Telecommun Syst (2011) 46: 149–161 DOI 10.1007/s11235-010-9278-2 Telecommunications network design with multiple technolog Fatma Gzara · Erhan Erkut Published online: 5 March 2010 © Springer Science+Business Media, LLC 2010 Abstract In this paper we consider a telecommunications network design problem allowing for multiple technologies. The problem arises in wide-area network and metro-area network design for which a combination of technologies may be necessary due to high traffic volumes, long-distance transmission, and design restrictions. The network design problem builds the best network to channel traffic between a setof origins and destinations, which requires selecting links,equipping them with fiber, deciding on the type of technology, and locating switches. The goal is to minimize the total costof the network, which accounts for the flow cost, the fiber and technology costs, and the switch-location cost.We model the problem using a multicommodity net- work design formulation with side constraints. We apply Benders decomposition to the problem and develop a two- phase solution method that uses a number of improvements over the basic Benders algorithm. We present promising re- sults on randomly generated test problems. Keywords Telecommunications network design · Multiple technologies · Multicommodity network design · Benders decomposition F. Gzara Department of Management Sciences, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada e-mail: fgzara@uwaterloo.ca E. Erkut ( ) Ozyegin University, Istanbul, Turkey e-mail: erhan.erkut@ozyegin.edu.tr 1 Introduction Telecommunications network design spans a wide range o problems from determining the best topology to locating hardware, maximizing reliability, and pursuing new tech- nologies. In this paper we consider a telecommunications network design problem that arises in wide-area network (WAN) and metro-area network (MAN) designs for which it may be necessary to implement a combination of tech- nologies due to high traffic volumes, long-distance trans- mission, and design restrictions. The problem is to build t least-cost network that channels traffic between a set of o gins and destinations. The latter may represent smaller ac cess networks. It requires selecting links from a given net work, equipping the selected links with fiber, and decidin on the type of technology. The network is composed of po sible links along which fiber can be laid, usually the road network. It follows that the nodes of the network are the i tersections of the roads, and the edges are the links betw intersections. Even though only one kind of fiber is avail- able, a number of different technologies can be used both parallel (multiple technologies can use the same fiber) an series (a signal can use different technologies on consecu links).For example, two technology types can be SONET and DWDM, which are the most widely used in WANs and MANs. Technology types can also represent different wav lengths in optical networks. If a signal uses different tech- nologies on two adjacent links, a switch is required. The g is to minimize the total cost of the network, which include the flow cost, the fiber and technology costs, and the swit location cost. In summary, the telecommunications netwo design problem (NDP) finds the optimal topology to route a set of communication demands, determines the number fibers, assigns the technology types, and locates switches The NDP isclosely related to other network design problems such as the network loading/capacity installatio