Showing papers on "Network planning and design published in 2009"

Energy-Minimized Design for IP Over WDM Networks

Abstract: As the Internet expands in reach and capacity, the energy consumption of network equipment increases. To date, the cost of transmission and switching equipment has been considered to be the major barrier to growth of the Internet. But energy consumption rather than cost of the component equipment may eventually become a barrier to continued growth. Research efforts on ldquogreening the Internetrdquo have been initiated in recent years, aiming to develop energy-efficient network architectures and operational strategies so as to reduce the energy consumption of the Internet. The direct benefits of such efforts are to reduce the operational costs in the network and cut the greenhouse footprint of the network. Second, from an engineering point of view, energy efficiency will assist in reducing the thermal issues associated with heat dissipation in large data centers and switching nodes. In the present research, we concentrate on minimizing the energy consumption of an IP over WDM network. We develop efficient approaches ranging from mixed integer linear programming (MILP) models to heuristics. These approaches are based on traditional virtual-topology and traffic grooming designs. The novelty of the framework involves the definition of an energy-oriented model for the IP over WDM network, the incorporation of the physical layer issues such as energy consumption of each component and the layout of optical amplifiers in the design, etc. Extensive optimization and simulation studies indicate that the proposed energy-minimized design can significantly reduce energy consumption of the IP over WDM network, ranging from 25% to 45%. Moreover, the proposed designs can also help equalize the power consumption at each network node. This is useful for real network deployment, in which each node location may be constrained by a limited electricity power supply. Finally, it is also interesting and useful to find that an energy-efficient network design is also a cost-efficient design because of the fact that IP router ports play a dominating role in both energy consumption and network cost in the IP over WDM network.

Developments in hydrometric network design: A review

Abstract: [1] Hydrometric network design for surface water monitoring is employed to address a wide range of environmental and water resources problems. Historical overview of hydrometric network design is provided along with a discussion on new developments and challenges in the design of optimal hydrometric networks. This review starts with precise examples of decline in hydrometric network density, then highlights the increasing requirement of optimal network design in a context of climate and land use changes. An extensive survey of methodological development in hydrometric network design is provided along with discussion on the issue of uncertainty in hydrometric network design and the evolution in data collection techniques and technology. Finally, some conclusions are drawn on the future of hydrometric network design.

Dynamic network design for reverse logistics operations under uncertainty

Abstract: The design of reverse logistics network has attracted growing attention with the stringent pressures from environmental and social requirements In general, decisions about reverse logistics network configurations are made on a long-term basis and factors influencing such reverse logistics network design may also vary over time This paper proposes dynamic location and allocation models to cope with such issues A two-stage stochastic programming model is further developed by which a deterministic model for multiperiod reverse logistics network design can be extended to account for the uncertainties A solution approach integrating a recently proposed sampling method with a heuristic algorithm is also proposed in this research A numerical experiment is presented to demonstrate the significance of the developed stochastic model as well as the efficiency of the proposed solution method

Transit Route Network Design Problem: Review

Abstract: Efficient design of public transportation networks has attracted much interest in the transport literature and practice, with many models and approaches for formulating the associated transit route network design problem (TRNDP) having been developed. The present paper systematically presents and reviews research on the TRNDP based on the three distinctive parts of the TRNDP setup: design objectives, operating environment parameters and solution approach.

On-Chip Networks

Abstract: With the ability to integrate a large number of cores on a single chip, research into on-chip networks to facilitate communication becomes increasingly important. On-chip networks seek to provide a scalable and high-bandwidth communication substrate for multi-core and many-core architectures. High bandwidth and low latency within the on-chip network must be achieved while fitting within tight area and power budgets. In this lecture, we examine various fundamental aspects of on-chip network design and provide the reader with an overview of the current state-of-the-art research in this field. Table of Contents: Introduction / Interface with System Architecture / Topology / Routing / Flow Control / Router Microarchitecture / Conclusions

FiConn: Using Backup Port for Server Interconnection in Data Centers

Abstract: The goal of data center networking is to interconnect a large number of server machines with low equipment cost, high and balanced network capacity, and robustness to link/server faults. It is well understood that, the current practice where servers are connected by a tree hierarchy of network switches cannot meet these requirements (8), (9). In this paper, we explore a new server-interconnection struc- ture. We observe that the commodity server machines used in today's data centers usually come with two built-in Ethernet ports, one for network connection and the other left for backup purpose. We believe that, if both ports are actively used in network connections, we can build a low-cost interconnection structure without the expensive higher-level large switches. Our new network design, called FiConn, utilizes both ports and only the low-end commodity switches to form a scalable and highly effective structure. Although the server node degree is only two in this structure, we have proven that FiConn is highly scalable to encompass hundreds of thousands of servers with low diameter and high bisection width. The routing mechanism in FiConn balances different levels of links. We have further developed a low- overhead traffic-aware routing mechanism to improve effective link utilization based on dynamic traffic state. Simulation results have demonstrated that the routing mechanisms indeed achieve high networking throughput.

Autonomous component carrier selection: interference management in local area environments for LTE-advanced

Abstract: Low-power base stations such as femtocells are one of the candidates for high-data-rate provisioning in local areas, such as residences, apartment complexes, business offices, and outdoor hotspot scenarios. Unfortunately, the benefits are not without new challenges in terms of interference management and efficient system operation. Due to the expected large number of user-deployed cells, centralized network planning becomes impractical, and new scalable alternatives must be sought. In this article we propose a fully distributed and scalable solution to the interference management problem in local areas, basing our study case on LTE-Advanced. We present extensive network simulation results to demonstrate that a simple and robust interference management scheme, called autonomous component carrier selection, allows each cell to select the most attractive frequency configuration; improving the experience of all users and not just the few best ones, while overall cell capacity is not compromised.

Optical network design with mixed line rates and multiple modulation formats

Abstract: We propose a design method for mixed-line-rate (MLR) optical networks with transceivers employing different modulation formats. Our results demonstrate the tradeoff between a transceiver's cost and its optical reach in overall network design.

Physical layer impairment aware routing (PLIAR) in WDM optical networks: issues and challenges

Abstract: In WDM optical networks, the physical layer impairments (PLIs) and their significance depend on network type-opaque, translucent, or transparent; the reach-access, metro, or core/long-haul; the number and type of network elements-fiber, wavelengths, amplifiers, switching elements, etc.; and the type of applications-real-time, non-real time, missioncritical, etc. In transparent optical networks, PLIs incurred by non-ideal optical transmission media accumulate along an optical path, and the overall effect determines the feasibility of the lightpaths. If the received signal quality is not within the receiver sensitivity threshold, the receiver may not be able to correctly detect the optical signal and this may result in high bit-error rates. Hence, it is important to understand various PLIs and their effect on optical feasibility, analytical models, and monitoring and mitigation techniques. Introducing optical transparency in the physical layer on one hand leads to a dynamic, flexible optical layer with the possibility of adding intelligence such as optical performance monitoring, fault management, etc. On the other hand, transparency reduces the possibility of client layer interaction with the optical layer at intermediate nodes along the path. This has an impact on network design, planning, control, and management. Hence, it is important to understand the techniques that provide PLI information to the control plane protocols and that use this information efficiently to compute feasible routes and wavelengths. The purpose of this article is to provide a comprehensive survey of various PLIs, their effects, and the available modeling and mitigation techniques. We then present a comprehensive survey of various PLI-aware network design techniques, regenerator placement algorithms, routing and wavelength assignment algorithms, and PLI-aware failure recovery algorithms. Furthermore, we identify several important research issues that need to be addressed to realize dynamically reconfigurable next-generation optical networks. We also argue the need for PLI-aware control plane protocol extensions and present several interesting issues that need to be considered in order for these extensions to be deployed in real-world networks.

The design of single allocation incomplete hub networks

Abstract: The hub location problem deals with finding the location of hub facilities and allocating the demand nodes to these hub facilities so as to effectively route the demand between any origin–destination pair. In the extensive literature on this challenging network design problem, it has widely been assumed that the subgraph induced by the hub nodes is complete. Relaxation of this basic assumption constitutes the starting point of the present work. In this study, we provide a uniform modeling treatment to all the single allocation variants of the existing hub location problems, under the incomplete hub network design. No network structure other than connectivity is imposed on the induced hub network. Within this context, the single allocation incomplete p-hub median, the incomplete hub location with fixed costs, the incomplete hub covering, and the incomplete p-hub center network design problems are defined, and efficient mathematical formulations for these problems with Oðn 3 Þ variables are introduced. Computational analyses with these formulations are presented on the various instances of the CAB data set and on the Turkish network.

A Study of Demand Stochasticity in Service Network Design

Abstract: The objective of this paper is to investigate the importance of introducing stochastic elements into service network design formulations. To offer insights into this issue, we take a basic version of the problem in which periodic schedules are built for a number of vehicles and where only the demand may vary stochastically. We study how solutions based on uncertain demand differ from solutions based on deterministic demand and provide qualitative descriptions of the structural differences. Some of these structural differences provide a hedge against uncertainty by using consolidation. This way we get consolidation as output from the model rather than as an a priori required property. Service networks with such properties are robust, as seen by the customers, by providing operational flexibility.

SCARAB: a single cycle adaptive routing and bufferless network

Abstract: As technology scaling drives the number of processor cores upward, current on-chip routers consume substantial portions of chip area and power budgets. Since existing research has greatly reduced router latency overheads and capitalized on available on-chip bandwidth, power constraints dominate interconnection network design. Recently research has proposed bufferless routers as a means to alleviate these constraints, but to date all designs exhibit poor operational frequency, throughput, or latency. In this paper, we propose an efficient bufferless router which lowers average packet latency by 17.6% and dynamic energy by 18.3% over existing bufferless on-chip network designs. In order to maintain the energy and area benefit of bufferless routers while delivering ultra-low latencies, our router utilizes an opportunistic processor-side buffering technique and an energy-efficient circuit-switched network for delivering negative acknowledgments for dropped packets.

Manufacturing network configuration in supply chains with product recovery

Abstract: Efficient implementation of product recovery requires appropriate network structures. In this paper, we study the network design problem of a firm that manufactures new products and remanufactures returned products in its facilities. We examine the capacity decisions and expected performance of two alternative manufacturing network configurations when demand and return flows are both uncertain. Concerning the market structure, we further distinguish between the case where newly manufactured and remanufactured products are sold on the same market and the case where recovered products have to be sold on a secondary market. We consider network structures where manufacturing and remanufacturing are both conducted in common plants as well as structures that pool all remanufacturing activities in a separate plant. The underlying decision problems are formulated as two-stage stochastic programs with recourse. Based on numerical studies with normally distributed demands and returns, we show that particularly network size, investment costs of (re-)manufacturing capacity, and market structure have a strong impact on the choice of a network configuration. Concerning the general role of manufacturing configuration in a system with product recovery, our results indicate that the investigated structures can lead to very different expected profits. We also examine the sensitivity of network performance to changes in return volumes, return variability and correlation between return and demand. Based on these results, we find that integrated plants are more beneficial in the common market setting. This relative advantage tends to diminish when demand is segmented, thus investing in more specialized, dedicated resources should be considered.

Models and Tabu Search Metaheuristics for Service Network Design with Asset-Balance Requirements

Abstract: This paper focuses on a generic model for service network design, which includes asset positioning and utilization through constraints on asset availability at terminals. We denote these relations as “design-balance constraints” and focus on the design-balanced capacitated multicommodity network design model, a generalization of the capacitated multicommodity network design model generally used in service network design applications. Both arc-and cycle-based formulations for the new model are presented. The paper also proposes a tabu search metaheuristic framework for the arc-based formulation. Results on a wide range of network design problem instances from the literature indicate the proposed method behaves very well in terms of computational efficiency and solution quality.

Multi-period transportation network design under demand uncertainty

Abstract: The ability to make optimal transportation network investments decision is central to the strategic management of transportation systems. The presence of uncertainty in transportation systems presents new challenges in making optimal network investment decisions. In this paper, the authors develop a multi time period network design problem considering both demand uncertainty and demand elasticity. Such an approach affords the planner the flexibility to delay, change, or even abandon the future network investment. The authors measure the flexibility of investing over multiple time periods as compared to a single-stage network design decision. Initially, the authors provide a taxonomy and define many dimensions of transportation network flexibility. This is followed with the development of a flexible network design formulation (FNDP), in which the investment is staged over multiple time periods. The demand is assumed to be separable and the demand elasticity is captured using a negative exponential distribution. The authors develop the FNDP formulation as bilevel stochastic mathematical programming with complementarity constraints (STOCH-MPEC) in which the bi-level formulation is converted to a single level using non-linear complementarity constraint conditions for user equilibrium (UE) problem. The formulation is implemented on two test networks and the results show the benefits of FNDP over single-stage NDP--measured in terms of increase in present expected system consumer surplus (PESCS)--are in the range of 10-30%. The results clearly demonstrate that under demand uncertainty there are potential benefits of introducing flexibility in investment decisions. Finally, the authors conduct a sensitivity analysis of FNDP with different budget values and it is observed that certain paradoxical sharp corners are observed at certain budget values.

Network design for reverse and closed-loop supply chains: An annotated bibliography of models and solution approaches

Abstract: Historically, both the theory and practice of supply chain management have placed an emphasis on manufacturing and distribution operations, i.e., the forward channel, which consists of suppliers, manufacturers, distributors, retailers, and customers. Recently, increased attention to product recovery practices has extended the scope of traditional supply chain management by drawing attention to collection, demanufacturing, and remanufacturing operations, i.e., the reverse channel, which consists of final-users, collectors, demanufacturers, and remanufacturers. To optimize the performance of the extended supply chain, there is a need to establish an effective and efficient infrastructure via optimal network design. As a result, network design for product recovery has attracted the attention of a growing number of researchers in the past decade. In an attempt to draw more academic attention to this area, this annotated bibliography provides a detailed account of the published literature. The article is organized into two main sections that focus on (i) reverse supply chain network design, which is concerned with establishing an infrastructure to manage the reverse channel only and (ii) closed-loop supply chain network design, which is concerned with establishing an infrastructure to manage both forward and reverse channels in a coordinated manner. Specifically, we describe the operational characteristics of the underlying supply chain system considered in each paper, highlight the features of the network design model proposed therein, and discuss the proposed solution approach along with a brief description of significant computational work, if available. In conclusion, a critical review of the published literature is given and potential areas for future research are identified. © 2008 Wiley Periodicals, Inc. NETWORKS, 2009

Duty-Cycle-Aware Broadcast in Wireless Sensor Networks

Abstract: Broadcast is one of the most fundamental services in wireless sensor networks (WSNs). It facilitates sensor nodes to propagate messages across the whole network, serving a wide range of higher-level operations and thus being critical to the overall network design. A distinct feature of WSNs is that many nodes alternate between active and dormant states, so as to conserve energy and extend the network lifetime. Unfortunately, the impact of such cycles has been largely ignored in existing broadcast implementations that adopt the common assumption of all nodes being active all over the time. In this paper, we revisit the broadcast problem with active/dormant cycles. We show strong evidence that conventional broadcast approaches will suffer from severe performance degradation, and, under low duty-cycles, they could easily fail to cover the whole network in an acceptable timeframe. To this end, we remodel the broadcast problem in this new context, seeking a balance between efficiency and latency with coverage guarantees. We demonstrate that this problem can be translated into a graph equivalence, and develop a centralized optimal solution. It provides a valuable benchmark for assessing diverse duty-cycle-aware broadcast strategies. We then extend it to an efficient and scalable distributed implementation, which relies on local information and operations only, with built-in loss compensation mechanisms. The performance of our solution is evaluated under diverse network configurations. The results suggest that our distributed solution is close to the lower bounds of both time and forwarding costs, and it well resists to the network size and wireless loss increases. In addition, it enables flexible control toward the quality of broadcast coverage.

Service network design with asset management: Formulations and comparative analyses

Abstract: In this paper, we address the service network design with asset management problem, which integrates asset management considerations into service network design models for consolidation-based freight carriers. We propose model formulations based on arc variables for both flow and design, as well as formulations with path flow variables and new cycle design variables. Problem instances reflecting actual planning problems are used in the computational study to analyze the strengths and weaknesses of the various model formulations and the impact of asset management considerations on the transportation plan and the computational effort. Experimental results indicate that formulations based on cycle variables outperform traditional arc-based formulations, and that considering asset management issues may significantly impact the outcome of service planning models.

Survey of Wireless Sensor Networks Simulation Tools for Demanding Applications

Abstract: Requirements for Wireless Sensor networks will increase in the future. Requirements are demanding, especially in industrial real time networks which require high reliability and performance. Network simulation tools are often needed in the network design phase before actual implementation. In this paper, we selected 5 common wireless sensor networks simulation tools and estimated their suitability for high-performance network planning and verification. According to the study, some tools managed the requirements for demanding simulation but needed some extension.

Efficient multi-objective optimal design of water distribution networks on a budget of simulations using hybrid algorithms

Abstract: The design of water distribution networks is a large-scale combinatorial, non-linear optimisation problem, involving many complex implicit constraint sets, such as nodal mass balance and energy conservation, which are commonly satisfied through the use of hydraulic network solvers. These problem properties have motivated several prior studies to use stochastic search optimisation, because these derivative-free global search algorithms have been shown to obtain higher quality solutions for large network design problems. Global stochastic search methods, however, require many iterations to be performed in order to achieve a satisfactory solution, and each iteration may involve running computationally expensive simulations. Recently, this problem has been compounded by the evident need to embrace more than a single measure of performance into the design process, since by nature multi-objective optimisation methods require even more iterations. The use of metamodels as surrogates for the expensive simulation functions has been investigated as a possible remedy to this problem. However, the identification of reliable surrogates is not always a viable alternative. Under these circumstances, methods that are capable of achieving a satisfactory level of performance with a limited number of function evaluations represent a valuable alternative. This paper represents a first step towards filling this gap. Two recently introduced multi-objective, hybrid algorithms, ParEGO and LEMMO, are tested on the design problem of a real medium-size network in Southern Italy, and a real large-size network in the UK under a scenario of a severely restricted number of function evaluations. The results obtained suggest that the use of both algorithms, in particular LEMMO, could be successfully extended to the efficient design of large-scale water distribution networks.

Systems, methods, and computer readable media for providing dynamic steering of roaming in a telecommunications network

Abstract: Systems, methods, and computer readable media for providing dynamic steering of roaming in a telecommunications network are disclosed According to one aspect, a method for providing dynamic steering or roaming in a telecommunications network includes a method for providing dynamic steering or roaming in a telecommunications network The method includes, at a mobile telecommunications device, the device being associated with a subscriber of a first network, detecting a trigger condition for updating a roaming preference, where the trigger condition is not controlled by the operator of the first network, determining an identity of a second network, and performing at least one of: making a change to a preferred roaming network for the device by setting the second network as a preferred roaming network for the device, and connecting to the second network

Optimal integration of energy storage in distribution networks

Abstract: Energy storage, traditionally well established in the form of large scale pumped-hydro systems, is finding increased attraction in medium and smaller scale systems. Such expansion is entirely complementary to the wider uptake of intermittent renewable resources and to distributed generation in general, which are likely to present a whole range of new business opportunities for storage systems and their suppliers. In the paper, by assuming that Distribution System Operator has got the ownership and operation of storage, a new software planning tool for distribution networks able to define the optimal placement, rating and control strategies of distributed storage systems that minimize the overall network cost is proposed. This tool will assist the System Operators in defining the better integration strategies of distributed storage systems in distribution networks and in assessing their potential as an option for a more efficient operation and development of future electricity distribution networks.