Browsing by Subject "Hub-and-spoke networks"

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Open Access
Comparison of the formulations for a hub-and-spoke network design problem under congestion
(Elsevier, 2016) Kian, Ramer; Kargar, Kamyar
In this paper, we study the hub location problem with a power-law congestion cost and propose an exact solution approach. We formulate this problem in a conic quadratic form and use a strengthening method which rests on valid inequalities of perspective cuts in mixed integer nonlinear programming. In a numerical study, we compare two well known types of mathematical modeling in the hub-location problems which are solved with different branch and cut strategies. The strength and weakness of the formulations are summarized based on an extensive numerical study over the CAB data set. © 2016 Elsevier Ltd
Open Access
Perspectives on modeling hub location problems
(Elsevier, 2020-10-02) Alumur, S. A.; Campbell, J. F.; Contreras, I.; Yetiş Kara, Bahar; Marianov, V.; O’Kelly, M. E.
The aim of this paper is to provide insights for better modeling hub location problems to help create a road map for future hub location research. We first present a taxonomy to provide a framework for the broad array of hub location models, and then seek to identify key gaps in the literature that provide opportunities for better models. We provide some new perspectives in several areas, including the historical evolution of hub location research, models for economies of scale, and relevant characteristics of different applications. We also provide a succinct summary of state-of-the-art formulation and solution approaches. We conclude with a set of themes that can be addressed in the future for better modeling hub location problems.
Open Access
Survivable fiber optical network design
(2015-09) Sözüer, Seçil
This thesis presents a study on a survivable extension of a network design problem of one of the largest Internet service providers operating in Turkey. In a previous study, this problem is defined as the "Green Field Network Design Problem" where the aim is to design a cost effective fiber optical network that will provide high speed and high quality Internet access from a prelocated central station to a set of aggregated demand nodes. In order to attain a required service level, insertion loss, speed level and distance limitations are considered simultaneously. The Internet access from the central station to the demand nodes can be provided either directly by installing fiber optical wires or indirectly by utilizing special telecommunication devices called "Passive Splitters". Passive splitters copy and split the data into the output ports, and they can be considered as hubs since they consolidate and disseminate the data. In this study, we consider the survivable version of this problem: "Survivable Green Field Network Design Problem". In order to ensure survivability, we seek to find 2-node disjoint paths for every demand node such that the fixed costs of installing passive splitters and the fiber wiring costs are minimized. A mathematical model is constructed. In order to solve problems with higher dimensions, heuristic algorithms are also proposed. A data set belonging to Kartal district of İstanbul is used to test the performances of mathematical model and the heuristics, and the results of the computational study are reported.