Showing papers on "Network planning and design published in 2005"

Cross-layer design of ad hoc networks for real-time video streaming

Abstract: Cross-layer design breaks away from traditional network design where each layer of the protocol stack operates independently. We explore the potential synergies of exchanging information between different layers to support real-time video streaming. In this new approach information is exchanged between different layers of the protocol stack, and end-to-end performance is optimized by adapting to this information at each protocol layer. We discuss key parameters used in the cross-layer information exchange along with the associated cross-layer adaptation. Substantial performance gains through this cross-layer design are demonstrated for video streaming.

Stochastic Transportation-Inventory Network Design Problem

Abstract: We study the stochastic transportation-inventory network design problem involving one supplier and multiple retailers Each retailer faces some uncertain demand, and safety stock must be maintained to achieve suitable service levels However, risk-pooling benefits may be achieved by allowing some retailers to serve as distribution centers for other retailers The problem is to determine which retailers should serve as distribution centers and how to allocate the other retailers to the distribution centers Shen et al (2003) formulated this problem as a set-covering integer-programming model The pricing problem that arises from the column generation algorithm gives rise to a new class of the submodular function minimization problem In this paper, we show that by exploiting certain special structures, we can solve the general pricing problem in Shen et al efficiently Our approach utilizes the fact that the set of all lines in a two-dimension plane has low VC-dimension We present computational results on several instances of sizes ranging from 40 to 500 retailers Our solution technique can be applied to a wide range of other concave cost-minimization problems

Solution algorithm for the bi-level discrete network design problem

Abstract: The discrete network design problem deals with the selection of link additions to an existing road network, with given demand from each origin to each destination. The objective is to make an optimal investment decision in order to minimize the total travel cost in the network, while accounting for the route choice behaviors of network users. Because of the computational difficulties experienced with the solution algorithm of nonlinear bi-level mixed integer programming with a large number of 0–1 variables, the discrete network design problem has been recognized as one of the most difficult yet challenging problems in transport. In this paper, at first a traditional bi-level programming model for the discrete network design problem is introduced, and then a new solution algorithm is proposed by using the support function concept to express the relationship between improvement flows and the new additional links in the existing urban network. Finally, the applications of the new algorithm are illustrated with two numerical examples. Numerical results indicate that the proposed algorithm would be efficient in practice.

Network planning in wireless ad hoc networks: a cross-Layer approach

Abstract: In this paper, the network planning problem in wireless ad hoc networks is formulated as the problem of allocating physical and medium access layer resources or supplies to minimize a cost function, while fulfilling certain end-to-end communication demands, which are given as a collection of multicast sessions with desired transmission rates. We propose an iterative cross-layer optimization, which alternates between: 1) jointly optimizing the timesharing in the medium access layer and the sum of max of flows assignment in the network layer and 2) updating the operational states in the physical layer. We consider two objectives, minimizing aggregate congestion and minimizing power consumption, respectively, corresponding to operating in a bandwidth-limited regime and in an energy-limited regime. The end result is a set of achievable tradeoffs between throughput and energy efficiency, in a given wireless network with a given traffic pattern. We evaluate our approach quantitatively by simulations of community wireless networks and compare with designs that decouple the layers. We demonstrate that significant performance advantages can be achieved by adopting a full-fledged cross-layer optimization. Furthermore, we observe that optimized solutions generally profit from network coding, physical-layer broadcasting, and traffic-dependent physical states.

Bilevel programming for the continuous transport network design problem

Abstract: A Continuous Network Design Problem (CNDP) is to determine the set of link capacity expansions and the corresponding equilibrium flows for which the measures of performance index for the network is optimal. A bilevel programming technique can be used to formulate this equilibrium network design problem. At the upper level problem, the system performance index is defined as the sum of total travel times and investment costs of link capacity expansions. At the lower level problem, the user equilibrium flow is determined by Wardrop’s first principle and can be formulated as an equivalent minimization problem. In this paper we exploit a descent approach via the implementation of gradient-based methods to solve CNDP generally where the Karush–Kuhn–Tucker points can be obtained. Four variants of gradient-based methods are presented and numerical comparisons are widely made with the previous on three kinds of test networks. The proposed methods have achieved substantially better results in terms of the robustness to the initials and the computational efficiency in solving equilibrium assignment problems than did others especially when the congested road networks are considered.

Network localization in partially localizable networks

Abstract: Knowing the positions of the nodes in a network is essential to many next generation pervasive and sensor network functionalities. Although many network localization systems have recently been proposed and evaluated, there has been no systematic study of partially localizable networks, i.e., networks in which there exist nodes whose positions cannot be uniquely determined. There is no existing study which correctly identifies precisely which nodes in a network are uniquely localizable and which are not. This absence of a sufficient uniqueness condition permits the computation of erroneous positions that may in turn lead applications to produce flawed results. In this paper, in addition to demonstrating the relevance of networks that may not be fully localizable, we design the first framework for two dimensional network localization with an efficient component to correctly determine which nodes are localizable and which are not. Implementing this system, we conduct comprehensive evaluations of network localizability, providing guidelines for both network design and deployment. Furthermore, we study an integration of traditional geographic routing with geographic routing over virtual coordinates in the partially localizable network setting. We show that this novel cross-layer integration yields good performance, and argue that such optimizations will be likely be necessary to ensure acceptable application performance in partially localizable networks.

Sparse Regeneration in Translucent Wavelength-Routed Optical Networks: Architecture, Network Design and Wavelength Routing

Abstract: In this paper we study an alternate network architecture, called translucent network, to the fully transparent and fully opaque network architectures. In a translucent wavelength-routed optical network, a technique called sparse regeneration is used to overcome the severe lightpath blocking due to signal quality degradation and wavelength contention in a fully transparent network while using much less regenerators than in a fully opaque network. In this paper, we present a node model and a network model that perform sparse regeneration. We address the problem of translucent network design by proposing several regenerator placement algorithms based on different knowledge of future network traffic patterns. We also address the problem of wavelength routing under sparse regeneration by incorporating two regenerator allocation strategies with heuristic wavelength routing algorithms. We compare the performance of different regenerator placement algorithms and wavelength routing schemes through simulation experiments. The benefit of sparse regeneration is quantitatively measured under different network settings.

The problem of synthetically generating IP traffic matrices: initial recommendations

Abstract: There exist a wide variety of network design problems that require a traffic matrix as input in order to carry out performance evaluation. The research community has not had at its disposal any information about how to construct realistic traffic matrices. We introduce here the two basic problems that need to be addressed to construct such matrices. The first is that of synthetically generating traffic volume levels that obey spatial and temporal patterns as observed in realistic traffic matrices. The second is that of assigning a set of numbers (representing traffic levels) to particular node pairs in a given topology. This paper provides an in-depth discussion of the many issues that arise when addressing these problems. Our approach to the first problem is to extract statistical characteristics for such traffic from real data collected inside two large IP backbones. We dispel the myth that uniform distributions can be used to randomly generate numbers for populating a traffic matrix. Instead, we show that the lognormal distribution is better for this purpose as it describes well the mean rates of origin-destination flows. We provide estimates for the mean and variance properties of the traffic matrix flows from our datasets. We explain the second problem and discuss the notion of a traffic matrix being well-matched to a topology. We provide two initial solutions to this problem, one using an ILP formulation that incorporates simple and well formed constraints. Our second solution is a heuristic one that incorporates more challenging constraints coming from carrier practices used to design and evolve topologies.

Routing of Uncertain Traffic Demands

Abstract: Due to the success of the Internet and the diversity of communication applications, it is becoming increasingly difficult to forecast traffic patterns. To capture the traffic variations, we introduce a flexible model where traffic belongs to a polytope. We assume that the traffic demands between nodes can be carried on many paths, with respect to network resources. Moreover, to guarantee the network stability and to make the routing easy to implement, the proportions of traffic flowing through each path have to be independent of the current traffic demands. We show that a minimum-cost routing satisfying the previous properties can be efficiently computed by column and constraint generations. We then present several strategies related to certain algorithmic details. Finally, theoretical and computational studies show that this new flexible model can be much more economical than a classical deterministic model based on a given traffic matrix. This paper can be considered as a mathematical framework for a new flexible virtual private network service offer. It also introduces a new concept: the routing of a polytope.

Logistics systems : design and optimization

Abstract: Foreword.- Contributing Authors.- Preface.- The Network of Logistics Decisions.- Facility Location in Supply Chain Design.- Distribution Centres in Supply Chain Operations.- Operational Research Methods for Efficient Warehousing.- Models and Methods for Facilities Layout Design from an Applicability to Real-World Perspective.- The Design, Planning, and Optimization of Reverse Logistics Networks.- Models and Methods for Operations in Port Container Terminals.- Strategic Network Design for Motor Carriers.- New Heuristics for the Vehicle Routing Problem.- Routing Propane Deliveries.- Synchronized Production-Distribution Planning in the Pulp and Paper Industry.- Production Planning Optimization Modeling in Demand and Supply Chains of High-Value Consumer Products.

Dynamic Traffic Assignment: Properties and Extensions

Abstract: Dynamic Traffic Assignment (DTA) is long recognized as a key component for network planning and transport policy evaluations as well as for real-time traffic operation and management. How traffic is encapsulated in a DTA model has important implications on the accuracy and fidelity of the model results. This study compares and contrasts the properties of DTA modelled with point queues versus those with physical queues, and discusses their implications. One important finding is that with the more accurate physical queue paradigm, under certain congested conditions, solutions for the commonly adopted dynamic user optimal (DUO) route choice principle just do not exist. To provide some initial thinking to accommodate this finding, this study introduces the tolerance-based DUO principle. This paper also discusses its solution existence and uniqueness, develops a solution heuristic, and demonstrates its properties through numerical examples. Finally, we conclude by presenting some prospective future research di...

Network testing systems

Abstract: A method of testing a digital mobile phone network such as a GPRS or 3 G network comprises creating test traffic using an unmodified test mobile phone coupled to a computer, and using the computer to measure a parameter associated with the network's response to the test traffic. The measurements made by the computer are encoded into the test traffic to create a data stream within the mobile phone network comprising test traffic, measurements relating to the test traffic, and signalling relating to the test traffic, whereby this data stream can be captured at points within the network and analysed to investigate the functioning of the network dynamically as the network is exercised with the test traffic. Software and test equipment for performing the method are also described.

Method and apparatus for traffic control of dynamic denial of service attacks within a communications network

Abstract: A method and apparatus for providing traffic management for distributed denial of service (DDOS) traffic. Within a communications network, a DDOS detection system monitors network traffic to identify traffic that is designed to attack a particular server within the network and their entry points into the network. A traffic routing control unit is requested to deny service to the DDOS traffic. By selectively manipulating the routing information propagated to network edge routers, the traffic that is denied service is limited to mostly DDOS traffic and is routed to a cleaning center or a null address in the most effective fashion.

Application of Ant System to network design problem

Abstract: Network design problem (NDP) is the problem of choosing from among a set of alternative projects which optimizes an objective (e.g., minimizes total travel time), while keeping consumption of resources (e.g., budget) within their limits. This problem is difficult to solve, because of its combinatorial nature and nonconvexity of the objective function. Many algorithms are presented to solve the problem more efficiently, while trading-off accuracy with computational speed. This increase in speed stems from certain approximations in the formulation of the problem, decomposition, or heuristics. This study adapts a meta – heuristic approach to solve NDP, namely Ant System (AS). The algorithm is first designed, and then calibrated to solve NDP for the Sioux Falls test network. The behavior of the algorithm is then investigated. The result seems encouraging.

A multi-level approach for network design of integrated supply chains

Abstract: Integrated e-supply chains are distributed manufacturing systems composed of various resources belonging to different companies and integrated with streamlined material, information and financial flow. The configuration of the supply-chain network is essential for business to pursue a competitive advantage and to meet the market demand. This paper proposes a three-level hierarchical methodology for a supply chain network design at the planning-management level. The integrated supply chain network is described as a set of consecutive stages connected by communication and transportation links, and the configuration aim consists in selecting the actors of the stages on the basis of transportation connection and information flow. More precisely, the first level evaluates the performance of the entities candidate to join the network and singles out efficient elements. The second level solves a multi-criteria integer linear optimization problem to configure the network. Finally, the third level is devoted to ev...

Network design for information networks

Abstract: We define a new class of network design problems motivated by designing information networks. In our model, the cost of transporting flow for a set of users (or servicing them by a facility) depends on the amount of information requested by the set of users. We assume that the aggregation cost follows economies of scale, that is, the incremental cost of a new user is less if the set of users already served is larger. Naturally, information requested by some sets of users might aggregate better than that of others, so our cost is now a function of the actual set of users. not just their total demand.We provide constant-factor approximation algorithms to two important problems in this general model. In the Group Facility Location problem, each user needs information about a resource. and the cost is a linear function of the number of resources involved (instead of the number of clients served). The Dependent Maybecast Problem extends the Karger-Minkoff maybecast model to probabilities with limited correlation and also contains the 2-stage stochastic optimization problem as a special case. We also give an O(ln n)-approximation algorithm for the Single Sink Information Network Design problem.We show that the Stochastic Steiner Tree problem can be approximated by dependent maybecast, and using this we obtain an O(1)-approximation algorithm for the k-stage stochastic Steiner tree problem for any fixed k. This is the first approximation algorithm for multi-stage stochastic optimization. Our algorithm allows scenarios to have different inflation factors, and works for any distribution provided that we can sample the distribution.

Power transmission network design by greedy randomized adaptive path relinking

Abstract: This work presents results obtained by a new metaheuristic approach called greedy randomized adaptive path relinking (GRAPR), applied to solve static power transmission network design problems. This new approach uses generalized GRASP concepts to explore different trajectories between two "high-quality" solutions previously found. The results presented were obtained from two real-world case studies of Brazilian systems.

Demand-wise Shared Protection for Meshed Optical Networks

Abstract: In this paper, a new shared protection mechanism for meshed optical networks is presented. Significant network design cost reductions can be achieved in comparison to the well-known 1+1 protection scheme. Demand-wise Shared Protection (DSP) is based on the diversification of demand routings and exploits the network connectivity to restrict the number of backup lightpaths needed to provide the desired level of protection. Computational experiments illustrate the benefits of the DSP concept for cost efficient optical network designs.

The design of production-distribution networks: A mathematical programming approach

Abstract: This text proposes a mathematical programming approach to design international production-distribution networks for make-to-stock products with convergent manufacturing processes. Various formulations of the elements of production-distribution network design models are discussed. The emphasis is put on modeling issues encountered in practice which have a significant impact on the quality of the logistics network designed. The elements discussed include the choice of an objective function, the definition of the planning horizon, the manufacturing process and product structures, the logistics network structure, demand and service requirements, facility layouts and capacity options, product flows and inventory modeling, as well as financial flows modeling. Major contributions from the literature are reviewed and a number of new formulation elements are introduced. A typical model is presented, and the use of successive mixed-integer programming to solve it with commercial solvers is discussed. A more general version of the model presented and the solution method described were implemented in a commercial supply chain design tool which is now available on the market.

Seamless mobility management with service detail records

Abstract: A method for enhancing mobility of a subscriber in a telecommunications environment. The method includes deploying with a first network operator a service that is accessible by a subscriber via a first network. The method continues with creating a service detail record containing information related to an identity of the service, e.g., defining the service. The method then involves publishing the service detail record in a service registry that is accessible by a second network operator operating a second network. The second network operator receives over the second network a request from the subscriber for the service and in response, processes the service detail record and based on such processing provides the service to the subscriber via the second network. To provide the services, the service is executed on the first network using resources of the first network allocated to the service, such as by the service detail record.

A Reliability-Based Network Design Problem

Abstract: This paper presents a reliability-based network design problem. A network reliability concept is embedded into the continuous network design problem in which travelers' route choice behavior follows the stochastic user equilibrium assumption. A new capacity-reliability index is introduced to measure the probability that all of the network links are operated below their capacities when serving different traffic patterns deviating from the average condition. The reliability-based network design problem is formulated as a bi-level program in which the lower level sub-program is the probit-based stochastic user equilibrium problem and the upper level sub-program is the maximization of the new capacity reliability index. The lower level sub-program is solved by a variant of the method of successive averages using the exponential average to represent the learning process of network users on a daily basis that results in the daily variation of traffic-flow pattern, and Monte Carlo stochastic loading. The upper level sub-program is tackled by means of genetic algorithms. A numerical example is used to demonstrate the concept of the proposed framework.

Topology adaptive network-on-chip design and implementation

Abstract: Network-on-chip designs promise to offer considerable advantages over the traditional bus-based designs in solving the numerous technological, economic and productivity problems associated with billion-transistor system-on-chip development. The authors believe that different types of networks will be required, depending on the application domain. Therefore, a very flexible network design is proposed that is highly scalable, and can be easily changed to accomodate various needs. A network-on-chip design, realised as part of the platform that the authors are developing for reconfigurable systems, is presented. This design is suitable for building networks with irregular topologies, and with low latency and high throughput.

Strong formulations for network design problems with connectivity requirements

Abstract: The network design problem with connectivity requirements lNDCr includes as special cases a wide variety of celebrated combinatorial optimization problems including the minimum spanning tree, Steiner tree, and survivable network design problems. We develop strong formulations for two versions of the edge-connectivity NDC problem: unitary problems requiring connected network designs, and nonunitary problems permitting nonconnected networks as solutions. We l1r present a new directed formulation for the unitary NDC problem that is stronger than a natural undirected formulation; l2r project out two classes of valid inequalities—partition inequalities, and combinatorial design inequalities—that generalize known classes of valid inequalities for the Steiner tree problem to the unitary NDC problem; and l3r show how to strengthen and direct nonunitary problems. Our results provide a unifying framework for strengthening formulations for NDC problems, and demonstrate the power of flow-based formulations for network design problems with connectivity requirements. © 2005 Wiley Periodicals, Inc. NETWORKS, Vol. 45l2r, 61–79 2005