Le stockage de contenu populaire dans des caches disponibles aux utilisateurs, est une technique émergente qui permet de réduire le trafic dans les réseaux sans fil. En particulier, le coded caching proposée par Maddah-Ali et Niesen a été considéré comme une approche prometteuse pour atteindre un temps de livraison constant au fur et à mesure que la dimension augmente. Toutefois, plusieurs limitations empêchent ses applications. Nous avons adressé les limitations de coded caching dans les réseaux sans fil et avons proposé des schémas de livraison qui exploitent le gain de coded caching. Dans la première partie de la thèse, nous étudions la région de capacité pour un canal à effacement avec cache et retour d'information. Nous proposons un schéma et prouvons son optimalité pour des cas particuliers. Ces résultats sontgénéralisés pour le canal à diffusion avec desantennes multiples et retour d'information. Dans la deuxième partie, nous étudions la livraison de contenu sur un canal d'atténuation asymétrique, où la qualité du canal varie à travers les utilisateurs et le temps. En supposant que les demandes des utilisateurs arrivent de manière dynamique, nous concevons un schéma basé sur une structure de queues et nous prouvons qu’il maximise la fonction d'utilité par rapport à tous les schémas limités au cache décentralisé. Dans la dernière partie, nous étudions la planification opportuniste pour un canal d'atténuation asymétrique, en assurant une métrique de justice entre des utilisateurs. Nous proposons une politique de planification simple à base de seuil avec une complexité linéaire et qui exige seulement un bit de retour de chaque utilisateur. / Caching, i.e. storing popular contents at caches available at end users, has received a significant interest as a technique to reduce the peak traffic in wireless networks. In particular, coded caching proposed by Maddah-Ali and Niesen has been considered as a promising approach to achieve a constant delivery time as the dimension grows. However, several limitations prevent its applications in practical wireless systems. Throughout the thesis, we address the limitations of classical coded caching in various wireless channels. Then, we propose novel delivery schemes that exploit opportunistically the underlying wireless channels while preserving partly the promising gain of coded caching. In the first part of the thesis, we study the achievable rate region of the erasure broadcast channel with cache and state feedback. We propose an achievable schemeand prove its optimality for special cases of interest. These results are generalized to the multi-antenna broadcast channel with state feedback. In the second part, we study the content delivery over asymmetric block-fading broadcast channels, where the channel quality varies across users and time. Assuming that user requests arrive dynamically, we design an online scheme based on queuing structure and prove that it maximizes the alpha-fair utility among all schemes restricted to decentralized placement. In the last part, we study opportunistic scheduling over the asymmetric fading broadcast channel and aim to design a scalable delivery scheme while ensuring fairness among users. We propose a simple threshold-based scheduling policy of linear complexity that requires only a one-bit feedback from each user.

Traditional call button networks that control elevator systems utilize a wired connection for communication. The communication cables are run through the elevator shaft from one call button to another and finally to the controller on the roof. Installing this wired link is highly time consuming. In this thesis, we propose the design for a wireless call button network. Two important features of this wireless network design are low cost and low power consumption. Controller Area Network (CAN) is a widely used protocol for wired networks and has been proposed for use in next generation elevator control systems. A modified CAN for wireless (MCANW) protocol has been developed for the wireless call button network. The wireless link will be implemented via the use of data radios. A modified form of traditional Binary Phase Shift Keying (BPSK) modulation scheme for the radios is proposed. The proposed modulation scheme, like differential BPSK, can be detected non-coherently but it offers better performance than differential BPSK. Its implementation includes an innovative tracking algorithm to maintain synchronization at the receiver. / Master of Science

Yes / Recently there is a high demand from the Internet Service Providers to transmit multimedia services over high speed wireless networks. These networks are characterized by high mobility receivers which perform frequent handoffs across homogenous and heterogeneous access networks while maintaining seamless connectivity to the multimedia services. In order to ensure secure delivery of multimedia services to legitimate group members, the conventional cluster based group key management (GKM) schemes for securing group communication over wireless mobile multicast networks have been proposed. However, they lack efficiency in rekeying the group key in the presence of high mobility users which concurrently subscribe to multiple multicast services that co-exist in the same network. This paper proposes an efficient multi-service group key management scheme (SMGKM) suitable for high mobility users which perform frequent handoffs while participating seamlessly in multiple multicast services. The users are expected to drop subscriptions after multiple cluster visits hence inducing huge key management overhead due to rekeying the previously visited cluster keys. The already proposed multi-service SMGKM system with completely decentralised authentication and key management functions is adopted to meet the demands for high mobility environment with the same level of security. Through comparisons with existing GKM schemes and simulations, SMGKM shows resource economy in terms of reduced communication and less storage overheads in a high speed environment with multiple visits.

Today many large scale sensor networks have emerged, which span many different sensing applications. Each of these sensor networks often consists of millions of sensors collecting data and supports thousands of users with diverse data needs. Between users and wireless sensors there are often a group of powerful servers that collect and process data from sensors and answer users' requests. To build such a large scale sensor network, we have to answer two fundamental research problems: i) what data to transmit from sensors to servers? ii) how to transmit the data over wireless links? Wireless sensors often can not transmit all collected data due to energy and bandwidth constraints. Therefore sensors need to decide what data to transmit to best satisfy users' data requests. Sensor network users can often tolerate some data errors, thus sensors may transmit data in lower fidelity but still satisfy users' requests. There are generally two types of requests-raw data requests and meta-data requests. To answer users' raw data requests, we propose a model-driven data collection approach, PRESTO. PRESTO splits intelligence between sensors and servers, i.e., resource-rich servers perform expensive model training and resource-poor sensors perform simple model evaluation. PRESTO can significantly reduce data to be transmitted without sacrificing service quality. To answer users' meta-data request, we propose a utility-driven multi-user data sharing approach, MUDS. MUDS uses utility function to unify diverse meta-data metrics. Sensors estimate utility value of each data packet and sends packets with highest utility first to improve overall system utility. After deciding what data to transmit from sensors to servers, the next question is how to transmit these data over wireless links. Wireless transport often suffers low bandwidth and unstable connectivity. In order to improve wireless transport, I propose a clean-slate re-design of wireless transport, Hop. Hop uses reliable perhop block transfer as a building block and builds all other components including hidden-terminal avoidance, congestion avoidance, and end-to-end reliability on top of it. Hop is built based on three key ideas: a) hop-by-hop transfer adapts to the lossy and highly variable nature of wireless channel significantly better than end-to-end transfer, b) the use of blocks as the unit of control is more efficient over wireless links than the use of packets, and c) the duplicated functionality in different layers in the network stack should be removed to simplify the protocol and avoid complex interaction.

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