Showing papers on "Network planning and design published in 1987"

Equilibrium Decomposed Optimization: A Heuristic for the Continuous Equilibrium Network Design Problem

Abstract: For applications of realistic size, both the discrete and continuous versions of the equilibrium network design problem are too computationally intensive to be solved exactly with the algorithms proposed to date. This intractibility owes to Braess' paradox which makes it necessary to constrain the flow pattern to be a noncooperative Nash or user equilibrium. This paper suggests a new heuristic for finding an approximate solution to the continuous equilibrium network design problem. Numerical tests are reported which indicate that, for networks with significant congestion, the heuristic is markedly more efficient than the Hooke-Jeeves algorithm which has been employed previously. The efficiency of the heuristic results from decomposition of the original problem into a set of interacting optimization subproblems. This decomposition is such that, at each iteration of the algorithm, only one user equilibrium needs to be calculated in order to update the improvement variables of all arcs of the network. This c...

Issues in packet radio network design

Abstract: There are many design choices that must be made in the development of a packet radio network. There is usually no single correct choice, and the decisions are dependent on the environment that the network must work in, the requirements for performance and other functionalities, and the cost and other limitations, in addition, as new hardware and software technologies become available, the parameters governing the decisions change and often result in different selections. This paper outlines a number of design issues and choices available. The intent is to provide an overview of the design decisions that must be made so as to provide a context for the decisions made in a number of existing and developing packet radio networks. It is hoped that this will allow future designs to take advantage of both the wealth of experience available as well as new technologies. Three areas of design decisions are identified. The first area deals with the physical aspects of the network and concentrates on the radio connectivity and channel sharing. The second area deals with the automated management of the network and concentrates on issues such as link management and routing. The third area deals with the interface of the network to the users and some practical aspects of operating and maintaining a network.

Design of a Self-Timed VLSI Multicomputer Communication Controller,

Abstract: : We describe the design of the network design frame, (NDF), a self-timed routing chip for a message-passing concurrent computer The NDF uses a partitioned data path, low-voltage output drivers, and a distributed token-passing arbiter to provide a bandwidth of 450Mbits/sec into the network Wormhole routing and bidirectional virtual channels are used to provide low latency communications, less than micro seconds latency to deliver a 216 bit message across the diameter of a 1K node machine To support concurrent software systems, the NDF provides two logical networks, one for user messages and one for system messages, that share the same set of physical wires To facilitate the development of network nodes, the NDF is a design frame The NDF circuitry is integrated into the pad frame of a chip leaving the center of the chip uncommitted

Current and future use of systems analysis in water distribution network design

Abstract: Computer use in the design of water distribution networks was inititated through the use of network analysis techniques to determine system performance in terms of heads and flows. The last fifteen years, however, have seen the introduction of systems analysis optimization techniques to the range of computer models available for network design purposes. These optimization models differ markedly from the ‘traditional’ network analysis models in that they ‘design’ systems for specified loading conditions rather than just analysing the performance of predetermined systems under given loading conditions. Cost was the primary or only objective in almost all these early optimization models. Water distribution network design has, however, a number of other important objectives, such as maximizing reliability. Issues related to reliability concern include probability of component failure, probability of actual demands being greater than design values, and the system redundancy inherent within the layout ...

Network measurement of the VMTP request-response protocol in the V distributed system

Abstract: Communication systems are undergoing a change in use from stream to request-response or transaction communication In addition, communication systems are becoming increasingly based on high-speed, low delay, low error rate channels These changes call for a new generation of networks, network interfaces, and transport protocol design The performance characteristics of request-response protocols on these high-performance networks should guide the design of this new generation, yet relatively little data of this nature is availableIn this paper, we present some preliminary measurements of network traffic for a cluster of workstations connected by Ethernet running the V distributed operating system We claim that this system, with its use of a high-speed local area network and a request-response transport protocol tuned for RPC, provides some indication of the performance characteristics for systems in the next generation of communication systems In particular, these measurements provide an indication of network traffic patterns, usage characteristics for request-response protocols, and the behavior of the request-response protocol itself These measurements suggest in general that a key design focus must be on minimizing network latency and that a request-response protocol is well-suited for this goal This focus has implications for protocol design and implementation as well as for the design of networks and network interfaces

Network Synthesis and Dynamic Network Optimization

Abstract: Publisher Summary Determining a minimum cost network designed in such a way as to meet a given set of specifications is a fundamental class of problems that arise in a wide variety of contexts of applications, such as transportation science, telecommunication network engineering, distribution systems, energy networks, and water distribution networks. The chapter discusses two important problems arising in the area of distributed telecommunication networks: (1) network synthesis under non-simultaneous single- commodity or multi-commodity flow requirements and (2) determining an optimal investment policy for meeting increasing multi-commodity flow requirements over a given time period. The importance of the latter problem stems from the fact that most optimum network design problems are essentially dynamic in nature in the sense that the time factor should be explicitly taken into account. The chapter discusses how the most practically applicable solution methods are related to the work on static models.

Comprehensive design of highway networks

Abstract: In this paper, the sequel to “A Family of Methods for Preliminary Highway Alignment,” we apply results from the latter, in addition to some network design models which include locating road junctions (“Generalized Steiner Points”) to the design of complete highway networks connecting n given points on any given terrain. The objective is to satisfy given bilateral transportation demands at minimal total cost—including construction and users' costs.

Adaptive, tariff dependent traffic routing and automatic network management system for multiservice telecommunication networks

Abstract: An adaptive, tariff dependent traffic routing system, which controls routing of traffic and performs management of network resources in multi-node telecommu­nication networks, where the cost for a communication depends on the type of service provided and on the dis­tance between the originating node and the destination. Each node can originate traffic, receive and/or transit traffic over inter-node trunks. The system is realized by means of a central computer, which has connections to the SPC nodes of the network over two-way data links. The computer has access to data stored in the computer's memo­ry, containing the actual distance- and service sensitive tariffs applied in the network. By frequent scanning of the network, the computer has a global view of the actual out-of-service and traffic load status in the nodes and in the different trunk groups. Based on the tariffs and on the global network status view the system determines the policy for routing traffic in the network, such that the revenue is maximized. When determining the routing deci­sions, the out-of-service and overloaded network equipment is automatically by-passed. Similarly, traffic to out-of-­service, overloaded or hard-to-reach destinations is not allowed to enter the network. The same applies to traffic destined to access-restricted nodes. The routing policy is transmitted to the SPC nodes in terms of routing instruc­ tions, specific for each originating node and each destina­tion as well as specific for each type of a service. Since new instructions are issued after each network scanning, these will vary with the actual traffic and out-of-service situation in the network. In this way an adaptive, revenue maximizing traffic routing and network management system is achieved.

The design of bus route systems — An interactive location-allocation approach

Abstract: An interactive modelling approach is developed to solve the practical problem of bus route network design. Possible bus routes are identified with facilities which can be “located”. Zones or pairs of zones in the urban area are identified with customers who will be “allocated” to the established facilities. It is shown that the classical Set Covering Problem is useful under the assumption of fixed demand; the Simple Plant Location Problem is effective under the assumption of demand which is sensitive to the level of bus service provided.

Planning and managing a corporate network utility

Abstract: This paper describes the processes used by Digital Equipment Corporation in planning and managing its worldwide networks. As a corporate communications utility that has evolved into a strategic and tactical business tool, it is a critical success factor in today's business environment. It is designed with an open architecture for easy adaptability to growth and change. Descriptions of the network planning and management strategies and techniques demonstrate how DIGITAL meets its voice, data, and video requirements. This paper makes recommendations on how to plan for and manage a network utility with no disruption of dayto-day business operations.

Methods for equilibrium network traffic signal setting

Abstract: Traffic signal setting as a tool for traffic management of urban networks is introduced. A brief state of art about Traffic Signal Setting and Network Equilibrium Assignment is reported. Then Equilibrium Network Traffic Signal Setting is analyzed together with the principal methods for its solution. Global optimization and iterative procedure approaches are described in detail. Finally, after some theoretical remarks, research perspectives are outlined.

LP extreme points and cuts for the fixed-charge network design problem

Abstract: Many design decisions in transporation, communication, and manufacturing planning can be modeled as problems of routing multiple commodities between various origin and destination nodes of a directed network. Each arc of the network is uncapacitated and carries a fixed charge as well as a cost per unit of flow. We refer to the general problem of selecting a subset of arcs and routing the required multi-commodity flows along the chosen arcs at a minimum total cost as the fixed charge network design problem. This paper focuses on strenghthening the linear programming relaxation of a path-flow formulation for this problem. The considerable success achieved by researchers in solving many related design problems with algorithms that use strong linear programming-based lower bounds motivates this study. We first develop a convenient characterization of fractional extreme points for the network design linear programming relaxation. An auxiliary graph introduced for this characterization also serves to generate two families of cuts that exclude some fractional solutions without eliminating any feasible integer solutions. We discuss a separation procedure for one class of inequalities and demonstrate that many of our results generalize known properties of the plant location problem.

Videoconference Traffic and Network Design

Abstract: Recent technological progress is making possible the creation of a new form of videoconference service based on a public network interconnecting private studios located on user premises. We suppose that transmission links in such a network would be reserved in advance by users as and when they arrange their meeting. This and other significant differences with telephony-like services make the use of traditional teletraffic models inappropriate for network dimensioning and performance evaluation. In this paper, we propose an original model of the videoconference reservation traffic process in which essential parameters are the size and distribution of the studio population and the mean studio busy hour utilization rate. This model is used to study certain network architectures in order to identify the effect on link and node dimensions of major design options. First conclusions suggest that the most economical structure might be a simple star network where all studios are connected directly to a central switching facility. Advance reservation makes it possible to employ elaborate routing algorithms, such as call rearrangement, which might be exploited to optimize network or switching node design.

Remarks on radio network planning

Abstract: The models, methods, and tools related to mobile radio network planning are reviewed. A fundamental dichotomy between powerful but imprecise geometric ideas and the more exact but nonconstructive analytic viewpoint is found.

A methodology for feeder-bus network design

Abstract: The U.S. transit industry faces financial difficulties. Among the strategies suggested for improving transit financial conditions, the development of better-integrated intermodal systems has the advantage of potentially achieving both cost reduction and improved service. A network optimization methodology for the design of an integrated feeder-bus--rail rapid transit system is presented. The Feeder-Bus Network Design Problem (FBNDP) is defined as that of designing a set of feeder-bus routes and determining the frequency on each route so as to minimize operator and user costs. The FBNDP is first considered under many-to-one demand and its formulation is discussed as a mathematical programming problem. Then the generalization of the formulation to the many-to-many demand pattern is reviewed. The FBNDP is a larger and complex routing-type problem that can be solved only heuristically. A heuristic method that generalizes the savings approach to consider operating frequency is presented. The analysis presented illustrates the capabilities of the proposed model as a strategic planning tool for feeder-bus network design. It indicates that changes that increase the relative weight of operator cost often result in feeder-bus networks with less circuitous routes operated at lower frequencies, whereas changes that increase the relative weight of user cost result in feeder routes operated at higher frequencies. The solutions provided by the proposed model have been tested and found superior to manually designed networks, particularly under variable demand.

Heuristic ranking and selection procedures for network design problems

Abstract: Two heuristic approaches to solving discrete non-linear network design problems and other subset selection problems are described and tested. These heuristics operate similarly to other add, delete and interchange heuristics that have been applied to network design problems. However, the selection criterion adopted here is the ratio of objective function change per unit of resource cost, which other authors have described as an effective gradient measure for zero-one integer programming problems. Optimal branch-and-bound algorithms previously developed and tested are reviewed, and those results serve as benchmarks with which to compare these heuristics described in this paper. The first heuristic ranks and deletes alternative network modifications from an entire set of candidate projects, such as new links or link improvements, until the subset of remaining projects fits within the constraint space. This method was found to achieve optimal or near-optimal solutions to each of the test cases, even when the number of candidate projects deleted in each iteration was increased from one to many. The quality of those results led us to investigate a constrained random sampling procedure in which candidate projects are ranked with regard to randomly generated networks, and a solution is then chosen on the basis of these rankings. This second approach was found to achieve solutions that were almost as good as those obtained with the rank and delete heuristic.

Interconnection Protocols for Interorganization Networks

Abstract: This paper analyzes the technical implications of interconnecting networks across organization boundaries. Such Interorganizational Networks (ION's) are used increasingly to support exchange of CAD/CAM data between manufacturers and subcontractors, software distribution from vendors to users, customer input to suppliers' orderentry systems, and the shared use of expensive computational resources by research laboratories, as examples. We begin by demonstrating that interorganization connections are not satisfied by traditional network design criteria of connectivity and transparency. A primary high-level requirement is access control, and therefore, participating organizations must be able to limit connectivity and make network boundaries visible. We summarize an approach to access control in ION's, based on nondiscretionary control, that allows interconnecting organizations to combine gateway, network, and system-level mechanisms to enforce cross-boundary control over invocation and information flow while minimizing interference with internal operations [6], [4]. The focus of this paper is on the underlying interconnection protocols that are needed to support these access control mechanisms. We describe in detail a particular protocol, called a visa scheme [7]. The visa scheme uses access control servers to authorize a session request and visas to authenticate that successive packets belong to the authorized connection. Control is distributed among the ION participants and each may make its own design tradeoffs between performance and trust. In order to support interorganization communication two (or more) organizations must be able to communicate with one another's access control servers and their respective packet-level gateways and nodes (source/destination) must implement the visa scheme. The security of the proposed mechanism varies according to the security of an organization's components (access control server, gateway, and select hosts) and the encryption function used. The visa scheme's purpose is to allow an organization to modify and trust only those internal systems that require ION access; all other internal systems are inaccessible from and to the ION gateway. We conclude by comparing and contrasting the visa approach to the use of higher level gateways.

An implicit enumeration method for ltl network design

Abstract: The optimal design of less-than-truckload (LTL) motor carrier networks is cast as a fixed-charge network design problem. A recently developed lower bound is applied iteratively with a link inclusion heuristic in an implicit enumeration framework. Initial computational results for solving this class of problems are reported.

Modeling, analysis, and optimal routing of flow-controlled communication networks

Abstract: Closed queueing networks have been advocated by several authors to be a more desirable model than open queueing networks (Kleinrock's model) for network design. We compare open and closed network models and demonstrate the accuracy of a particular closed network model with experimental results. The proportional approximation method (PAM) is presented for evaluating performance measures of closed queueing networks. PAM algorithms have computational time and space requirements of O(KM), where M denotes the number of queues and K denotes the number of virtual channels in the network. Thus, PAM is the first (and only) method that can be used for solving industrial-strength network design problems using a closed network model.We formulate the following optimal routing problem: Find a route for a new virtual channel to be added to a network with existing flow-controlled virtual channels. A fast heuristic algorithm is presented. The algorithm uses PAM and exploits the following empirical observation: The route that maximizes the individual throughput of a virtual channel coincides in most cases with the route that maximizes the total network throughput (this is not true in general). We present statistical results from studies of 100 randomly generated networks to demonstrate the accuracy of PAM algorithms and the effectiveness of the optimal routing algorithm. (Exact solutions obtained by the tree convolution algorithm were used as benchmarks in our statistical studies.)

Communications network planning in the evolving information age

Abstract: Communications networks are undergoing major changes in equipment technologies, network architectures, and service offerings. These changes reflect the new capabilities of the evolving information age: high bandwidth technologies, flexible and controllable networks utilizing advanced database and signaling systems, and intelligent network elements. Planning these new communications networks presents a major challenge. However, information age technologies also allow the design of efficient and flexible processes and systems to plan new modern networks. In fact, these new database oriented, intelligent planning systems must evolve in synchronism with the new information age communications networks. In the long term, as the networks increase in flexibility and intelligence, the networks themselves can take over many of the responsibilities of network planning and administration, leaving planners to study business strategies and new network architectures and services. In any event, planning decisions, whether made by the network or the planner, will be based on large amounts of information that are efficiently organized and quickly processed by the integrated network and operations support systems.

Designing optimal transportation networks: an expert systems approach

Abstract: A knowledge-based expert system (KBES) approach can be used to solve the single-mode (automobile), fixed-demand, discrete, multicriteria, equilibrium transportation network design problem. Previous work on this problem revealed that mathematical programming methods perform well on small networks with only one objective. A solution technique is needed that can be used on large networks that have multiple, conflicting criteria with different weights of relative importance. The KBES approach discussed in this paper represents a new way to solve network design problems. The development of an expert system involves three major tasks: knowledge acquisition, knowledge representation, and testing. For knowledge acquisition, a computer-aided network design and evaluation model (UFOS) was developed to explore the design space. This study investigated the problem of designing an optimal transportation network by adding and deleting capacity increments to or from any link in the network. Three weighted criteria were adopted for use in evaluating each design alternative: cost, average volume-to-capacity ratio, and average travel time. The best nondominated design is determined by a multicriteria evaluation technique called concordance analysis. The research started with a design exercise conducted by a group of students who were asked to find a series of link capacity changes that would produce a series of successively better designs. The results were carefully examined and used to generate the facts and rules that make up the knowledge base of the network design expert system (EXPERT-UFOS). It has two phases of analysis. The macrolevel analysis recommends a total budget using trade-off functions for each pair of criteria. The microlevel analysis provides advice about how to add or delete capacity on each link to avoid paradoxes. Test results show that EXPERT-UFOS found, with fewer design cycles, designs that were better than any of the 76 student designs included in the test. EXPERT-UFOS may have enough simplicity to deal with large networks. The results of this study, in which a laboratory-based knowledge acquisition method was employed successfully to generate a functional knowledge base, suggest that the KBES approach is an appropriate method for dealing with the computational complexities of network design problems.

Design and Evaluation of Regional Weather Monitoring Networks

Abstract: IRRIGATION scheduling on a regional level is often supported by a weather monitoring network for estimating reference evapotranspiration, E^r- The estimation error for E^^ can be used as a quantitative basis for designing new networks or modifying exisiting networks. Kalman filtering provides a convenient means for both estimating E^^ in multistation networks and quantifying the estimation error. The procedure explicitly considers spatial and temporal correlation of the E^r stochastic process as well as measurement error. Application of the Kalman filtering approach to network design and evaluation is illustrated using an existing network in Colorado. The procedure is used to develop contour maps of estimation error for proposed network configurations. These maps are then used to evaluate adequacy of station density and locations.

An optimal road network design model with variable od travel demand

Abstract: Previous studies on the optimal transportation network design assume that the travel demand between origin and destination is given and fixed. However, travel demand will usually shift according to the improvement of the network. This study proposes a model that includes the variable travel demand in the optimal road network design. The model is formulated as a system optimizing model that is constrained by the lower optimizing model; a user equilibrium network flow model with variable demand. The model can give the link capacity and the UE network flow simultaneously. The exact solution method and heuristic iterative one are discussed and a numerical example of small size is executed to test the validity of the solution method. The model is applied to the large scale of the actual network and the feasibility for the road planning is discussed.

A lower bound for uncapacitated, multicommodity fixed charge network design problems

Abstract: Network design problems concern flows over networks in which a fixed charge must be incurred before an arc becomes available for use. The uncapacitated, multicommodity network design problem is modeled with (1) aggregate, and (2) disaggregate "forcing" constraints. Forcing constraints ensure logical relationships between the fixed charge-related and the flow-related decision variables. A new lower bound for this problem- -referred to as the capacity improvement (CI) bound--is presented; and an efficient implementation scheme (using shortest path and linearized knapsack programs) is described. A key feature of the CI lower bound is that based on the LP relaxation of the aggregate version of the problem. A numerical example illustrates that the CI lower bound (1) can be as tight as the disaggregate LP relaxation, and (2) can converge to the optimal objective function value of the IP formulation.

Implications of the ISDN concept on telecommunication network planning

Abstract: In the next 10 years the classical way of telecommunication will change basically. Instead of having for each communication service appropriate terminals with its own subscriber number, a future telecommunication subscriber will exchange information using different services (telephone, teletext, facsimile, videotex etc.) on one subscriber line at the same time. For this purpose, he will use a terminal equipment with only one subscriber number in a multi-service telecommunication network. Therefore, telecommunication administrations are going to establish a network in which the different forms of information can be switched and transmitted. For this purpose, all information to be transported will be transformed into digital signals and, therefore, such a network has been named Integrated Services Digital Network (ISDN). This paper explains the principles of a telecommunication network and discusses planning problems of a future ISDN. It shows how the technical progress influences the planning process in telecommunication networks. Particularly, topics in network design and network security are considered. For the development of pertinent computer-supported planning procedures new considerations in mathematical models and solution procedures arise. Since these procedures are based on graph-theoretical algorithms, further requirements for these algorithms will result.

Netplan: a network optimization model for tactical planning in the less-than-truckload motor-carrier industry

Abstract: This paper reports on the use of a network optimization model for assisting motor-carriers in the analysis of various operating strategies and network configurations by globally considering the design of the service network of the company and the routing of freight through this network under the double criteria of economic efficiency and service quality The methodological aspect of the approach is presented, along with experimental results obtained from various scenario analyses at two large motor-carriers (A)

A discrete optimization model for joint communication network design and facility engineering

Abstract: Optimal network design and facility engineering constructs network topologies that minimize total network cost while selecting facility types, allocating capacity, and routing traffic to accommodate demand and performance requirements. Such problems are characterized by large dimensionality even when relatively small networks are considered. This paper describes a data network design model based on a Mixed Integer/Linear Programming (MILP) formulation that does not, as do most other approaches, separate link capacity and facility selection from routing and topological design but fully integrates these processes in order to capture the very important couplings that exist between them. The performance constraints are incorporated into the model in such a way that they are linear but lead to the same grade of service as nonlinear average network delay constraints. Even the basic single-facility network design problem is NP-complete, and no exact solution can be obtained for large-scale networks. The multifacility problem adds even more computational complexity. We present a fast link reduction algorithm that efficiently designs single-facility or multifacility networks and yields robust local extrema. This algorithm is based on a special-purpose greedy drop procedure. In the absence of capacity allocation constraints, the capacity and flow assignment problem is solved optimally and efficiently as part of the overall design process. Numerical results are provided to demonstrate the computational efficiency of the algorithm. A dual relaxation procedure for the computation of a lower bound on network cost is also suggested. In addition, the properties of optimal multifacility, networks are discussed by comparing single-facility and multifacility assignment policies under various network traffic scenarios.