Chaos Synchronization in Complex Networks

In this paper, we study chaos synchronization in complex networks with time-invariant, time-varying and switching configurations based on the matrix measure of complex matrices. To begin with, we propose an analytical condition for chaos synchronization in complex networks with a time-invariant configuration. Secondly, we obtain some less conservative synchronization conditions for networks with a time-varying configuration. Thirdly, we consider chaos synchronization in networks with time-average and switching configurations. If complex subnetworks satisfy certain conditions, the networks with time-average and switching configurations are $M$-synchronizable. At last, we analyze the nonsynchronizability of complex networks. Chaos synchronization in complex networks can't be realized if the coupling configuration and the inner-coupling matrix satisfy certain conditions. Theoretical analysis and numerical simulations verify the effectiveness of the proposed synchronization criteria.      

非线性有源电阻网络的拓扑分析

将线性网络的拓扑分析法推广到非线性有源电阻网络,采用了非线性元件分段线性化的模型,将非线性有源电阻网络转化为分段线性有源网络。提出了非线性有源电阻网络"通解"、"特解"、"真特解"等新概念,使非线性有源电阻网络有了类似于线性网络的解析解。实验结果表明,这种方法具有良好的收敛性。     

A Kind of Topology Aggregation Algorithm in Hierarchical Wavelength-Routed Optical Networks

In large scale networks composed of several hierarchical subnetworks, topology aggregation is implemented for both scalability and security consideration. However, due to the special characteristic of optical wavelength-routed networks, existing topology aggregation algorithms cannot be applied directly for topology compression. In this paper, we propose a kind of topology aggregation algorithm suitable for hierarchical wavelength-routed optical networks, thereby considering information of residual wavelengths on network links. Basically, our topology aggregation algorithm is based on a transition matrix technique for constructing a full mesh topology and asymmetric star approach for a more compact topology. Simulations with randomly-generated networks show that topology information compression can be achieved with a little loss of its accuracy: the ratio of border node pairs with representation deviation being well below 10%. Results also indicate that the advantage of our algorithm is also behaved on reducing the amount of link-state-advertisement messages and making networks less vulnerable to propagation delay of these messages over communication links. This work is supported by National 863 Program 2003AA122220.     

The capacity of multi‐channel multi‐interface wireless networks with multi‐packet reception and directional antenna

The capacity of wireless networks can be improved by the use of multi‐channel multi‐interface (MCMI), multi‐packet reception (MPR), and directional antenna (DA). MCMI can provide the concurrent transmission in different channels for each node with multiple interfaces; MPR offers an increased number of concurrent transmissions on the same channel; DA can be more effective than omni‐DA by reducing interference and increasing spatial reuse. This paper explores the capacity of wireless networks that integrate MCMI, MPR, and DA technologies. Unlike some previous research, which only employed one or two of the aforementioned technologies to improve the capacity of networks, this research captures the capacity bound of the networks with all the aforementioned technologies in arbitrary and random wireless networks. The research shows that such three‐technology networks can achieve at most capacity gain in arbitrary networks and capacity gain in random networks compared with MCMI wireless networks without DA and MPR. The paper also explored and analyzed the impact on the network capacity gain with different , θ, and k‐MPR ability. Copyright © 2012 John Wiley & Sons, Ltd.     

Incorporating QoS into IP Enterprise Network Design

Recent trends in enterprise networks are radically changing the composition of these systems. Instead of having diverse data networks, each of which is dedicated to a single class of applications, corporations are moving to a unified IP (Internet Protocol) Intranet. Traffic demands on these Intranets include delay-sensitive traffic that requires better than the standard best effort service provided by IP networks. As a result, various new technologies and strategies to provide end-to-end Quality of Service (QoS) within IP enterprise networks are being developed and implemented. However, current IP network design methodologies are limited in that they can only design networks providing best effort service or else, a single delay constraint for all traffic. In this paper, we discuss a new design methodology for IP enterprise networks that takes into account the new technologies and techniques that can provide QoS. In particular, we identify and discuss the most crucial design issues that must be addressed when specialized queuing-based QoS strategies are used in the network. We describe the new constraints introduced by the underlying technologies and discuss how these factors affect the formulation of the IP Enterprise Network Design Problem. We then describe some specific features and methodologies that have been incorporated into a network design-planning tool for IP enterprise networks with QoS.     

Protocol Traps in Computer Networks--A Catalog

This paper is a compendium of potential protocol "traps" compiled from relevant literature on computer networks. The diversity of deadlocks and message ping-ponging conditions that can arise in computer networks is presented together with associated methods of solution.     

The OSI network layer: Standards to cope with the real world

Two key aspects of the OSI Network Layer which require standardization are the definition of the "service" provided by the Network Layer to the Transport Layer and the specification of the way in which "real networks" are to be utilized to provide this "Network Service." This paper describes the results of the work to date by CCITT and ISO in these two very important areas: 1) the Network Service Definition which is near final agreement; and 2) the emerging Network Layer "internal architecture" which is being used to discuss and develpoment strategies for internetworking with real networks.     

Analysis of Connection Survivability in Complex Strategic Communications Networks

Military communications networks have to retain their connectivity when subject to quite severe damage. The "survivability" of such networks is conveniently defined by the probability of retaining a connection between representative pairs of terminals. Many methods of calculating this parameter analytically, or of estimating it statistically, have been published. However, because of the "combinatorial explosion," none have so far proved viable except for relatively simple networks (and often also unjustifiable implicit assumptions). A new approach is therefore developed in this paper, which reduces the computational load by several orders of magnitude, and makes significant practical networks amenable to analysis.     

Optimizing routing in packet-switched networks with non-Poisson offered traffic

Routing models for packet-switched networks have traditionally been based on the assumption that the offered traffic is Poisson. This is unrealistic since for many applications, real life data streams tend to be extremely bursty, contradicting the Poisson assumption. This paper introduces a centralized bifurcated routing optimization model for networks with significantly non-Poisson offered traffic. The central purpose of the work is to assess the impact of non-Poisson traffic on routing algorithm developed for Poisson flows. A systematic testing plan for networks with a simple topology and variable levels of capacity, demand and packet length was designed. The results confirmed that Poisson delay formulas together with classical Poisson routing are not appropriate when significant demand is highly variable. The results also show that non-Poisson delay formulas are crucial to the assessment of average delay in these cases.     

The Observable Part of a Network

The union of all shortest path trees $G_{cup {rm spt}}$ is the maximally observable part of a network when traffic follows shortest paths. Overlay networks such as peer to peer networks or virtual private networks can be regarded as a subgraph of $G_{cup {rm spt}}$. We investigate properties of $G_{cup {rm spt}}$ in different underlying topologies with regular i.i.d. link weights. In particular, we show that the overlay $G_{cup {rm spt}}$ in an ErdÖs–RÉnyi random graph $G_{p}left (Nright)$ is a connected $G_{p_{c}}left (Nright)$ where $p_{c}sim {{ log N}over { N}}$ is the critical link density, an observation with potential for ad-hoc networks.      

Private Computation: k-Connected versus 1-Connected Networks

We study the role of connectivity of communication networks in private computations under information theoretical settings in the honest-but-curious model. We show that some functions can be 1-privately computed even if the underlying network is 1-connected but not 2-connected. Then we give a complete characterisation of non-degenerate functions that can be 1-privately computed on non-2-connected networks. Furthermore, we present a technique for simulating 1-private protocols that work on arbitrary (complete) networks on k-connected networks. For this simulation, at most additional random bits are needed, where L is the number of bits exchanged in the original protocol and n is the number of players. Finally, we give matching lower and upper bounds for the number of random bits needed to compute the parity function on k-connected networks 1-privately, namely random bits for networks consisting of n players.     

On the use of wireless networks at low level of factory automation systems

Wireless communication systems are rapidly becoming a viable solution for employment at the lowest level of factory automation systems, usually referred to as either "device" or "field" level, where the requested performance may be rather critical in terms of both transmission time and reliability. In this paper, we deal with the use of wireless networks at the device level. Specifically, after an analysis of the communication requirements, we introduce a general profile of a wireless fieldbus. Both the physical and data link layers are taken directly from existing wireless local area networks and wireless personal area networks standards, whereas the application layer is derived from the most popular wired fieldbuses. We discuss implementation issues related to two models of application layer protocols and present performance results obtained through numerical simulations. We also address some important aspects related to data security and power consumption.     

IP智能与WDM技术的融合

讨论了在IP over WDM directly分层结构下,IP层网络与光层网络的三种基本融合方式—静态重叠模型、动态重叠模型和动态对等模型,这三种融合方式体现了IP over WDM directly的演变过程。同时还对各种融合方式中网络的组成结构及相应的控制平面技术作了详尽的阐述。     

Design and Analysis of an Efficient Communication Strategy for Hierarchical and Highly Changing Ad-hoc Mobile Networks

In this work we introduce two practical and interesting models of ad-hoc mobile networks: (a) hierarchical ad-hoc networks, comprised of dense subnetworks of mobile users interconnected by a very fast yet limited backbone infrastructure, (b) highly changing ad-hoc networks, where the deployment area changes in a highly dynamic way and is unknown to the protocol. In such networks, we study the problem of basic communication, i.e., sending messages from a sender node to a receiver node. For highly changing networks, we investigate an efficient communication protocol exploiting the coordinated motion of a small part of an ad-hoc mobile network (the runners support) to achieve fast communication. This protocol instead of using a fixed sized support for the whole duration of the protocol, employs a support of some initial (small) size which adapts (given some time which can be made fast enough) to the actual levels of traffic and the (unknown and possibly rapidly changing) network area, by changing its size in order to converge to an optimal size, thus satisfying certain Quality of Service criteria. Using random walks theory, we show that such an adaptive approach is, for this class of ad-hoc mobile networks, significantly more efficient than a simple non-adaptive implementation of the basic runners support idea, introduced in [9,10]. For hierarchical ad-hoc networks, we establish communication by using a runners support in each lower level of the hierarchy (i.e., in each dense subnetwork), while the fast backbone provides interconnections at the upper level (i.e., between the various subnetworks). We analyze the time efficiency of this hierarchical approach. This analysis indicates that the hierarchical implementation of the support approach significantly outperforms a simple implementation of it in hierarchical ad-hoc networks. Finally, we discuss a possible combination of the two approaches above (the hierarchical and the adaptive ones) that can be useful in ad-hoc networks that are both hierarchical and highly changing. Indeed, in such cases the hierarchical nature of these networks further supports the possibility of adaptation.     

Simulation‐based performance evaluation of routing protocols for mobile ad hoc networks

In this paper we evaluate several routing protocols for mobile, wireless, ad hoc networks via packetlevel simulations. The ad hoc networks are multihop wireless networks with dynamically changing network connectivity owing to mobility. The protocol suite includes several routing protocols specifically designed for ad hoc routing, as well as more traditional protocols, such as link state and distance vector, used for dynamic networks. Performance is evaluated with respect to fraction of packets delivered, endtoend delay, and routing load for a given traffic and mobility model. Both small (30 nodes) and medium sized (60 nodes) networks are used. It is observed that the new generation of ondemand routing protocols use much lower routing load, especially with small number of peertopeer conversations. However, the traditional link state and distance vector protocols provide, in general, better packet delivery and endtoend delay performance.     

Network Coding for Efficient Multicast Routing in Wireless Ad-hoc Networks

Network coding is a powerful coding technique that has been proved to be very effective in achieving the maximum multicast capacity. It is especially suited for new emerging networks such as ad-hoc and sensor networks. In this work, we investigate the multicast routing problem based on network coding and put forward a practical algorithm to obtain the maximum flow multicast routes in ad-hoc networks. The "conflict phenomenon" that occurs in undirected graphs will also be discussed. Given the developed routing algorithm, we will present the condition for a node to be an encoding node along with a corresponding capacity allocation scheme. We will also analyze the statistical characteristics of encoding nodes and maximum flow in ad-hoc networks based on random graph theory.     

地理信息系统支持下Spot/vegetation NDVI影像的大尺度神经网络分类

以内蒙古地区Spot/vegetation归一化植被指数（NDVI）影像为基本信息源,综合应用地理信息系统（GIS）技术进行了大尺度神经网络分类实验研究.建立多年份高分辨影像数据库,通过GIS软件集成与遥感影像目视解译方法,在全区范围选取了“纯净”样本数据,并辅助应用DTM数据和影像化多年气像观测数据,完成土地覆盖类型的BP人工神经网络分类.结果表明,GIS技术支持下,大面积区域尺度上spot/vegetation NDVI影像的BP神经网络分类可达到较高的分类精度.     

Evolution of optical core networks

Optical networks have developed rapidly over the last ten years and show every sign of continuing to grow and adapt to the newchallenges of supporting more traffic, more reliably and flexibly, at lower cost. We briefly review the developments of the last tenyears and then discuss current thinking on how core optical networks will develop into the future, exploring the similarities anddifferences with the previous generation of technologies. We have attempted to provide a low-jargon paper with links to moredetailed studies where appropriate.     

Design of Protected WDM Wheel Networks under Various Traffic Conditions

Wavelength-division-multiplexing networks dimensioned for static connections could be used to accommodate an unpredictable increase of lightpath requests. We analyze the problem of the new carriers to deploy networks that provide them flexibility to deliver long-lived lightpaths on demand without capacity upgrade of the existing infrastructures. We investigate the influence of the connectivity factor in both the initial optimization and on the probability of accommodating the traffic expansion. We consider multifiber WDM wheel networks, a sequence of regular ring-to-mesh architectures, under various static traffic conditions. The optimization is carried out by means of a heuristic aimed at minimizing the number of fibers. The maximum allowable traffic scaling factor is evaluated by simulations with different initial network states that have already accommodated the static traffic.