Abdelilah Ghammaz

Energy Detection Approach for Spectrum Sensing in Cognitive Radio Systems with the Use of Random Sampling

In radiomobile contexte, radio frequency spectrum is a ressource that needs to be used with appropriate efficiency. This can be achieved by the mean of spectrum sensing operation. This function consists to analyze the occupancy of the radio frequency spectrum in order to detect which bands are unused. This concept is largely appreciated in cognitive radio where more flexibility is required to adapt to the communication environment. Different techniques are presented in the literature. In this paper, we are interested by the application of the energy detector method for spectrum sensing. This application is performed in cognitive radio systems with the use of random sampling. The performance of this approach is evaluated in term of its receiver operating characteristic curve and compared to the uniform sampling case.

Development of Wideband Planar Inverted-F Antennas for Wireless Application

Problem statement: Due to the rapid development in wireless communication, the antennas capable of broad-band operations are very demanding in cellular communications systems. Among various possible antennas, planar inverted-F antennas (PIFAs) have the advantages of low profile and compact size and are very suitable for present-day wireless communication application. Approach: This study demonstrates a very effective method of bandwidth enhancement for planar inverted-F antenna. It was done by optimizing the width of feed plate and shorting plate, then by adding a parasitic element. Results: The obtained results of our developed wideband antenna was an impedance bandwidth of 72.8% for S11<-10 dB from 1.74-3.54 GHz which could cover GPS, DCS, IMT-2000, 2.4GHz WLAN, 3.5 GHz WIMAX applications. Conclusion: As the antenna was successfully researched and well optimized, and desired results were achieved.

Effects of changing dimensions on the planar inverted-F antenna performances

With the rapid growth of the wireless mobile communication technology, the future technologies need a very small antenna with a good performance, the advantage of planar inverted-F antenna (PIFA) make them very popular in many applications requiring a low profile antenna. This letter is aimed at addressing this problem by investigating the effects of changing the dimensions of each parameter of the planar inverted-F antenna on the impedance bandwidth, resonance frequency and gain. It is shown that a PIFA with a good performance can be achieved by optimizing the dimensions of the radiating plate, the ground plane and the height of the antenna.

Broadband triple-band CPW-fed patch antenna for WLAN/WiMAX operations

A triple-frequency patch antenna with coplanar waveguide (CPW)-fed structure is presented in this paper for simultaneously satisfying wireless local area network (WLAN) and worldwide interoperability for microwave access (WiMAX) applications. The proposed antenna mainly consists by three radiating elements: Stub1, Stub2 and Stub3 with a defected ground plane for band broadening. By adjusting the lengths of the three Stubs, three resonant frequencies can be achieved and adjusted separately. The simulated 10 dB bandwidth for return loss is from 2.07 to 2.73 GHz, 2.89 to 4.35 GHz and 4.6 to 7.06 GHz, covering all the 2.4/5.2/5.8 GHz WLAN bands and 2.5/3.5/5.5 GHz WiMAX bands. Furthermore, the patch antenna has a simple planar structure and occupies a small size of about 20×37 mm2; including the finite ground CPW feeding mechanism. Good dipole-like radiation characteristics over the operating bands are obtained.

A compact triple-band patch antenna for WLAN/WiMAX applications

A novel triple frequency patch antenna for WLAN/WiMAX applications is proposed and investigated in this paper. The antenna proposed is composed of three radiating elements: Stub1, Stub2 and Stub3. By adjusting the lengths of the three Stubs, three resonant frequencies can be achieved and adjusted separately. We present a microstrip patch antenna for worldwide interoperability for microwave access (WiMAX) standard at 3.5/5.5 GHz bands and wireless local area network (WLAN) operates at 2.4/5.2 GHz bands. This design results in a reduction in size and weight and allows integration in hand-held devices. Furthermore, nearly omnidirectional radiation patterns, reflection coefficient and gain over the operating bands have been obtained.

Modeling of Human Head Interaction with Planar Antenna for Multi Standard Cellular Phones

Many wireless communication devices are used with their antennas in close proximity of the human head. This fact changes the antenna characteristics and affects the communications performance on one hand, and causes the deposition of microwave energy in the users head, on the other hand. The amount of power absorbed by the human body is limited to a given maximum value, according to the two standards IEEEC95.1 and EN 50360. In this paper the design of a multiband compact antenna for integration into the multifunction mobile phones is presented. The specific absorption rate SAR of the planar antenna is calculated.

An Enhancement for the Autonomic Middleware-Level Scalability Management Within IoT System Using Cloud Computing

The integration of Clouds with IoT will help dealing with the incapability to scale automatically according to the overload caused by the massive growth of the connected devices number in the IoT networks. In this paper we aim to promote the scalability management, by improving the architectural design of the monitoring components using autonomic middleware for IoT systems based on Cloud Computing hybrid oriented scalability solution, in order to satisfy a maximum number of requests, while maintaining the system performances at an acceptable level. Experiments have been done so as to evaluate our solution performances, for different scenarios testbed. Generally, our results are better than existing cloud-based solution that tackles the scalability issue in IoT networks.

Numerical Analysis of Transmission Lines Equation by new β-method Schemes

Abstract In this paper we develop a new β-method applied to the resolution of homogeneous transmission lines. A comparison with conventional methods used for this type of problems like FDTD method or classical β-method is also given. Furthermore, various numerical experiments are presented to confirm the accuracy, efficiency and stability of our proposed method. In particular, these simulations show that our new scheme is unconditionally stable and fourth-order accurate in space and time.

Compact triband CPW-fed F-shaped monopole antenna with inverted L-slot for 2.1-GHz/WLAN/WiMAX applications

A novel coplanar waveguide (CPW)-fed F-shaped monopole antenna with inverted L-slot for 2.1-GHz band, Wireless Local Area Network (WLAN) and Worldwide Interoperability for Microwave Access (WiMAX) applications is proposed and investigated in this paper. The proposed antenna is composed of a CPW-fed F-shaped planar monopole and an inverted-L slot, which occupies a compact size of 25 (W) × 40 (L) mm2 including the ground plane. By adjusting the dimensions of the monopole and slot, three desired resonant frequencies can be achieved and tuned independently. The antenna exhibits three resonances covering the 2.1-GHz band, 5.2/5.8 GHz WLAN bands and 3.5/5.5 GHz WiMAX bands. The parameters which affect the performance of the antenna in terms of its frequency domain characteristics are studied in this paper. Details of the antenna design and simulation results are presented and discussed.

Computation of multiconductor transmission line capacitance using method of moment

The resolution of the telegraphers equations allow to determine the voltage and current magnitudes at any point on the line provided that the per-unit-length parameters of the components of the connections are rigorously determined. In this context, various formulations and methods have been developed to determine the per-unit-length parameters. In this paper, we are particularly interested in the resolution of the linear parameters of a multiconductor transmission line (MTL) with two numerical methods based on the method of moments.