International University of Rabat

of Rabat, Morocco

International University of Rabat

of Rabat, Morocco

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Cardenas-Juarez M.,University of Leeds | Ghogho M.,University of Leeds | Ghogho M.,International University of Rabat
IEEE Communications Letters | Year: 2011

The spectrum sensing duration and the secondary user's achievable throughput trade-off is optimized under outage constraints in a cooperative cognitive radio network over Nakagami fading conditions. The optimum trade-off depends not only on the maximum outage probability allowed by the primary user and the number of cognitive users involved in the sensing but also on the fading operational conditions of the cognitive radio. The parameters of the Nakagami fading distribution can be adjusted to fit different fading environments. The fading parameter (also called shape parameter) of the Nakagami distribution affects the optimum sensing time, which increases when the fading conditions are worse than Rayleigh fading. For the energy detector, the expression for the probability of false alarm is obtained in terms of a new threshold, which is derived considering an outage constraint on the channel-dependent probability of detection. Then, the optimization problem is formulated. Simulation results quantify the effects of different fading parameters on the optimum spectrum sensing duration. © 2006 IEEE.


Romero-Zurita N.,University of Leeds | Ghogho M.,University of Leeds | Ghogho M.,International University of Rabat | McLernon D.,University of Leeds
Physical Communication | Year: 2011

In this paper we address physical layer security in multiple-input-multiple-output (MIMO) frequency selective wireless channels in the presence of a passive eavesdropper, i.e., the associated channel is unknown to the transmitter. Signalling is based on orthogonal frequency division multiplexing (OFDM). Spatial beamforming and artificial noise broadcasting are chosen as the strategy for secure transmission. The contribution of channel frequency selectivity to improve secrecy is presented by performance and probabilistic analysis. Moreover, we investigate the capability of the eavesdropper to jeopardize the security of the system (defined as the SNR difference between the intended receiver and the eavesdropper) by mitigating the interfering effect of the artificial noise using zero forcing as a receive beamforming strategy. The results show that although zero forcing is not the optimal strategy to maximize the SNR, it offers (from the eavesdropper's perspective) a better performance than MMSE for MIMO frequency selective channels and thus threatens the overall security of the system. © 2011 Elsevier B.V.


Waqar O.,University of Leeds | Ghogho M.,University of Leeds | Ghogho M.,International University of Rabat | McLernon D.,University of Leeds
IEEE Communications Letters | Year: 2011

Since a closed-form expression for the exact ergodic capacity of dual-hop fixed-gain relay networks is not mathematically tractable, thus we will present tight closed-form bounds for the ergodic capacity in Rayleigh fading channels. First we express the exact ergodic capacity in terms of a Lommel function and a single integral and then we apply integral inequalities to present one upper bound and two lower bounds on the ergodic capacity. We also show that our closed-form bounds match perfectly with Monte-Carlo simulations, particularly for moderate and high average signal-to-noise ratio (SNR) of the first hop. © 2011 IEEE.


Romero-Zurita N.,University of Leeds | McLernon D.,University of Leeds | Ghogho M.,University of Leeds | Ghogho M.,International University of Rabat | Swami A.,U.S. Army
IEEE Signal Processing Letters | Year: 2013

We address physical layer security in multiple-input-multiple-output (MISO) communications in the presence of an unknown passive eavesdropper. Beamforming and artificial noise broadcasting are chosen to increase communications security. We first study the effect of a close eavesdropper on security and then we define a 'Protected Zone' in the transmitter's vicinity. We present an optimisation strategy that intelligently sets the transmission power and the size of the protected zone to probabilistically achieve secrecy at a specified target secrecy rate. The results show that this strategy can achieve a high probability of secrecy by efficiently prioritising the use of the available resources. © 1994-2012 IEEE.


Cardenas-Juarez M.,University of Leeds | Ghogho M.,University of Leeds | Ghogho M.,International University of Rabat
Electronics Letters | Year: 2011

For a cognitive radio, there is a trade-off between time used for spectrum sensing and the achievable throughput. For given constraints on the probability of detection, finding the optimum sensing time that maximises secondary users'throughput is of great importance. This issue has been addressed previously but the effect of the unknown fading channel was not taken into account. When the fading channel is random and unknown, the constraints on the probability of detection cannot be met for all instantaneous signal-to-noise ratios. Here, a more realistic approach is adopted, which allows the constraint on the probability of detection to be in outage with a specified percentage. The spectrum sensing time/secondary user's achievable throughput trade-off is then formulated and optimised accordingly. © 2011 The Institution of Engineering and Technology.


Waqar O.,University of Leeds | McLernon D.C.,University of Leeds | Ghogho M.,University of Leeds | Ghogho M.,International University of Rabat
IEEE Transactions on Vehicular Technology | Year: 2010

The closed-form expressions of the probability density function (pdf) and the moment-generating function for the exact end-to-end signal-to-noise ratio (SNR) of variable-gain relay networks are unknown for generalized fading models; thus, the exact evaluation for the ergodic capacity of these systems is cumbersome. In this paper, we develop a new unified framework for the exact ergodic capacity of multihop networks equipped with variable-gain relays, assuming that channel-state information (CSI) is available only at the receiving terminals. The resulting expression (which is based on the exact end-to-end SNR) is in the form of a single truncated infinite series and is valid for an arbitrary number of hops and for various fading models that are typically encountered in realistic scenarios. Furthermore, we show that the exact ergodic capacity of dual-hop variable-gain relay networks can be written in terms of the ergodic capacities of two equivalent single-inputsingle-output (SISO) channels and one single-input-multiple-output channel (SIMO), the closed-form expressions of which are already available for many commonly used fading/shadowing models. Finally, we show that there is an exact match between the Monte Carlo simulation and theoretical results over a whole range of per-hop average SNR. © 2006 IEEE.


Salman N.,University of Leeds | Ghogho M.,University of Leeds | Ghogho M.,International University of Rabat | Kemp A.H.,University of Leeds
IEEE Sensors Journal | Year: 2014

Localization of sensor nodes in wireless sensor networks (WSNs) promotes many new applications. A longer life time is imperative for WSNs, this requirement constrains the energy consumption and computation power of the nodes. To locate sensors at a low cost, the received signal strength (RSS)-based localization is favored by many researchers. RSS positioning does not require any additional hardware on the sensors and does not consume extra power. A low complexity solution to RSS localization is the linear least squares (LLS) method. In this paper, we analyze and improve the performance of this technique. First, a weighted least squares (WLS) algorithm is proposed, which considerably improves the location estimation accuracy. Second, reference anchor optimization using a technique based on the minimization of the theoretical mean square error is also proposed to further improve performance of LLS and WLS algorithms. Finally, to realistically bound the performance of any unbiased RSS location estimator based on the linear model, the linear Cramer-Rao bound (CRB) is derived. It is shown via simulations that employment of the optimal reference anchor selection technique considerably improves system performance, while the WLS algorithm pushes the estimation performance closer to the linear CRB. Finally, it is also shown that the linear CRB has larger error than the exact CRB, which is the expected outcome. © 2001-2012 IEEE.


Bakhouya M.,International University of Rabat | Gaber J.,University of Technology of Belfort - Montbéliard
Procedia Computer Science | Year: 2014

Adaptive systems are composed of different heterogeneous parts or entities that interact and perform actions favouring the emer-gence of global desired behavior. In this type of systems entities might join or leave without disturbing the collective, and the system should self-organize and continue performing their goals. Furthermore, entities must self-evolve and self-improve by learn-ing from their interactions with the environment. The main challenge for engineering these systems is to design and develop distributed and adaptive algorithms that allow system entities to select the best suitable strategy/action and drive the system to the best suitable behavior according to the current state of the system and environment changes. This paper describes existing work related to the development of adaptive systems and approaches and shed light on how features from natural and biological systems could be exploited for engineering adaptive approaches. © 2014 Published by Elsevier B.V.


Li W.,National University of Defense Technology | Ghogho M.,University of Leeds | Ghogho M.,International University of Rabat | Chen B.,National University of Defense Technology | Xiong C.,National University of Defense Technology
IEEE Communications Letters | Year: 2012

A novel approach for ensuring confidential wireless communication is proposed and analyzed from an information-theoretic standpoint. In this approach, the legitimate receiver generates artificial noise (AN) to impair the intruder's channel. This method is robust because it does not need the feedback of channel state information (CSI) to the transmitter and does not assume that the number of Eve's antennas should be smaller than that of Bob. Furthermore, we propose a new concept of outage secrecy region to evaluate the secrecy performance from a geometrical perspective. This should be useful if we need to know what zone should be protected (or militarized). Analysis and simulation results in practical environments show that the proposed method has a good performance. © 2012 IEEE.


Romero-Zurita N.,University of Leeds | Ghogho M.,University of Leeds | Ghogho M.,International University of Rabat | McLernon D.,University of Leeds
IEEE Signal Processing Letters | Year: 2012

In this letter, we address physical layer security in MISO communications in the presence of passive eavesdroppers, i.e., the eavesdroppers' channels are unknown to the transmitter. Spatial beamforming and artificial noise broadcasting are chosen as the strategy for secure transmission. With the aim of guaranteeing a given probability of secrecy, defined by quality of service constraints at the intended receiver and at the eavesdroppers, an optimum power allocation strategy between transmitted information and artificial noise is proposed. Both power constrained and power unconstrained systems are considered. Our proposed outage probability-based approach compares favourably to an existing second-order-statistic-based approach. © 2006 IEEE.

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