The emergence of connected vehicles paradigm has made secure communication a key concern amongst the connected vehicles. Communication between the vehicles and Road Side Units (RSUs) is critical to disseminate message among the vehicles. We focus on secure message transmission in connected vehicles using multi-hop social networks environment to deliver the message with varying trustworthiness. We proposed a Geographic Social Trust Routing (GSTR) approach; messages are propagated using multiple hops and by considering the various available users in the vehicular network. GSTR is proposed in an application perspective with an assumption that the users are socially connected. The users are selected based on trustworthiness as defined by social connectivity. The route to send a message is calculated based on the highest trust level of each node by using the node's social network connections along the path in the network. GSTR determines the shortest route using the trusted nodes along the route for message dissemination. GSTR is made delay tolerant by introducing message storage in the cloud if a trustworthy node is unavailable to deliver the message. We compared the proposed approach with Geographic and Traffic Load based Routing (GTLR), Greedy Perimeter Stateless Routing (GPSR), Trust-based GPSR (T-GPSR). The performance results obtained show that GSTR ensures efficient resource utilization, lower packet losses at high vehicle densities.

The realization of high data rate wireless communication and large-scale connectivity with seamless coverage has been enabled by the introduction of various advanced transmission technologies, such as multiple access (MAC) technology and relay-assisted communications. However, beyond the accurate representation and successful transmission of information, in many applications it is the semantic aspect of that information that is really of interest. This thesis makes contributions to both the technology of conventional wireless communications and the theory of semantic communication. The main work is summarized as follows: We first consider an uplink system with K single-antenna users and one base station equipped with a single antenna, where each user utilizes a binary constellation to carry data. By maximizing the minimum Euclidean distance of the received sum constellation, the optimal user constellations and sum constellation are obtained for K=3 users. Using the principle of lattice coding, that design is extended to the K-user case. In both settings, the sum constellation belongs to additively uniquely decomposable constellation group (AUDCG). That property enables us to reduce the maximum likelihood multi-user detector to a single-user quantization based receiver. The symbol error probability (SEP) formula is derived, showing that our proposed non-orthogonal multiple access (NOMA) scheme outperforms the existing time division multiple access (TDMA) designs for the same system. Our design also sheds light on the general complex constellation designs for the MAC channel with arbitrary user constellation size. Specifically, K-user constellations with any 2^Mk size can be obtained using combinations of the proposed binary constellations. Next we concentrate on a multi-hop relay network with two time slots, consisting of single-antenna source and amplify-and-forward relay nodes and a destination node with M antennas. We develop a novel uniquely-factorable constellation set (UFCS) based on a PSK constellation for such system to allow the source and relay nodes to transmit their own information concurrently at the symbol level. By taking advantage of the uniquely-factorable property, the optimal maximum likelihood (ML) detection was equivalently reduced to a symbol-by-symbol detection based on phase quantization. In addition, the SEP formula was given, while enable us to show that the diversity gain of the system is one. For semantic communication, a new source model is considered, which consists of an intrinsic state part and an extrinsic observation part. The intrinsic state corresponds to the semantic feature of the source. It is not observable, and can only be inferred from the extrinsic observation. As an instance of the general model, the case of Gaussian distributed extrinsic observations is studied, where we assume a linear relationship between the intrinsic and extrinsic parts. We derive the rate-distortion function (in both centralized encoding and distributed encoding) of semantic-aware source coding under quadratic distortion structure by converting the semantic distortion constraint of the source to a surrogate distortion constraint on the observations. With proposed AUDCG and UFCS-based designs, high data rates as well as low detection latency can be achieved. Our modulation division method will be one of the promising technologies for the next generation communication and the analysis of the source coding with semantic information constraints also provides some insights that will guide the future development of semantic communication systems. / Thesis / Doctor of Philosophy (PhD) / The proliferation of smart phones and electronic devices has spurred explosive growth in high-speed multimedia services over the next generation of wireless cellular networks. Indeed, high data rates and large-scale connectivity with seamless coverage are the dominant themes of wireless communication system design. Moreover, beyond the accurate representation and successful transmission of information, the interpretation of its meaning is being paid more attention nowadays, which requires the development of approaches to semantic communication. The goal of this thesis is to contribute to the development of both conventional and semantic communication systems. Two advanced transmission technologies, namely, multiple access and relay-assisted communications are considered. By taking advantage of the special structures of digital communication signals, new approaches to multiple access and relay-assisted communications are developed. These designs enable high data rates, while simultaneously facilitating low-latency detection. Since there has been very limited analysis of the source coding of a vector source subject to semantic information constraints, we also study the rate distortion to trade-off for vector sources in both the case of centralized encoding and the case of distributed encoding, and we establish some insights that will guide the future development of semantic communication systems.

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Traditionally, achieving good performance for a multi-hop wireless network is known to be difficult. The main approach to control the operation of such a network relies on a distributed paradigm, assuming that a centralized approach is not feasible. Relying on a distributed paradigm could be justified at the time when the basic technical building blocks (e.g., node computational power, communication technology, positioning technology) were the bottlenecks. Recent advances and breakthroughs in these technical areas along with the emergence of programmable networks with softwarized control plane intelligence allow us to consider employing a centralized optimization paradigm to control and manage the operation of a multi-hop wireless network. The programmable control provides a platform on which the centralized global network optimization paradigm can be supported. The benefits of a centralized network optimization lie specially in that a network may be configured in such a way that offers optimal performance, which is hardly possible for a network relying on distributed operation. The objectives of this dissertation are to fully understand the potential benefits of a centralized control plane for a multi-hop wireless network, to identify any new challenges under this new paradigm, and to devise innovative solutions for optimal performance via a centralized control plane. Given that the performance of a wireless network heavily depends on its physical layer capabilities, we will consider a number of advanced wireless technologies, including MIMO, full duplex, and interference cancellation at the physical layer. The focus is on building tractable computational models for these wireless technologies that can be used for modeling, analysis and optimization in the centralized control plane. Problem formulation and efficient solution procedures are developed for various centralized optimization problems across multiple layers. End-to-end throughput maximization is a key objective among these optimization problems on the centralized control plane and is used to demonstrate the superior advantage of this paradigm. We study several problems: • Integration of SIC and MIMO DoF IC. We propose to integrate MIMO Degree-of-Freedom (DoF) interface cancellation (IC) and Successive Interference Cancellation (SIC) in MIMO multi-hop network under DoF protocol model. We show that DoF-based IC and SIC can be jointly integrated to combat the interference more effectively and improve the end-to-end throughput significantly. We develop the necessary mathematical models to realize the idea in a multi-hop wireless network. • Full-Duplex MIMO Wireless Networks Throughput. We investigate the performance of MIMO full-duplex (FD) in a multi-hop network. We show that if IC is exploited, MIMO FD can achieve significant throughput gain over MIMO HD in a multi-hop network, which is contrary to the recent literature suggesting an unexpected marginal gain. Our proposed model handles the additional network interference by joint efficient link scheduling and interference cancellation. • PCP in Tactical Wireless Networking. We propose the idea of the Programmable Control Plane (PCP) for the tactical wireless network under the protocol model. PCP decouples the control and data plane and allows the network control layer functionalities to be dynamically configured to adapt to specific wireless channel conditions, customized applications and/or certain tactical situations. The proposed PCP functionalities are cast into a centralized optimization problem, which can be updated as needed and provide a centralized intelligence to manage the operation of a wireless MIMO multi-hop network under the protocol model. • UPCP in Heterogeneous Wireless Networks. We propose the idea of the Unified Programmable Control Plane (UPCP) for tactical heterogeneous wireless networks with interference management capabilities under the SINR model. The UPCP abstracts the complexity of the underlying network comprised of heterogeneous wireless technologies and provides a centralized intelligence over the network resources. We develop necessary mathematical model to realize the UPCP. / Ph. D.

Real-time channels are established between a source and a destination to guarantee in-time delivery of real-time messages in multi-hop networks. In this thesis, we propose two schemes to establish real-time channels for soft real-time applications whose timeliness properties are characterized using Jensen's Time Utility Functions (TUFs) that are non-increasing. The two algorithms are (1) Localized Decision for Utility accrual Channel Establishment (LocDUCE) and (2) Global Decision for Utility accrual Channel Establishment (GloDUCE). Since finding a feasible path optimizing multiple constraints is an NP-Complete problem, these schemes heuristically attempt to maximize the system-wide accrued utility. The channel establishment algorithms assume the existence of a utility-aware packet scheduling algorithm at the interfaces. The route selection is based on delay estimation performed at the source, destination, and all routers in the path, from source to destination. We simulate the algorithms, measure and compare their performance with open shortest path first (OSPF). Our simulation experiments show that for most of the cases considered LocDUCE and GloDUCE perform better than OSPF. We also implement the schemes in a proof-of-concept style routing module and measure the performance of the schemes and compare them to OSPF. Our experiments on the implementation follow the same trend as the simulation study and show that LocDUCE and GloDUCE have a distinct advantage over OSPF and accrue higher system-wide utility. These schemes also react better to variation in the loading of the links. Among the two proposed approaches, we observe that GloDUCE performs better than LocDUCE under conditions of increased downstream link loads. / Master of Science

Les systèmes de gestion de données distribuées deviennent de plus en plus complexes. Ils interagissent avec des réseaux de dispositifs fixes et/ou mobiles, tels que des smartphones ou des tablettes, dispositifs hétérogènes, autonomes et possédant des limitations physiques. Ces dispositifs exécutent des applications permettant l'interaction des usagers (i.e. jeux virtuels, réseaux sociaux). Ces applications produisent et consomment des données à tout moment voire même en continu. Les caractéristiques de ces systèmes ajoutent des dimensions au problème de l'optimisation de requêtes, telles que la variabilité des objectifs d'optimisation, l'absence d'information sur les données (métadonnées) ou le manque d'une vision globale du système. Les techniques traditionnelles d'optimisation des requêtes n'abordent pas (ou très peu) les systèmes autonomes. Elles se basent sur les métadonnées et font des hypothèses très fortes sur le comportement du système. En plus, la majorité de ces techniques d'optimisation ciblent uniquement l'optimisation du temps d'exécution. La difficulté d'évaluation des requêtes dans les applications modernes incite à revisiter les techniques traditionnelles d'optimisation. Cette thèse fait face aux défis décris précédemment par l'adaptation du paradigme du Raisonnement à partir de cas (CBR pour Case-Based Reasoning) au problème de l'optimisation des requêtes. Cette adaptation, associée à une exploration pseudo-aléatoire de l'espace de solutions fournit un moyen pour optimiser des requêtes dans les contextes possédant très peu voire aucune information sur les données. Cette approche se concentre sur l'optimisation de requêtes en utilisant les cas générés précédemment dans l'évaluation de requêtes similaires. Un cas de requête et composé par : (i) la requête (le problème), (ii) le plan d'exécution (la solution) et (iii) les mesures de ressources utilisés par l'exécution du plan (l'évaluation de la solution). Cette thèse aborde également la façon que le processus CBR interagit avec le processus de génération de plan d'exécution de la requête qui doit permettre d'explorer l'espace des solutions. Ce processus utilise les heuristiques classiques et prennent des décisions de façon aléatoire lorsque les métadonnées viennent à manquer (e.g. pour l'ordre des jointures, la sélection des algorithmes, voire même le choix des protocoles d'acheminement de messages). Ce processus exploite également le CBR pour générer des plans pour des sous-requêtes, accélérant ainsi l'apprentissage de nouveaux cas. Les propositions de cette thèse ont été validées à l'aide du prototype CoBRA développé dans le contexte du projet UBIQUEST. / Distributed data systems are becoming increasingly complex. They interconnect devices (e.g. smartphones, tablets, etc.) that are heterogeneous, autonomous, either static or mobile, and with physical limitations. Such devices run applications (e.g. virtual games, social networks, etc.) for the online interaction of users producing / consuming data on demand or continuously. The characteristics of these systems add new dimensions to the query optimization problem, such as multi-optimization criteria, scarce information on data, lack of global system view, among others. Traditional query optimization techniques focus on semi (or not at all) autonomous systems. They rely on information about data and make strong assumptions about the system behavior. Moreover, most of these techniques are centered on the optimization of execution time only. The difficulty for evaluating queries efficiently on nowadays applications motivates this work to revisit traditional query optimization techniques. This thesis faces these challenges by adapting the Case Based Reasoning (CBR) paradigm to query processing, providing a way to optimize queries when there is no prior knowledge of data. It focuses on optimizing queries using cases generated from the evaluation of similar past queries. A query case comprises: (i) the query, (ii) the query plan and (iii) the measures (computational resources consumed) of the query plan. The thesis also concerns the way the CBR process interacts with the query plan generation process. This process uses classical heuristics and makes decisions randomly (e.g. when there are no statistics for join ordering and selection of algorithms, routing protocols). It also (re)uses cases (existing query plans) for similar queries parts, improving the query optimization, and therefore evaluation efficiency. The propositions of this thesis have been validated within the CoBRa optimizer developed in the context of the UBIQUEST project .

Important sujet de recherche dans les télécommunications contemporaines, les réseaux de capteurs sont des réseaux sans fil constitués de plusieurs nœuds pouvant communiquer entre eux. Chaque capteur est autonome et possède une durée de vie limitée, liée à la taille de sa batterie. Dans ce contexte, l’énergie est une ressource critique qui peut être économisée en minimisant le nombre de paquets émis. De part la nature du médium radio, les données transmises subissent des pertes du canal. La fiabilisation de données dans ce contexte n’est pas simple et devient d’autant plus problématique lorsque la taille de réseau augmente. C’est dans ce contexte que s’inscrit cette thèse qui vise à fournir une technique de fiabilisation des transmissions dans un réseau de capteur. Pour cela, nous proposons de mettre en oeuvre un mécanisme de transmission qui exploite le code fontaine. Ce code est sans rendement et les symboles de redondance sont générés à la volée. Il permet de fiabiliser la transmission avec l’utilisation d’un canal de retour limité. Le code fontaine permet d’alléger le mécanisme de contrôle des transmissions tout en assurant un lien complètement fiable, ce qui permet de réduire la latence et la consommation énergétique d’une transmission. Afin d’optimiser la performance globale du réseau, nous étudions également dans cette thèse le cas où les nœuds sont autorisés à coopérer pour le relayage multi-sauts de paquets destinés à des nœuds distants. Nous montrons dans cette thèse que la technique de codage réseau permet d’introduire de la diversité d’information et ainsi d’améliorer la performance globale de transmissions multi-sauts mono-chemin. Ce résultat a été étendu à la transmission coopérative pour laquelle nous avons à la fois pu exploiter la diversité d’information et la diversité spatiale. / This thesis is dedicated to the deployment of fountain codes and network coding in a wireless sensor network (WSN). A WSN is composed of sensor nodes with restricted capacities : memory, energy and computational power. The nodes are usually randomly scattered across the monitored area and the environment may vary. In the presence of fading, outage and node failures, fountain codes are a promising solution to guaranty reliability and improve transmission robustness. The benefits of fountain codes are explored based on an event-driven WSNet simulator considering realistic implementation based on standard IEEE802.15.4. Fountain codes are rateless and capable of adapting their rate to the channel on the fly using a limited feedback channel. In this thesis, we highlight the benefits brought by fountain code in terms of energy consumption and transmission delay. In addition to the traditional transmission with fountain code, we propose in this thesis to study the network coding transmission scheme where nodes are allowed to process the information before forwarding it to their neighbors. By this means, we can say that packet diversity is exploited as each individual packet is unique and contains different representations of binary data. Redundancy is thus optimized since repetitions are avoided and replaced with diversified information. This can further lead to an overall improved performance in cooperative communication where nodes are allowed to assist in relaying packets from the source the destination. We highlight in this thesis the benefits of fountain code combined to network coding and show that it leads to a reduction in transmission delay and energy consumption. The latter is vital to the life duration of any wireless sensor network.

Les réseaux sans fil multi-saut (WMN : Wireless multi-hop Networks) sont passés du stade de simple curiosité pour revêtir aujourd'hui un intérêt certain aussi bien du point de vue de la communauté de recherche que des opérateurs de réseaux et services. En analysant les services et applications fournis au sein des réseaux WMNs, nous pouvons constater que certaines applications telles que la visioconférence, la VoIP, etc sont sensibles au délai et nécessitent une certaine qualité de service (QoS). D'autres applications telles que le transfert de fichier, le streaming vidéo, etc. sont gourmands en terme d'utilisation de bande passante. Par conséquent, les architectures de communication des réseaux WMNs doivent intégrer des mécanismes de routage efficaces et adaptés pour répondre aux besoins des services et applications envisagés. Dans cette thèse, Nous nous intéressons à la problématique du routage dans les réseaux WMNs. Notre objectif est de proposer une nouvelle approche de routage qui prend en compte différents métriques de coûts. Tout d'abord, nous avons montré que le routage sous contraintes multiples est un problème NP complet et que trois étapes sont nécessaires à la conception d'une nouvelle solution de routage: (i) modélisation de l'interférence, (ii) l'estimation de la de la bande passante restante, (iii) l'estimation du délai à un saut. Suivant cette vision, nous avons proposé deux variantes du protocole de routage OLSR (SP-OLSR, S2P-OLSR) se basant sur la métrique SINR. Les résultats des simulations ont montré l'intérêt de la proposition dans un contexte de communication vocale (VoIP). Ensuite, nous avons proposé un algorithme d'estimation d'interférence à 2 sauts (2-HEAR) afin d'estimer la bande passante disponible. Puis, et sur la base de cet algorithme, nous avons proposé une nouvelle métrique de routage pour les WMNs: Estimated Balanced Capacity (EBC) en vue de parvenir à l'équilibrage de charge entre des différents flux. La dernière question abordée dans cette thèse est celle de l'estimation du délai à un saut. La solution proposée donne une borne du délai en se basant sur un modèle de file d'attente de type G/G/1. Enfin, nous avons englobé toutes les précédentes contributions pour mettre en place une nouvelle approche de routage hybride sous contraintes multiples. Ce protocole comporte une partie proactive utilisant la nouvelle métrique de routage (EBC) et une partie réactive qui permet de prendre en compte le délai relative à une connexion donné. / There is a growing interest in wireless multi-hop networks (WMNs) since there are promising in opening new business opportunity for network operators and service providers. This research field aims at providing wireless communication means to carry different types of applications (FTP, Web browsing, video streaming, in addition to VoIP). Such applications have different constraints and their specific requirements in terms of Quality of Service (QoS) or performance metrics (delay jitter, end-to-end delay). We examine, in this thesis, the problem of routing in WMNs. Our main goal is to propose a new multi-metrics routing capable to fit these particular needs. In this thesis, we make several contributions toward WMN multi-constrained routing. First, we show that the multi-constrained path finding problem is NP-Complete and inherently a cross-layer issue, and that three steps are necessary to design the multi-metric routing protocol: (i) modeling of the inferring signal, (ii) estimation of the remaining bandwidth, (iii) estimation of the one-hop delay. Second, moving in such direction, we propose two enhanced versions of the OLSR routing protocol. The suggested protocols consider the SINR as a routing metric to build a reliable topology graph. Performance evaluation shows that utilizing such routing metric helps to improve significantly the VoIP application quality in the context of ad hoc network while maintaining a reasonable overhead cost. Third, we have proposed a 2-Hop interference Estimation Algorithm (2-HEAR) in order to estimate the available bandwidth. Then, and based on such algorithm, we have proposed a novel routing metric for WMNs: Estimated Balanced Capacity (EBC) in order to achieve load-balancing among the different flows. The next issue tackled in this thesis is the one-hop delay estimation, the one-hop delay is estimated by means of an analytical model based on G/G/1 queue. Finally, we have encompassed all the previous contributions to address our main goal, i.e. the design of a multi-constrained routing protocol for WMNs. A hybrid routing protocol is then proposed. This protocol is a junction of two parts : a proactive part that makes use of the previously estimated constraint, and a reactive part, which is triggered ”on demand” when news applications are expressed.