Showing papers on "Network planning and design published in 1991"

Stable adaptive neural network controller

Abstract: An adaptive control system uses a neural network to provide adaptive control when the plant is operating within a normal operating range, but shifts to other types of control as the plant operating conditions move outside of the normal operating range. The controller uses a structure which allows the neural network parameters to be determined from minimal information about plant structure and the neural network is trained on-line during normal plant operation. The resulting system can be proven to be stable over all possible conditions. Further, with the inventive techniques, the tracking accuracy can be controlled by appropriate network design.

When trees collide: an approximation algorithm for the generalized Steiner problem on networks

Abstract: We give the first approximation algorithm for the {\em generalized network Steiner tree problem}, a problem in network design. An instance consists of a network with link-costs and, for each pair ${i,j}$ of nodes, an edge-connectivity requirement. The goal is to find a minimum-cost network using the available links and satisfying the requirements. Our algorithm outputs a solution whose cost is within $ 2 \log R $ of optimal, where $R$ is the highest requirement value. In the course of proving the performance guarantee, we prove a combinatorial min-max approximate equality relating minimum-cost networks to maximum packings of certain kinds of cuts. As a consequence of the proof of this theorem, we obtain an approximation algorithm for optimally packing these cuts; we show that this algorithm has application to estimating the reliability of a probabilistic network.

A Modelling Framework for Integrating Layout Design and flow Network Design

Abstract: This chapter introduces a comprehensive modelling framework for integrating layout design and material flow network design toward the direct generation of net layouts including the design of the physical aisle system. Eight models are developed, each being specialized to deal with various facets of this integrated design. The framework offers an alternative conceptual platform to the Quadratic Assignment Problem for layout design researchers.

An information criterion for optimal neural network selection

Abstract: The choice of an optimal neural network design for a given problem is addressed. A relationship between optimal network design and statistical model identification is described. A derivative of Akaike's information criterion (AIC) is given. This modification yields an information statistic which can be used to objectively select a 'best' network for binary classification problems. The technique can be extended to problems with an arbitrary number of classes. >

MENTOR: an algorithm for mesh network topological optimization and routing

Abstract: The problem of obtaining a minimum cost topology for a mesh network given matrices specifying the cost of links between all pairs of nodes and the internode requirements is considered. A heuristic algorithm which works in terms of general network design principles and uses utilization as a figure of merit is presented. The procedure is applicable to a wide variety of networks, especially to the problem of obtaining starting topologies for other network design procedures. The algorithm's computational complexity is shown to be of order N/sup 2/, a significant improvement over currently used algorithms and fast enough to be embedded in the inner loop of other more general design procedures, e.g., node selection procedures. Computational experience is presented which shows that the procedure is fast and simple and yields solutions of a quality competitive with other much slower procedures. >

A Network Design Algorithm Using a Stochastic Incremental Traffic Assignment Approach

Abstract: In this paper, a branch and bound algorithm is presented for solving network design problems (NDP). Route selection for the NDP is based on a stochastic incremental traffic assignment approach. Experiments are performed to compare the behaviors of three assignment methods. Numerical examples are presented to illustrate the algorithm for solving the NDP.

State-dependent queueing models in emergency evacuation networks

Abstract: Planning and design of evacuation networks is both a complex and critically important problem for a number of emergency situations. One particularly critical class of examples concerns the emergency evacuation of chemical plants, high-rise buildings, and naval vessels due to fire, explosion or other emergency. The problem is a highly transient, stochastic, nonlinear, integer programming problem and previous methodologies utilizing queueing network models have proved useful in the design of emergency evacuation plans. We enhance this class of queueing network models by adding state-dependent queueing models to capture the nonlinear effects of increased occupant traffic flow along emergency evacuation routes. A mean value analysis algorithm and computational experience of the methodology illustrates our model's usefulness for this class of network design problems.

A layered broadband switching architecture with physical or virtual path configurations

Abstract: The authors describe a multilayer connection control architecture for broadband communications. A graph framework is introduced to describe network layers of network design, path configurations, dynamic call routing, burst switching, and asynchronous transfer mode (ATM) cell switching. These hierarchical layers of switching are performed at decreasing time scales, respectively. Switching at the higher layer is performed to reduce blocking at the next smaller time scale. A layered notion of equivalent bandwidth for satisfying layered grade-of-service parameters is introduced for making connections at these time scales. The authors then focus on the path configuration layer. Two path setup methods, namely, physical and virtual path setup, are described. Mathematical programs minimizing path bandwidth usage subject to meeting grade-of-service requirements are formulated for both methods. The relative merits of these methods are compared. In one example, physical path setup is shown to require roughly 50% more bandwidth than virtual path setup. >

An algorithm for designing rings for survivable fiber networks

Abstract: The authors present an algorithm for routing fiber around a ring in a network, when the network nodes, links, connectivity, and which offices are to be used on that ring together are known. The algorithm aids automated survivable network planning. The algorithm was programmed in C, and run on a SPARC-station. Under certain conditions, the problem degenerates to the traveling salesman problem, and the ring routing algorithm degenerates to the nearest neighbor method of solving that problem. >

Network planning tool

Abstract: A computer is provided with a network planning facility, which displays in map form a network comprising a plurality of nodes each serving a plurality of subtending nodes, and in which the network is characterized by data stored in the computer. The operation of the planning facility is initiated in response to a user entering an appropriate command. Specifically, responsive to the command, the computer displays a plurality of symbols representing respective ones of the nodes, in which each such symbol is arranged so that it is indicative of the number of traffic terminations at its associated node. The user may then select, in a conventional manner, one of the displayed symbols and then invoke either an automatic mode or a manual mode. In the automatic mode, the computer itself develops a plan for rehoming to another network node individual ones of the subtending nodes associated with the selected node, in which the rehomed subtending nodes are selected based on their having a predetermined traffic relationship with the other node. In the manual mode, it is the user, rather than the computer, which develops the rehoming plan.

Design of survivable communications networks under performance constraints

Abstract: The authors describe a network design algorithm that uses a set of deterministic connectivity measures which result in topologically survivable network designs that also meet processing and performance requirements. The authors briefly describe some applicable graph theoretic concepts and recently developed connectivity measures. They describe systematic procedures for improving the topological survivability of a network, and the overall network design process. A design example is presented. >

Interfacing heat exchanger network synthesis and detailed heat exchanger design

Abstract: Current heat exchanger network synthesis targeting and design procedures involve the use of assumed stream heat transfer coefficients. However, during detailed heat exchanger design, allowable pressure drops are often the most critical factors. The result can be big differences between the exchanger sizes and costs anticipated by the network designer and those realised by the exchanger designer. This in turn prejudices any optimisation attempted at the network design stage. In the paper it is shown how allowable pressure drop can be used as a basis of network design and consistency between expectation and realisation achieved

An intercomparison of hydrological network-design technologies

Abstract: Two network-design technologies are compared by random sub-sampling of actual streamflow data. The technologies, Network Analysis for Regional Information (NARI) and Network Analysis Using Generalized Least Squares (NAUGLS), have a common objective, viz. to maximize regional information within a limited budget and time horizon. The data used for intercomparison are from a network of 146 streamgauges in the central part of the United States. In general, the results for the illustrative example indicate that the NAUGLS method conveys more information than the NARI method to the network designer interested in maximizing regional information about mean annual flows with a limited budget.

The Hierarchical Network Design Problem: A New Formulation and Solution Procedures

Abstract: In this paper we develop a new heuristic for the hierarchical network design problem. The heuristic is based upon Lagrangian relaxation of a reformulation of the problem. In addition, we develop a branch and bound algorithm to identify the optimal solution for the 5% of the test problems for which the new heuristic failed to do so. This algorithm proved to be very efficient due to the tight bounds generated by the heuristic.

Using Kalman Filtering to Improve and Quantify the Uncertainty of Numerical Groundwater Simulations: 2. Application to Monitoring Network Design

Abstract: Integrating Kalman filtering and a deterministic groundwater flow model not only improves and quantifies the uncertainty of numerical groundwater simulation, but also provides the dynamic relation between the variance of the estimation error and the measurement strategy. This relation is applied to Zhengzhou city and Spannenburg for the analysis and design of networks for monitoring groundwater levels. For both cases, the network is designed in such a way that the network density is minimized under the constraint of given threshold values for the standard deviations of the estimation errors. Several network alternatives are analyzed and a best alternative is selected by trial and error. In the case of Zhengzhou city, much attention is also paid to the sensitivity analysis of the deterministic and stochastic parameters of the standard deviation of the estimation error. The results indicate that the density of the network depends on the characteristics of geohydrological systems. The Zhengzhou city and Spannenburg cases are compared and the difference between them is discussed using a hypothetical example. It is found that the difference in the behavior of the estimation variance in time is attributable to the characteristic response time of the system on which the network density and observation frequency depend.

Self-healing rings in a synchronous environment

Abstract: An overview of different self-healing network architectures, focusing on ring architectures, is presented. Digital cross-connect systems-based self-healing and diversely routed protection are briefly discussed. Since a typical self-healing network design may use all of the self-healing architectures, a discussion on applications perspectives, illustrating how the various self-healing technologies may best fit in the evolving network, is included. >

Optimal topologies for survivable fiber optic networks using SONET self-healing rings

Abstract: One aspect of network planning, topology design, requires choosing the most economical routing of the fibers for the rings and diverse protection systems. The methodologies and algorithms described generate and optimize the topology of a survivable fiber network. Route mileage, fiber, and regenerator costs are considered. Numerical results for these algorithms run on a variety of example networks show that the algorithms do reduce the costs and run fast enough to be of use to a network planner. >

A multi-layered model for survivability in intra-LATA transport networks

Abstract: The intra local access and transport area (LATA) transport network is modeled into four layers: the switched layer, the cross-connect layer, the multiplex layer, and the physical layer. Capacity provided to meet demand at a given layer in turn becomes demand for the next lower layer. Thus, survivability provided for a subnetwork at a given layer protects the demand originating at that layer as well as higher layer subnetworks. The author defines the layered model, gives a general characterization of survivability restoral methods, and then compares principal existing and proposed methods at each layer, especially the cross-connect layer. In particular, he discusses routing efficiency, speed, control architectures, feasibility, and potential integration with other operations functions, such as demand provisioning, network operations, customer control, and network planning. >

Dynamic programming based heuristics for the topological design of local access networks

Abstract: This paper deals with the terminal layout problem, which is a problem arising in data communication network design. The problem consists of finding the best way to link terminals to a computer site and, in graph-theoretical terms, it resorts to determining a minimal spanning tree with an additional constraint (CMST). We present a class of heuristics that combine dynamic programming with clustering and decomposition techniques. More specifically, the original problem is transformed, either by clustering or decomposition, in order to obtain smaller size problems that can be handled by a dynamic programming approach. Such heuristics were specifically aimed at improving solutions produced by the Esau-Williams algorithm, which is one of the most effective heuristics presented in the literature for the CMST. Actually, computational experience confirms that such improvements can be achieved by the new heuristic.

Network Design Programming of U.S. Highway Improvements

Abstract: This paper describes a network design approach to the selection and programming of alternative route improvements to the U.S. highway network of interstates, four-lane urban highways, and principal rural arterials. Alternative route-improvement strategies are defined as mutually exclusive sets of link improvements that can be programmed for construction within any decade of a multidecade planning horizon. The two improvement strategies considered for each route are: (1) To make every link median divided with controlled access and at least four lanes; or (2) to make every link at least four lanes, but without any changes to median division of access control. The examples of this paper evaluate 536 potential improvements to 289 major highway routes between adjacent Bureau of Economic Analysis (BEA) regions, or nearly two improvement strategies per route. Route-improvement strategies programmed for each decade are constrained by 10-year funding allocations. A trip distribution model is used to distribute commodity shipments forecast for each decade among regions. Route-improvement benefits are computed as changes in the value of the objective function, which is the total discounted interregional shipment cost for all years of the planning period. Since different routes and interregional shipments can share common links, a rank-add-and-swap heuristic solution procedure was developed and applied that accounts for the interdependent costs and benefits of route improvements. Implications of this network design approach for planning future expansions and improvements of the interstate highway network are discussed.

Designing a public data network

Abstract: The search for a network design that can preserve service quality in the presence of malice, malfunction, and accident is addressed. The different quality requirements that users may have are outlined. Protocol and network performance studies are discussed. The impact of new technology is considered. Current trends in telecommunications are summarized. >

Survey of techniques for prevention and control of congestion in an ATM network

Abstract: Some of the congestion control methods commonly considered to be suitable for an ATM (asynchronous transfer mode) network are reviewed. Attention is given to issues such as characteristics of bursty traffic, bandwidth allocation, call admission, and rate control schemes. The high processing speed changes the focus of network design from bandwidth efficiency to processing efficiency. It also moves the focus from feedback control to a preventive forward control. It is concluded that the schemes that are most likely to succeed in ATM emphasize congestion prevention (such as call admittance, bandwidth policing, and rate control) over reactive congestion control based on feedback. >

An efficient method for determining economical configurations of elementary packet-switched networks

Abstract: The packet-switched network design problem can be formulated as a capacity and flow assignment (CFA) problem. The CFA problem is investigated for an elementary network consisting of one tandem switch and n local switches. It is regarded as the structural unit of a hierarchical network. It is assumed that any line speed is available and the cost of each line is a linear function of its speed with a fixed charge for installation. This CFA problem is shown to be equivalent to a 0-1 integer programming problem with a discontinuous cost function. A threshold rule and a row-wise or column-wise improvement (RCI) iteration are proposed to solve the problem. The threshold rule assigns all the traffic between two local switches to a direct route if the required traffic exceeds a predetermined threshold value, and otherwise to a tandem route. The RCI iteration searches the vertices of the unit cube of 2n-dimensional Euclidean space by a procedure roughly like the simplex method. Whenever the network has external traffic, direct application of the threshold rule ensures a global optimum. When there is no external traffic, a simple modification of the RCI iteration yields almost a global optimum within 2n steps. >

Theory and practice of metro network design

Abstract: This paper presents a theoretical analysis of transit lines and networks and its applications. The focus is on network geometry and operational characteristics. The basic design and operational elements, such as geometric forms of lines, headways, schedules, etc., are discussed in general terms, valid for any mode; however, the main focus is on metro systems because of the particular importance of these analyses for fixed, permanent system.