Browsing by Subject "Regenerators"

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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
Regenerator placement and traffic engineering with restoration in GMPLS networks
(Springer, 2003) Yetginer, E.; Karasan, E.
In this paper, we study regenerator placement and traffic engineering of restorable paths in generalized multiprotocol label switching (GMPLS) networks. Regenerators are necessary in optical networks in order to cope with transmission impairments. We study a network architecture where regenerators are placed only at selected nodes for decreasing cost of regeneration. We propose two heuristic algorithms for optimum placement of these regenerators. Performances of these algorithms in terms of required number of regenerators and computational complexity are evaluated. In this network architecture with sparse regeneration, off-line computation of working and restoration paths is studied for traffic engineering with path rerouting as the restoration scheme. We study two approaches for selecting working and restoration paths from a set of candidate paths and formulate each method as an integer linear programming (ILP) problem. A traffic uncertainty model is developed in order to compare these methods based on their robustness with respect to changing traffic patterns. Traffic engineering methods are compared based on number of additional demands resulting from traffic uncertainties that can be carried over the network. Proposed heuristic regenerator placement algorithms are also evaluated from a traffic engineering point of view.