Operator interviews and anecdotal evidence suggest that an operator’s ability to manage a network decreases as the network becomes more complex. However, there is currently no way to systematically quantify how complex a network’s design is nor how complexity may impact network management activities. In this paper, we develop a suite of complexity models that describe the routing design and con...

We present a layered graph model for delay-constrained minimum tree problems with a polynomial number of constraints which can be solved well for instances with lowto medium-sized sets of achievable delay values and not too high bounds. Layered graph models have been recently shown to frequently yield tight bounds in the context of hopor delay-constrained network design problems. However, since...

We consider a multi-product distribution network design problem arising from a case-study in the automotive industry. Based on realistic assumptions, we introduce minimum volume, maximum covering distance and single sourcing constraints, making the problem difficult to solve for large-size instances. We thus develop several heuristic procedures using various relaxations of the original MIP form...

This paper highlights the complexity and challenges of providing reliable services in the evolving communications infrastructure. The hurdles in providing end-to-end availability guarantees are discussed and research problems identified. Avenues for overcoming some of the challenges examined are presented. This includes the use of a highly available network spine embedded in a physical network ...

Optimization is accepted by logisticians as the appropriate approach to network design. While network design is used to make decisions regarding many aspects of logistics networks, one set of important decisions relates to the number, location, and size of warehouses in the network. Managers must also determine the customers to be supplied from each warehouse. Because of the costs involved in o...

The network design problem with relays (NDPR) is defined on an undirected graph G = (V,E,K), where V = {1, . . . ,n} is a vertex set, E = {(i, j) : i, j 2 V, i < j} is an edge set. The set K = {(o(k),d(k))} is a set of communication pairs (or commodities): o(k) 2 V and d(k) 2 V denote the origin and the destination of the kth commodity, respectively. With each edge (i, j) are associated a cost ...

The rapid transit network design problem consists on the location of the train alignments and stations in an urban traffic context. The location problem incorporates the demand decisions about the mode and route that they choose to realize the urban trips. The capacity expansion incorporates to the location problem some relevant criteria about the cost of the investment and the future utilizati...

In this paper, we study a Steiner tree related problem called “Terminal Steiner Tree with Bounded Edge Length”: given a set of terminal points P in a plane, one is asked to find a Steiner tree T such that any point in P is a leaf in T and the length of each edge in T is no more than a constant b. The objective of the problem is to minimize the number of Steiner points in T . This problem is mot...

The paper addresses the scheduled service network design problem for freight rail transportation. The proposed model integrates service selection and scheduling, car classification and blocking, train make up, and routing of time-dependent customer shipments, based on a cyclic three-layer space-time network representation of the associated operations and decisions, their relations and time dime...

We describe the first multilevel cooperative tabu search for the capacitated multicommodity network design problem. Main design challenges are associated to the specification of the problem instance addressed at each level in cooperation, as well as to the definition of the cooperation operators. The paper proposes a first approach to address these challenges and tests it on a set of well-known...