Jalel Chebil

Properties of digital image watermarking

Digital image watermarking techniques have been developed widely in recent years to maintain the broadcasting media and content authentication, broadcast monitoring, copy control, and many other applications. Therefore, many studies have used digital image watermarking to solve these problem. This paper highlights digital image watermarking. It starts with a basic model of digital image watermarking, it discusses the main requirements and applications. Moreover, it reviews some of the techniques and algorithm used in image watermarking. In addition, digital image watermarking attacks are discussed. Lastly, Watermarking evaluation system is described.

Carrier aggregation in Long Term Evolution-Advanced

Long Term Evolution-Advanced (LTE-Advanced) provides considerably higher data rates than even early releases of LTE. One key enhancement feature is bandwidth extension by the use of multicarrier technology to support deployment bandwidth up to 100 MHz. In order to achieve up to 1 Gb/s peak data rate in IMT-Advanced mobile systems, carrier aggregation technology is introduced by the 3GPP to support very-high-data-rate transmissions over wide frequency bandwidths (e.g., up to 100 MHz) in its new LTE-Advanced standards. The carrier aggregation (CA) technology allows scalable expansion of effective bandwidth provided to a user terminal through simultaneous utilization of radio resources across multiple carriers. The CA in LTE-Advanced is designed to support aggregation of a variety of different arrangements of component carriers (CCs), including CCs of the same or different bandwidths, contiguous or non- contiguous CCs in the same frequency band, and CCs in different frequency bands. The CA is supported by both formats of LTE, specifically the frequency Division Duplex (FDD) and Time Division Duplex (TDD) variants. This guarantees that both FDD LTE and TDD LTE are able to meet the high data throughput requirements placed upon them. This paper provides an outline of carrier aggregation including aggregation structure, deployment scenarios, implementation, main design features and backward compatibility with legacy LTE systems.

Comparison of empirical propagation path loss models for mobile communications in the suburban area of Kuala Lumpur

The empirical propagation path loss models have important influence in mobile communication systems design. They become important tools in both research and industrial communities owing to their speed of implementation and their limited dependence on detailed knowledge of the terrain. The mobile services are increasing rapidly and hence the mobile stations are required to design with best quality of service. Path loss models are considered frequently to estimate power budgets and cell coverages. Four empirical models namely, the Lee model, the Stanford University Interim (SUI) model, the COST-231 Hata model and Egli model have been investigated in this work. The measurements were carried out at University Putra Malaysia (UPM) campus and Gombak area. The measured data is used to validate the applicability of the four models mentioned previously in suburban environments. The results show that Egli model, COST-231 Hata model and SUI model over-predict the path loss in all coverage areas. The Lee model shows the best performance to the measured path loss.

Design of a triple-band h slot patch antenna

This paper attempts to design a triple band h-slot antenna by using feed line technique. These bands cover GSM mobile phone system (0.9 and 1.8 GHz) and ISM band which is used for Bluetooth and wireless local area network bands applications. The CST microwave studio software is used as a tool for simulation. This antenna is an attractive candidate for important applications like mobile phone communication systems, mobile phone jammer application, and so on.

Femtocell interference mitigation

The demand for the Femtocells deployment is in the rise since it enhances the wireless link and increase the capacity for the wireless network. Femtocell is a home base station designed for use in residential and business areas such as houses, apartments, offices, schools, and markets. It connects to the service providers network via broadband and normally supports 2 to 6 mobile phones in a small area. Using femtocell will enhance the indoor coverage, save power since it reduces the transmitted power, and in the same time reduce the traffic on microcell. However, the most important challenge in femtocell deployment is interference mitigation and management. In this paper, a state of the art literature review on mitigating interference is presented. First, interference in femtocell environment is classified from different point of views. Then, open issues for femtocell interference research are discussed.

Identification of linearized regions of non-linear transducers responses

Transducers have found wide applications in industries, though, they possess nonlinear responses. The nonlinearity feature does not prevail over the entire range; rather there are sections (or regions) on the response curves that are easily regarded as linear. This work focuses on analyzing transducer characteristics by finding regions exhibiting larger level of linearity. The point of inflection is a joint between two consecutive linear segments, and it is where changes in the output signal in response to external parameter variations remain at minimum compared to its immediate neighboring points. It is shown through simulations on how, assuming that a given system does not operate over the entire range of the response curve, a linear response is assured. This is done by translating the circuit operating over the linear section by employing additional external circuit elements. This paper attempts at analyzing a transducer characteristics by showing regions around the points of inflections where variations remain most linear.

Development of an Empirical Dust Storm Attenuation Prediction Model for Microwave Links in Arid Area - A Proposed Framework

Wireless communication service providers are currently facing challenges due to the congested frequencies spectrum which has imposed the use of higher and higher frequencies. However, higher frequency bands are more sensitive to weather condition and the microwave signal attenuation due to atmospheric particles increases rapidly at higher frequency bands. Consequently dust storms and all related phenomena may cause signal attenuation which can consequently limit the performance of wireless communication systems specially frequencies above 10GHz for arid area. The aim of this paper is to show that real dust storm is a complex phenomena which is difficult to be described by the theoretical physical or mathematical models. An empirical dust storm prediction model based on the long term statistical observations of dust storm properties and its corresponding microwave signal levels will be a step forward to provide microwave link designers with a precise tool to rely on. This paper has proposed a research framework to collect necessary data from Khartoum, Sudan and develop an empirical attenuation prediction model.

A novel scheme for performing wireless distributed computing with strip spectral correlation algorithm

Various techniques are introduced for cognitive radio (CR) technology to perform on the spectrum sensing. The most important factor to distinguish between these techniques is the accuracy. However, computational complexity, consumed power and sensing duration are increasing proportionally with the higher accuracy rate. Cyclostationary feature detection is one of those accurate and computationally taxing approaches. To the best of our knowledge, this paper can be considered as the first research for applying wireless distributed computing (WDC) with spectrum sensing which introduces a novel technique to reduce the complexity of one of the practical methods used in cyclostationary feature detection i.e. the strip spectral correlation algorithm (SSCA) by performing WDC. First, the paper demonstrates the capability of distributing the workload for computing the spectral correlation function (SCF) between the cooperative CRs. Second, it discusses the channel effect on the reliability of SCF.

Rain attenuation analysis using synthetic storm technique in Malaysia

Generated rain attenuation time series plays an important role for investigating the rain fade characteristics in the lack of real fade measurements. A suitable conversion technique can be applied to measured rain rate time series to produce rain attenuation data and be utilized to understand the rain fade characteristics. This paper focuses on applicability of synthetic storm technique (SST) to convert measured rain rate data to rain attenuation time series. Its performance is assessed for time series generation over a tropical location Kuala Lumpur, in Malaysia. From preliminary analysis, it is found that SST gives satisfactory results to estimate the rain attenuation time series from the rain rate measurements over this region.

Preliminary Analysis of Dust Effects on Microwave Propagation Measured in Sudan

Dust storms are meteorological phenomena which occur for a percentage of time in arid and semi arid areas especially at African Sahara and Middle East. Measurements at existing microwave links have showed dust storms can potentially result in serious attenuation in signal level especially at Ku band and higher frequencies with direct impact on telecommunications system performance. Only a limited amount of research has been carried out and the available data was very scarce. Few prediction models have been developed to estimate microwave signal attenuation during the dust storm based on scattering theory and approximation of dust properties. However, real dust storm is a complex phenomenon which is difficult to be described by theoretical physical or mathematical models [5–6]. In this paper, an evaluation of the existing attenuation prediction models has been done based on the measured dust storm properties and measured attenuation in Sudan.