Abstract

This thesis focuses on the QoS-constrained Traffic Engineering (TE) of Wireless Mesh Networks (WMNs) affected by Multiple Access Interference (MAI). The goal is to develop a tool for the optimization of network/physical resource allocation that enable to design WMNs supporting multicast multimedia sessions with different Quality of Service (QoS) requirements when intra-session Network Coding (NC), besides routing, can be performed at the network nodes. A wide-applicability integrated framework is proposed, that allows to jointly optimize session utilities, flow control, QoS differentiation, intra-session network coding, Media Access Control (MAC) design and power control. To cope with the nonconvex nature of the resulting cross-layer optimization problem, this thesis proposes a two-level decomposition that provides the means to attain the optimal solution through suitably designed convex subproblems. Sufficient conditions for the feasibility of the primary (nonconvex) problem and for the equivalence to its related (convex) version are derived. Furthermore, a general procedure to devise simple polyhedral outer-bounds of the capacity region, which will be shown to have a key role in the decomposition, has been developed. Algorithmic implementation of the two-level decomposition is discussed in both centralized and distributed approaches. Moreover, the asynchronous, iterative Distributed Resource Allocation Algorithm (DRAA), that quickly self-adapts to network time-evolutions (e.g., node failures and/or fading fluctuations), is developed. Numerical results that delve into the potential of both the proposed solution and the resource allocation algorithm, are provided. In detail, the two-level decomposition will be tested in unicast, multicast and multisource scenarios so as to show the performance gain achievable by the joint optimization with respect to the conventional solutions.

Abstract

This thesis aims to improve a satellite communication network which carries both data streams and Voice over IP (VoIP) communication sessions with resource reservation. The resource reservations are made using the standard protocols for Traffic Engineering: MPLS-TE and RSVP-TE. The goal of this thesis project is to optimize the number of concurrent VoIP calls that can be made, in order to use the available bandwidth while maintaining a guaranteed Quality of Service (QoS) level, which is not possible in the existing system. This thesis proposes and evaluates a solution to this optimization problem in the specific context of a satellite modem system that was developed by Thales Communications. This optimization improves the system's ability to carry VoIP communications through better use of the available transmission resources. A solution to this problem would also increase the  exibility in bandwidth allocation within the modem system, and could provide a framework for future development. The proposed solution allows all of the reservable bandwidth to be used.  The amount of reservable bandwidth must be at least a little lower than the channel's available bandwidth in order to avoid congestion. Some areas of future work are proposed. Detta projekt har försökt förbättra ett datornätverk bestående av satelliter som används till både data och Voice over IP (VoIP) kommunikation. VoIP använder sig av resursreservation som bestäms av standardprotokollen för Traffic Engineering, MPLS-TE och RSVP-TE.  Målet är att optimera antalet samtidiga VoIP samtal så att det mesta av den befintliga bandbredden kan utnyttjas samtidigt som Quality of Service (QoS) kan garanteras. Detta är omöjligt i det befintliga systemet. Projektet föreslår en lösning för problemet med modemet som utvecklas av Thales Communications och utvärderar därefter lösningen. Dessa optimeringar förbättrar systemets förmåga att driva VoIP kommunikationer genom att bättre använda de befintliga resurserna. En lösning för det här problemet skulle höja systemets flexibilitet och kunna användas som underlag för kommande utvecklingar. Tack vare lösningen kan hela utsedda bandbredden reserveras. Antalet bandbredd som kan reserveras måsta vara minst lite lågre än total befintling bandbredd för att undvika överbelastning. även några möjliga ideer för vidare undersökning föreslås. Ce projet a pour but d'améliorer un réseau de communication par satellite utilisé pour transporter des flux de données ainsi que des sessions de communication Voix sur IP (VoIP) avec réservation de ressources. Les réservations sont prises en charge par les protocoles standard de Traffic Engineering que sont MPLS-TE et RSVP-TE. L'objectif de ce projet est d'optimiser le nombre d'appels VoIP pouvant être passés en parallèle afin d'utiliser autant de bande passante que possible tout en offrant un niveau de Qualité de Service (QoS) garanti, chose impossible dans le système actuel. Ce rapport propose et évalue une solution à ce problème d'optimisation dans le contexte spécifique du modem satellite développé par Thales Communications. Ces optimisations amélioreraient la capacité du système à transporter des communications VoIP grâce à une meilleure utilisation des ressources disponibles pour la transmission. Une solution à ce problème rendrait aussi l'allocation de ressources plus flexible au sein du système, et pourrait fournir une base à de futurs développements. La solution proposée permet l'utilisation de toute la bande passante réservable. La quantité réservable doit être un peu inférieure à la bande passante totale disponible afin d'éviter la congestion. Les résultats de ces évaluations sont exposés. Enfin, ce rapport propose de futurs développements possibles.