Academic literature on the topic 'Transport Resource Allocation'

The world's hunger for connectivity appears to be endlessly growing, yet the capacity of the networks that underpin that connectivity is anything but endless. This thesis explores both short and long term solutions for increasing the capacity of the largest and most capacious of these networks, the backbones upon which the Internet is built: optical transport networks. In the short term, Flexi-grid technology has emerged as the evolution of fixed-grid WDM optical networks, providing higher potential throughput but suffering from an aggravated form of the spectrum ragmentation problem that affects fixed-grid networks. A novel path-based metric to better evaluate the fragmentation of spectral resources in flexi-grid networks is presented, which considers both the fact that free spectrum slices may not be available on all the links of a path, and the likelihood that an end-to-end spectral void is usable to route incoming connections, and tested by means of simulations, finding that it outperforms existing ones from literature. For the longer term, Space Division Multiplexing (SDM) is a promising solution to overcome the looming fiber capacity crunch, and, perhaps more importantly, can offer a beneficial ratio between the expected capacity gains and the resulting increase in the cost of the network thanks to Joint and Fractional Joint Switching architectures and integrated transceivers and amplifiers. A model for such network is presented, and multiple heuristics for solving the Routing, Space and Spectrum Allocation problem are described, studied via simulations and iteratively improved, with the objective of quantifying the likely performance of several SDM architectures under multiple traffic scenarios. In addition, possible improvements to joint switching architectures, and an experimental SDN control plane for SDM networks, are presented and characterized, again by means of simulations. SDM is shown to be an attractive technology for increasing future transport networks capacity, at a reasonable cost.

Le contrôle de congestion des canaux sans fil pour la communication véhiculaires (V2X) basée sur IEEE 802.11p ont été conçus pour un seul service de sécurité routière notamment ‘Cooperative Awareness’. Les futurs véhicules connectés seront basés sur plusieurs services V2X, avec un besoin de communication hétérogène, auxquels les mécanismes existants ne répondent pas. Dans cette thèse, on analyse plusieurs protocoles de contrôle de congestion et d’allocation de ressources de canaux, normalisés en Europe pour le déploiement V2X initial. Nous présentons des problèmes liés à l’approche existante, notamment l’utilisation inefficace de la capacité des canaux, la coordination dans la pile protocolaire, la gestion des ressources parmi plusieurs services et l’allocation des ressources pour un besoin asymétrique par les véhicules. On propose des améliorations en tenant compte des exigences des futurs scénarios V2X. Nous montrons les limites de la classification statique des services V2X pour la qualité de service et proposons une classification dynamique. Nous concevons un orchestrateur de ressources afin d'améliorer la coordination dans la pile protocolaire et de répartir dynamiquement la ressource de canal parmi plusieurs services d'un véhicule. En outre, on présente un mécanisme permettant d'orchestrer de manière décentralisée les ressources de canal parmi une distribution mixte de véhicules ayant des exigences d'utilisation de canal diverse, dans un canal de communication congestionné. Les résultats analytiques et résultats par simulations montrent la validité de notre approche qui améliore la performance des applications V2X, par rapport aux protocoles standardisés existants<br>Wireless channel congestion control and decentralized resource allocation for 802.11p based V2X communication have been widely investigated for a single Cooperative Awareness service, considering mostly homogenous communication requirement per vehicle. Future connected vehicles will be based on multiple V2X services, with heterogenous number of services and communication needs, which existing resource allocation mechanisms does not address. In this thesis, we analyze several decentralized congestion control and channel resource allocation protocols standardized in Europe for initial V2X deployment. We present issues with the existing approach, in particular the inefficient channel capacity utilization, problematic cross layer coordination, inability to balance resources among multiple V2X safety services and distributed resource allocation for asymmetric number of services per vehicle. We propose improvements to the shortcomings, considering the requirements of future V2X scenarios. We demonstrate the limitations of classifying V2X services using static priority for Quality of Service and propose dynamic prioritization. We design a resource orchestrator at the Service Layer to improve cross layer coordination and dynamically distribute the limited channel resource among multiple services of a vehicle. Furthermore, we present a mechanism to decentrally orchestrate channel resource among a mixed distribution of vehicles with diverse channel usage requirements under channel congestion. Analytical and simulation-based results show the validity of our proposed approach, and the V2X application performance improvement it renders, compared to existing standardized protocols

In the last years the steady development of autonomous driving technology has enabled the deployment of more mature autonomous vehicles. These vehicles have been applied in several pilot projects worldwide, most commonly in the form of small buses. At the same time, the amount of people traveling in especially urban areas is continuously growing, resulting in more trips in the transportation system. An efficient transportation system is therefore required to serve the growing passenger demand. Autonomous buses (AB) are assumed to have lower operational costs and with that public transport (PT) systems can potentially be designed more efficiently to facilitate the increased demand better. In this study, an AB specific simulation-based optimization framework is proposed which allows analyzing the impacts AB have on line-based PT systems. The thesis focuses on the transition from existing PT systems towards line-based PT systems operated partially or exclusively by AB. Existing work on PT service design is extended so that realistic AB systems can be investigated. This is achieved by (i) using AB specific operator cost formulations, (ii) integrating infrastructure costs required for AB operations, (iii) utilizing a dynamic, stochastic and schedule-based passenger assignment model for the simulation of PT networks and by (iv) formulating a multi-objective optimization problem allowing to investigate the stakeholder-specific impacts of AB. In Paper I the effects of AB, concerning service frequency and vehicle capacity, on fixed-line PT networks are investigated. Among other metrics, the changes are evaluated based on differences in level of service and passenger flow. Additionally, the sequential introduction of AB in existing PT systems is studied. The framework addresses a case study in Kista, Sweden. The study confirmed the initial hypothesis that the deployment of AB leads to an increase in service frequency and a marginal reduction in vehicle capacity. Furthermore, it could be seen that the deployment of AB increases the passenger load on AB lines and that passengers can shift from other PT modes towards the AB services. Paper II incorporates a multi-objective heuristic optimization algorithm in the simulation framework. The study investigates changes in transport network design based on the deployment of AB. The differences in user-focused and operator-focused network design are analyzed and the impact of AB on these is quantified. This study is applied to a case study in Barkarby, Sweden where a full-sized, line-based PT network is designed to exclusively operate AB. Among other findings, we show that the autonomous technology reduces the number of served bus stops and reduces the total PT network size. Additionally, average passenger waiting time can be reduced when deploying AB on user-focused PT networks, which in turn leads to a further reduction of user cost.<br>De senaste årens framsteg inom autonom körteknik har lett till mer mogna autonoma fordon. Dessa fordon har setts tillämpas i flera pilotprojekt över hela världen, oftast i form av små bussar. Samtidigt växer mängden människor som reser, särskilt i stadsområden, kontinuerligt vilket resulterar i fler resor i transportsystemet. Därför krävs ett effektivt transportsystem för att tillgodose det växande antalet passagerare. Autonoma bussar (AB) antas ha lägre driftskostnader och därmed kan system för kollektivtrafik (public transport, PT) potentiellt utformas mer effektivt för att underlätta den ökade efterfrågan bättre. I denna studie föreslås ett AB-specifikt simuleringsbaserat optimeringsramverk som gör det möjligt att analysera effekterna AB har på linjebaserade PT-system. Avhandlingen fokuserar på övergången från befintliga PT-system till linjebaserade PT-system som delvis eller uteslutande drivs av AB. Befintligt arbete med PT-tjänstdesign utvidgas så att realistiska AB-system kan undersökas. Detta uppnås genom att (i) använda AB-specifika operatörskostnadsformuleringar, (ii) integrera infrastrukturkostnader som krävs för AB-verksamhet, (iii) använda en dynamisk, stokastisk och schemabaserad modell för att tilldela passagerare vid simulering av PT-nät samt genom att (iv) formulera ett multifunktionellt optimeringsproblem som gör det möjligt att undersöka AB: s intressespecifika effekter. I artikel I undersöks effekterna av AB, med avseende på servicefrekvens och fordonskapacitet, på fasta linjer i PT-nät. Förändringar utvärderas bland annat utifrån skillnader i servicenivå och passagerarflöde. Dessutom studeras den sekventiella introduktionen av AB i befintliga PT-system. Det föreslagna ramverket tillämpas på en fallstudie i Kista, Sverige. Studien bekräftade den initiala hypotesen att utplaceringen av AB leder till en ökning av servicefrekvensen och en marginell minskning av fordonens kapacitet. Vidare kunde man se att utplaceringen av AB ökar passagerarbelastningen på AB-linjer och att passagerare kan skifta från andra PT-former mot AB-tjänsterna. Artikel II integrerar en multifunktionell heuristisk optimeringsalgoritm i ramverket för simuleringen. Studien undersöker förändringar i transportnätverkets design baserat på implementeringen av AB. Skillnaderna i användarfokuserad och operatörsfokuserad nätverksdesign analyseras och AB: s inverkan på dessa kvantifieras. Denna studie tillämpas på en fallstudie i Barkarby, Sverige, där ett fullstort linjebaserat PT-nät är utformat för att exklusivt driva AB. Vi visar bland annat att den autonoma tekniken reducerar antalet använda busshållplatser och reducerar den totala PT-nätstorleken. Dessutom kan implementeringen av AB på användarfokuserade PT-nät ytterligare förbättra servicenivån främst genom att minska den genomsnittliga väntetiden per passagerare.

Pour accompagner le développement des fermes urbaines professionnelles et des circuits courts et de proximité dans les grandes métropoles, nous proposons des outils à base de programmes mathématiques d'aide à la conception de fermes maraîchères diversifiées ciblant les demandes de différents types de clients en fruits et légumes frais locaux. Les solutions techniques de culture en ville se développent rapidement, mais compte-tenu des contraintes fortes de la production agricole urbaine (foncier limité, coûts opérationnels élevés), la définition de modèles économiques viables pour des fermes pérennes est un vrai défi pour les maraîchers urbains. Trois modèles en programmation linéaire mixte sont présentés et confrontés aux résultats du terrain : un modèle de dimensionnement stratégique annuel, un modèle de sélection de la meilleure combinaison de clients et un modèle de dimensionnement stratégique pluri-annuel des fermes maraîchères. Des résultats numériques et les performances des modèles sont présentés à partir de cas concrets multi-produits, multi-techniques et multi-périodes. Nos contributions résident dans la prise en compte de la périssabilité des produits frais dans le dimensionnement stratégique des systèmes de production, incluant le dimensionnement de la main d’œuvre agricole<br>To support the urban farm emergence trend in large metropolises, we propose decision support tools based on mathematical programs to design market gardening farms targetting the demands of different categories of clients in local fresh fruits and vegetables. Technical solutions develop rapdily, but the strong constraints linked to urban farming, such as limited surface and high operating costs, make difficult to define viable and sustainable business models for urban market gardeners. Three mixed integer linear programming models are presented: An annual strategic sizing model, a client combination selection model and a plurennial strategic sizing model for diversified fruit and vegetable farms. Numerical results and model performances are presented, based on multi-products, multi-techniques and multi-periods real cases. Our main contributions are the consideration of the perishable nature of fruits and vegetables in strategic production systems sizing models, including notably the investments and workforce sizing