Showing papers on "Network planning and design published in 1990"

The LAMBDANET multiwavelength network: architecture, applications, and demonstrations

Abstract: A summary is presented of research conducted over the last few years concerning the LAMBDANET multiwavelength optical network. Descriptions are given of some variations, including several applications based on these architectures. Experimental results demonstrate the technological feasibility of this approach. The LAMBDANET design incorporates three basic ingredients: (1) it associates a unique optical wavelength with each transmitting node in a cluster of nodes; (2) the physical topology is that of a broadcast star; and (3) each receiving node identifies transmitting nodes based on the transmission wavelength through wavelength demultiplexing. This network design features full connectivity among the nodes, large nonblocking throughput, data format transparency, and flexible control. The LAMBDANET network is used for both point-to-point and point-to-multipoint applications. >

Trust: a lisp program for the analysis of transit route configurations

Abstract: TRUST is a program to analyze and evaluate a given set of bus transit routes and associated frequencies, in terms of several descriptors, including measures of user costs, service quality, and operator resources. The procedure assigns a known demand matrix to the transit network according to a path choice logic that explicitly considers transfers. As such, it calculates the percentages of the total demand trips that are able to reach their destination with no transfer, via one transfer, via two transfers, or simply cannot be satisfied (with two or fewer transfers). Also computed are several node-level and route-level descriptors for use in the route network planning and design process. After the assignment is executed, the program determines the service frequency necessary on each route to maintain the passenger load factor below a specified maximum. The procedure can be used iteratively until the calculated frequencies are consistent with the input frequencies. TRUST is written in the LISP language because the latter's "list" data structure representation is particularly well suited to support the path search and enumeration activities inherent in the assignment logic and path choice rules appropriate in a transit network. The application of the program to the transit network of the Austin, Texas, urban area (with some simplifying assumptions) is presented, illustrating the program's capabilities and computational performance.

Fiber network survivability

Abstract: At the transport layer in interoffice and interexchange networks, shared protection rings (SPRINGS) interconnected at matched nodes can provide 100% restoration in milliseconds after cable cuts and central office failures. The author introduces the SPRING and explains how its capacity advantage over other ring configurations enables it to be the most economical solution in more applications. Transport restoration technologies-1+1 diversity, digital crossconnect systems, and SPRINGS-in interoffice and interexchange environments are compared. A representative network study is presented to justify the choice of SPRINGs and matched nodes for the target architecture. Recommendations on how to evolve today's asynchronous networks in preparation for a fully survivable SONET ring-based network are also provided. Generic ring planning guidelines and network examples are presented to demonstrate how today's networks can be evolved to provide end-to-end survivable SONET transport. An approach to ring-based network design that simplifies the planning process and minimizes network cost is provided. >

Algorithm for Reliability‐Based Optimal Design of Water Networks

Abstract: This paper proposes a heuristic method to obtain a leastcost water distribution network design with a given reliability. The method first attempts an optimal design using a model without the consid...

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. >

A capacity improvement lower bound for 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 aggregate and 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 it is based on the LP relaxation of the aggregate version of the problem. A numerical example illustrates that the CI lower bound can converge to the optimal objective function value of the IP formulation.

Service assurance in modern telecommunications networks

Abstract: Modern telecommunications network design and examples of possible causes of service interruption are examined, using AT&T 800 Service for illustration. Different methods of assuring service technically are presented. It is shown how end-to-end service reliability can be improved by using the techniques described, applying them to 800 Service as an example. Techniques used to restore generic switched services or private line services after a failure within a network are also presented. >

Teletraffic issues in ATM networks

Abstract: This paper addresses the traffic issues in ATM networks and reviews some recent results. Design of ATM networks is divided into a call level and a cell level. Modelling of a cell arrival process, which is an essential part of a network design, is surveyed. Traffic control also consists of a call level and a cell level. It includes a call admission control, routing, policing, a GOS control and a congestion control. Proposed controls are investigated.

Cost-effective network design for groundwater flow monitoring

Abstract: The extensive use of groundwater resources has increased the need for developing cost-effective monitoring networks to provide an indication of the degree to which the subsurface environment has been affected by human activities. This study presents a cost-effective approach to the design of groundwater flow monitoring networks. The groundwater network design is formulated with two problem formats: maximizing the statistical monitoring power for specified budget constraint and minimizing monitoring cost for statistical power requirement. The statistical monitoring power constraint is introduced with an information reliability threshold value. A branch and bound technique is employed to select the optimal solution from a discrete set of possible network alternatives. The method is tested to the design of groundwater flow monitoring problem in the Pomona County, California.

A two-phase network design heuristic for minimum cost water distribution systems under a reliability constraint

Abstract: This paper presents a two-phase design and optimization procedure for constructing a pipe network water distribution system having a built-in degree of reliability. The first phase is comprised of an algorithm called TREESEARCH which iteratively constructs a tree pipe network. Starting with a shortest-path based tree, the procedure employs a linear programming subproblem to systematically modify this tree by adding and deleting one link at a time, with the aim of reducing the cost of the network while satisfying the flow continuity, energy balance, and pressure head requirement constraints. The second phase of the algorithm, called REDUNDANCY, is concerned with the issue of reliability. In this phase, the tree network constructed by the algorithm TREESEARCH is augmented through the addition of links so that there are at least two arc-disjoint paths from each source node to every demand node it serves. This augmentation is performed through the use of a set covering problem which recommends the links to be...

Traffic engineering problems in multiservice circuit switched networks

Abstract: This paper overviews traffic engineering problems encountered in the design of multiple networks. We mainly inspect the problem of introducing an n x 64kbit/s service into a non-hierarchial telephone network and focus on network dimensioning.

Incorporating survivability considerations directly into the network design process

Abstract: A procedure for designing survivable, distributed communications networks is described. The approach uses a version of the cut-saturation algorithm modified to include considerations for survivability while adding and deleting link resources to meet specified throughput goals. This approach improves on the original design process, which made decisions on which link should be added or deleted based strictly on link utilization and link cost. Link distance was used for link cost when all links had the same capacity. Survivability considerations were directly integrated into the design process by using the information provided by the node decomposition (ND) and link tree (LT) indexes to indicate which links to add or to delete. If a link must be dropped, low LT index links make good candidates from a survivability standpoint. If a link must be added, low ND index nodes would be good termination points for adding the link. This replaces the original selection process with one oriented towards maintaining network survivability. >

An Artificial Intelligence Approach to Improving Computer Communications Network Topologies

Abstract: This paper presents an artificial intelligence approach to solving the network design problem. The major issue under consideration is the various topological aspects of a design, especially in the case of large computer networks. The combinatorial explosion can only be dealt with, hopefully, by means of heuristics, which drastically reduce the search space of candidate topologies. The proposed approach is essentially a general framework for integrating conventional approximate methods and knowledge-based systems. An inference engine is then a means suited to extending the realm of local transformations used in conventional heuristics. Sophisticated goal-directed searches can be achieved by using knowledge bases, which are large sets of detailed design rules.

Advanced techniques for managing telecommunications networks

Abstract: The advanced techniques presently used by AT&T to manage traffic flow in its Worldwide Intelligent Network are described. The role of traffic network management strategies is reviewed, and the scope and routing plan of the AT&T Worldwide Intelligent Network are characterized. Three examples of modern protective controls are considered: selective trunk reservation, hard-to-reach process, and selective dynamic overload control. Advanced network management expansive controls and AT&T's traffic network management support systems are examined. Dynamic graphical analysis of network data, interactive training of network managers, and future trends impacting traffic network management are discussed. >

Performance analysis of hybrid ARQ protocols in a slotted direct-sequence code division multiple-access network: jamming analysis

Abstract: An examination is made of the performance of type-I hybrid ARQ (automatic repeat request) protocols in a slotted direct-sequence CDMA (code-division multiple access) network operating in a hostile jamming environment. The network consists of an arbitrary number of transceivers arranged in a paired-off topology. The traffic arrival process is derived by means of a Markov model. Throughput-delay expressions are derived in terms of the channel cutoff rate and capacity. The effects of jammer state information are discussed. Network design parameters are identified and their dependency on system parameters is examined in detail. It is shown that, for a given population size, traffic intensity, and bit energy/jammer noise ratio, there is an optimal probability of retransmission, code rate, and processing gain that maximizes network performance in the presence of worst-case pulse jamming. >

Designing metropolitan area networks for high-performance applications☆

Abstract: This paper describes ongoing work in the design and analysis of the Wavelength-Division Optical Network (WON). The WON is a multichannel, multihop lightwave network suitable for use as a metropolitan area network. A unique feature of the WON is that a great number of virtual topologies can be mapped onto a given physical topology . The specific goal of this paper is to describe the problems of virtual- and physical-topology design in the WON, present techniques for their solution, and study the interplay between these problems.

Design and operation of packet-switched networks with uncertain message requirements

Abstract: An important concern when choosing the link design and message routes is the uncertainty regarding future average hourly message requirements between sources and destinations. A model is proposed for this problem which accounts for the uncertain average number of source-destination messages by representing them as random variables. The model also allows use of the public switched telephone network (PSTN) to accommodate some of the message requirements. This is especially important with the advent of ISDN, which will offer high-speed capacity on a universal basis. Most previous research on packet-switched network design and operation has assumed known average message requirements (although actual message requirements vary according to a Poisson process) and has focused exclusively on the use of leased lines without the availability of the PSTN. These leased lines have fixed monthly costs for specific point-to-point transmission, whereas PSTN lines can access any node from a given location. It is shown how to accelerate convergence of the flow-deviation algorithm for solving the model. Computational results are reported. >

Network management algebra

Abstract: A vector algebra environment for highly-survivable network planning and control is described. This environment incorporates deterministic and stochastic parameters and can be readily automated. The algebra is useful in determining best network routes for transmitting information under normal and disturbed conditions. Algorithms that can handle node loss and path disruption due to physical faults, environmental variability, and enemy interception or jamming are discussed. >

Noise assessment when it matters: environmental evaluation integrated with road network planning

Abstract: The paper reports the application of a novel approach to the assessment of the environmental impact of a road network concurrently with the development and testing of alternative roadway systems in a transportation planning study. While the application of traffic noise prediction models in assessing proposed new road facilities is now almost standard practice, most applications are restricted to a single route, or sometimes several alternative routes, for which need has been identified through network modelling. By contrast, the traffic noise modelling described here shifts the traffic noise evaluation several steps earlier into the planning process by assessing the noise impact of the network while it is still being developed, modelled and tested. An important feature of the procedure is that it predicts noise imission to dwellings rather than noise emission from the roadways to provide an unambiguous measure of impact. The procedure means that the road planner can routinely have immediate feedback, each time a new network is trialled, as to whether the network as a whole has adverse noise consequences and which particular links contribute to noise impact. The utility of this approach has been demonstrated in a practical study and it is recommended that it should be incorporated as standard practice in network modelling studies (A).

An AI/OR hybrid expert system for data network design

Abstract: Summarises the philosophy and results to date in building AI /OR hybrid expert systems to aid human users in designing large-scale (upwards of 250 nodes), low cost, packet-switched data communication networks using distributed, adaptive routing, where the goal design has constraints on node degree, node utilization, arc (channel) utilization, min-hop, node connectivity, end-to-end delay, and average packet delay. a The work described has been implemented and tested in DESI, the US Defense Communications Agency's (DCA's) network design system, which is DCA's principal tool for defense data network (DDN) design. A functional description of the expert system, known as XPRT, is given. Also provided are a short example, analysis of the system, and a discussion of areas for future work. >

Planning a SONET network

Abstract: The author examines the transition from today's asynchronous network to tomorrow's advanced all-SONET (synchronous optical network) network. Network planning studies have identified three phases in the development of a SONET network: initial SONET entry, SONET penetration, and the introduction of new broadband services. The author presents the results of studies conducted to establish deployment strategies and triggers which guarantee the maximum benefit from SONET at each phase of its deployment. The S/DMS product family, which is specifically designed to capture these benefits in a multivendor environment, is discussed. It is noted that the planning guidelines provided should assist operating company and interexchange planners in deploying SONET cost-effectively, establishing a SONET infrastructure quickly, and growing the network to trigger and accommodate a variety of new broadband services. >

Using and abusing bounds for network reliability

Abstract: The roles of reliability analysis and connectivity analysis, in the selection of a network topology that can support the intended traffic at acceptable speed and acceptable cost are considered. The use of bounds for network reliability is studied, focusing on the effective use of the bounds in network design and indicating where their use is inappropriate. A number of strategies for bounding network reliability that can be applied in the network design process are studied. >

A comparison of strategies for survivable network design: reconfigurable and conventional approaches

Abstract: A novel approach to network survivability, based on the rapid reconfiguration of highspeed digital cross-connect systems (DCS), is compared with the conventional approach, based on 1:1 protection switching using diverse routes. Two sample networks are modeled, one ring and one mesh, and the installed first cost of the required network elements is calculated. By varying the network parameters, the sensitivity of both approaches to link length, degree of network connectivity and repeaterless span length can be quantified. While no approach consistently minimizes installed first costs, the results provide insight into the preferred range of applications for the different survivability strategies. >

Local-area internetworks: measurements and analysis

Abstract: : The effectiveness of a local-area internetwork is evident in its end-to-end performance and reliability. The dominant factors limiting end-to-end performance are router delay and the "fit" of traffic patterns to the topology. Internetwork reliability may be enhanced by conservative topological design, even in the face of unreliable network or router technology. These issues are crucial to network design. This dissertation describes the results of studying the Stanford University Network, a large internetwork consisting of interconnected, local-area networks. To prove this thesis, I made measurements of router delay, local traffic characteristics, network topology, and traffic patterns in the Stanford internet. This report reproduces a dissertation submitted to the Department of Electrical Engineering and the Committee on Graduate Studies of Stanford University in partial fulfillment of the requirements for the degree of Doctor of Philosophy.

A broad-band distributed-star network using subcarrier fiber transmission

Abstract: The development of British Telecom's distributed-star system through the 1980s is described, with particular reference to the development of the optical transmission of video channels. The latest all-fiber network design is detailed, with an explanation of the thinking behind the transmission parameters for the subcarrier scheme adopted. The future policy on modulation techniques is reviewed in light of likely technology and service developments. >