Brunilde Sansò

Telecommunications Network Planning

From the Publisher: Telecommunications Network Planning will benefit both telecommunications practitioners looking for efficient methods to solve their problems and operations researchers interested in telecommunications. The book examines network design and dimensioning problems; it explores Operation Research issues related to a new standard Asynchronous Transfer Mode (ATM); it overviews problems that arise when designing survivable SDH/SONET Networks; it considers some broadband network problems; and it concludes with three chapters on wireless and mobile networks. Leading area researchers have contributed their recent research on the telecommunications and network topics treated in the volume.

Energy Management Through Optimized Routing and Device Powering for Greener Communication Networks

Recent data confirm that the power consumption of the information and communications technologies (ICT) and of the Internet itself can no longer be ignored, considering the increasing pervasiveness and the importance of the sector on productivity and economic growth. Although the traffic load of communication networks varies greatly over time and rarely reaches capacity limits, its energy consumption is almost constant. Based on this observation, energy management strategies are being considered with the goal of minimizing the energy consumption, so that consumption becomes proportional to the traffic load either at the individual-device level or for the whole network. The focus of this paper is to minimize the energy consumption of the network through a management strategy that selectively switches off devices according to the traffic level. We consider a set of traffic scenarios and jointly optimize their energy consumption assuming a per-flow routing. We propose a traffic engineering mathematical programming formulation based on integer linear programming that includes constraints on the changes of the device states and routing paths to limit the impact on quality of service and the signaling overhead. We show a set of numerical results obtained using the energy consumption of real routers and study the impact of the different parameters and constraints on the optimal energy management strategy. We also present heuristic results to compare the optimal operational planning with online energy management operation .

A tabu search heuristic for the Steiner Tree Problem

The Steiner Tree Problem (STP) in graphs is a well-known NP-hard problem. It has regained attention due to the introduction of new telecommunication technologies, such as ATM, since it appears as the inherent mathematical structure behind multicast communications. In this paper, we present a tabu search algorithm for the STP in graphs. The main feature of this algorithm is a sophisticated strategy for quickly obtaining a very good solution and powerful diversification mechanisms. Computational results on the benchmark problems of the OR-Library, for which optimal solutions are known, indicate that the proposed algorithm outperforms other recent heuristics.

Multicommodity flow models, failure propagation, and reliable loss network design

Multicommodity flow (MF) models are well known and have been widely used in the design of packet-switched networks. They have also been used as approximations in the design of circuit-switched networks with reliability constraints. We investigate the usefulness of multicommodity models both as routing models and as an integral part of design models conceived under the failure propagation strategy. First, we compare the performance measures calculated by the models with results produced by a real-time technique. Next, we study the performance of networks dimensioned with flow models and with known adaptive models under failures of transmission facilities when a real-time routing technique is used. Results obtained using realistic data show that the MF models compare favorably with exact dimensioning algorithms when failures are considered.

A Tabu Search Algorithm for the Location of Data Centers and Software Components in Green Cloud Computing Networks

The ubiquity of cloud applications requires the meticulous design of cloud networks with high quality of service, low costs, and low CO2 emissions. This paper presents a planning problem and an extremely efficient tabu search heuristic for optimizing the locations of cloud data centers and software components while simultaneously finding the information routing and network link capacities. The objectives are to optimize the network performance, the CO2 emissions, the capital expenditures (CAPEX), and the operational expenditures (OPEX). The problem is modeled using a mixed-integer programming model and solved with both an optimization solver and a tabu search heuristic. A case study of a web search engine is presented to explain and optimize the different aspects, showing how planners can use the model to direct the optimization and find the best solutions. The efficiency of the tabu search algorithm is presented for networks with up to 500 access nodes and 1,000 potential data center locations distributed around the globe.

Improving the Reliability of Wireless Networks Using Cognitive Radios

To ensure widespread deployment and popularity, next generation wireless services will require a Quality of Service (QoS), and particularly a reliability, that is independent of the radio transmission medium. However, because of the failure-prone nature of wireless networks, providing a reliable communication link and guaranteeing a consistent QoS to users become key issues. In this tutorial, we describe the most common source of failures in wireless networks and provide a systematic failure classification procedure. Drawing from the vast literature on reliability in wireline networks, we then explain how cognitive radios can use their inherent capabilities to implement efficient prevention and recovery mechanisms to combat failures and thereby provide reliable communications and consistent QoS under all circumstances.

On the evaluation of telecommunications network reliability using routing models

A reliability measure that takes into account routing and rerouting policies after failures as well as the capacity of the network to satisfy its demand is proposed. The measure, based on the evaluation of the lost call traffic, needs resolution of a routing model for the states of perfect functioning as well as the most probable failure states. A type of routing model useful for network planning is also proposed. The model is closer to reality and easier to implement than the other classical multicommodity formulations. A convex-simplex implementation with a reoptimization feature explicitly adapted to the proposed model is used. >

On reliability, performance and Internet power consumption

With the increasing concern for global warming, the impact of Internet power consumption is gaining interest. In this paper, we explore, for the first time, the relationship between network robustness, performance and Internet power consumption. We first discuss such a relationship based on data collected from Internet sources. Next, we propose a modeling framework to size that relationship. It is shown that when designing networks based on power consumption, careful attention should be paid to the trade-off between energy consumption and network performance since doing otherwise would lead to unreliable networks.

Systemic behavior of cooperative search algorithms

Abstract Distributed computer systems may be used in various ways to find good solutions to difficult combinatorial optimization problems. An interesting approach consists in executing concurrently different search methods that exchange information gathered in previously explored regions of the solution space. This cooperation mechanism strongly impacts how the solution space is explored. We introduce a formal representation of such cooperative procedures based on discrete-time dynamical systems. We describe how the search behavior of cooperative programs depends on systems of complex and correlated interactions. We derive the notion of systemic cooperation and illustrate through simulations the relevance of this notion to the understanding of the search behavior of cooperative procedures.

Review of facts, data and proposals for a greener internet

The issue of Internet energy consumption and its contribution to global warming has been gaining importance lately. In this paper we present a compilation of facts and data extracted from scattered Internet sources and provide an overview of the basic ideas and most relevant methods suggested to reduce consumption.