Browsing by Subject "Survivable network design"

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Open Access
Regenerator location problem and survivable extensions: a hub covering location perspective
(Elsevier, 2015) Yıldız, B.; Karaşan, O. E.
In a telecommunications network the reach of an optical signal is the maximum distance it can traverse before its quality degrades. Regenerators are devices to extend the optical reach. The regenerator placement problem seeks to place the minimum number of regenerators in an optical network so as to facilitate the communication of a signal between any node pair. In this study, the Regenerator Location Problem is revisited from the hub location perspective directing our focus to applications arising in transportation settings. Two new dimensions involving the challenges of survivability are introduced to the problem. Under partial survivability, our designs hedge against failures in the regeneration equipment only, whereas under full survivability failures on any of the network nodes are accounted for by the utilization of extra regeneration equipment. All three variations of the problem are studied in a unifying framework involving the introduction of individual flow-based compact formulations as well as cut formulations and the implementation of branch and cut algorithms based on the cut formulations. Extensive computational experiments are conducted in order to evaluate the performance of the proposed solution methodologies and to gain insights from realistic instances.
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.