scispace - formally typeset
Search or ask a question

Showing papers on "Network planning and design published in 2003"


Proceedings ArticleDOI
25 Aug 2003
TL;DR: A new method of traffic characterization that automatically groups traffic into minimal clusters of conspicuous consumption that can be used to automatically classify new traffic patterns, such as network worms or peer-to-peer applications, without knowing the structure of such traffic a priori.
Abstract: The Internet service model emphasizes flexibility -- any node can send any type of traffic at any time. While this design has allowed new applications and usage models to flourish, it also makes the job of network management significantly more challenging. This paper describes a new method of traffic characterization that automatically groups traffic into minimal clusters of conspicuous consumption. Rather than providing a static analysis specialized to capture flows, applications, or network-to-network traffic matrices, our approach dynamically produces hybrid traffic definitions that match the underlying usage. For example, rather than report five hundred small flows, or the amount of TCP traffic to port 80, or the "top ten hosts", our method might reveal that a certain percent of traffic was used by TCP connections between AOL clients and a particular group of Web servers. Similarly, our technique can be used to automatically classify new traffic patterns, such as network worms or peer-to-peer applications, without knowing the structure of such traffic a priori. We describe a series of algorithms for constructing these traffic clusters and minimizing their representation. In addition, we describe the design of our prototype system, AutoFocus and our experiences using it to discover the dominant and unusual modes of usage on several different production networks.

314 citations


Journal ArticleDOI
TL;DR: In this paper, some network topologies for such a pan-European fiber-optic backbone network are presented and a distinction is made between different recovery options in the optical layer for the different traffic types considered.
Abstract: The traffic to be carried by today's European backbone networks increases very rapidly. An important portion of this traffic consists of data traffic (mainly IP-related). In the future data traffic is expected to become the abundantly dominant traffic type, while voice traffic will only account for a very small portion of the total traffic volume. In this paper, some network topologies for such a pan-European fiber-optic backbone network are presented (more details can be found in [1]). These topologies are compared in terms of the efficiency of the network design both from a cost and capacity point of view and in terms of the availability of the connections routed over this network. In order to be able to assess the network topologies under realistic circumstances, the expected traffic demand is forecasted. This enables to make the comparison for the current traffic volume as well as for the traffic patterns of the future. As not all types of (data) traffic require the same degree of survivability and in order to leverage the total capacity cost of the network design, a distinction is made between different recovery options in the optical layer for the different traffic types considered.

240 citations


Book
14 Mar 2003
TL;DR: This book discusses Fixed Broadband Wireless Systems, Electromagnetic Wave Propagation, and Point--to--Multipoint (PMP) Network Design, as well as Atmospheric and Rain Data and Channel Assignment Strategies.
Abstract: Preface Fixed Broadband Wireless Systems Electromagnetic Wave Propagation Propagation and Channel Modes Fading Models Propagation Environment Models Fixed Wireless Antenna Systems Modulation, Equalizers, and Coding Multiple--Access Techniques Traffic and Application Mix Models Single and Multilink System Design Point--to--Multipoint (PMP) Network Design Channel Assignment Strategies Appendix A: Atmospheric and Rain Data Appendix B: PDF of a Signal with Interference and Noise Index

207 citations


Proceedings ArticleDOI
09 Jun 2003
TL;DR: A simple and easy-to-analyze randomized approximation algorithms for several well-studied NP-hard network design problems and a simple constant-factor approximation algorithm for the single-sink buy-at-bulk network design problem.
Abstract: We give simple and easy-to-analyze randomized approximation algorithms for several well-studied NP-hard network design problems. Our algorithms improve over the previously best known approximation ratios. Our main results are the following.We give a randomized 3.55-approximation algorithm for the connected facility location problem. The algorithm requires three lines to state, one page to analyze, and improves the best-known performance guarantee for the problem.We give a 5.55-approximation algorithm for virtual private network design. Previously, constant-factor approximation algorithms were known only for special cases of this problem.We give a simple constant-factor approximation algorithm for the single-sink buy-at-bulk network design problem. Our performance guarantee improves over what was previously known, and is an order of magnitude improvement over previous combinatorial approximation algorithms for the problem.

201 citations


Journal ArticleDOI
TL;DR: In this article, a cycle-based neighbourhood structure for metaheuristics aimed at the fixed-charge capacitated multicommodity network design formulation is proposed, which defines moves that explicitly take into account the impact on the total design cost of potential modifications to the flow distribution of several commodities simultaneously.
Abstract: We propose new cycle-based neighbourhood structures for metaheuristics aimed at the fixed-charge capacitated multicommodity network design formulation. The neighbourhood defines moves that explicitly take into account the impact on the total design cost of potential modifications to the flow distribution of several commodities simultaneously. Moves are identified through a shortest-pathlike network optimization procedure and proceed by redirecting flow around cycles and closing and opening design arcs accordingly. These neighbourhoods are evaluated and tested within a simple tabu search algorithm. Experimental results show that the proposed approach is quite powerful and outperforms existing methods reported in the literature.

183 citations


Proceedings ArticleDOI
11 Oct 2003
TL;DR: This work develops a general method for turning a primal-dual algorithm into a group strategy proof cost-sharing mechanism and uses it to design approximately budget balanced cost sharing mechanisms for two NP-complete problems: metric facility location, and single source rent-or-buy network design.
Abstract: We develop a general method for turning a primal-dual algorithm into a group strategy proof cost-sharing mechanism. We use our method to design approximately budget balanced cost sharing mechanisms for two NP-complete problems: metric facility location, and single source rent-or-buy network design. Both mechanisms are competitive, group strategyproof and recover a constant fraction of the cost. For the facility location game our cost-sharing method recovers a 1/3rd of the total cost, while in the network design game the cost shares pay for a 1/15 fraction of the cost of the solution.

175 citations


Journal ArticleDOI
TL;DR: In this article, the authors proposed a simultaneous route and frequency coded model, which considers the frequency of the route as the variable, thus differing from the earlier models in terms of coding scheme adopted.
Abstract: Transit route network design for urban bus systems involves the selection of a set of routes and the associated frequencies that achieve the desired objective, subject to the operational constraints. This can be formulated as an optimization problem that minimizes the total system cost, which can be expressed as a function of bus operating cost and passenger total travel time. In the first phase of a two-phase solution process, a large set of candidate route is generated using a candidate route generation algorithm. In the second phase, a solution route set is selected from the candidate route set using genetic algorithms, a search and optimization method based on natural genetics. The simultaneous route and frequency coded model proposed in this investigation considers the frequency of the route as the variable, thus differing from the earlier models in terms of coding scheme adopted. A sample study on a medium-sized network has established that the coding scheme adopted for the route network design enhanced the performance of the model.

171 citations


Journal ArticleDOI
TL;DR: The proposed solution is to model the traffic at the flow level by a Poisson shot-noise process, which provides a good approximation of the real traffic observed in the backbone and of its variation.
Abstract: Our goal is to design a traffic model for noncongested Internet backbone links, which is simple enough to be used in network operation, while being as general as possible. The proposed solution is to model the traffic at the flow level by a Poisson shot-noise process. In our model, a flow is a generic notion that must be able to capture the characteristics of any kind of data stream. We analyze the accuracy of the model with real traffic traces collected on the Sprint Internet protocol (IP) backbone network. Despite its simplicity, our model provides a good approximation of the real traffic observed in the backbone and of its variation. Finally, we discuss the application of our model to network design and dimensioning.

154 citations


Proceedings ArticleDOI
01 Dec 2003
TL;DR: A new formula is proposed to quantify the effects of packet loss and delay jitter on speech quality in voice over Internet protocol (VoIP) scenarios and incorporated into ITU-T G.107, the E-model, which is very useful in MOS prediction as well as network planning.
Abstract: The paper investigates the effects of packet loss and delay jitter on speech quality in voice over Internet protocol (VoIP) scenarios. A new formula is proposed to quantify these effects and incorporated into ITU-T G.107, the E-model. In the simulation, codecs ITU-T G.723.1 and G.729 are used; random packet loss and Pareto distributed network delay are introduced. The prediction errors range between -0.20 and +0.12 MOS (mean opinion score). The formula extends the coverage of the current E-model, and is very useful in MOS prediction as well as network planning.

150 citations


Journal ArticleDOI
TL;DR: A new model showing how genetic algorithms can be manipulated to help optimize bus transit routing design, incorporating unique service frequency settings for each route is proposed and shown to be more efficient than the binary-coded genetic algorithm benchmark, in which problem content cannot be utilized.
Abstract: In this paper we propose a new model showing how genetic algorithms can be manipulated to help optimize bus transit routing design, incorporating unique service frequency settings for each route. The main lesson is in the power that can be given to heuristic methods if problem content is exploited appropriately. In this example, seven proposed genetic operators are designed for this specific problem to facilitate the search within a reasonable amount of time. In addition, headway coordination is applied by the ranking of transfer demands at the transfer terminals. The model is applied on a benchmark network to test its efficiency, and performance results are presented. It is shown that the proposed model is more efficient than the binary-coded genetic algorithm benchmark, in which problem content cannot be utilized.

148 citations


Journal ArticleDOI
TL;DR: From the results, it is observed that the connection bandwidth-granularity distribution has a large impact on network throughput and network resource efficiency and should be carefully considered for network design and traffic provisioning.
Abstract: This paper investigates the characteristics and performance of different optical grooming switches, i.e., optical cross-connects (OXCs) capable of traffic grooming, under a dynamic traffic environment. We present four optical grooming-OXC architectures, namely, single-hop grooming OXC, multihop partial-grooming OXC, multihop full-grooming OXC, and light-tree-based source-node grooming OXC. After exploring their grooming capabilities, we propose three grooming schemes and two corresponding algorithms, grooming using auxiliary graph and grooming using light-tree. Through the algorithms, we evaluate the performance of different optical grooming OXCs in a dynamic traffic environment under different connection bandwidth-granularity distributions. Our investigation uncovers the following results: (1) the multihop full-grooming OXC can achieve the best network performance, but it may encounter cost and scalability constraints; (2) by using significantly less low-granularity electronic processing and intelligent traffic-grooming algorithms, the multihop partial-grooming OXC shows reasonable network performance and, hence, can be viewed as a cost-effective alternative when a network node does not require full-grooming capability; (3) the single-hop grooming OXC may cause a large amount of capacity waste and lead to poor network performance; and (4) through its multicast capability, a light-tree-based source-node grooming OXC can significantly out-perform the performance of a single-hop grooming OXC in terms of network throughput and network resource efficiency. From our results, we also observe that the connection bandwidth-granularity distribution has a large impact on network throughput and network resource efficiency and, therefore, should be carefully considered for network design and traffic provisioning.

Journal ArticleDOI
TL;DR: In this paper, a network of potential links is given and each link can be either constructed or not at a given cost, and each constructed link can also be constructed either as a one-way or two-way link.
Abstract: In this paper we introduce new network design problems. A network of potential links is given. Each link can be either constructed or not at a given cost. Also, each constructed link can be constructed either as a one-way or two-way link. The objective is to minimize the total construction and transportation costs. Two different transportation costs are considered: (i) traffic is generated between any pair of nodes and the transportation cost is the total cost for the users and (ii) demand for service is generated at each node and a facility is to be located on a node to satisfy the demand. The transportation cost in this case is the total cost for a round trip from the facility to each node and back. We will consider two options in regard to the links between nodes. They can either be two-way only, or mixed, with both two-way and one-way (in either direction) allowed. When these options are combined with the two objective functions, four basic problems are created. These problems are solved by a descent algorithm, simulated annealing, tabu search, and a genetic algorithm. Extensive computational results are presented.

Proceedings ArticleDOI
01 Jan 2003
TL;DR: An autonomous network of underwater vehicles is considered in which there is no central node, but the vehicles communicate in a distributed manner over multiple hops, and the focus of network design is on a scalable multiple access technique applicable to varying coverage areas as well as varying number of vehicles.
Abstract: An autonomous network of underwater vehicles is considered in which there is no central node, but the vehicles communicate in a distributed manner over multiple hops. The focus of network design is on a scalable multiple access technique which is applicable to varying coverage areas as well as varying number of vehicles. The proposed scheme relies on grouping the adjacent vehicles into clusters, and using time-division multiple access within each cluster. Interference among clusters is managed by assigning different spreading codes to adjacent clusters, while scalability is achieved by spatial reuse of the codes. Network operation begins with an initialization phase, and moves on to continuous maintenance during which mobility is managed. Performance is quantified through measures of connectivity, successful transmission rate, average delay and energy consumption. Simulation analysis is used to obtain optimal cluster size and transmission power for a network with given density of vehicles.

Proceedings ArticleDOI
19 Oct 2003
TL;DR: An algorithmic approach for providing p-cycle survivable transport network designs is developed and test, which entirely avoids the step of enumerating all cycles, which is a preliminary step in both ILP and heuristic solution methods based on preselection.
Abstract: We develop and test an algorithmic approach for providing p-cycle survivable transport network designs. The basic approach is to first identify a set of primary p-cycles, then to search for improvements on those cycles through various operations to create a final set of cycles of high individual and collective efficiency, before finally placing one p-cycle at a time, iteratively, until all working capacity of the network is protected. We compare the solution quality of the algorithm to optimal designs obtained with ILP methods. The primary advantage of this algorithmic approach is that it entirely avoids the step of enumerating all cycles, which is a preliminary step in both ILP and heuristic solution methods based on preselection. This method proceeds initially with no more than S "primary" p-cycles, and in the worst case will enumerate no more than S/sup 2/-N other candidate cycles during its execution, where S is the number of spans in the network and N is the number of nodes. We also find that the set of candidate cycles developed by the algorithm can themselves be used as a quite small but highly effective set of eligible cycles in an ILP design model.

Proceedings ArticleDOI
09 Jun 2003
TL;DR: A model of selfish routing in which the latency experienced by network traffic on an edge of the network is a function of the edge congestion, and network users are assumed to selfishly route traffic on minimum-latency paths is considered.
Abstract: We study economic incentives for influencing selfish behavior in networks. We consider a model of selfish routing in which the latency experienced by network traffic on an edge of the network is a function of the edge congestion, and network users are assumed to selfishly route traffic on minimum-latency paths. The quality of a routing of traffic is historically measured by the sum of all travel times, also called the total latency.It is well known that the outcome of selfish routing (a Nash equilibrium) does not minimize the total latency and can be improved upon with coordination, and that marginal cost pricing---charging each network user for the congestion effects caused by its presence---eliminates the inefficiency of selfish routing. However, the principle of marginal cost pricing assumes that (possibly very large) taxes cause no disutility to network users; this is appropriate only when collected taxes can be feasibly returned (directly or indirectly) to the users, for example via a lump-sum refund. If this assumption does not hold and we wish to minimize the total user disutility (latency plus taxes paid)---the total cost---how should we price the network edges? Intuition may suggest that taxes should never be able to improve the cost of a Nash equilibrium, but the famous Braess's Paradox shows this intuition to be incorrect.We consider strategies for pricing network edges to reduce the cost of a Nash equilibrium. Since levying a sufficiently large tax on an edge effectively removes it from the network, our study generalizes previous work on network design citend_hard. In this paper, we prove the following results.

Journal ArticleDOI
TL;DR: It is shown that the proposed adaptable neural-network architecture simulates a recursive nonlinear autoregressive model (RNAR) similar to the notation used in the linear case, and presents low computational complexity and high efficiency in tracking traffic rates in contrast to conventional retraining schemes.
Abstract: Multimedia services and especially digital video is expected to be the major traffic component transmitted over communication networks [such as internet protocol (IP)-based networks]. For this reason, traffic characterization and modeling of such services are required for an efficient network operation. The generated models can be used as traffic rate predictors, during the network operation phase (online traffic modeling), or as video generators for estimating the network resources, during the network design phase (offline traffic modeling). In this paper, an adaptable neural-network architecture is proposed covering both cases. The scheme is based on an efficient recursive weight estimation algorithm, which adapts the network response to current conditions. In particular, the algorithm updates the network weights so that 1) the network output, after the adaptation, is approximately equal to current bit rates (current traffic statistics) and 2) a minimal degradation over the obtained network knowledge is provided. It can be shown that the proposed adaptable neural-network architecture simulates a recursive nonlinear autoregressive model (RNAR) similar to the notation used in the linear case. The algorithm presents low computational complexity and high efficiency in tracking traffic rates in contrast to conventional retraining schemes. Furthermore, for the problem of offline traffic modeling, a novel correlation mechanism is proposed for capturing the burstness of the actual MPEG video traffic. The performance of the model is evaluated using several real-life MPEG coded video sources of long duration and compared with other linear/nonlinear techniques used for both cases. The results indicate that the proposed adaptable neural-network architecture presents better performance than other examined techniques.

Journal ArticleDOI
C S Sung1, Sang Hwa Song1
TL;DR: This paper considers an integrated service network design problem for a given set of freight demands that is concerned with integration of locating cross-docking (CD) centers and allocating vehicles for the associated direct (transportation) services from origin node to a CD centers or from a CD center to the destination node.
Abstract: This paper considers an integrated service network design problem for a given set of freight demands that is concerned with integration of locating cross-docking (CD) centers and allocating vehicles for the associated direct (transportation) services from origin node to a CD center or from a CD center to the destination node. For the vehicle allocation, direct services (sub-routes) should be determined for the given freight demands, and then the vehicle allocation has to be made in consideration of routing for the associated direct service fulfillment subject to vehicle capacity and service time restriction. The problem is modeled as a path-based formulation for which a tabu-search-based solution algorithm is proposed. To guarantee the performance of the proposed solution algorithm, strong valid inequalities are derived based on the polyhedral characteristics of the problem domain and an efficient separation heuristic is derived for identifying any violated valid inequalities. Computational experiments are performed to test the performance of the proposed solution algorithm and also that of a valid-inequality separation algorithm, which finds that the solution algorithm works quite well and the separation algorithm provides strengthened lower bounds. Its immediate application may be made to strategic (integrated) service network designs and to tactical service network planning for the CD network.

Journal ArticleDOI
TL;DR: This work considers pricing for multiple services offered over a single telecommunications network, and derives optimality conditions and a solution method for this class of problems, and applies to a realistic model of a multiservice communications network.
Abstract: We consider pricing for multiple services offered over a single telecommunications network. Each service has quality-of-service (QoS) requirements that are guaranteed to users. Service classes may be defined by the type of service, such as voice, video, or data, as well as the origin and destination of the connection provided to the user. We formulate the optimal pricing problem as a nonlinear integer expected revenue optimization problem. We simultaneously solve for prices and the resource allocations necessary to provide connections with guaranteed QoS. We derive optimality conditions and a solution method for this class of problems, and apply to a realistic model of a multiservice communications network.

Journal Article
TL;DR: There are two basic ways to deploy wireless LAN access points in an indoor scenario: manual deployment using a site survey based on empirical measurements or planning using a software tool with built-in signal propagation models.
Abstract: There are two basic ways to deploy wireless LAN access points in an indoor scenario: manual deployment using a site survey based on empirical measurements or planning using a software tool with built-in signal propagation models. In this paper advantages and disadvantages of both ways are discussed. The planning based on propagation modeling is recognized as a highly preferable approach for design of large WLANs. Experimental data in this paper were processed in MATLAB.

Patent
08 Jul 2003
TL;DR: In this paper, a target device makes observations of at least one signal quality parameter in a wireless communication environment, and a selection logic selects an optimal device model for each target device and the observations made by the target device are processed with the selected device model and applied to an application, such as a positioning application or network planning.
Abstract: A method and apparatus for using at least one signal quality parameter in an application. A target device makes observations of at least one signal quality parameter in a wireless communication environment. Because there are gross differences between different target devices' observations, there are one or more device models that compensate for the differences. A selection logic selects an optimal device model for each target device. The observations made by the target device are processed with the selected device model and applied to an application, such as a positioning application or network planning.

Journal ArticleDOI
M. Unbehaun1, M. Kamenetsky
TL;DR: Deployment strategies for wireless Internet service providers installing public WLANs in airports, hotels, and other frequently trafficked areas are analyzed, specifically for possible future systems utilizing bands of up to 60 GHz.
Abstract: Wireless LANs are becoming increasingly common in both home and office networks. Additionally, wireless Internet service providers have begun installing public WLANs in airports, hotels, and other frequently trafficked areas. This article analyzes deployment strategies for such networks, specifically for possible future systems utilizing bands of up to 60 GHz. A major part of the installation cost stems from network planning, wiring, and manpower for setting up base stations. It is therefore crucial to find ways to simplify the network installation and reduce the deployment costs, while at the same time maintaining the desired system performance. We show that even simple installation rules can often achieve adequate coverage results. However, proper network planning is in some situations necessary to achieve adequate coverage. Therefore, we examine different combinatorial optimization methods for obtaining close to optimal positioning of WLAN access points and compare the performance of the proposed algorithms to the simple installation methods. The optimization algorithms used in this article evaluate an objective function that aims to maximize both the coverage area and the overall signal quality over a discrete search space. Random search algorithms can yield very good solutions, but often exhibit difficult convergence properties. Successive removal algorithms, such as pruning, converge in polynomial time, but usually produce suboptimal solutions. We therefore propose a combination of the two approaches, using pruning to obtain an initial set of the base station positions and refining these by using neighborhood search or simulated annealing.

Journal ArticleDOI
01 Jan 2003
TL;DR: An approach to network topology design, modeling, and generation that is based on the concept of Highly Optimized Tolerance (HOT), which opens up new areas of research that focus on the causal forces at work in network design and aim at identifying the economic and technical drivers responsible for the observed large-scale network behavior.
Abstract: We propose a novel approach to the study of Internet topology in which we use an optimization framework to model the mechanisms driving incremental growth. While previous methods of topology generation have focused on explicit replication of statistical properties, such as node hierarchies and node degree distributions, our approach addresses the economic tradeoffs, such as cost and performance, and the technical constraints faced by a single ISP in its network design. By investigating plausible objectives and constraints in the design of actual networks, observed network properties such as certain hierarchical structures and node degree distributions can be expected to be the natural by-product of an approximately optimal solution chosen by network designers and operators. In short, we advocate here essentially an approach to network topology design, modeling, and generation that is based on the concept of Highly Optimized Tolerance (HOT). In contrast with purely descriptive topology modeling, this opens up new areas of research that focus on the causal forces at work in network design and aim at identifying the economic and technical drivers responsible for the observed large-scale network behavior. As a result, the proposed approach should have significantly more predictive power than currently pursued efforts and should provide a scientific foundation for the investigation of other important problems, such as pricing, peering, or the dynamics of routing protocols.

Proceedings ArticleDOI
01 Nov 2003
TL;DR: The present design allows us to instantiate arbitrary network topologies, has a low latency and high throughput, and is part of the platform the author is developing for reconfigurable systems.
Abstract: An efficient methodology for building the billion-transistors systems on chip of tomorrow is a necessity. Networks on chip promise to be the solution for the numerous technological, economical and productivity problems. We believe that different types of networks are required for each application domains. Our approach therefore is to have a very flexible network design, highly scalable, that allows to easily accommodate the various needs. This paper presents the design of our network on chip, which is part of the platform we are developing for reconfigurable systems. The present design allows us to instantiate arbitrary network topologies, has a low latency and high throughput.

Proceedings ArticleDOI
09 Jul 2003
TL;DR: A novel integer linear programming (ILP) formulation based on an hop-indexed approach, which is called the HOP model, is proposed and a two-phase heuristic, derived from a decomposition of the Hop model in two simpler ILP models that are solved sequentially, is developed.
Abstract: MPLS (multiprotocol label switching) over WDM (wavelength division multiplexing) networks are gaining significant attention due to the efficiency in resource utilization that can be achieved by jointly considering the two network layers. This paper addresses the design of MPLS over WDM networks, where some of the WDM nodes may not have packet switching capabilities. Given the WDM network topology and the offered traffic matrix, which includes the location of the edge LSRs (label switched routers), we jointly determine the location of the core LSRs (i.e. the core WDM nodes that also need to include packet switching capabilities) and the lightpath routes (which are terminated on the LSRs) that minimize the total network cost. We consider constraints both at the optical and packet layers: an MPLS hop constraint on the maximum number of LSRs traversed by each LSP (label switched path), which guarantees a given packet level QoS, and a WDM path constraint on the maximum length of lightpaths, which accommodates the optical transmission impairments. A novel integer linear programming (ILP) formulation based on an hop-indexed approach, which we call the HOP model, is proposed. A two-phase heuristic, derived from a decomposition of the HOP model in two simpler ILP models that are solved sequentially, is also developed. The computational results show that the heuristic is efficient and produces good quality solutions, as assessed by the lower bounds computed from the HOP model. In some cases, the optimal solution is obtained with the branch-and-bound method.

Proceedings ArticleDOI
05 Apr 2003
TL;DR: The IP Network Design Workbench is presented which supports collaborative network design and simulation by a group of experts and customers and is based on a tangible user interface platform called "Sensetable," which can wirelessly detect the location and orientation of physical pucks.
Abstract: We present the IP Network Design Workbench which supports collaborative network design and simulation by a group of experts and customers. This system is based on a tangible user interface platform called "Sensetable," which can wirelessly detect the location and orientation of physical pucks. Using this system, users can directly manipulate network topologies, control parameters of nodes and links using physical pucks on the sensing table, and simultaneously see the simulation results projected onto the table in real-time.

Journal ArticleDOI
TL;DR: It is shown that employing local search during evolution of the genetic algorithm, a memetic algorithm, yields the best network designs and does so at a reasonable computational cost.
Abstract: In many computer communications network design problems, such as those faced by hospitals, universities, research centers, and water distribution systems, the topology is fixed because of geographical and physical constraints or the existence of an existing system. When the topology is known, a reasonable approach to design is to select components among discrete alternatives for links and nodes to maximize reliability subject to cost. This problem is NP-hard with the added complication of a very computationally intensive objective function. This paper compares the performance of three classic metaheuristic procedures for solving large and realistic versions of the problem: hillclimbing, simulated annealing and genetic algorithms. Three alterations that use local search to seed the search or improve solutions during each iteration are also compared. It is shown that employing local search during evolution of the genetic algorithm, a memetic algorithm, yields the best network designs and does so at a reasonable computational cost. Hillclimbing performs well as a quick search for good designs, but cannot identify the most superior designs even when computational effort is equal to the metaheuristics.

Journal ArticleDOI
TL;DR: A genetic algorithm based methodology is developed and evaluated for finding the optimal throughput-delay tradeoff curve, the so-called Pareto-optimal frontier, and provides the network architecture and the medium access control protocol parameters that achieve the Pare to-optima in a computationally efficient manner.
Abstract: We consider the multi-objective optimization of a multi-service arrayed-waveguide grating-based single-hop metro WDM network with the two conflicting objectives of maximizing throughput while minimizing delay. We develop and evaluate a genetic algorithm based methodology for finding the optimal throughput-delay tradeoff curve, the so-called Pareto-optimal frontier. Our methodology provides the network architecture (hardware) and the medium access control (MAC) protocol parameters that achieve the Pareto-optima in a computationally efficient manner. The numerical results obtained with our methodology provide the Pareto-optimal network planning and operation solutions for a wide range of traffic scenarios. The presented methodology is applicable to other networks with a similar throughput-delay tradeoff.

Journal ArticleDOI
TL;DR: A new accessibility–maximization approach to inter–urban road network long–term planning based on a nonlinear combinatorial optimization model used to analyze the ongoing transformation of the Portuguese main road network is presented.
Abstract: Accessibility, is a key, factor in defining the quality, of life and potential for development of both cities and regions. This article presents a new accessibility maximization approach to inter-urban road network long-term planning. The approach is based on a nonlinear combinatorial optimization model. Two heuristics have been developed for solving the model, based on local search and,simulated annealing principles, respectively. The efficiency, of the heuristics was evaluated on a sample of test problems involving 10-, 20-, and 40-node networks. In the analysis both solution quality and computing effort were taken into account. The approach was used to analyze the ongoing transformation of the Portuguese main road network. The results obtained so far indicate that the model is a valuable decision-aid tool for inter-urban road network long-term planning.

Patent
27 Jun 2003
TL;DR: In this article, a network operator identifier is used to uniquely identify each network operator to support international roaming, which includes a Mobile Country Code (MCC) that identifies the country in which the network operator belongs and a Network Operator Code (NOC) that distinguishes network operators within a given MCC.
Abstract: A network operator identifier is used to uniquely identify each network operator to support international roaming. The network operator identifier includes (1) a Mobile Country Code (MCC) that identifies the country in which a network operator belongs and (2) a Network Operator Code (NOC), which may be a Mobile Network Code (MNC), that distinguishes network operators within a given MCC. Each network operator is assigned a unique combination of MCC and NOC that distinctly identifies the network operator, and the network operator identifier can be stored in a single entry in a preferred roaming list. The base stations of each network operator broadcast the network operator identifier in signaling messages. A mobile station receives a signaling message from a base station, obtains the network operator identifier, searches its preferred roaming list for an entry with the network operator identifier, and determines whether or not the current CDMA network is accessible.

Proceedings ArticleDOI
08 Aug 2003
TL;DR: Demand-wise shared protection bases on the diversification of demand routings and exploits the network connectivity to restrict the number of backup lightpaths needed to provide the desired level of protection.
Abstract: In this paper, a new shared protection mechanism for meshed optical networks is presented. Significant network design cost reductions can be achieved in comparison to the well-known 1+1 protection scheme. Demand-wise shared protection (DSP) bases on the diversification of demand routings and exploits the network connectivity to restrict the number of backup lightpaths needed to provide the desired level of protection. Computational experiments approve the benefits of the concept DSP for cost efficient optical network designs.