具有失效相关链路的2D-Torus网络的可靠性分析

对网络可靠性的分析通常需要假定链路失效是相互独立的。由于网络中失效链路和其他链路是共享通信负载的,链路失效将会影响其他链路的失效率,即链路失效相关。以3×3 Torus为例,采用M arkov模型方法建立了具有单向链路的2D-Torus的可靠性模型,并分析了链路失效独立和链路失效相关条件下的网络可靠性。通过对模型的仿真表明,链路失效相关时的网络可靠性要比链路失效独立时的网络可靠性低。     

具有可维修链路的E-2DMesh网络可靠性研究*

对E-2DMesh网络中单工失效链路模式进行了研究,提出了基于子网的状态转移模型。基于该方法分别对不可维修和可维修链路模式进行了分析,证明了对较大规模的E-2DMesh网络,不可维修链路模式的可靠性要比可维修链路模式低。提出的方法能够用于研究其他层次结构网络和其他网络通信问题。     

E-2DMesh网络中链路失效模型的可靠性分析

提出了基于子网的E-2DMesh网络结构在存在链路故障情况下的状态转移模型。通过马尔科夫链过程建立了具有单向链路的E-2DMesh网络的可靠性模型,并分别对链路失效独立和链路失效相关条件下的网络可靠性进行了分析。运用概率分析的方法,通过组合模型计算出了较大规模的E-2DMesh网络的可靠性。通过对模型的仿真表明,链路失效相关时的网络可靠性要比链路失效独立时的网络可靠性低。     

基于简单网络断层扫描的失效链路定位研究

失效链路是无线传感器网络中一种典型的网络故障现象,严重影响了无线传感器网络的运行与服务质量,必须加以发现并修复。主要研究了基于简单网络断层扫描方法定位失效链路的技术。引入二元分离模型描述链路状态,在已知链路状态先验分布条件下,失效链路定位问题描述为最大后验估计问题。通过将失效链路定位问题映射为加权最小集合覆盖问题,提出了一种基于启发策略的失效链路定位算法。仿真实验结果表明,该算法具有可行性和有效性。     

基于内容的发布/订阅拓扑模型设计和自配置协议研究

拓扑结构和自配置特性是实现大规模基于内容的发布/订阅系统的关键问题之一,决定了系统的可扩展性。为了提高发布/订阅系统性能,引入了空间划分的概念,设计了一个具有空间划分的层次拓扑模型。针对节点或者链路失效所带来的网络分割问题,本文在静态拓扑模型的基础上提出了一个自配置协议,提高了系统的可靠性和扩展性。     

无线传感器网络启发式失效链路推断算法

无线传感器网络的实际应用产生了对网络故障管理的迫切需求。严重报文丢失的失效链路影响无线传感器网络的性能,需加以发现并修复。受有限资源的约束,采用被动端到端测量的方法,利用网络断层扫描技术推断失效链路。通过将失效链路推断问题映射为最小集合覆盖问题,提出了一种基于启发策略的失效链路推断算法。仿真实验结果表明该算法具有可行性和有效性。     

Ad hoc通信网络的局部路由修复仿真

为了解决Ad hoc通信网络的局部路由中节点或链路失效引起的通信可靠性降低等问题,提出了基于节点能量的Ad hoc通信网络的局部路由修复方法。根据Ad hoc通信网络节点路由链路分析结果,当网络通信数据包传输中发现问题节点时,待传输数据包所在节点通过检测自身所对应的父、子及近邻节点,获取各节点的相关信息,并从中选择有效节点替换故障节点;替换节点的选取过程,采用节点剩余能量与方位角差值相结合的方式;确定替换节点后,结合蚁群算法自适应优化网络链路,完成Ad hoc通信网络的局部路由修复。仿真结果表明,所提路由修复方法能够有效缩短路由修复耗时,减少修复过程的控制开销,提高基站节点的吞吐量,提升网络通信的可靠性与时效性,具有较好的鲁棒性。     

传感器网络通信延迟的实时预测

针对使用CSMA/CA通信机制的无线传感器网络提出一种通信延迟估计算法。利用链路质量具有时间和空间相关性的特点建立组合的链路模型,预测链路可靠性,使用简化的冲突概率模型预测信道竞争延迟,结合预测的链路可靠性得到通信延迟。分析了算法的开销,在ns2模拟器上对信道竞争延迟预测算法进行了模拟,结果表明预测算法能够比较准确地预测网络的竞争延迟。     

一种基于拓扑结构的网络两终端可靠性评估方法

为了评估一个大规模的实时长距离通信网络的可靠性,提出一种基于拓扑结构的网络两终端可靠性的计算方法。在化简网络拓扑结构的基础上,充分考虑链路和节点的可靠性,通过转置矩阵的积来表示两终端可靠性。实验结果表明,有向链路对不同网络性能测量产生影响,虽然失效频率和链接失效率很相似,但两终端可靠性多项式的复零点的位置相差很大,同时,转置矩阵的尺寸随着网络增大而增大。该方法对于优化网络、合理分配平均维修时间有实际应用价值。     

AODV的本地修复算法*

提出了一种新的路由本地修复算法,将修复尽量限制在断链的局部范围内,减少了修复时间和降低路由维护的开销, 且不用考虑失效链路在整个路由上的相对位置,均可对其进行修复,提高了处理失效链路的能力,有利于提高网络的可扩展性.仿真表明,这种新的路由本地修复算法明显地提高了网络多方面的性能.     

Bi-directional self-healing ring network planning

In this paper we study the network planning problem of bi-directional self-healing ring (BSHR), which is a network structure providing higher survivability when there is a failure on link or node. Given a network with nodes, links, and demand pairs, our target is to design an optimal network comprising rings, which use only the existing links to satisfy all demands. The objective is to minimize the total amount of equipment (add/drop multiplexer) on nodes, thus reducing the major cost of SHR structure. We propose two integer programming models. For larger networks, we have developed an efficient solution procedure based on its hierarchical network structure. Computational results are given to show that the solution procedure is effective in obtaining an optimal or near-optimal solution.Scope and purposeThe merging of information networking and telecommunication services has created an increasing demand for telecommunication networks of high bandwidth, aiming to exchange ever larger volumes of data in a very short time interval. The self-healing ring (SHR) is a ring network that provides redundant bandwidth in which disrupted services can be automatically restored following network failures. In this paper, we study the network planning problem of bi-directional SHR aiming to minimize the amount of equipment.     

一种新型双向联想记忆神经网络

提出了一种新型双向联想记忆神经网络,此网络将两个相互关联的模式以模式对的形式存储在由N个连接构成的模式环中,记忆容量为22N数量级,完全消除了假模式对、能够全部或部分地回忆出与输入模式对具有最小Hamming距的被记忆的模式对,同时具有较高的记忆效率和可靠性。连接由“连接状态”和“禁止路径”组成,前者直接存储二进制模式对向量的分量,后者用于消除假模式;此神经网络具有正向联想、逆向联想和自联想方式,使得网络能更灵活有效地满足不同的回忆要求。     

Modelling a Learning-Based Dynamic Tree Routing Model for Wireless Mesh Access Networks

Link asymmetry in wireless mesh access networks (WMAN) of Mobile ad-hoc Networks (MANETs) is due mesh routers’ transmission range. It is depicted as significant research challenges that pose during the design of network protocol in wireless networks. Based on the extensive review, it is noted that the substantial link percentage is symmetric, i.e., many links are unidirectional. It is identified that the synchronous acknowledgement reliability is higher than the asynchronous message. Therefore, the process of establishing bidirectional link quality through asynchronous beacons underrates the link reliability of asymmetric links. It paves the way to exploit an investigation on asymmetric links to enhance network functions through link estimation. Here, a novel Learning-based Dynamic Tree routing (LDTR) model is proposed to improve network performance and delay. For the evaluation of delay measures, asymmetric link, interference, probability of transmission failure is evaluated. The proportion of energy consumed is used for monitoring energy conditions based on the total energy capacity. This learning model is a productive way for resolving the routing issues over the network model during uncertainty. The asymmetric path is chosen to achieve exploitation and exploration iteratively. The learning-based Dynamic Tree routing model is utilized to resolve the multi-objective routing problem. Here, the simulation is done with MATLAB 2020a simulation environment and path with energy-efficiency and lesser E2E delay is evaluated and compared with existing approaches like the Dyna-Q-network model (DQN), asymmetric MAC model (AMAC), and cooperative asymmetric MAC model (CAMAC) model. The simulation outcomes demonstrate that the anticipated LDTR model attains superior network performance compared to others. The average energy consumption is 250 J, packet energy consumption is 6.5 J, PRR is 50 bits/sec, 95% PDR, average delay percentage is 20%.     

管道泄漏监测传感器网络的路由路径算法研究

分析管道流量泄漏监测的传感器网络特点,对传感器节点数据流量进行建模分析,如何保障在线监测网络设施的可用性,而链路通信质量随时空变化很大,并且有5%到15%的非对称链路存在。链路层服务不但可以发现邻居传感器节点,测量和预测邻居节点间的链路通信质量,而且还能提供链路数据转发机制减轻单向链路对其他协议的影响。为了提高路由路径的可靠性和减少能量损耗,利用链路层服务和分布式算法,为每个传感器节点建立到汇聚节点的最可靠路由路径,理论分析该算法的性能,在模拟器TOSSIM上进行仿真,实验结果表明基于链路层服务的最可靠路由路径建立算法,可充分利用单向链路建立更可靠的路由路径,有多于17%的节点建立更可靠的路由路径,路由路径的可靠性提高2%到51%。     

A trust evaluation scheme for complex links in a social network: a link strength perspective

Potential security threats pose a significant challenge to evaluating the trustworthiness of complex links among users in a social network. Traditional trust computation methods typically consider user comments or interaction, thereby reflecting the trustworthiness between users according to their past experiences. However, the tie strength, which reflects the closeness of user relationships, is also a potential factor for estimating the trustworthiness of links among users. To incorporate this indicator, we propose a trust evaluation scheme for complex links comprising two aspects: the reliability and strength of links among uses. Our main contributions are (1) a trust calculation method, including direct trust for directly linked users and indirect trust for indirectly linked users, which is established based on the comment factor, forwarding factor, and approving factor; (2) a link strength evaluation method to determine the trustworthiness of direct and indirect links between users considering comment stability, mutual trust, interaction frequency, and common neighbours and community similarity, and (3) a link trust evaluation algorithm based on the link trust matrix synthesizing the reliability and strength of links. The experimental results and analysis show that our proposed scheme is feasible and effective in improving the performance of trust evaluation in a social network.     

可靠电压频率岛感知的异步片上网络能耗优化

针对采用2D-Torus拓扑结构且支持电压频率岛（VFI）的异步片上网络能耗优化问题,提出了具有可靠性的、基于电压频率岛的划分和分配及片上网络任务映射的能耗优化方法．该方法采用递进优化的方式,根据IP核的动态处理能耗,不同电压频率岛之间的转换能耗和可靠性带来的能耗开销定义了IP核在电压频率岛之间移动的阈值函数,并通过对阈值函数进行判断完成电压频率岛的划分和分配,应用基于三元相关性量子粒子群优化算法完成处理单元到资源节点的映射,在映射中考虑保证系统可靠性的通信开销,对异步片上网络系统的可靠性进行优化．实验结果表明,该算法可以在不过多消耗能耗的情况下显著的改善片上网络系统的可靠性,且可有效降低NOC系统的能耗.     

面向超大规模计算系统的监控、调度及网络优化实践

【目的】为应对超大规模计算系统所带来的监控数据风暴、作业调度稳定性及灵活性、网络复杂度及高效性等实际挑战,本文分享了近期真实实践的经验和解决办法。【应用背景】当计算系统从P级逐渐向E级过渡,节点数量可超过10000个。在计算系统设计之初就需要确定网络拓扑的选型,而在系统的具体使用中更是离不开高效的调度和及时的监控。【方法】本文采用了基于动态负载均衡的分布式监控架构设计,基于高速缓存的分布式告警架构设计,基于SLURM的源码和配置优化,以及nd-Torus网络拓扑仿真对比等相关技术手段,基本满足了实际业务使用需求。【结果】数据表明,对于~10000节点的计算系统,实时告警数据库表的数据量大小基本可以控制在100万条以内。优化后的SLURM调度系统,可满足系统的业务级调度需求。网络方面,6D-Torus网络由于网络直径低、平均通信距离短,性能和网卡线缆用量较Fat-Tree网络和3D-Torus有一定提升,饱和吞吐率超过40%。【结论】分布式监控架构和告警架构可以有效解决监控数据风暴问题。SLURM在优化后可以实现对超大规模计算系统的作业调度功能。就线缆和交换机使用数量而言,6D-Torus相对于传统Fat-Tree网络更加经济,且性能优于3D-Torus,更适合超大规模计算系统。     

基于GO法融合共因失效的接触网可靠性分析

为分析共因失效对接触网系统可靠性的影响,采用共因失效β因子搭建接触网模型。根据Markov过程理论,导出可修部件的共因失效概率随时间t的近似表达式。对某段电气化铁路接触网系统的特性进行分析,建立其等效失效模型和GO图。根据是否考虑共因失效两种情况,运用MATLAB绘制相应的可靠度变化曲线。对接触网系统的定量分析结果表明:系统在考虑共因失效后,各项可靠性参数值更加贴近实际。实现接触网系统的定性评估,并找出其薄弱环节,为接触网系统的运营维护提供理论依据。