Nadhir Ben Halima

A novel approach of digital image watermarking using HDWT-DCT

Watermarking is an interesting technique for message hiding and authentication. We have applied 3- level Haar-DWT and thereafter, DCT transformation on each selected HH3 subband is computed. In extraction the same procedure is used to retrieve watermark logo image from the DCT component of middle frequency subband of selected HH3 subband. To ensure the accuracy and image quality between watermarked image and host image the Mean Absolute Error, Peak SNR, and Weighted Peak SNR is computed. The simulation result shows that the proposed algorithm has significantly higher robustness against Gaussian noise, Salt & Pepper noise and cropping attack of watermarked image.

3D WLS hybrid and non hybrid localization using TOA, TDOA, azimuth and elevation

In this paper, we propose a Three Dimensional (3D) Weighted Least Square (WLS) estimation of mobile position using Time Of Arrival (TOA), Time Difference Of Arrival (TDOA), Direction of Arrival (DOA) given by azimuth and elevation measurement. We present both hybrid and non hybrid localization techniques. Hybrid localization techniques use a combination of TOA, TDOA and DOA whereas non hybrid localization use only TOA or TDOA or DOA measurement. This is the first paper to tackle the problem of 3D hybrid localization using TOA, TDOA, azimuth and elevation. We also present a theoretical performance analysis of the hybrid localization technique where the covariance matrix of the WLS estimator is derived in closed form expression. The theoretical derivation is valid for any distribution of the observation noise. We show that the WLS estimator is unbiased and equivalent to the Maximum Likelihood estimator when the observation noise is Gaussian. We also optimize the localization accuracy by optimizing the base station location in order to minimize the Mean Square Error. Base station location optimization to enhance localization accuracy has not been yet proposed.

Design, Implementation and Testing of a Cost Function Based Scheduling Mechanism for a Water Management System

Abstract The IEEE 802.15.4 standard for low data rate and low power devices is currently in use by many Internet of Things (IoT) networks and control networks based on wireless sensor networks. One such application area is the water management systems for water supply and usage control. With the implementation of this standard in Contiki, no mechanism is present for control messages when other packets are being transmitted as well in the network. The gateway devices in these networks are usually exposed to more load in the network. During periods of high demand, packet dropping can occur at these nodes as well as other intermediate nodes that forward data. To address the high packet loss and congestion that takes place when the load level is high in a water telemetry management network, we propose a novel scheduling mechanism. This scheduling mechanism was implemented in the COOJA simulator using the Contiki operating system for wireless sensor nodes as an enhancement to carrier sense multiple access with collision avoidance (CSMA/CA). The results show that with the application of the proposed cost function (CF) scheduling strategy, packet loss is reduced and throughput is improved in multi-hop networks over the default scheduling mechanism. This mechanism can also be implemented in other rapid growing Internet of Things (IoT) networks and can improve performance when carrying high loads.

Reactivity and social cooperation in a Multi-Robot System

Multi-Robot System (MRS) is an important research area within Robotics and Artificial Intelligence. The balancing between reactivity and social cooperation in autonomous robots is really considered as a challenge to get an effective solution. To do so, we propose to use the concept of five capabilities model which is based on Environment, Self, Planner, Competence and Communication. We illustrate our line of thought with a Benchmark Production System used as a running example to explain our contribution.

Building Multi-Robot System based on five capabilities model

Multi-Robot System (MRS) is considered as a particular form of Multi Agent System (MAS) by specifically addressing planning and social abilities. The design of autonomous robots includes the design of team behaviors constituted by several intelligent agents each one has to interact with the other autonomous robots. The problem faced is how to ensure a distributed planning through the cooperation of the distributed robotic agents. To do so, we propose to use the conept of five capabilities model which is based on Environment, Self, Planner, Competence and Communication. We illustrate our line of thought with a Benchmark Production System used as a running example to explain our contribution.

Routing in Cognitive Wireless Mesh Networks - An Intelligent Framework

Wireless Networks are limited in energy and resources, are subject to development constraints. The difficulties are such as the increasing RF spectrum saturation and efficient path discovery. The Cognitive Wireless Networks, leaning on a form communication model, develop new strategies to mitigate the inefficient use of the spectrum. The first application of the concept of cognitivity to communications was focused on exploiting the dynamics in spectrum utilization (cognitive radio), nevertheless network-wide deployment of such concepts is foreseen in the framework of the “cognitive networks”, where the cognitive process will be employed to support end-to-end network-wide goals such as QoS. This paper presents a state-of-art of cognitive networks and proposes a framework, architecture for cognitive networks. This paper will also discuss mechanisms for self-adaptation, learning and evolutionary functionalities to support users/applications end-to-end goals.

Empirical Experiments for Sensors' Distance Estimation in Smart Places

Considerable amount of research is being conducted to realize the emerging smart places technologies. The underlying infrastructure required to build a smart place technology consists of many sensors distributed in the target area. Sensors need to communicate with each other in an efficient way, hence, it requires knowing the distance with all of its neighbors. Several techniques are used to estimate distances between nodes (sensors) using Received Signal Strength Indicator (RSSI). However, many factors may affect the calculation of the exact distance using RSSI such as interference and noise levels. In this paper, we examined the RSSI behavior by conducting real experiments aimed at developing RSSI-Distance error model. We have conducted real experiments to measure the RSSI values between different sensors in various scenarios (both indoor and outdoor). The main goal for these experiments is to better understand the nature of RSSI fluctuations and its effect on distance calculations.