Showing papers on "Network planning and design published in 2011"

A multi-objective optimization for green supply chain network design

Abstract: In this paper, we study a supply chain network design problem with environmental concerns. We are interested in the environmental investments decisions in the design phase and propose a multi-objective optimization model that captures the trade-off between the total cost and the environment influence. We conduct a comprehensive set of numerical experiments. The results show that our model can be applied as an effective tool in the strategic planning for green supply chain. Meanwhile, the sensitivity analysis provides some interesting managerial insights for firms.

A Survey of Network Design Problems and Joint Design Approaches in Wireless Mesh Networks

Abstract: Over the last decade, the paradigm of Wireless Mesh Networks (WMNs) has matured to a reasonably commonly understood one, and there has been extensive research on various areas related to WMNs such as design, deployment, protocols, performance, etc. The quantity of research being conducted in the area of wireless mesh design has dramatically increased in the past few years, due to increasing interest in this paradigm as its potential for the "last few miles", and the possibility of significant wireless services in metropolitan area networks. This recent work has focused increasingly on joint design problems, together with studies in designing specific aspects of the WMN such as routing, power control etc. in isolation. While excellent surveys and tutorials pertaining to WMNs exist in literature, the explosive growth of research in the area of specific design issues, and especially joint design, has left them behind. Our objective in this paper is to identify the fundamental WMN design problems of interference modeling, power control, topology control, link scheduling, and routing, and provide brief overviews, together with a survey of the recent research on these topics, with special stress on joint design methods. We believe this paper will fulfill an outstanding need in informing the interested student and researcher in getting familiar with this abundant recent research area, and starting research.

Characterizing and modeling internet traffic dynamics of cellular devices

Abstract: Understanding Internet traffic dynamics in large cellular networks is important for network design, troubleshooting, performance evaluation, and optimization In this paper, we present the results from our study, which is based upon a week-long aggregated flow level mobile device traffic data collected from a major cellular operator's core network In this study, we measure and characterize the spatial and temporal dynamics of mobile Internet traffic We distinguish our study from other related work by conducting the measurement at a larger scale and exploring mobile data traffic patterns along two new dimensions -- device types and applications that generate such traffic patterns Based on the findings of our measurement analysis, we propose a Zipf-like model to capture the volume distribution of application traffic and a Markov model to capture the volume dynamics of aggregate Internet traffic We further customize our models for different device types using an unsupervised clustering algorithm to improve prediction accuracy

Assessing the vulnerability of the fiber infrastructure to disasters

Abstract: Communication networks are vulnerable to natural disasters, such as earthquakes or floods, as well as to physical attacks, such as an electromagnetic pulse (EMP) attack. Such real-world events happen in specific geographical locations and disrupt specific parts of the network. Therefore, the geographical layout of the network determines the impact of such events on the network's connectivity. In this paper, we focus on assessing the vulnerability of (geographical) networks to such disasters. In particular, we aim to identify the most vulnerable parts of the network. That is, the locations of disasters that would have the maximum disruptive effect on the network in terms of capacity and connectivity. We consider graph models in which nodes and links are geographically located on a plane. First, we consider a simplistic bipartite graph model and present a polynomial-time algorithm for finding a worst-case vertical line segment cut. We then generalize the network model to graphs with nodes at arbitrary locations. We model the disaster event as a line segment or a disk and develop polynomial-time algorithms that find a worst-case line segment cut and a worst-case circular cut. Finally, we obtain numerical results for a specific backbone network, thereby demonstrating the applicability of our algorithms to real-world networks. Our novel approach provides a promising new direction for network design to avert geographical disasters or attacks.

Liner shipping service network design with empty container repositioning

Abstract: This paper proposes a liner shipping service network design problem with combined hub-and-spoke and multi-port-calling operations and empty container repositioning. It first introduces a novel concept – segment – defined as a pair of ordered ports served by one shipping line and subsequently develops a mixed-integer linear programming model for the proposed problem. Extensive numerical experiments based on realistic Asia–Europe–Oceania shipping operations show that the proposed model can be efficiently solved by CPLEX for real-case problems. They also demonstrate the potential for large cost-savings over pure hub-and-spoke or pure multi-port-calling network, or network without considering empty container repositioning.

TANGO: traffic-aware network planning and green operation

Abstract: This article addresses the potential paradigm shift of the next-generation cellular networks from the viewpoint of energy efficiency. In particular, it reveals that networks planning and operation should be more energy efficiency oriented; and in the meantime, the radio resources distributed over different cellular networks, and base stations should be optimized in a global way to be globally resource-optimized and energy-efficient networks (GREEN). A new framework, called traffic-aware network planning and green operation (TANGO), is proposed toward GREEN. Some key technologies for the migration to TANGO are then presented and evaluated. Theoretical modeling and simulation studies show that TANGO schemes can greatly improve the energy efficiency of cellular networks, while keeping QoS at a satisfactory level.

IP Over WDM Networks Employing Renewable Energy Sources

Abstract: With network expansion, the energy consumption and CO2 emissions associated with networks are increasing rapidly. In this paper we propose an approach for energy minimization in IP over WDM networks and furthermore propose the use of renewable energy to further reduce the CO2 emissions at a given energy consumption level. We develop a Linear Programming (LP) model for energy minimization in the network when renewable energy is used and propose a novel heuristic for improving renewable energy utilization. Compared with routing in the electronic layer, routing in the optical layer coupled with renewable energy nodes significantly reduces the CO2 emission of the IP over WDM network considered by 47% to 52%, and the new heuristic introduced hardly affects the QoS. In order to identify the impact of the number and the location of nodes that employ renewable energy on the non-renewable energy consumption of whole network, we also constructed another LP model. The results show that the nodes at the center of the network have more impact than other nodes if they use renewable energy sources. We have also investigated the additional energy savings that can be gained through Adaptive Link Rate (ALR) techniques where different load dependent energy consumption profiles are considered. Our optimized REO-hop routing algorithm with renewable energy and ALR results in a maximum energy saving of 85% (average of 65%) compared to a current network design where all nodes are statically dimensioned for the maximum traffic in terms of IP ports and optical layer and hence consume power accordingly. Furthermore, when all the nodes have access to typical levels of renewable power we show that the associated reduction in non-renewable energy consumption reduces the network's CO2 emissions by 97% peak, 78% average.

Complex network analysis of water distribution systems

Abstract: This paper explores a variety of strategies for understanding the formation, structure, efficiency and vulnerability of water distribution networks. Water supply systems are studied as spatially organized networks for which the practical applications of abstract evaluation methods are critically evaluated. Empirical data from benchmark networks are used to study the interplay between network structure and operational efficiency, reliability and robustness. Structural measurements are undertaken to quantify properties such as redundancy and optimal-connectivity, herein proposed as constraints in network design optimization problems. The role of the supply-demand structure towards system efficiency is studied and an assessment of the vulnerability to failures based on the disconnection of nodes from the source(s) is undertaken. The absence of conventional degree-based hubs (observed through uncorrelated non-heterogeneous sparse topologies) prompts an alternative approach to studying structural vulnerability based on the identification of network cut-sets and optimal connectivity invariants. A discussion on the scope, limitations and possible future directions of this research is provided.

Random Access Compressed Sensing for Energy-Efficient Underwater Sensor Networks

Abstract: Inspired by the theory of compressed sensing and employing random channel access, we propose a distributed energy-efficient sensor network scheme denoted by Random Access Compressed Sensing (RACS). The proposed scheme is suitable for long-term deployment of large underwater networks, in which saving energy and bandwidth is of crucial importance. During each frame, a randomly chosen subset of nodes participate in the sensing process, then share the channel using random access. Due to the nature of random access, packets may collide at the fusion center. To account for the packet loss that occurs due to collisions, the network design employs the concept of sufficient sensing probability. With this probability, sufficiently many data packets - as required for field reconstruction based on compressed sensing - are to be received. The RACS scheme prolongs network life-time while employing a simple and distributed scheme which eliminates the need for scheduling.

Intermodal hub-and-spoke network design: Incorporating multiple stakeholders and multi-type containers

Abstract: This paper develops a mathematical program with equilibrium constraints (MPEC) model for the intermodal hub-and-spoke network design (IHSND) problem with multiple stakeholders and multi-type containers. The model incorporates a parametric variational inequality (VI) that formulates the user equilibrium (UE) behavior of intermodal operators in route choice for any given network design decision of the network planner. The model also uses a cost function that is capable of reflecting the transition from scale economies to scale diseconomies in distinct flow regimes for carriers or hub operators, and a disutility function integrating actual transportation charges and congestion impacts for intermodal operators. To solve the MPEC model, a hybrid genetic algorithm (HGA) embedded with a diagonalization method for solving the parametric VI is proposed. Finally, the comparative analysis of the HGA and an exhaustive enumeration algorithm indicates a good performance of the HGA in terms of computational time and solution quality. The HGA is also applied to solve a large-scale problem to show the applicability of the proposed model and algorithm.

Complex network analysis of water distribution systems

Abstract: This paper explores a variety of strategies for understanding the formation, structure, efficiency, and vulnerability of water distribution networks. Water supply systems are studied as spatially organized networks for which the practical applications of abstract evaluation methods are critically evaluated. Empirical data from benchmark networks are used to study the interplay between network structure and operational efficiency, reliability, and robustness. Structural measurements are undertaken to quantify properties such as redundancy and optimal-connectivity, herein proposed as constraints in network design optimization problems. The role of the supply demand structure toward system efficiency is studied, and an assessment of the vulnerability to failures based on the disconnection of nodes from the source(s) is undertaken. The absence of conventional degree-based hubs (observed through uncorrelated nonheterogeneous sparse topologies) prompts an alternative approach to studying structural vulnerability based on the identification of network cut-sets and optimal-connectivity invariants. A discussion on the scope, limitations, and possible future directions of this research is provided.

Network cooperation for energy saving in green radio communications

Abstract: Financial and environmental considerations have motivated a trend in wireless communication network design and operation to minimize the amount of energy consumption. This trend is referred to as green radio communications. In this article, network cooperation is investigated as a means of energy saving. Networks with overlapped coverage can cooperate to reduce their energy consumption by alternately switching on and off their resources according to the traffic load conditions. We present an optimal resource on-off switching framework that adapts to the fluctuations in the traffic load and maximizes the amount of energy saving under service quality constraints in a cooperative networking environment. For the system model under consideration, unlike the existing solutions in the literature, the proposed technique can achieve energy saving while avoiding an increase in transmission power. Numerical results demonstrate the validity of the proposed technique.

Analysis of Access and Connectivity Probabilities in Vehicular Relay Networks

Abstract: IEEE 802.11p and 1609 standards are currently under development to support Vehicle-to-Vehicle and Vehicle-to-Infrastructure communications in vehicular networks. For infrastructure-based vehicular relay networks, access probability is an important measure which indicates how well an arbitrary vehicle can access the infrastructure, i.e. a base station (BS). On the other hand, connectivity probability, i.e. the probability that all the vehicles are connected to the infrastructure, indicates the service coverage performance of a vehicular relay network. In this paper, we develop an analytical model with a generic radio channel model to fully characterize the access probability and connectivity probability performance in a vehicular relay network considering both one-hop (direct access) and two-hop (via a relay) communications between a vehicle and the infrastructure. Specifically, we derive close-form equations for calculating these two probabilities. Our analytical results, validated by simulations, reveal the tradeoffs between key system parameters, such as inter-BS distance, vehicle density, transmission ranges of a BS and a vehicle, and their collective impact on access probability and connectivity probability under different communication channel models. These results and new knowledge about vehicular relay networks will enable network designers and operators to effectively improve network planning, deployment and resource management.

Mobile service routing in a network environment

Abstract: A data flow is received from a mobile network relating to a mobile subscriber. Subscriber data is received for the subscriber identifying a service path corresponding to the subscriber and at least one service policy corresponding to the subscriber, the service path including a set of network service nodes in a plurality of network service nodes. Packets of the data flow are routed according to the service path, the packets corresponding to a request for a resource. At least one packet is appended with service header data identifying the service policy. Each service node performs at least one service based on received request data, each service node in the set of service nodes performing a service defined in a service subscription of the subscriber. At least one particular service node in the set of network service nodes performs a particular service based at least in part on the service policy.

Fleet deployment, network design and hub location of liner shipping companies

Abstract: A mixed integer linear programming formulation is proposed for the simultaneous design of network and fleet deployment of a deep-sea liner service provider. The underlying network design problem is based on a 4-index (5-index by considering capacity type) formulation of the hub location problem which are known for their tightness. The demand is elastic in the sense that the service provider can accept any fraction of the origin–destination demand. We then propose a primal decomposition method to solve instances of the problem to optimality. Numerical results confirm superiority of our approach in comparison with a general-purpose mixed integer programming solver.

Lane-based evacuation network optimization: An integrated Lagrangian relaxation and tabu search approach

Abstract: This paper formulates and solves a lane-based evacuation network optimization problem that integrates lane reversal and crossing elimination strategies. To tackle the combinatorial complexity arising from this combined treatment of discrete network capacity and connectivity settings, an integrated Lagrangian relaxation and tabu search solution method is developed. The method takes advantage of Lagrangian relaxation for problem decomposition and complexity reduction while its algorithmic logic is designed based on the principles of tabu search. Numerical results from optimizing a regional evacuation network for a nuclear power plant illustrate the validness and usefulness of the modeling and solution methodology in evacuation planning practice.

Progressive hedging-based metaheuristics for stochastic network design

Abstract: We consider the stochastic fixed-charge capacitated multicommodity network design (S-CMND) problem with uncertain demand. We propose a two-stage stochastic programming formulation, where design decisions make up the first stage, while recourse decisions are made in the second stage to distribute the commodities according to observed demands. The overall objective is to optimize the cost of the first-stage design decisions plus the total expected distribution cost incurred in the second stage. To solve this formulation, we propose a metaheuristic framework inspired by the progressive hedging algorithm of Rockafellar and Wets. Following this strategy, scenario decomposition is used to separate the stochastic problem following the possible outcomes, scenarios, of the random event. Each scenario subproblem then becomes a deterministic CMND problem to be solved, which may be addressed by efficient specialized methods. We also propose and compare different strategies to gradually guide scenario subproblems to agree on the status of design arcs and aim for a good global design. These strategies are embedded into a parallel solution method, which is numerically shown to be computationally efficient and to yield high-quality solutions under various problem characteristics and demand correlations. © 2011 Wiley Periodicals, Inc. NETWORKS, 2011. © 2011 Wiley Periodicals, Inc.

LTE, WIMAX and WLAN Network Design, Optimization and Performance Analysis: Korowajczuk/LTE, WIMAX and WLAN Network Design, Optimization and Performance Analysis

Abstract: LTE, WiMAX and WLAN Network Design, Optimization and Performance Analysis provides a practical guide to LTE and WiMAX technologies introducing various tools and concepts used within. In addition, topics such as traffic modelling of IP-centric networks, RF propagation, fading, mobility, and indoor coverage are explored; new techniques which increase throughput such as MIMO and AAS technology are highlighted; and simulation, network design and performance analysis are also examined. Finally, in the latter part of the book Korowajczuk gives a step-by-step guide to network design, providing readers with the capability to build reliable and robust data networks.

A case for heterogeneous on-chip interconnects for CMPs

Abstract: Network-on-chip (NoC) has become a critical shared resource in the emerging Chip Multiprocessor (CMP) era. Most prior NoC designs have used the same type of router across the entire network. While this homogeneous network design eases the burden on a network designer, partitioning the resources equally among all routers across the network does not lead to optimal resource usage, and hence, affects the performance-power envelope. In this work, we propose to apportion the resources in an NoC to leverage the non-uniformity in network resource demand. Our proposal includes partitioning the network resources, specifically buffers and links, in an optimal manner. This approach results in redistributing resources such that routers that require more resources are allocated more buffers and wider links compared to routers demanding fewer resources. This results in a novel heterogeneous network, called HeteroNoC, which is composed of two types of routers -- small power efficient routers, and big high performance routers. We evaluate a number of heterogeneous network configurations, composed of big and small routers, and show that giving more resources to routers along the diagonals in a mesh network provides maximum benefits in terms of performance and power. We also show the potential benefits of the HeteroNoC design by co-evaluating it with memory-controllers and configuring it with an asymmetric CMP consisting of heterogeneous cores.

Service reliability and urban public transport design

Abstract: The last few decades have shown a substantial increase in personal mobility. Urban traffic and transport volumes have been increasing for years. However, the share of public transport in this mobility growth did not change much and still remains rather limited. To ensure the accessibility and liveability of our cities for future generations, however, a substantial quality leap in public transport is necessary. This will facilitate a desired modal shift from car traffic towards public transport, which is safer, cleaner and produces less congestion. In this thesis, we demonstrate that several promising opportunities exist to improve service reliability (i.e. the certainty of service aspects compared to the schedule as perceived by the user), being one of the most important quality aspects of public transport. Literature shows that in urban public transport substantial attention is given to ways to improve service reliability at the operational level. It is not clear how and to what extent strategic and tactical design decisions in public transport systems might affect service reliability. Only traffic light priority and exclusive lanes are considered during the planning of urban public transport in order to improve the level of service reliability. We expect that more instruments at these planning levels enable high-quality services at the operational level, especially with regard to service reliability. In this thesis, we present several planning instruments that facilitate enhanced service reliability. In addition, we show forecasting tools we developed and we introduce a new indicator that expresses the impacts of service reliability more effectively than traditional indicators, namely the additional travel time per passenger. This way, the assessment of public transport benefits will be substantially improved, thereby enabling cost-effective quality improvements. We show the impacts of unreliable services on passengers, being average travel time extension, increased travel time variability and a lower probability of finding a seat in the vehicle. We demonstrate how actual vehicle trip time variability (i.e. service variability) affects service reliability and passenger travel time. In order to gain insights into the mechanisms between these two aspects, we performed research based on empirical data of the public transport system in The Hague. Furthermore, we conducted an international survey of service reliability. Several traditional quantifications of service reliability are presented, such as punctuality and regularity. We demonstrate the shortcomings of these traditional indicators, namely a lack of attention for passenger impacts. Traditional indicators focus too much on the supply side of public transport, which does not allow a proper analysis of passenger effects. To deal with the shortcomings of traditional indicators, we developed a new indicator, being the average additional travel time per passenger. This indicator translates the supply-side indicators, for instance punctuality, into the additional travel time that a passenger on average needs to travel from the origin to the destination stop due to service variability. The average additional travel time may be calculated per stop or per line and enables explicit consideration of service reliability in cost-benefit calculations, since the level of service reliability may be translated into regular travel time. In our research we demonstrate that our indicator enables optimization of network and timetable planning and that the use of traditional indicators may lead to conflicting conclusions in terms of service reliability. We also demonstrate the benefits of using reliability buffer time (RBT, as described by Furth and Muller 2006) as an indication of the effects of uncertain arrivals for passengers (i.e. the variability of the average additional travel time per passenger). To improve service reliability through enhanced network and timetable design, we selected five planning instruments by analysing the causes of service variability. The main external causes are the weather, other traffic, irregular loads and passengers’ behaviour. Other public transport, driver behaviour, schedule quality and network and vehicle design are the main internal causes of unreliability. Since the arrival pattern of passengers is very important when calculating service reliability effects, we performed a passenger survey in The Hague. It showed that passengers tend to arrive at random at their departure stop if scheduled headways are 10 minutes or less. In the case of longer headways, passengers on average plan their arrival about 2 minutes prior to the scheduled vehicle departure time. Applying instruments during the planning stages will reduce the impacts of these causes. At the strategic level, these instruments are: - Terminal design; The configuration and number of tracks and switches at the terminal determines the expected vehicle delay and thus service reliability. - Line length; The length of a line is often related to the level of service variability and thus service reliability. - Line coordination. Multiple lines on a shared track may offer a higher level of service reliability than one line (assuming equal frequencies). The following instruments may be applied at the tactical level: - Trip time determination; In long-headway services, scheduled vehicle departure times at the stop, derived from scheduled trip times, determine the arrival pattern of passengers at their departure stop. Adjusting the scheduled trip time may affect the level of service reliability and passenger waiting time. - Vehicle holding. Holding early vehicles reduces driving ahead of schedule and increases the level of service reliability. The design of the schedule affects the effectiveness of this instrument. The terminal design instrument relates to (new) rail lines with tail tracks as terminal or short-turning facilities. For high-frequency, distributed lines, we recommend compact tail tracks with double crossovers directly after the stop. Concerning (new) lines with a clear break point in passenger pattern, we recommend to split the line or to apply holding points. For long-headway services we propose to use the 35-percentile value for scheduled trip time. And if parts of lines are very crowded, we suggest investigating the effects of coordination. A tentative cost-effectiveness assessment showed that the tactical instruments (trip determination and vehicle holding) are cost-effective in almost every case. Their benefits are substantial and the costs are nil. These instruments should be considered in the design of every public transport system. However, the vehicle holding instrument is only beneficial if the passenger pattern has a clear break point and trip time determination only is relevant in long-headway services. It is presented that strategic instruments have considerable benefits as well. Optimized terminal design enables enhanced service reliability. Coordination and shorter lines may result in reduced passenger travel times as well. However, these instruments may look costly due to necessary additional infrastructure and or (occasionally) additional vehicles. We demonstrated that the costs are limited in relation to the potential welfare benefits. We roughly estimated the costs of unreliability at € 12 million per year in The Hague and we estimated the potential savings at € 8 million per year by applying the five planning instruments we analysed in our research. The estimated costs of these instruments are assessed to be only a part of the benefits with a maximum of € 3 million per year, showing the added value of the instruments. The results of our international survey show that similar results are achievable in other cities as well. In this thesis we presented planning instruments that facilitate enhanced service reliability. To achieve a higher level of service reliability in practice, we recommend considering service reliability explicitly in the design of infrastructure networks, service networks and timetables using our developed control framework and tools. Service reliability effects should be incorporated in a sophisticated way into cost-benefit analyses of public transport projects, using the average additional travel time per passenger we introduced. This way, welfare gains and additional revenues may be calculated. Optimized strategic and tactical design improves service reliability and also simplifies the operational process with regard to service reliability. Enhanced service planning will allow passengers to benefit from improved service reliability tomorrow!

A bi-objective supply chain design problem with uncertainty

Abstract: The authors consider the design of a two-echelon production distribution network with multiple manufacturing plants, customers and a set of candidate distribution centers. The main contribution of the study is to extend the existing literature by incorporating the demand uncertainty of customers within the distribution center location and transportation mode allocation decisions, as well as providing a network design satisfying the both economical and service quality objectives of the decision maker within two levels supply network setting. The authors formulate the problem as two stage integer recourse problem to find a set of optimal network configuration and assignment of transportation modes and the respective flows in order to minimize total cost and total service time, simultaneously. The authors develop a stochastic optimization model under demand uncertainty, where the inherent risk is modeled by scenarios. Finally, they propose solution methods for our stochastic optimization problem based on L-shaped algorithm within an e-optimality framework and present numerical results demonstrating the computational effectiveness.

Experimental Demonstration of an Impairment Aware Network Planning and Operation Tool for Transparent/Translucent Optical Networks

Abstract: Core optical networks using reconfigurable optical switches and tunable lasers appear to be on the road towards widespread deployment and could evolve to all-optical mesh networks in the coming future. Considering the impact of physical layer impairments in the planning and operation of all-optical (and translucent) networks is the main focus of the Dynamic Impairment Constraint Optical Networking (DICONET) project. The impairment aware network planning and operation tool (NPOT) is the main outcome of DICONET project, which is explained in detail in this paper. The key building blocks of the NPOT, consisting of network description repositories, the physical layer performance evaluator, the impairment aware routing and wavelength assignment engines, the component placement modules, failure handling, and the integration of NPOT in the control plane are the main contributions of this study. Besides, the experimental result of DICONET proposal for centralized and distributed control plane integration schemes and the performance of the failure handling in terms of restoration time is presented in this study.

Survivable transparent Flexible optical WDM (FWDM) networks

Abstract: We propose an efficient survivable FWDM network design algorithm for the first time. Survivable FWDM networks are efficient in terms of spectral utilization, power consumption, and cost compared to the conventional survivable fixed grid networks.

Branch and Price for Service Network Design with Asset Management Constraints

Abstract: We address the service network design problem with asset management considerations for consolidation-based freight carriers. Given a set of demands to be transported from origins to destinations and a set of transshipment facilities, the objective is to select services and their schedules, build routes for the assets (vehicles) operating these scheduled services, and move the demands (commodities) through the resulting service network as efficiently as possible. We propose a first branch-and-price framework for the mixed-integer formulation of the problem with integer cycle design and continuous flow-path variables. The proposed method includes particular column generation subproblems for dynamically constructing these cycles and paths, as well as an acceleration technique to identify integer solutions rapidly. The computational study shows that the proposed method finds better solutions for large network instances than reported previously.

Enhancing network performance by edge addition

Abstract: Transmission efficiency and robustness are two important properties of various networks and a number of optimization strategies have been proposed recently. We propose a scheme to enhance the network performance by adding a small fraction of links (or edges) to the currently existing network topology, and we present four edge addition strategies for adding edges efficiently. We aim at minimizing the maximum node betweenness of any node in the network to improve its transmission efficiency, and a number of experiments on both Barabasi–Albert (BA) and Erdos–Renyi (ER) networks have confirmed the effectiveness of our four edge addition strategies. Also, we evaluate the effect of some other measure metrics such as average path length, average betweenness, robustness, and degree distribution. Our work is very valuable and helpful for service providers to optimize their network performance by adding a small fraction of edges or to make good network planning on the existing network topology incrementally.

On progressive network recovery after a major disruption

Abstract: A major disruption may affect many network components and significantly lower the capacity of a network measured in terms of the maximum total flow among a set of source-destination pairs. Since only a subset of the failed components may be repaired at a time due to e.g., limited availability of repair resources, the network capacity can only be progressively increased over time by following a recovery process that involves multiple recovery stages. Different recovery processes will restore the failed components in different orders, and accordingly, result in different amount of network capacity increase after each stage. This paper aims to investigate how to optimally recover the network capacity progressively, or in other words, to determine the optimal recovery process, subject to limited available repair resources. We formulate the optimization problem, analyze its computational complexity, devise solution schemes, and conduct numerical experiments to evaluate the algorithms. The concept of progressive network recovery proposed in this paper represents a paradigm-shift in the field of resilient and survivable networking to handle large-scale failures, and will motivate a rich body of research in network design and other applications.