Network Design Issues Research Articles

Minimum cost dimensioning of ring optical networks

We consider the problem of traffic grooming of low-rate traffic circuits in WDM rings where circuits are associated with a set of heterogeneous granularities. While networks are no longer limited by transmission bandwidth, the key issue in WDM network design has evolved towards the processing capabilities of electronic switches, routers and multiplexers. Therefore, we focus here on traffic grooming with minimum interconnecting equipment cost. We first formulate the problem as an integer linear programming (ILP) or a mixed integer linear programming (MILP) problem depending on the design specifications: UPSR vs BLSR, fixed vs variable wavelength capacities, non-bifurcated vs bifurcated flows, wavelength continuity vs possible signal regeneration on a different wavelength. Considering the case study of the second SONET ring generation with MSPP like interconnection equipment, we define the cost by a function of the number of transport blades, taking into account that the number of MSPP transport blades makes up a significant portion of the overall network design cost. Using the CPLEX linear programming package, we next compare the optimal solutions of the ILP or MILP programs for different design assumptions, including the classical ring network design scheme with a single hub where the lightpaths directly connect the hub to all other nodes.

Joint optimization of hardware and network systems

Multiple combinations of hardware and network components can be selected to design an information technology (IT) infrastructure that satisfies requirements. The professional criterion to deal with these degrees of freedom is cost minimization. However, a scientific approach has been rarely applied to cost minimization, especially for the joint optimization of hardware and network systems. This paper provides an algorithm combining hardware and network design issues in a single cost-minimization problem. The algorithm is empirically verified with a database of costs that has also been built as part of this research. Results show how a joint cost-minimization approach provides significant cost reductions with respect to the separate optimization of hardware and network sub systems. This indicates that the generally adopted divide et impera professional principle can be cost inefficient with respect to a rigorous scientific approach. Sensitivity and scalability analyses show that the algorithm's results are also robust and do not involve cost disadvantages over time.

Key techniques and radio network planning in TD-SCDMA systems

Receiving significant support from China's government and enterprises in themobile communication industry federation, Time Division Synchronous Code Division Multiple Access (TD-SCDMA) has become the fastest growing 3G technology standard in China. Since TD-SCDMA has adopted some key techniques, such as Time Division Duplex (TDD), joint detection, uplink synchronisation, Smart Antenna (SA), dynamical channel allocation and baton handover, the radio network design issues are distinguished from WCDMA and cdma2000. In this paper, the key techniques and issues impacting on TD-SCDMA radio network planning are introduced. The advanced radio network design issues, such as capacity planning, coverage planning, scrambling code planning, N frequency planning, inter-system interference cancellation and Radio Resource Management (RRM) schemes, are investigated. Particular planning strategies are also proposed, which include the network evolution architecture design and the base station co-sites design. Finally, some challenges for TD-SCDMA commercial deployments are presented.

Hub-Spoke Network Choice Under Competition with an Application to Western Europe

The aim of this paper is to present a model structure that analyzes the hub-spoke network design issue within a competitive framework. Under deregulation, airlines have developed hub-and-spoke networks, enabling them to increase frequency by aggregating demand and to prevent entry into the marketplace by reducing airfares. While liberalization in the United States and Europe was undertaken to increase competition, the results in this direction are unclear. This research evaluates airline profits based on a microeconomic theory of airline behavior under deregulation and the effect on hub-and-spoke networks. Through a two-stage, Nash best-response game, we search for equilibria in the air transportation industry. The game is applied to Western Europe, where profitable hubs and monopolistic equilibria are clearly identifiable, and duopolistic equilibria are potentially viable, given sufficient demand.

Applying tabu search to backup path planning for multicast networks

More and more multimedia applications rely on the ability of networks to provide multicast communications. Network survivability becomes a critical issue in network planning, design, and operation to reduce the impacts of failures in high-speed networks. A rapid and cost-effective restorable network must be planned to maintain network survivability and use network bandwidth effectively. This paper considers the problem of preplanning delay-constrained backup path for multicast networks to minimize the total cost of all the backup paths. Based on the path restoration scheme, a tabu search (TS) algorithm is proposed to find a near optimal solution for the problem under investigation. Diversification and intensification strategies are suggested. The computational experiments are conducted to demonstrate the performance of the proposed TS algorithm. The results show that it offers high-quality solutions within a short amount of time.

Transport Network Life-Cycle Modelling

The ability to co-ordinate network and traffic information into a single and usable form that can be accessed by different teams within the same organisation, provides an operator with significant leverage in controlling their costs and maximising their revenue potential. BT's pan-European platform has accomplished this through the use of a facility that integrates network inventory information with forecasting information and the current and future functionality of equipment elements. This allows BT to constantly monitor their network ‘off-line’ and also plan its short, medium and long-term network evolution with confidence. This paper describes the issues that this facility addresses, its functionality and how the outputs provide BT with quantitative solutions to their pan-European network design and architectural issues.

Uplink–downlink design issues for next generation satellite networks

AbstractNext Generation Mobile Systems will implement one's dream of anywhere, anytime communications. Providing global coverage and mobility, satellite systems will play an important role in order for this to be achieved. The design options of satellite systems include several choices. The basic ones are the choice of orbit, processing and switching, intersatellite links, and link layers technologies. In addition to the network architecture, the protocols must be developed for efficient use of the satellite radio resources. The most important protocol design issues concentrate on Medium Access Control (MAC) techniques, routing and traffic management. In this paper some of the special features of satellite systems are considered. Emphasis is given in MAC protocols design, as well as in research programmes that led to their development. Finally, an adaptive hybrid access scheme that combines CDMA technology and random access techniques is presented. This new scheme is called CDMA/PRMA and from the results obtained it is a very promising access technique for next generation satellite systems. Copyright © 2002 John Wiley & Sons, Ltd.

Interleaved Polling with Adaptive Cycle Time (IPACT): A Dynamic Bandwidth Distribution Scheme in an Optical Access Network

While in recent years backbone bandwidth has experienced substantial growth, little has changed in the access network. “Last mile” still remains the bottleneck between a high capacity LAN or home network and the backbone. Passive optical network (PON) is a technology viewed by many as an attractive solution to this problem. In this study, we discuss and evaluate design issues for PON access networks. Specifically, to drive the cost of an access network down, it is very important to have an efficient, scalable solution. We believe that a PON based on polling, with data encapsulated in Ethernet frames, possesses the best qualities, such as dynamic bandwidth distribution, use of a single downstream and a single upstream wavelength, ability to provision a fractional wavelength capacity to each user, and ease of adding a new user. To support dynamic bandwidth distribution, we propose an interleaved polling algorithm. We then suggest a scheme for in-band signaling that allows using a single wavelength for both downstream data and control message transmission. To obtain realistic simulation results, we generated synthetic traffic that exhibits the properties of self-similarity and long-range dependence. We then analyzed the network performance and its effect on various types of traffic, e.g., best-effort data traffic, VBR video traffic and CBR streams.

IPACT a dynamic protocol for an Ethernet PON (EPON)

We investigate design issues for access networks based on passive optical network technology. A PON based on polling, with data encapsulated in Ethernet frames, possesses many desirable qualities, such as dynamic bandwidth distribution, use of a single downstream and a single upstream wavelength, ability to provision a fractional wavelength capacity to each user, and ease of adding a new user. To support dynamic bandwidth distribution, we propose an interleaved polling algorithm called IPACT. We also suggest a scheme for in-band signaling that allows using a single wavelength for both downstream data and control message transmission. To obtain realistic simulation results, we generated synthetic traffic that exhibits the properties of self-similarity and long-range dependence. We then analyzed the network performance under varying offered loads.

Power-efficient Interconnection Networks: Dynamic Voltage Scaling with Links

Power consumption is a key issue in highperformanceinterconnection network design. Communicationlinks, already a aignificant consumer of power now,will take up an ever larger portion of the power budgetas demand for network bandwidth increases. In this paper,we motivate the use of dynamic voltage scaling (DVS)for links, where the frequency and voltage of links are dynamicallyadjusted to minimize power consumption. Wepropose a history-based DYS algorithm that jjlidiciously adjustsDVS poIicies based on past link utilization. Despitevery conservative assumptions about DVS link characteristics,our approach realizes up to 4.5X power savings (3.2Xaverage), with just an average 27.4% Iatency increase and2.5% throughput reduction. To the best of our knowledge,this is the first study that targets dynamic power optimizationof interconnection networks.

Unresolved Issues in Supply Chain Network Design

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.

MULTICOMMODITY NETWORK EXPANSION UNDER ELASTIC DEMANDS

We analyze some issues of network design and bandwidth allocation in telecommunication systems with congestible resources. The work is closely related to network monitoring and traffic measurement functions that must be carried out on line, in order to overcome congestion caused by an unfavorable traffic pattern or by a failure. In addition to the traditional use of routing controls, our approach achieves network efficiency with capacity assignment and also imposing variable prices for the consumers. A generalized Benders decomposition method is applied to a mixed integer nonlinear programming formulation of the integrated problem of network design and operation. The method exploits the nature of the continuous subproblem, that is a large-scale convex network flow problem with demands sensitive to commodity prices. Some numerical experience suggests that the method is usefull to address both questions of global optimality and competitive pricing in such systems.

Photonic network design issues and applications to the IP backbone

This paper overviews network design issues of the photonic transport network (PTN), which employs wavelength division multiplexing (WDM) and wavelength routing. The design issues are considered on the level of newly created high-speed transmission access paths, i.e., optical paths (OPs). These include the routing and wavelength assignment (RWA) problems involved in making the best use of network resources such as wavelengths and fibers. With this objective, design issues for ring and meshed type PTN are addressed by presenting the results of case studies in which existing heuristic RWA algorithms were employed. By utilizing the design tools, the possible network scale is then estimated, while considering state-of-the-art hardware realization technologies. Further consideration is given assuming an environment where PTN serves as a high-speed IP-backbone. An extensive case study shows the cost-effectiveness of IP-over-PTN over other scenarios such as IP-over-(point-to-point) WDM.

Neural-network-based demand forecasting in a deregulated environment

The traditional approach to load forecasting is based on processing time series of load and weather factors recorded in the past. In the dynamic environment of the deregulated power industry, historical load data may not always be available. This paper explores the possibility of an alternative approach towards load forecasting based on indirect demand estimation from available customer data. This approach requires utilization of demand models for different customer categories. This paper presents a neural network based method of demand modeling. Neural networks are designed and trained based on the aggregate demands of the groups of surveyed customers of different categories. The performance of such models depends on the neural network design and representativeness of the training data. The forecast accuracy is also affected by the forecasted group size, customer characteristics, customer classification system, and the extent of demand survey. This paper discusses the issues of neural network design and illustrates the proposed method by its application to forecasting demand of residential customers.

Modeling and simulation of broadband satellite networks. II. Traffic modeling

For p.I see ibid., vol.37, no.3, p.72-9 (1999). Traffic models for satellite network simulation must cover a broad range of traffic types and characteristics because the type of users/terminals that will access a satellite channel will range from a single home user (low traffic aggregation) to Internet backbone nodes (very high traffic aggregation). In addition, since satellite resources are generally considered more scarce than their fiber counterparts, the accuracy and practicality of traffic models play a crucial role. We address these challenges by identifying three traffic modeling areas for satellite network simulation, and propose an effective and flexible traffic model for each area: a discrete autoregressive process for MBone video source modeling; the superposition of fractal renewal processes (Sup-FRP) model for Web request arrivals; and a generalized shot-noise-driven Poisson point process (GSNDP) for aggregate traffic flows modeling. The efficacy of the first two models is demonstrated based on statistical analysis of various video and Web traces. These simulation-oriented models provide accurate descriptions of source traffic at various levels of traffic aggregation, and thus enable satellite network researchers and practitioners to understand key network design and engineering issues such as QoS provisioning based on simulation.

Enterprise network planning and design: methodology and application

The paper describes a business-driven enterprise network planning and design methodology that has an iterative structure to periodically assess, update, and extend the network architecture to support new business applications and requirements, account for changes in business direction, and analyze the implications of technology advances on business processes and functions. The paper focuses on the network infrastructure design and analysis task of the proposed methodology and discusses the network design and analysis of a multi-protocol application environment characterized by a client/server architecture, integration of legacy and distributed database structures, frame relay wide area network, and token ring local area networks. Detailed workload characterization and performance modeling of the application environment is presented, and network design issues are addressed. The model is used to study network performance under various load conditions, identify bottlenecks and compare design alternatives.

Scalability of Wavelength Division Multiplexed Optical Passive Star Networks with Range Limited Tunable Transceivers

The number of stations attached to a single optical passive star is limited by current state of the art in optical technology. Also, the wavelength range of tunable optical transceivers is limited by current technology. Many high performance computing applications require the use of large size regular topologies for communication between computing nodes. Scalability of passive star networks built with these two limitations becomes an important issue for building larger networks. This is the subject of our study in this paper. In a previous related work we explored the design issues for networks built on a single passive star employing transceivers of a limited tuning range. Here we extend that study by considering the problem of connecting several optical passive stars, each embedded with a given virtual topology, to create larger aggregate networks. The design issues are analyzed and a number of design rules are proposed for building such aggregate networks. We study the scalability of embedded optical passive stars by considering the most commonly employed virtual topologies—complete graph, mesh and hypercube.

Transportation, facility location and inventory issues in distribution network design

Examines the interdependence between facility location, transportation and inventory issues in a distribution network design problem. Management of inventories, determination of transportation policy, and location of plants and distribution centers are normally carried out by different groups of people in an organization. These activities interact, however, when the transportation is used to replace inventory, an increase in the number of warehouses increases total system inventory or location of warehouses would dictate the type of transportation mode choice or carrier that needs to be used. The proposed model, FLITNET, is expected to provide a more complete representation of the trade‐offs that exist among the location, transportation and inventory cost components, and lead to an optimal solution.

Architectures for ATM network survivability

This article surveys the restoration architectures for asynchronous transfer mode (ATM) network survivability that have been actively studied in this decade. Network reliability is critical for recent and future networks that will advance the information era. Moreover, it is one of the biggest factors in designing and managing networks. Since the early telecom network era, many restoration systems have been developed for plesiochronous digital hierarchy (PDH), synchronous digital hierarchy (SDH), synchronous optical network (SONET), leased lines and so on; and they were surveyed in many papers and books. This article focuses on new restoration techniques for ATM networks. First, the requirement studies are introduced. This includes the scant results published on the influence of failure and the state of failure analysis. Next, restoration schemes are categorized and briefly introduced. Examples include centralized control, automatic protection switch (APS), self-healing ring (SHR), self-healing network (SHN) and failure resistant virtual path (FRVP). In order to achieve adequate restoration probability with minimum cost, a network design scheme is necessary; thus, network design issues are introduced. Finally, this article focuses on the issues, future work, and problems that remain to be solved.

A workload model for performance evaluation of multimedia signalling systems

The signalling system of future integrated services multimedia telecommunication networks is expected to be modular but also complex. The user ability to define service characteristics dynamically will lead to high interaction rates expressed as considerable signalling loads for the network. Towards the objective to test signalling protocols and to recommend on network design issues of a signalling system for demanding services and users, this paper presents a Workload Model Tool (WMT) developed to accurately represent the signalling activity of a user of any service. The WMT adopts a multilevel approach reflecting a classification of users and services according to the generated signalling load and also to the type of the invoked signalling processes. Paradigms of the WMT further show its applicability in studying several issues related to signalling system design.