Browsing by Author "Khalgui, Mohamed"
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- Cyber-OF: An Adaptive Cyber-Physical Objective Function for Smart Cities ApplicationsPublication . Ghazi Amor, Mohamed; Koubâa, Anis; Tovar, Eduardo; Khalgui, MohamedRPL is the standard routing protocol for the Internet of Things. It is designed for low-power and lossy networks. Several works designed different objective functions for RPL to optimize routing decisions for a particular category of applications. However, these objective functions do not take into account the cyber-physical properties of the environment. In addition, they are tailored to satisfy a particular application requirement (e.g. energy efficiency or delay), so are not adaptive to possible changes of data criticality. This paper improves on the state-of-the-art with the design of a cyber-physical objective function tailored for smart city applications, that addresses the aforementioned gaps. Initial simulation results demonstrate the effectiveness of Cyber-OF in coping with dynamic changes of the criticality of events data and in providing a good performance trade-off between conflicting performance metrics, namely energy.
- Dronemap Planner: A Service-Oriented Cloud-Based Management System for the Internet-of-DronesPublication . Koubaa, Anis; Qureshi, Basit; Sriti, Mohamed-Foued; Allouch, Azza; Javed, Yasir; Alajlan, Maram; Cheikhrouhou, Omar; Khalgui, Mohamed; Tovar, EduardoLow-cost Unmanned Aerial Vehicles (UAVs), also known as drones, are increasingly gaining interest for enabling novel commercial and civil Internet-of-Things (IoT) applications. However, there are still open challenges that restrain their real-world deployment. First, drones typically have limited wireless communication ranges with the ground stations preventing their control over large distances. Second, these low-cost aerial platforms have limited computation and energy resources preventing them from running heavy applications onboard. In this paper, we address this gap and we present Dronemap Planner (DP), a service-oriented cloud-based drone management system that controls, monitors and communicates with drones over the Internet. DP allows seamless communication with the drones over the Internet, which enables their control anywhere and anytime without restriction on distance. In addition, DP provides access to cloud computing resources for drones to offload heavy computations. It virtualizes the access to drones through Web services (SOAP and REST), schedules their missions, and promotes collaboration between drones. DP supports two communication protocols: (i.) the MAVLink protocol, which is a lightweight message marshaling protocol supported by commodities Ardupilot-based drones. (ii.) the ROSLink protocol, which is a communication protocol that we developed to integrate Robot Operating System (ROS)-enabled robots into the IoT. We present several applications and proof-of-concepts that were developed using DP. We demonstrate the effectiveness of DP through a performance evaluation study using a real drone for a real-time tracking application.
- Dual Mode for Vehicular Platoon Safety: Simulation and Formal VerificationPublication . Karoui, Oussama; Khalgui, Mohamed; Koubâa, Anis; Guerfala, Emna; Li, Zhiwu; Tovar, EduardoIn order to cope with uncertainties in a platoon, this paper proposes a reconfigurable multi-agent architecture to address the platoon safety problem by handling two modes: the normal mode and the degraded mode. At this stage of research, the normal mode is characterized by the interaction between agents over a Vehicle-to-Vehicle (V2V) communication network while the degraded mode simply involves sensors for a local perception. The switching from the normal mode to the degraded one is triggered when the communication quality is considered not fully reliable. A PID (Proportional Integral Derivative) controller is proposed to regulate the inter-vehicle distance and orientation. Two models are proposed in this paper: in the first one, the management operations such as splitting and joining are set up while the second is mainly modeled to assess the implemented controller quality. In this paper, the safety of a platoon is represented by the quality of tracking and the inter-vehicle distance. The mentioned features are assessed for both modes through a formal verification using the Uppaal software. We prove the efficiency of the proposed platoon model for several situations such as merging, following or leaving the platoon by verifying different properties using the model checking. The evaluation of the second model, simulated by the Webots software, proves the impact of the number of vehicles on the platoon performance and the vehicle tracking quality. We conclude that when the platoon reaches a certain number of vehicles, the safety criterion is no more reliable.
- MAVSec: Securing the MAVLink Protocol for Ardupilot/PX4 Unmanned Aerial SystemsPublication . Allouch, Azza; Cheikhrouhou, Omar; Koubaa, Anis; Khalgui, Mohamed; Abbes, TarekThe MAVLink is a lightweight communication protocol between Unmanned Aerial Vehicles (UAVs) and ground control stations (GCSs). It defines a set of bi-directional messages exchanged between a UAV (aka drone) and a ground station. The messages carry out information about the UAV’s states and control commands sent from the ground station. However, the MAVLink protocol is not secure and has several vulnerabilities to different attacks that result in critical threats and safety concerns. Very few studies provided solutions to this problem. In this paper, we discuss the security vulnerabilities of the MAVLink protocol and propose MAVSec, a security-integrated mechanism for MAVLink that leverages the use of encryption algorithms to ensure the protection of exchanged MAVLink messages between UAVs and GCSs. To validate MAVSec, we implemented it in Ardupilot and evaluated the performance of different encryption algorithms (i.e. AES-CBC, AES-CTR, RC4 and ChaCha20) in terms of memory usage and CPU consumption. The experimental results show that ChaCha20 has a better performance and is more efficient than other encryption algorithms. Integrating ChaCha20 into MAVLink can guarantee its messages confidentiality, without affecting its performance, while occupying less memory and CPU consumption, thus, preserving memory and saving the battery for the resource-constrained drone
- Micro Air Vehicle Link (MAVLink) in a Nutshell: A SurveyPublication . Koubaa, Anis; Allouch, Azza; Alajlan, Maram; Javed, Yasir; Belghith, Abdelfettah; Khalgui, MohamedThe micro air vehicle link (MAVLink in short) is a communication protocol for unmanned systems (e.g., drones and robots). It specifies a comprehensive set of messages exchanged between unmanned systems and ground stations. This protocol is used in major autopilot systems, mainly ArduPilot and PX4, and provides powerful features not only for monitoring and controlling unmanned systems missions but also for their integration into the Internet. However, there is no technical survey and/or tutorial in the literature that presents these features or explains how to make use of them. Most of the references are online tutorials and basic technical reports, and none of them presents comprehensive and systematic coverage of the protocol. In this paper, we address this gap, and we propose an overview of the MAVLink protocol, the difference between its versions, and it is potential in enabling Internet connectivity to unmanned systems. We also discuss the security aspects of the MAVLink. To the best of our knowledge, this is the first technical survey and tutorial on the MAVLink protocol, which represents an important reference for unmanned systems users and developers.
- Multi-agent Adaptive Architecture for Flexible Distributed Real-time SystemsPublication . Chniter, Hamza; Li, Yonghui; Khalgui, Mohamed; Koubaa, Anis; Li, Zhiwu; Jarray, FethiRecent critical embedded systems become more and more complex and usually react to their environment that requires to amend their behaviors by applying run-time reconfiguration scenarios. A system is defined in this paper as a set of networked devices, where each of which has its own operating system, a processor to execute related periodic software tasks, and a local battery. A reconfiguration is any operation allowing the addition-removal-update of tasks to adapt the device and the whole system to its environment. It may be a reaction to a fault or even optimization of the system functional behavior. Nevertheless, such scenario can cause the violation of real-time or energy constraints, which is considered as a critical run-time problem. We propose a multi-agent adaptive architecture to handle dynamic reconfigurations and ensure the correct execution of the concurrent real-time distributed tasks under energy constraints. The proposed architecture integrates a centralized scheduler agent (ScA) which is the common decision making element for the scheduling problem. It is able to carry out the required run-time solutions based on operation research techniques and mathematical tools for the system's feasibility. This architecture assigns also a reconfiguration agent (RA p ) to each device p to control and handle the local reconfiguration scenarios under the instructions of ScA. A token-based protocol is defined in this case for the coordination between the different distributed agents in order to guarantee the whole system's feasibility under energy constraints.
- On Feasibility of Multichannel Reconfigurable Wireless Sensor Networks Under Real-Time and Energy ConstraintsPublication . Ben Aissa, Yousra; Bachir, Abdelmalik; Khalgui, Mohamed; Koubaa, Anis; Li, Zhiwu; Qu, TingThis paper deals with the medium between two reconfigurable sensor nodes characterized by radio interfaces that support multiple channels for exchanging real-time messages under energy constraints. These constraints are violated if the consumed energy in transmission is higher than the remaining quantity of energy. A reconfiguration, i.e., any addition or removal of tasks in devices and consequently of messages on the medium, can cause the violation of real-time or energy constraints at run time. To achieve a feasible scheduling in time (i.e., message deadlines will be respected) and energy (i.e., there is available energy) on the medium, we propose new dynamic solutions: Balance, Dilute, and a Combination of them to manage any addition or removal of messages. The proposed approach utilizes the energy harvesting techniques and the PowerControl algorithm to reduce the nonharvested consumed energy. The proposed strategies achieve significant improvement over existing methods and provide the highest percentage of adding messages, with a lower average in response time and energy consumption. They reach a percentage of success in adding the highest priority messages while meeting deadlines up to 85%.
- Performance Evaluation of Vehicular Platoons using WebotsPublication . Karoui, Oussama; Guerfala, Emna; Koubâa, Anis; Khalgui, Mohamed; Tovar, Eduardo; Wu, Naiqi; Al-Ahmari, Abdulrahman; Li, ZhiwuSafety issue of vehicular platoons remains a critical challenge and is still open for investigation. In this study, the authors propose an accurate simulation model for vehicular platoons, taking into consideration of the kinematics and dynamics aspects of the platoon and its physical constraints. A hybrid controller formed by two different longitudinal and lateral proportional–integral–derivative controllers and two operation modes at the same time is developed and simulated using Webots. By this study, the aim is to deeply study the performance of the platoon and reveal its weakness in real scenarios. The latter includes normal/degraded operating modes, different speeds, full brake scenarios and various global positioning system accuracies. Results show the efficiency of the platoon controller even in the predefined degraded mode.
- QCOF: New RPL Extension for QoS and Congestion-Aware in Low Power and Lossy NetworkPublication . Ben Aissa, Yousra; Grichi, Hanen; Khalgui, Mohamed; Koubaa, Anis; Bachir, AbdelmalikLow power and lossy networks (LLNs) require a routing protocol under real-time and energy constraints, congestion aware and packet priority. Thus, Routing Protocol for Low power and lossy network (RPL) is recommended by Internet Engineering Task force (IETF) for LLN applications. In RPL, nodes select their optimal paths towards their preferred parents after meeting routing metrics that are injected in the objective function (OF). However, RPL did not impose any routing metric and left it open for implementation. In this paper, we propose a new RPL objective function which is based on the quality of service (QoS) and congestion-aware. In the case paths fail, we define new RPL control messages for enriching the network by adding more routing nodes. Extensive simulations show that QCOF achieves significant improvement in comparison with the existing objective functions, and appropriately satisfies real-time applications under QoS and network congestion.
- System and method for operating a follower vehicle in a vehicle platoonPublication . Li, Zhiwu; Karoui, Oussama; Koubaa, Anis; Khalgui, Mohamed; Guerfala, Emna; Tovar, Eduardo; Wu, NaiqiA method for operating a follower vehicle in a vehicle platoon includes determining, during operation, whether the follower vehicle is operating in a normal state or an abnormal state based on an operation condition of a component of the follower vehicle, or a communication between the follower vehicle and a preceding vehicle in the vehicle platoon. The method further includes selecting a first control mode if the follower vehicle is in the normal state and a second control mode if the follower vehicle is in the abnormal state so as to control movement of the follower vehicle using the selected control mode. In the first control mode, the follower vehicle uses communication data received from the preceding vehicle in the vehicle platoon to control its movement. In the second control mode, the follower vehicle uses data obtained by one or more of its sensors to control its movement.