paper, we propose a new code-aided (CA) timing recovery algorithm for various linear constant modulus constellations based on the Maximum Likelihood (ML) estimator. The first contribution is the derivation of a soft estimator expression of the transmitted symbol instead of its true or hard estimated value which is fed into the timing error detector (TED) equation. The proposed expression includes the Log-Likelihood Ratios (LLRs) obtained from a turbo decoder. Our results show that the proposed CA approach achieves almost as good results as the data-aided (DA) approach over a large interval of SNR values while achieving a higher spectral efficiency. We also derive the corresponding CA Cramer Rao Bounds (CRB) for various modulation orders. Contrarily to former work, we develop here the CRB analytical expression for different M-PSK modulation orders and validate them through comparison to empirical CRB obtained by Monte Carlo iterations. The proposed CA estimator realizes an important gain over the nondata-aided approach (NDA) and achieves a smaller gap when compared to its relative CA CRB, especially at moderate SNR values where modern systems are constrained to work.
international conference on communications | 2014
Imen Nasr; Leila Najjar Atallah; Sofiane Cherif; Benoit Geller; Jianxiao Yang
Time delay synchronization is crucial for the reception quality in digital transmission systems. In this contribution, we consider a maximum likelihood approach and incorporate a soft-demapper to improve the synchronization performance. In particular, the proposed scheme allows to update the time delay at each symbol with an adaptive loop using the Log-Likelihood Ratio (LLR) of each bit provided by the demapper. Simulation results show that the proposed approach provides improvements compared to non data aided approach while avoiding data aided approach overhead.
personal, indoor and mobile radio communications | 2013
Safa Essassi; Sofiane Cherif; Mohamed Siala
The universal frequency reuse has been targeted for the Long Term Evolution. It leads to a harmful inter-cell interference experienced notably by the cell-edge users. The uplink inter-cell interference coordination becomes among the most important challenges. Throughout literature, many techniques were proposed to overcome this issue. Among these techniques, the soft frequency reuse concept grasped many attentions. Certainly, it succeeded in reducing the interference for edge-cell users by prohibiting the allocation of the same RB to two users in adjacent cells-edge. However, it presents several drawbacks in terms of spectral efficiency and overloaded cell-edge users. The most proposed approaches are based on this scheme. In this context, this study introduces a novel strategy that will avoid these shortcomings. Our idea aims to optimize the resource block allocation by using the genetic algorithm approach and maximizing channel capacity. We exploit information exchanged over the X2 interface. Simulation results show the effectiveness of our proposed approach.
Signal Processing | 2010
Rim Elasmi-Ksibi; Sofiane Cherif; Roberto López-Valcarce; Hichem Besbes
A novel unbiased frequency estimator for a single real-valued sinusoid in white noise is proposed, which is based on a normalized second-order infinite impulse response (IIR) notch filter, and can be seen as an extension of the Pisarenko harmonic decomposer (PHD) estimator. The new estimator inherits the simplicity of the PHD estimator and the high accuracy and selectivity achieved by an IIR filter. As the coefficient determining the pole angle of the IIR notch filter depends on the unknown frequency value, an iterative scheme is proposed in which this coefficient is computed from the frequency estimate from the previous iteration. An analytic expression for the mean square error at each iteration is derived. Simulation results show that this iterative method can approach the Cramer-Rao lower bound in a few iterations under different signal to noise ratio levels, provided that the data record length is sufficiently large.
international conference on communications | 2015
Imen Nasr; Leila Najjar Atallah; Benoit Geller; Sofiane Cherif
In this paper, we propose a maximum likelihood based Code-Aided (CA) timing recovery algorithm for square-QAM modulated signals. We also theoretically derive the analytical expression of the CA Crammaximum likelihood based Code-Aided (CA) timing recovery algorithmer-Rao Bound for time delay estimation. Our simulations show that the proposed CA approach realizes a performance equivalent to the Data-Aided (DA) approach over a large interval of signal to noise ratio (SNR) values.
vehicular technology conference | 2012
Imen Nasr; Sofiane Cherif
In cognitive radio systems, the accuracy of spectrum sensing depends on the received primary signal strength at the secondary user (SU). In fact, a single node sensing would be compromised if the received signal strength is not high enough to be detected by this node. In this paper, we propose a cooperative decision fusion rule based on adaptive linear combiner. The weights which correspond to confidence levels affected to SUs, are determined adaptively using the Normalized Least Mean Squares (NLMS) and the Recursive Mean Squares (RLS) algorithms. The proposed algorithms combine the SUs decisions with the adaptive confidence levels to track the surrounding environment. Simulation results show a high adaptability of the proposed scheme, as the operating conditions change. Furthermore, the proposed algorithms do not necessitate a prior knowledge about the PU features and are very efficient compared to conventional decision fusion techniques.