1. Introduction

Telecommunication networks have become strategic resources for private- and state-owned institutions, and its economic importance continuously increases. There are series of recent tendencies that have a considerable impact on the economy evolution such as growing integration of networks in the productive system, integration of different services in the same communication system, and important modification in the telephone network structure. Such evolutions accompany a significant growth of the design complexity of these systems. The integration of different sorts of traffics and services and the necessity of a more accurate management of the service quality are factors that make this type of systems very hard to design, to dimension, and therefore to optimize. This situation is aggravated with a very high competitiveness context in an area of critical strategic importance.

The conception of a WAN is a process in which dozens of sites with different characteristics require to be connected in order to satisfy certain reliability and performance restrictions with minimal costs. This design process involves the terminal site location, the concentrator location, the backbone (central network or kernel) design, the routing procedures, as well as the lines and nodes dimensioning. A key aspect on WAN design is the high complexity of the problem, as much in its globality as in the principal subproblems in which it is necessary to decompose it. Due to the high investment levels, a cost decrease of very few percentage points while preserving the service quality results in high economic benefits.

Typically, a WAN network global topology can be decomposed into two main components: the access network and the backbone network. These components have very different properties, and consequently they introduce specific design problems (although they are strongly interdependent). On the one hand, this causes complicated problems (particularly algorithmic ones); on the other hand, it leads to stimulating and difficult research problems.

A WAN access network is composed of a certain number of access subnetworks, having treelike topologies; and the flow concentration nodes allow to diminish the costs. These integrated flows reach the backbone which has a meshed topology, in order to satisfy security, reliability, vulnerability, survivability, and performance criteria. Consequently, the backbone is usually formed by high-capacity communication lines such as optic fiber links.

Modeling a WAN design by means of the formulation of a single mathematical optimization problem is very intricate due to the interdependence of its large amount of parameters. Therefore the design of a WAN is usually divided into different subproblems [1–4]. A good example of a possible decomposition approach for the WAN design process is the following [5]:


This work focuses on phase (1) of the decomposition of a WAN design process. More precisely, it deals with the topology planning process concerning the access network. Due to the NP-hard nature of the problem and even though there exist some results, there is still room for improving industrial practices applied today. In this sense, the authors believe it is of strategic importance to design powerful quantitative analysis techniques, potentially easy to integrate into tools. Combinatorial optimization models are introduced that formally define the topological design of the access networks. Moreover, different results related to the topological structure are introduced. Finally, different algorithms are proposed for the topological design which are based on Dynamic Programming and Dynamic Programming with State-Space Relaxation methodology.

Topological Properties and Dynamic Programming Approach for Designing the Access Network DOI: http://dx.doi.org/10.5772/intechopen.86223
