基于群智能优化技术的光网络资源动态分配研究

数据量以及光网络用户增多为光网络带来负担，导致广域骨干网拥堵，为此，提出基于群智能优化技术的光网络资源动态分配方法。描述光网络资源，计算平行链路的利用率，优化平行链路利用率，分配弹性光网络资源，构建光网络吞吐量最大化和光网络节点时延最小化的目标函数，通过粒子群算法，求解队列动态更新函数，获取最优解，为弹性光网络资源动态分配结果。实验结果表明，所提方法的资源动态分配速率式中在80%以上，带宽阻塞率最高仅为13.8%,光网络节点时延短。降低光网络拥堵程度，保证光网络资源利用的充分性。     

一种高能效低时延的LLN路由修复算法

由于低功耗有损网络(LLN)中无线链路的不稳定性和有损性,外部环境的干扰极易导致网络出现故障,从而严重影响网络性能,而LLN网络中现有路由修复算法存在控制开销冗余和修复时延较大等问题。为此,提出了一种高能效低时延的LLN路由修复算法(EELDR-RPL)。该算法通过采用“零额外控制开销通告链路故障及邻居节点信息”机制,使得链路故障节点的子节点能够及时获知链路故障以及链路故障节点的邻居情况;通过采用“自适应调整节点网络深度值”机制,使得链路故障节点能够快速地重新接入网络;通过采用“链路故障节点子节点自适应切换”机制,能够达到优化网络拓扑的目的。仿真结果表明,与现有路由修复算法相比,EELDR-RPL算法能够有效地降低路由修复时延和减少控制开销。     

基于阴性选择的网络限制洪泛算法

为使网络在洪泛故障信息时洪泛时延和业务质量两方面性能都能够得到改善,提出了一种基于阴性选择的限制洪泛算法.该算法根据网络环境对洪泛时延和业务损失的侧重程度,分别给出了洪泛时延与业务损失两方面代价函数以及综合两方面因素的优化目标函数,利用阴性选择算法进行寻优,计算出能够最大程度适应网络需求的限制洪泛范围,通过对故障的洪泛范围进行限制,将故障洪泛对网络造成的影响降低到最小.实验结果表明该算法能够改善网络的性能.     

考虑排队时延的系统保护通信网络路由选择算法

目前满足系统保护通信网络的路由算法是在综合时延和可靠性的要求下,计算一条快速且可靠传输的路径,而没有考虑到当电网发生故障或网络中通信量过大时,通信网络中许多节点的排队时延会极大地增加,忽略排队时延对路径传输总时延的影响会导致路径的错误选择,从而影响系统保护的实时性。针对此问题,提出了一种考虑排队时延的路由选择算法,用于计算信息传输总时延最小的最优路径,以提高系统保护通信的实时性。实验结果表明,通过本文提出的路由选择算法计算得到的路径在满足系统保护可靠性要求的基础上信息传输总时延最小。     

解决网络拥堵难题——中太力推智能流量控制产品

近几年,大量的VoIP业务运营与P2P软件下载应用, 不断冲击传统运营商的发展,同时造成了网络的严重拥堵,严重影响了宽带运营,给广大的网民也带来了许多不便。对此,许多电信解决方案和产品提供商相继推出了流量控制产品,以解决日益严重的网络拥堵问题,其中以中太数据推出的智能流量控制系统——Bgate6030尤为引人注意。它结合完善的智能流量解决方案,能有效地提高网络运营效率,帮助电信运营商解决网络拥堵难题。     

LTE系统随机接入过载控制的研究

在同一个小区内,由于随机接入资源的有限性,当大量终端同时接入基站时,会造成网络拥塞,这会导致终端接入碰撞的概率增大,使随机接入成功率降低,同时导致随机接入传输时延增大这种情况,提出一种在网络拥堵环境下进行随机接入过载控制的方法。该方法通过对系统负载进行提前估算,根据网络负载情况动态调整随机接入的用户数和随机接入的时频资源,通过仿真得出该方法有效改善系统性能,使得用户接入时延较原有流程减少约35%,同时使用户接入成功率提升约45%。     

基于内建自测技术的Mesh结构NoC无虚通道容错路由算法

 在Zhang's算法绕行思想的基础上,提出了一种2D-Mesh结构片上网络无虚通道容错路由算法,用于解决多故障节点情况下片上网络的无虚通道容错路由问题.算法利用内建自测试机制获取故障区域的位置信息,通过优化绕行策略来均衡故障区域周围链路的负载并减少部分数据的绕行距离.针对8×8的2D-Mesh网络的仿真表明,与Chen's算法相比,在故障区域大小为2×2,网络时延为70 cycles的情况下,随着故障区域位置的变化所提算法可提高1.2%到4.8%的网络注入率.且随着故障区域面积的扩大,所提算法在减少通信时延,提高网络吞吐量方面的作用更为明显.     

智能流量控制产品解决网络拥堵难题

近几年．大量的VOIP业务运营与P2P软件下载应用。不断冲击传统运营商的发展。同时造成了网络的严重拥堵．严重影响了宽带运营。给广大的网民也带来了许多不便。对此。许多电信解决方案和产品提供商相继推出了流量控制产品。以解决日益严重的网络拥堵问题．其中以中太数据推出的智能流量控制系统——Bgate6030尤为引人注意。它结合完善的智能流量解决方案．能有效地提高网络运营效率．帮助电信运营商解决网络拥堵难题。     

新型混联式涂装输送机构的PD滑模控制

针对一种新型混联式汽车电泳涂装输送机构,为解决滑模控制过分依赖于动力学模型的问题、弥补传统PD控制在强耦合强非线性系统中存在的不足,采用时延估计技术对动力学模型进行线性化处理,据此设计一种线性化PD滑模控制器。首先采用拉格朗日法建立机构的动力学模型,然后针对采用时延估计技术线性化的动力学模型设计滑模控制器,同时把时延估计误差作为扰动处理,通过PD控制保证系统的全局渐定稳定。其次,运用Lyapunov稳定性理论证明了所提出控制算法的稳定性,为PD滑模控制律参数的选择提供了准则。最后,分别对滑模控制和PD滑模控制进行MATLAB仿真比较。结果表明,所提出的PD滑模控制方法不仅使系统获得更好的跟踪性能,而且结构简单、易于实现、计算量小,从而实现对新型混联式汽车电泳涂装输送机构的高性能跟踪控制。     

地铁站移动通信实现无缝垂直切换的方法

下一代网络的发展是为用户提供无处不在的移动通信网络,使用户对其定制业务的体验始终如一,这就需要为用户提供不同网络之间尽可能小的切换时延。文中采用OPNET Modeler仿真软件,对紧耦合结构下通用移动通信系统（UMTS）到无线局域网（WLAN）的切换协议进行仿真。以地铁站为场景,设计考虑通用移动通信系统（UMTS）与无线局域网（WLAN）间的切换,对比紧耦合结构与松耦合结构下的切换时延,说明网络结构的耦合度越高,切换的时延就越小。     

Attack Vulnerability of Complex Communication Networks

The Internet has been studied as a typical example of real-world complex networks. In this brief, we study the traffic performance of the Internet when it encounters a random or intentional attack. Different from previous approaches, the congestion control protocols are considered so that the bandwidth can be reallocated among flows. In this way, cascading breakdown is less likely to happen. The flow rates are adjusted when a node is attacked and out of function. Consequently, the traffic utility and the utilization ratio of bandwidth are affected. We compare the real Internet data with the classic random graph and scale-free network models. The simulated results also show that the ldquorobust yet fragilerdquo property previously observed in the study of cascading failures in the scale-free networks is still valid in this scenario.     

非线性负载容量模型的小世界网络级联抗毁性研究

通过引入一种负载容量非线性模型,对小世界网络的级联抗毁性进行了深入研究。在局部加权的负载重分配准则下,仿真分析了权重系数、容量参数以及网络密度等对小世界网络级联抗毁性的影响,并对网络成本和抗毁性能约束下小世界网络的级联抗毁性进行了优化分析。研究表明小世界网络的级联抗毁性随权重系数的增大而减弱,不同密度的网络在权重系数较小时级联失效传播较慢,且级联抗毁性对网络密度的敏感程度相差较大。另外,存在最优容量参数组合使得小世界网络具有最强的级联抗毁性。研究成果能够为现实网络系统的抗毁性设计提供有益的参考和借鉴。     

通信网络级联失效建模与仿真分析

通信网络的级联失效会导致网络的鲁棒性下降,严重时会导致网络的大面积瘫痪, 对其进行理论建模是研究通信网络级联失效的基础和关键。在分析通信网络级联失效机理的基础上,建立了通信网络级联失效模型,并针对通信网络的级联失效模型进行了仿真分析,验证了模型的科学性和有效性,从而为研究级联失效对通信网络的影响提供了新的研究思路和方法。     

Self-similar traffic and network dynamics

One of the most significant findings of traffic measurement studies over the last decade has been the observed self-similarity in packet network traffic. Subsequent research has focused on the origins of this self-similarity, and the network engineering significance of this phenomenon. This paper reviews what is currently known about network traffic self-similarity and its significance. We then consider a matter of current research, namely, the manner in which network dynamics (specifically, the dynamics of transmission control protocol (TCP), the predominant transport protocol used in today's Internet) can affect the observed self-similarity. To this end, we first discuss some of the pitfalls associated with applying traditional performance evaluation techniques to highly-interacting, large-scale networks such as the Internet. We then present one promising approach based on chaotic maps to capture and model the dynamics of TCP-type feedback control in such networks. Not only can appropriately chosen chaotic map models capture a range of realistic source characteristics, but by coupling these to network state equations, one can study the effects of network dynamics on the observed scaling behavior We consider several aspects of TCP feedback, and illustrate by examples that while TCP-type feedback can modify the self-similar scaling behavior of network traffic, it neither generates it nor eliminates it     

Research on Methods for Improving Robustness of Cascading Failures of Interdependent Networks

The issue about cascading failures of interdependent networks is a hot research field based on the current complex network basic theories. This paper mainly researches methods for improving robustness of interdependent networks. At first, a model of interdependent network cascading failures was established to carry out robustness analysis of three different interdependent networks including BA–BA, WS–WS and ER–ER. Then, methods for improving robustness of interdependent networks under random attacks and targeted attacks were researched respectively. (1)Under random attacks, based on the overall idea of network addition, the paper summarized four common methods for improving robustness of a simple complex network, including random addition, low-degree node addition, low-betweenness node addition and addition based on algebra connectivity. After that, according to inherent characteristics of interdependent networks, the paper put forward an interdependent network addition algorithm based on internal similarities. It is shown in cascading failure simulation calculation results of three interdependent coupling networks, that the method put forward in this paper can most effectively improve robustness of interdependent networks under random attacks. (2)Based on the overall idea of protecting key nodes under targeted attacks, the paper put forward a method for analyzing key nodes of interdependent networks based on natural connectivity. Then, under the BA–BA interdependent network, the paper analyzed this method in comparison with the commonly approved Max-Cas algorithm. It is shown in simulation calculation results that, the method put forward in this paper can more obviously improve robustness of an interdependent network under targeted attacks and can be applied flexibly.     

Load Balanced Congestion Adaptive Routing for Randomly Distributed Mobile Adhoc Networks

In mobile ad hoc networks, congestion occurs due to limited sources of the network, which leads to packet losses, bandwidth degradation and wastes time and energy on congestion recovery. Various techniques have been developed in attempt to minimize congestion in uniformly distributed networks. In this paper, a load balanced congestion adaptive routing algorithm has been proposed for randomly distributed networks. In the proposed algorithm two metrics: traffic load density and life time associated with a routing path, have been used to determine the congestion status and weakest node of the route. The route with low traffic load density and maximum life time is selected for packet transmission.     

The frequency of CFVD speed report for highway traffic

The control signals of cellular networks have been used to infer the traffic conditions of the road network. In particular, consecutive handover events are being used to estimate the traffic speed. During traffic congestion, consecutive handover events may be rare because vehicles move slowly, and thus very few or no speed reports would be generated from the congested area.However, the traffic speed report rate during traffic congestion has not been investigated in the literature. In this paper, we present an analytic model to estimate the speed report rate from cellular network signaling in steady traffic conditions, that is, the traffic speed and flow are assumed constant. Real field trial data were used to validate our analytic model. In addition, computer simulations were conducted to study how speed reports are generated in dynamic traffic conditions when traffic speed and flow change rapidly. Our study indicates that in a typical cell of length 1.5 km with a typical expected call holding time of 1 min, no speed report was generated from a congested three‐lane highway. Our study demonstrates that the lack of speed reports from consecutive handover events during rush hours indicates severe traffic congestion, and new methods that can estimate traffic speed from cellular network data during severe traffic congestion need to be developed. Copyright © 2013 John Wiley & Sons, Ltd.     

Cooperative congestion control schemes in ATM networks

One of the basic problems faced in the design of efficient traffic and congestion control schemes is related to the wide variety of services with different traffic characteristics and quality of service (QoS) requirements supported by ATM networks. The authors propose a new way of organizing the control system so that complexity is easier to manage. The multi-agent system approach, which provides the use of adaptative and intelligent agents, is investigated. The authors show, through the two congestion control schemes proposed, how to take advantage of using intelligent agents to increase the efficiency of the control scheme. First, TRAC (threshold based algorithm for control) is proposed, which is based on the use of fixed thresholds which enables the anticipation of congestion. This mechanism is compared with the push-out algorithm and it is shown that the authors' proposal improves the network performance. Also discussed is the necessity of taking into account the network dynamics. In TRAC, adaptative agents with learning capabilities are used to tune the values of the thresholds according to the status of the system. However, in this scheme, when congestion occurs, the actions we perform are independent of the nature of the traffic. Subsequently, we propose PATRAC (predictive agents in a threshold based algorithm for control) in which different actions are achieved according to the QoS requirements and to the prediction of traffic made by the agents. Specifically, re-routing is performed when congestion is heavy or is expected to be heavy and the traffic is cell loss sensitive. This re-routing has to deflect the traffic away from the congestion point. In this scheme, we propose a cooperative and predictive control scheme provided by a multi-agent system that is built in to each node     

ACC: using active networking to enhance feedback congestion controlmechanisms

Active congestion control (ACC) uses active networking (AN) technology to make feedback congestion control more responsive to network congestion. Current end-to-end feedback congestion control systems detect and relieve congestion only at endpoints. ACC includes programs in each data packet that tell routers how to react to congestion without incurring the round-trip delay that reduces feedback effectiveness in wide area networks. The congested router also sends the new state of the congestion control algorithm to the endpoints to ensure that the distributed state becomes consistent. We present a model for extending feedback congestion control into an active network, apply that model to TCP congestion control, and present simulations that show that the resulting system exhibits up to 18 percent better throughput than TCP under bursty traffic. In simulations without bursty traffic, the systems behaved comparably     

基于权重均衡的光网络逻辑拓扑优化算法

对光网络的逻辑拓扑优化问题进行了研究,从2个重要的输入参量(业务量矩阵和时延矩阵)出发,通过定义2种新型的光网络权重,从权重均衡角度将光网络逻辑拓扑的2个主要优化目标(拥塞下限和时延)统一考虑,并基于这2种权重定义方法给出了一种光网络逻辑拓扑优化算法。算法仿真部分以NSFNET为网络模型,分别针对拥塞下限、拥塞概率、网络时延和负载均衡度4个指标,对提出的启发式算法与另外2种典型的优化算法进行了比较和分析。