Algorithme de récupération de porteuse pourdes systèmes de communication de lumièrevisible adaptées au contexte

International audienceLa communication parlumì ere visible (VLC) suscite beaucoup d'intérêt à la fois dans la communauté scientifique et industrielle. En dépit de cet intérêt croissant, VLC en est encorè a ses balbutiements et il a été réalisé que les techniques de communication de contrôle physique et d'accès au support (MAC) bien évaluées dans les contextes de communication traditionnels (sans fil) ne peuvent pas être appliquées dans le domaine VLC. En effet, les interférences externes sont de nature et d'impact différents. Les lumières artificielles et la lumière du soleil peuvent perturber la communication et nous avons observé que les conditions extérieures changent demanì ere imprévisible et abrupte. Sur la base de ces considérations, il a été réalisé que les émetteurs et les récepteurs doivent être équipés d'une sorte d'intelligence les rendant capables de réagir dynamiquement aux changements externes afin de rendre le système de communication plus robuste. Dans ce travail, nous avons étudié l'impact de la longueur du préambule afin de réaliser un mécanisme de récupération de porteuse efficace entre unémetteurun´unémetteur et un récepteur. Nous avons remarqué que différentes conditions externes nécessitent des longueurs de préambule différentes afin de réaliser une récupération de porteuse efficace avec un faible impact en termes de taux d'erreur de morsure (BER). Nous avons étudié les différentes conditions externes et leur impact sur le système de communication et nous avons proposé une formulation de bandit multi-bras de la définition de la longueur du préambule basée sur l'approche d' échantillonnage de Thompson. Cette logique d'intelligence artificielle a été implémentée côté récepteur et une preuve de concept a été implémentée afin de valider l'approche dans un environnement réel avec de réels changements externes. Les résultats montrent que l'approche d' échantillonnage de Thompson est très réactive aux conditions externes

A Channel Selection Model based on Trust Metrics for Wireless Communications

Dynamic allocation of frequency resources to nodes in a wireless communication network is a well-known method adopted to mitigate potential interference, both unintentional and malicious. Various selection approaches have been adopted in literature, to limit the impact of interference and keep a high quality of wireless links. In this paper, we propose a different channel selection method, based on trust policies. The trust management approach proposed in this work relies on the node’s own experience and trust recommendations provided by its neighbourhood. By means of simulation results in Network Simulator NS-3, we demonstrate the effectiveness of the proposed trust method, while the system is under jamming attacks, in respect of a baseline approach. We also consider and evaluate the resilience of our approach in respect of malicious nodes, providing false information regarding the quality of the channel, to induct bad channel selection of the node. Results show how the system is resilient in respect of malicious nodes, keeping around 10% of throughput more than an approach only based on the own proper experience, considering the presence of 40% of malicious nodes, both single and collusive attacks

Voice and Video Telephony Services in Smartphone

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Enabling molecular communication through chirality of enantiomers

International audienceWith the advancements of nanotechnology, there has been fervid research activity on new communication paradigms suitable for new challenging contexts, such as biological systems. Among different approaches, the most considered has been the artificial Molecular Communication, where entities such as synthetic molecules, enzymes, hormones, bacteria etc. are functionalized in order to implement information exchange with the surrounding system and with other entities. In this context, it is interesting to analyze specific features that could be exploited for effective communication paradigms. In this paper, we focus on chiral molecules (a.k.a. enantiomers) as novel enablers for molecular communication paradigm. Chirality is an interesting and appealing feature existing in nature and that can be replicated with strong emphasis in new types of materials, such as metasurfaces and metamaterials. A deep knowledge of chirality features and how chiral molecules interact to each other or with achiral molecules gives insights into designing a new molecular communication technique suitable for biological environments. In this contribution, we will highlight the main applications of chiral molecules and we will present chiral features as the viable way for realizing a nanocommunication system

A Noise Mitigation Approach for VLC Systems

International audienceVisible Light Communication (VLC) is based on the dual use of the illumination infrastructure for wireless data communication. The major interest on this communication technology lies on its specific features to be a secure, cost-effective wireless technology. Recently, this technology has gained an important role as potential candidate for complementing traditional RF communication systems. Anyway a major issue for the VLC development is a deep comprehension of the noise and its impact on the received signal at the receiver. In this work, we present a simple but effective approach to analyze the noise and drastically reduce it through a signal processing method. In order to validate the effectiveness of this analytical approach, we have developed an USRP-based testbed. Experimental results have been carried out by evaluating the symbol error rate (SER) and show the effectiveness of the noise mitigation approach in different interference conditions and at different distance between the transmitter and the receiver

Sécurité des objets connectés : attaquer pour mieux se défendre

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A consensus-based approach to reputational routing in multi-hop networks

International audienceWhen it comes to the security of the Internet of Things (IoT), securing their communications is paramount. In multi-hop networks, nodes relay information amongst themselves, opening the data up to tampering by an intermediate device. To detect and avoid such malicious entities, we grant nodes the ability to analyse their neighbours behaviour. Through the use of consensus-based validation, based upon blockchain's miners, all nodes can agree on the trustworthiness of all devices in the network. By expressing this through a node's reputation, it is possible to identify malicious devices and isolate them from network activities. By incorporating this metric into a multi-hop routing protocol such as AODV, we can influence the path selection process. Instead of defining the best route based upon overall length, we can chose the most reputable path available, thus traversing trustworthy devices. By performing extensive analyses through multiple simulated scenarios, we can identify a decrease in packet drop rates compared to AODV by ≈ 48% and ≈ 38% when subjected to black-hole attacks with 30 and 100 node networks respectively. Furthermore, by subjecting our system to varying degrees of grey-holes, we can confirm its adaptability to different types of threats

DIVINE: Data Offloading In Vehicular Networks with QoS Provisioning

International audienceIn vehicular networks, vehicles may carry various types of data that need to be offloaded to the RoadSide Units (RSUs) through Vehicle-to-Infrastructure (V2I) communications when vehicles come into their coverage. RSUs are not widely deployed everywhere, which causes intermittent connectivity between vehicles and RSUs. In this paper, we propose DIVINE, a Data offloading In VehIcular NEtworks scheme with QoS provisioning, which enables a vehicle to offload its data to RSU directly through V2I communications or using other neighboring vehicles through Vehicle-to-Vehicle (V2V) communications. DIVINE considers the connectivity time of an offloading vehicle with the RSU, with other vehicles heading either on the same or opposite direction, offloading capacity, expected time to reach RSU and contact duration with neighboring vehicles. Additionally, the Quality of Service (QoS) is an important consideration for data offloading in vehicular networks due to the coexistence of urgent data to offload (e.g., accident or emergency data). Therefore, for QoS provisioning, DIVINE uses three QoS functions: traffic classification, overload control and admission control. DIVINE is presented with algorithms and procedures, as well as with illustrative examples. The performance evaluation in network simulator OMNeT++ with Veins and SUMO frameworks shows that DIVINE outperforms other schemes in terms of average offloading delay, maximum offloading delay and running time for a varying number of vehicles, maximum speed values, number of RSUs and RSUs' capacity. It also best behaves in terms of amount of offloaded important data

Adaptive Modulation Control for Visible Light Communication Systems

International audienceVisible light communication (VLC) builds on the dual use of lightening infrastructure for communication. Even though the advantages of VLC are well known, as emerging communication paradigm, some open issues still need to be addressed in order to rely on it as a robust communication system. First of all, external interference as an extremely varying signal impacting on the reliability of the VLC system needs to be analyzed. In this paper, we propose a system where the link conditions (in terms of signal-to-noise-ratio (SNR)) drive the modulation scheme and this procedure is managed through the use of an uplink/channel, to assure a feedback path. The receiver is in charge of choosing the modulation scheme matching the requirement in terms of error rate on the basis of the measured SNR after noise mitigation. The feasibility of the system and its effectiveness are evaluated by designing and implementing a complete bi-directional system. In particular, an uplink channel sending the information regarding the specific selected modulation technique has been implemented and the whole system is based on a fine synchronization approach in order to "track" in real time the most suitable modulation scheme. Experimental results show the effectiveness of a bi-directional system in order to implement an adaptive VLC system able to follow the environmental changes (in terms of interference and noise)