Showing papers on "Network planning and design published in 2001"

A New Benders Decomposition Approach to Solve Power Transmission Network Design Problems

Abstract: In this paper we describe a new Benders decomposition approach to solve power transmission network expansion planning problems. This new approach is characterized by using a linear (0-1) disjuntctive model which ensures the optimality of the solution found and by using additional constraints, iteratively evaluated, besides the traditional Benders cuts. The results obtained, considering a real world power transmission network expansion planning study with the southeastern Brazilian system, show the efficiency of this approach.

Provisioning a virtual private network: a network design problem for multicommodity flow

Abstract: Consider a setting in which a group of nodes, situated in a large underlying network, wishes to reserve bandwidth on which to support communication. Virtual private networks (VPNs) are services that support such a construct; rather than building a new physical network on the group of nodes that must be connected, bandwidth in the underlying network is reserved for communication within the group, forming a virtual “sub-network.”Provisioning a virtual private network over a set off terminals gives rise to the following general network design problem. We have bounds on the cumulative amount of traffic each terminal can send and receive; we must choose a path for each pair of terminals, and a bandwidth allocation for each edge of the network, so that any traffic matrix consistent with the given upper bounds can be feasibly routed. Thus, we are seeking to design a network that can support a continuum of possible traffic scenarios.We provide optimal and approximate algorithms for several variants of this problem, depending on whether the traffic matrix is required to be symmetric, and on whether the designed network is required to be a tree (a natural constraint in a number of basic applications). We also establish a relation between this collection of network design problems and a variant of the facility location problem introduced by Karger and Minkoff; we extend their results by providing a stronger approximation algorithm for this latter problem.

System and method for providing peer-oriented control of telecommunications services

Abstract: In a telecommunications network environment including non-participating elements and participating elements, a method for providing a telecommunications service between a first peer element connected to the telecommunications network environment and a second peer element connected to the telecommunications network. At a first peer element, an indication of the type of telecommunications service to be provided between the first peer element and the second peer element is received. A telecommunications service template in association with the indicated telecommunications service is determined, the telecommunications service template including instructions for configuring the non-participating elements of the telecommunications network environment to provide the indicated telecommunications service and instructions for configuring the participating elements of the telecommunications network environment. The telecommunications service template may further comprise routing instructions for the non-participating elements of the telecommunications network environment and routing instructions for the participating elements of the telecommunications network environment. The instructions to configure the participating elements and non-participating elements of the telecommunications network environment are executed to provide the telecommunications service. Data between the first peer element and the second peer element is transmitted via a predefined transmission protocol indicated by the telecommunications service template, the data including the routing instructions for the non-participating elements of the telecommunications network environment in a header portion of the predefined transmission protocol and the routing instructions for the participating elements of the telecommunications network environment in a payload portion of the predefined transmission protocol.

Designer gene networks: Towards fundamental cellular control

Abstract: The engineered control of cellular function through the design of synthetic genetic networks is becoming plausible. Here we show how a naturally occurring network can be used as a parts list for artificial network design, and how model formulation leads to computational and analytical approaches relevant to nonlinear dynamics and statistical physics. We first review the relevant work on synthetic gene networks, highlighting the important experimental findings with regard to genetic switches and oscillators. We then present the derivation of a deterministic model describing the temporal evolution of the concentration of protein in a single-gene network. Bistability in the steady-state protein concentration arises naturally as a consequence of autoregulatory feedback, and we focus on the hysteretic properties of the protein concentration as a function of the degradation rate. We then formulate the effect of an external noise source which interacts with the protein degradation rate. We demonstrate the utility of such a formulation by constructing a protein switch, whereby external noise pulses are used to switch the protein concentration between two values. Following the lead of earlier work, we show how the addition of a second network component can be used to construct a relaxation oscillator, whereby the system is driven around the hysteresis loop. We highlight the frequency dependence on the tunable parameter values, and discuss design plausibility. We emphasize how the model equations can be used to develop design criteria for robust oscillations, and illustrate this point with parameter plots illuminating the oscillatory regions for given parameter values. We then turn to the utilization of an intrinsic cellular process as a means of controlling the oscillations. We consider a network design which exhibits self-sustained oscillations, and discuss the driving of the oscillator in the context of synchronization. Then, as a second design, we consider a synthetic network with parameter values near, but outside, the oscillatory boundary. In this case, we show how resonance can lead to the induction of oscillations and amplification of a cellular signal. Finally, we construct a toggle switch from positive regulatory elements, and compare the switching properties for this network with those of a network constructed using negative regulation. Our results demonstrate the utility of model analysis in the construction of synthetic gene regulatory networks.

An integrated model of facility location and transportation network design

Abstract: Network location models have been used extensively for siting public and private facilities In this paper, we investigate a model that simultaneously optimizes facility locations and the design of the underlying transportation network Motivated by the simple observation that changing the network topology is often more cost-effective than adding facilities to improve service levels, the model has a number of applications in regional planning, distribution, energy management, and other areas The model generalizes the classical simple plant location problem We show how the model can be solved effectively We then use the model to analyze two potential transportation planning scenarios The fundamental question of resource allocation between facilities and links is investigated, and a detailed sensitivity analysis provides insight into the model's usefulness for aiding budgeting and planning decisions We conclude by identifying promising research directions

Design of logical topologies: a linear formulation for wavelength-routed optical networks with no wavelength changers

Abstract: We consider the problem of constructing logical topologies over a wavelength-routed optical network with no wavelength changers. We present a general linear formulation which considers routing traffic demands, and routing and assigning wavelengths to lightpaths, as a combined optimization problem. The formulation also takes into account the maximum number of hops a lightpath is permitted to take, multiple logical links in the logical topology, multiple physical links in the physical topology, and symmetry/asymmetry restrictions in designing logical topologies. The objective is to minimize congestion. We show by examples how equality and inequality logical degree constraints have a bearing on congestion. We prove that, under certain conditions, having equality degree constraints with multiple edges allowed in the design of logical topologies does not affect congestion. This helps in reducing the dimensionality of the search space and hence speeds up the search for an optimal solution of the linear formulation. We solve the linear formulation for small examples and show the tradeoff between congestion, number of wavelengths available and the maximum number of hops a lightpath is allowed to take. For large networks, we solve the linear formulation by relaxing the integer constraints. We develop topology design algorithms for large networks based on rounding the solutions obtained by solving the relaxed problem. Since the whole problem is linearizable, the solution obtained by relaxation of the integer constraints yields a lower bound on congestion. This is useful in comparing the efficiency of our heuristic algorithms. Following Bienstock and Gunluk (1995), we introduce a cutting plane which helps in obtaining better lower bounds on congestion and also enables us to reduce the previously obtained upper bounds on congestion.

Hierarchical placement and network design problems

Abstract: Gives constant approximations for a number of layered network design problems. We begin by modeling hierarchical caching, where the caches are placed in layers and each layer satisfies a fixed percentage of the demand (bounded miss rates). We present a constant approximation to the minimum total cost of placing the caches and to the routing demand through the layers. We extend this model to cover more general layered caching scenarios, giving a constant combinatorial approximation to the well-studied multi-level facility location problem. We consider a facility location variant, the load-balanced facility location problem, in which every demand is served by a unique facility and each open facility must serve at least a certain amount of demand. By combining load-balanced facility location with our results on hierarchical caching, we give a constant approximation for the access network design problem.

Designing networks for selfish users is hard

Abstract: We consider a directed network in which every edge possesses a latency function specifying the time needed to traverse the edge given its congestion. Selfish, noncooperative agents constitute the network traffic and wish to travel from a source s to a sink t as quickly as possible. Since the route chosen by one network user affects the congestion (and hence the latency) experienced by others, we model the problem as a noncooperative game. Assuming each agent controls only a negligible portion of the overall traffic, Nash equilibria in this noncooperative game correspond to s-t flows in which all flow paths have equal latency. We give optimal inapproximability results and approximation algorithms for several network design problems of this type. For example, we prove that for networks with n nodes and continuous, nondecreasing latency functions, there is no approximation algorithm for this problem with approximation ratio less than n/2 (unless P = NP). We also prove this hardness result to be best possible by exhibiting an n/2-approximation algorithm. For networks in which the latency of each edge is a linear function of the congestion, we prove that there is no (4/3 - /spl epsi/)-approximation algorithm for the problem (for any /spl epsi/ > 0, unless P = NP); the existence of a 4/3-approximation algorithm follows easily from existing work, proving this hardness result sharp.

Topological network design of pedestrian networks

Abstract: The design and analysis of series, merge, and splitting topologies of pedestrian networks is presented and an analytical approximation methodology is developed to compute the network performance measures. State dependent queuing networks are appropriate tools for modelling congestion in vehicular and pedestrian traffic networks, and many others where congestion occurs due to a decay in the service rate with increased density of customer traffic. This paper focuses on models for pedestrian network design. Also, an optimization methodology is developed for determining the optimal capacity requirements of these networks and extensive experimental results are included.

Stochastic Dynamic Network Design Problem

Abstract: The continuous network design problem that occurs when the origindestination time-dependent demands are random variables with known probability distributions is described. A chance-constraint and two-stage linear programming formulation are introduced based on a system optimum dynamic traffic assignment model that propagates traffic according to the cell transmission model. The introduced approaches are limited to continuous link improvements and do not provide for new link additions. The chance-constrained model is tested on an example network that resembles a freeway corridor to demonstrate the simplicity and applicability of the approach. Initial results suggest that planning for an inflated demand may produce benefits in terms of system performance and reduced variance.

Reverse Logistics Network Structures and Design

Abstract: textLogistics network design is commonly recognized as a strategic supply chain issue of prime importance. The location of production facilities, storage concepts, and transportation strategies are major determinants of supply chain performance. This chapter considers logistics network design for the particular case of closed-loop supply chains. We highlight key issues that companies are facing when deciding upon the logistics implementation of a product recovery initiative. In particular, we point out differences and analogies with logistics network design for traditional 'forward' supply chains. Moreover, we discuss the strategic fit between specific supply chain contexts and logistics network structures. Conclusions are supported by a quantitative analysis.

Source Traffic Modeling of Wireless Applications

Abstract: Summary Data applications are expected to play an increasingly important role in the next generation mobile communication services. To plan these networks, detailed models of data users with diverse applications are required. The purpose of this study is to provide practically usable traffic models for data users in wireless networks, e.g. GPRS. We start with a discussion of well-known models in the literature, where the focus is on their applicability in mobile networks. A practical model of mobile HTTP users, based on an extrapolation of WWW users in current wire-line networks, is presented; this model is expected to be accurate enough to be used in simulation studies for network planning purposes. Finally, models for other emerging data applications are also taken into account.

Hub Location Problems in Urban Traffic Networks

Abstract: In this paper we present new hub location models which are applicable for urban public transportation networks. In order to obtain such models we relax some of the general assumptions that are usually satisfied in hub location problems, but which are not useful for public transportation networks. For instance we do not require that the hub nodes have to be completely interconnected. These new models are based on network design formulations, in which the constraint that all flow has to be routed via some hub nodes is formulated by a flow conservation law. We present some solution approaches for these new models and illustrate the results on a numerical example.

Unresolved Issues in Supply Chain Network Design

Abstract: Designing a supply chain network provides the basic structure for supply chain operations, where the network is a major element in a firm's competitiveness and a significant area of capital investment With the boundary-spanning scope encouraged by supply chain management, the question is whether existing analyses used for network design are adequate The general answer is yes, because the number of echelons that the analysis must span is self-limiting to a relative few However, there remain unresolved issues in network design analysis and in the models used to support the analysis that can enhance its accuracy, appropriateness, and acceptability to practitioners Issues discussed relate to the development of better models, the treatment of the data needed by them, and the need for comparing the various models for network design

A constant factor approximation for the single sink edge installation problems

Abstract: We present the first constant approximation to the single sink buy-at-bulk network design problem, where we have to design a network by buying pipes of different costs and capacities per unit length to route demands at a set of sources to a single sink. The distances in the underlying network form a metric. This result improves the previous bound of O(\log |R|), where R is the set of sources. Our algorithms are combinatorial and can be derandomized easily at the cost of a constant factor loss in the approximation ratio.

Network planning tool

Abstract: A communications packet network is planned by the use of a planning tool. The tool comprises an input for inputting requirements of the network; and an input for determining factors which effect the passage of packet based data through the network. A modelling module determines the performance of the network based on the requirements and factors. The performance of model is compared with that of an objective comparison model. A feedback mechanism iteratively adjusts the input factors to improve the performance and maintain the network requirements. When the desired performance level is achieved, a plan of the network is output from the planning tool.

On development planning of electricity distribution networks

Abstract: Future development of electric power systems must pursue anumber of different goals. The power system should beeconomically efficient, it should provide reliable energysupply and should not damage the environment. At the same time,operation and development of the system is influenced by avariety of uncertain and random factors. The planner attemptsto find the best strategy from a large number of possiblealternatives. Thus, the complexity of the problems related topower systems planning is mainly caused by presence of multipleobjectives, uncertain information and large number ofvariables. This dissertation is devoted to consideration of themethods for development planning of a certain subsystem, i.e.the distribution network.The dissertation first tries to formulate the networkplanning problem in general form in terms of Bayesian DecisionTheory. However, the difficulties associated with formulationof the utility functions make it almost impossible to apply theBayesian approach directly. Moreover, when approaching theproblem applying different methods it is important to considerthe concave character of the utility function. Thisconsideration directly leads to the multi-criteria formulationof the problem, since the decision is motivated not only by theexpected value of revenues (or losses), but also by theassociated risks. The conclusion is made that the difficultiescaused by the tremendous complexity of the problem can beovercome either by introducing a number of simplifications,leading to the considerable loss in precision or applyingmethods based on modifications of Monte-Carlo or fuzzyarithmetic and Genetic Algorithms (GA), or Dynamic Programming(DP).In presence of uncertainty the planner aims at findingrobust and flexible plans to reducethe risk of considerablelosses. Several measures of risk are discussed. It is shownthat measuring risk by regret may lead to risky solutions,therefore an alternative measure - Expected Maximum Value - issuggested. The general future model, called fuzzy-probabilistictree of futures, integrates all classes of uncertain parameters(probabilistic, fuzzy and truly uncertain).The suggested network planning software incorporates threeefficient applications of GA. The first algorithm searchessimultaneously for the whole set of Pareto optimal solutions.The hybrid GA/DP approach benefits from the global optimizationproperties of GA and local search by DP resulting in originalalgorithm with improved convergence properties. Finally, theStochastic GA can cope with noisy objective functions.Finally, two real distribution network planning projectsdealing with primary distribution network in the large city andsecondary network in the rural area are studied.

From network design to dynamic provisioning and restoration in optical cross-connect mesh networks: an architectural and algorithmic overview

Abstract: This article presents a broad overview of the architectural and algorithmic aspects involved in deploying an optical cross-connect mesh network, starting from the network design and capacity planning phase to the real-time network operation phase involving dynamic provisioning and restoration of lightpaths and online algorithms for route computation. Frameworks for offline design and capacity planning of optical networks based on projected future lightpath demands are discussed. The essential components of an IP-centric control architecture for dynamic provisioning and restoration of lightpaths in optical networks are outlined. These include neighbor discovery, topology discovery, route computation, lightpath establishment, and lightpath restoration. Online algorithms for route computation of unprotected, 1+1 protected and mesh-restored lightpaths are discussed in both the centralized and distributed scenarios.

A polynomial-time approximation scheme for base station positioning in UMTS networks

Abstract: We consider the following optimization problem for UMTS networks: For a specified teletraffic demand and possible base station locations, choose positions for base stations such that the construction costs are below a given limit, as much teletraffic as possible is supplied, the ongoing costs are minimal, and the intra-cell interference in the range of each base station is low. We prove that for a particular specification of teletraffic (the so called demand node concept), this problem has a polynomial-time approximation scheme, but cannot have a fully polynomial-time approximation scheme unless P = NP.

Multicell CDMA network design

Abstract: Traditional design rules for cellular networks are not directly applicable to code division multiple access (CDMA) networks where intercell interference is not mitigated by cell placement and careful frequency planning. For transmission quality requirements, a minimum signal-to-interference ratio (SIR) must be achieved. The base-station location, its pilot-signal power (which determines the size of the cell), and the transmission power of the mobiles all affect the received SIR. In addition, because of the need for power control in CDMA networks, large cells can cause a lot of interference to adjacent small cells, posing another constraint to design. In order to maximize the network capacity associated with a design, we develop a methodology to calculate the sensitivity of capacity to base-station location, pilot-signal power, and transmission power of each mobile. To alleviate the problem caused by different cell sizes, we introduce the power compensation factor, by which the nominal power of the mobiles in every cell is adjusted. We then use the calculated sensitivities in an iterative algorithm to determine the optimal locations of the base stations, pilot-signal powers, and power compensation factors in order to maximize the capacity. We show examples of how networks using these design techniques provide higher capacity than those designed using traditional techniques.

Effective Relaxations and Partitioning Schemes for Solving Water Distribution Network Design Problems to Global Optimality

Abstract: In this paper, we address the development of a global optimization procedure for the problem of designing a water distribution network, including the case of expanding an already existing system, that satisfies specified flow demands at stated pressure head requirements. The proposed approach significantly improves upon a previous method of Sherali et al. (1998) by way of adopting tighter polyhedral relaxations, and more effective partitioning strategies in concert with a maximal spanning tree-based branching variable selection procedure. Computational experience on three standard test problems from the literature is provided to evaluate the proposed procedure. For all these problems, proven global optimal solutions within a tolerance of 10−4% and/or within 1$ of optimality are obtained. In particular, the two larger instances of the Hanoi and the New York test networks are solved to global optimality for the very first time in the literature. A new real network design test problem based on the Town of Blacksburg Water Distribution System is also offered to be included in the available library of test cases, and related computational results are presented.

Fiber span failure protection in mesh optical networks

Abstract: A major challenge of optical network design is deciding where spare capacity is needed and how much, so that interrupted traffic may be rerouted in the event of a failure. Given the optical network topology and traffic forecast, the network design needs to map the traffic forecast into optical connection demands. For each optical connection demand, two paths need to be computed, i.e., a service path and a restoration path. In most cases, optical network design mainly considers single failure. If two service paths do not share any single failure, their restoration paths can share the same capacity on any links that they have in common. In this way, the total spare capacity needed for restoration can be dramatically reduced. However, due to the layered architecture in optical networks, a pair of diverse paths in a particular layer won't necessarily be diverse when the lower layer topology is considered. For example, optical networks are typically built on top of a network of fiber spans. A single span cut in the fiber network can cause multiple link failures in the optical layer. In this paper, we investigate fiber span failure protection scenarios in mesh optical networks. Specifically, we provide an algorithm to find two fiber span disjoint paths for each demand, such that the total spare capacity allocated in the network is minimized. Another problem that arises in restoration path computation is the existence of a trap topology. In a trap topology, the pre- selected service path may not have a diverse restoration path even though two diverse paths exist in the network. For simple link-disjoint protection, the min-cost max-flow algorithm can be used to avoid this problem. For fiber span failure protection, the trap topology problem becomes complicated. We show that it is NP-hard problem to find the maximum number of fiber-span disjoint paths between two nodes. We provide two heuristic algorithms to solve this trap topology problem. We have implemented fiber span failure protection in our restoration capacity planning toolkit Cplan. We describe an application of fiber span failure protection at the end of the paper.

Network planning traffic measurement program

Abstract: In a public switched telephone network, real time monitors on SS7 links will collect interoffice signaling messages. A site processor compiles data from the signaling messages relating to individual calls, to form call detail records (CDRs) for all interoffice call attempts. The site servers upload the CDRs to a central server. Automatic Message Accounting (AMA) records also are accumulated for at least selected central office switching systems and uploaded to a server. Programs running on the servers enable network operations personal to analyze a variety of network traffic patterns, for example to study the number of calls to particular numbers during various times periods and the hold time of the calls in order to identify the numbers of Internet Service Providers (ISPs). As another example, the traffic analysis may indicate the amount of traffic between two end offices and the percentage thereof routed through a tandem office, to allow network planners to design trunk upgrades between the various offices and/or to plan the addition of new offices.

Water Usage and Treatment Network Design Using Genetic Algorithms

Abstract: A mathematical programming model has been developed in this work to identify the cost-optimal and least-consumption water usage and treatment networks (WUTNs). The network configurations of WUTNs were generated on the basis of a superstructure embedded with the existing water-using units, the repeated water-treatment units, and the mixers. The benefits of using this model are clearly demonstrated in the examples. The genetic algorithms were used in this study to solve the WUTN optimization problem. Several techniques have been developed to enhance convergence in the evolution processes. First of all, by adopting the split fractions from splitting nodes as the design variables and devising an encoding strategy accordingly, the search space can be significantly reduced. Second, by cascading a series of evolution processes according to a set of inducing parameters, the appropriate ranges of the design variables can be efficiently determined. As a result, the need to obtain a good initial guess can be eliminated. The total number of generations to reach optimum can also be lowered to an acceptable level even for a large WUTN design problem.

An apparatus for facilitating realtime information interexchange between a telecommunications network and a service provider

Abstract: A Business-to-Business (B2B) engine, apparatus and method for facilitating information interexchange between a telecommunications network and an information service provider. The B2B engine includes an interface module for interfacing with the telecommunications network and with the information service provider. The interface module allows the B2B engine to receive realtime information from the telecommunications network and provide the realtime information to the information service provider. The B2B engine includes a processor that controls the operation of the B2B engine and at least one application module interconnected to the processor that enhances the monitoring and realtime information retrieval of mobile terminals within the telecommunications network. The B2B engine also facilitates the reporting of the realtime information within the telecommunications network to the information service provider, thereby enabling content data and/or services to be provided to the module terminal.

A system, method and apparatus for facilitating the receipt of realtime information from telecommunications nodes

Abstract: A system, method, and apparatus for facilitating information interexchange between a telecommunications network serving a wireless communications device and an information service provider. The telecommunications network includes at least one node that monitors realtime information associated with a telecommunications device within the telecommunications network. The node reports the realtime information associated with the telecommunications device to a Business-to-Business (B2B) engine, which, upon receiving the realtime information, forwards the realtime information to the information service provider. The information service provider, in turn, provides a service to a subscriber associated with the telecommunications device.