基于指数上鞅的统计端到端时延分析

借助有效的端到端时延分析可实现大规模网络的QoS控制,运用统计网络演算理论中最小加代数的卷积运算规则计算端到端时延界日益引起人们的重视.随着网络规模的不断扩大,统计端到端时延界应同时具有良好的可扩展性和一定的紧致性,而目前满足这一要求的理论成果还比较少.通过结合最小加代数的卷积运算规则和Doob不等式,并采用矩母函数(Moment Generating Function,MGF)对到达曲线和服务曲线进行描述,文中给出了一种基于指数上鞅的端到端时延界表达式.该时延界不仅可以线性扩展,而且数值分析结果表明,在相同假设条件下,该时延界比现有的线性时延界具有更好的紧致性.     

基于队列约束的多层无线网状网络容量研究

在常规和随机多层无线网络中,有研究已经得到了网络可以达到的吞吐量数量级,然而对单个节点吞吐量和端到端时延的研究却很少.为了解决这一问题,对多跳常规多层无线网状网络中的单节点最大吞吐量和端到端时延进行了研究.推导了网络中的分组吸收概率;根据网络的排队模型,在这个分组吸收概率的基础上,使用扩散近似法得到了单节点可达吞吐量和端到端时延.仿真分析了业务模式和网络拓扑对端到端时延和单节点最大吞吐量的影响,通过仿真结果可以发现使网络处理大量节点的最优辅助节点数,这有助于优化网络资源分配,且减少网络的拥塞.     

IP网端到端性能指标测试方法研究

IP网端到端传输性能与业务应用的关系最为直接和密切,在网络开通验收测试以及日常维护中都需要进行端到端性能指标测试。首先论述了端到端的基本性能指标,包括吞吐量、包时延、包时延抖动等。然后给出了针对每项性能指标的详细、规范的测试方法,以及待测链路的抽样方法。最后说明了各种测试方法的适用性。     

基于Internet的网络控制系统端到端时延分析

端到端时延是影响基于Internet网络控制系统(NCS)稳定性的一个重要因素。该文通过OPNET建模仿真，分析了系统的端到端时延特征、时延组成及时延瓶颈。讨论了不同的数据包大小对端到端时延的影响及其原因，把该时延用于一个NCS仿真实例，分析了其对系统稳定性的影响。在NCS的设计过程中，明确端到端时延特征有助于提高系统的稳定性。     

一种异构无线网络融合环境下的端到端QoS模型

提出了一种在异构无线网络融合环境下的端到端QoS模型。讨论了异构无线网络融合系统的架构,分析了在网络融合环境中提供端到端QoS保证的难点,提出了一种动态的、标准化的、基于多径接收端控制协议R2CP的端到端QoS支持模型,并以3G/WLAN融合系统作为典型应用环境来描述该模型。     

基于工业以太网的列车通信网络及其仿真研究

随着列车运行速度的提高,新型大容量业务不断出现,带宽已成为列车通信网络传输的主要瓶颈;根据列车通信网络的发展趋势,对未来工业以太网用于列车通信网络的两种可能形式进行了探讨,提出了基于工业以太网的列车通信网络体系结构,利用网络仿真软件对列车通信网络进行了拓扑结构建模、节点建模和进程建模.利用该模型研究了车载工业以太网传输大容量信息传输过程中网络载荷、以太网时延和端到端时延等关键因素;仿真结果表明,通过合理设置网络参数,工业以太网满足列车通信网络的带宽和传输要求,环形网络在中间出现故障情况下,仍然可以保证正常的网络通信.     

5G移动边缘计算在军事领域中的应用

5G移动网络开启了万物互联的时代,任务部队、武器装备、战场态势等都将与5G技术深度融合,催生新的指挥网络体系。在对时延和安全保密要求较高的移动应用中,移动边缘计算技术可将云计算平台从网络内部向网络边缘迁移,有效抑制网络拥塞,降低移动业务端到端时延。本文从5G移动网络特性和移动边缘计算技术出发,结合军事指挥需求,提出移动边缘计算技术在军事领域的应用场景并给出部署建议,同时指出5G移动边缘计算面临的问题与挑战。     

一种基于3G网络端到端加密的新型密钥管理方案研究

现今人与人之间传输数据时越来越依赖于3G移动通信网络,特别是第三代移动通信网络（3G）。尽管3G网络实现了网络组件内数据的机密性、完整性,但它并不提供用户端到端的机密性和完整性,而端到端加密的关键是有效地管理每一个密钥。因此文章提出了一种新的端到端加密的密钥管理方案,该方案基于三方Diffie、Hellman密钥协议算法,充分利用了3G的特殊性,只增加一种新的软件,几乎没有改变3G的物理结构。文章还对方案进行了评估,证明了该协议能够提供消息的机密性,以及通信双方双向认证的正确性。     

5G/B5G毫米波网络TCP传输性能分析

5G / B5G移动通信系统的高带宽、高可靠性和低延迟的通信需求需要更多新技术的支持. 毫米波由于其丰富的频谱资源和极高的带宽容量而成为5G/B5G移动通信系统的研究热点之一. 不同于以往由有线网络主导的互联网架构, 如今的移动互联网已经成为无线接入网和高速核心网的融合. 但是目前对毫米波端到端通信传输性能的研究工作还相对较少, 而且多采用仿真实验. 本文利用真实网络设备, 通过开展真实网络环境下的实验, 对毫米波链路基本传输性能和5G/B5G毫米波网络端到端通信系统中TCP传输性能进行测量分析, 研究5G/B5G毫米波网络传输过程中的链路瓶颈, 为设计毫米波端到端网络传输协议, 提高网络传输吞吐率奠定基础.     

多信道多跳无线网络端到端时延最小化路由评价指标的研究

提出一种适用于多接口多信道无线网络的路由评价指标,DSRM.与传统的评价指标单纯注重网络吞吐量相比,DSRM采用整条路径的端到端时延作为评价指标,以适应日益频繁的时延敏感的应用需求.在DSRM中,综合考虑了网络传输过程中的竞争接入时延、基于等效带宽计算的传输时延、节点内的信道队列因素,并分析了整条路径的端到端重传时延.通过Qualnet仿真,证明了DSRM较WCETT、WEED等路由评价指标在平均端到端时延等网络性能参数上有了明显提升.     

Deterministic delay analysis of AVB switched Ethernet networks using an extended Trajectory Approach

Audio Video Bridging (AVB) switched Ethernet is being considered as a promising network alternative solution for the automotive industry thanks to its high data transmission rate and dedicated bandwidth for real-time traffic. However, guaranteeing deterministic communications of an AVB switched Ethernet network remains a key issue for safety-critical applications in automotive domain. In order to ensure real-time timeliness constraints for any flow sent in AVB switched Ethernet networks, we establish new bounds on the worst-case end-to-end delay of any flow. Our contributions are the following: (i) We first develop a worst-case delay analysis in the context of AVB switched Ethernet network based on an extension of the Trajectory Approach. (ii) Then we take into account serialization constraints on frame transmissions to improve the computation of worst-case end-to-end delay bounds. (iii) Finally, we refine the proposed approach by taking into consideration the AVB traffic shaping characteristics. The performance of the proposed approach is illustrated on a set of representative automotive examples.     

Average end-to-end delay computation in IEEE 802.11 ad hoc networks

In this study, we present a new analytic model for evaluating average end-to-end delay in IEEE 802.11 multihop wireless networks. Our model gives closed expressions for the end-to-end delay in function of arrivals and service time patterns. Each node is modelled as a G/G/1/K queue from which we can derive expressions for service time via queueing theory. By combining this delay evaluation with different admission controls, we design a protocol called DEAN (Delay Estimation in Ad hoc Networks). DEAN is able to provide delay guarantees for quality of service applications in function of the application level requirements. Through extensive simulations, we compare the performance evaluation of DEAN with other approaches.     

以太网上实时业务服务质量保证策略的研究

首先分析了以太网上相关技术的进展,并指出了以太网上保证实时业务服务质量的迫切性,然后提出了以太网上保证实时业务服务质量的策略,并给出了该策略的实现结构。仿真验证了我们提出的策略对实时业务服务质量的保证是有效的。     

煤矿井下电网区域联锁保护方案及其实时性研究

针对煤矿井下供电系统通信网络无法满足数据传输实时性、可靠性的要求,很难同时实现保护速动性和选择性的问题,提出了基于交换式以太网的区域联锁保护方案,并采用OPNET网络仿真软件对交换式以太网进行了实时性研究。该方案采用树形结构的交换式以太网,在各综合保护装置上增加具备以太网通信接口的智能联锁装置,组成区域联锁系统。仿真结果表明,在同时有64个网络节点收发数据的极端情况下,网络整体延时最大值不超过0.65ms,端到端最大延时不超过1ms,整体数据收发流量比较平稳,说明交换式以太网具有很高的稳定性和可靠性,能够满足本区域联锁保护系统实时性要求,防止越级跳闸事故发生。     

基于网络演算的交换式以太网实时特性分析

交换式以太网在网络控制系统中的应用关键问题是实时能力,为此采用一种新型实时性能分析工具——网络演算,对交换式以太网实时能力进行确定性的分析和研究。针对FIFO调度算法,对两级树型拓扑结构的交换式以太网系统建立了通信模型,推导出各网络元素的到达曲线和服务曲线,由此得到了最大时延、所需缓冲区大小、输出突发量等实时业务流的主要参数解析表达式;利用推导所得结论计算了实时业务流的最大网络时延。     

Design and analysis of a frame-oriented dynamic bandwidth allocation scheme for triple-play services over EPONs

Ethernet Passive Optical Networks (EPONs) are regarded as an important technology for current access networks. However, EPONs perform poorly in differentiated service environments, and may therefore fail to meet the Quality of Service (QoS) demands of emerging triple-play services (i.e. Voice over IP, video and BE traffic). Accordingly, the present study proposes a novel Dynamic Bandwidth Allocation (DBA) scheme, designated as Frame-Oriented Interleaved Polling with Adaptive Cycle Time (FIPACT), to improve the differentiated QoS capability of EPON networks. In the proposed scheme, the Optical Line Terminal (OLT) divides the time domain of the upstream network bandwidth into a contiguous series of fixed-length frames. Within each frame, each Optical Network Unit (ONU) is guaranteed sufficient network resources to transmit a specific quota of each triple-play service. In this manner, the proposed DBA scheme can satisfy the differentiated QoS requirements of triple-play services. Therefore, based on the M/G/1 queueing analysis framework of multiuser cyclic polling systems, this study develops an analytical framework to derive the closed-form expressions for FIPACT mean packet delay. The simulation results validate the analytical results and confirm the efficiency and effectiveness of the proposed DBA scheme.     

Are ATM, Gigabit Ethernet ready for prime time

ATM and Gigabit Ethernet, the subjects of intense speculation by industry observers and potential users of the technologies, appear as if they may be ready to begin competing for their place in the networking sun. The demand for both technologies is being caused by the increasing adoption of Internet and intranet technology and the growing number of bandwidth-hungry applications. These factors make it necessary to move an increasing amount of data at faster rates over networks. Enterprises are thus beginning to adopt ATM and Gigabit Ethernet. In some cases, the two technologies are replacing FDDI backbones because they can be less expensive and provide higher speeds. In addition, ATM has quality of service features, while Gigabit Ethernet can provide seamless connectivity throughout LANs that already use Ethernet technology. Both technologies provide LAN services, such as scalable campus backbones, load sharing, and connections to WAN services. ATM has been available longer and is being deployed where high bandwidth performance is required. ATM and Gigabit Ethernet involve a variety of complex issues that will, in part, determine whether and how users adopt either or both technologies     

IEEE802网络上综合服务的实现技术

随着Internet上大量实时应用的出现,要求Internet必须在其各个环节上能够同时支持综合服务和提供端到端的服务质量。虽然IEEE802共享和交换的局域网技术被广泛地使用,而且是用户到Internet的重要环节,但是现有的IEEE802网络不支持综合服务,因此有必要使用一些技术来支持端到端的实时服务。该文从在IEEE802网络上支持综合服务的基本体系结构、综合服务到802网络的映射和执行许可控制的子网带宽管理协议三方面论述了如何在802网络上支持综合服务和提供服务质量。     

基于OPNET的CSMA/CD改进与仿真

以太网中采用CSMA/CD使得网络时延不确定和时变与时延的随机性导致控制品质的下降,为了改善以太网的延迟抖动性能,对以太网采用的TBEB算法进行改进,提出自适应退避算法,并用OPNET对改进的算法进行仿真分析.     

Real-time performance evaluation of line topology switched Ethernet

Recently, switched Ethernet has become an active area of research because of its wide uses in industry. However, its uses have various real-time constraints on data communications. This paper analyzes the performance of the line topology switched Ethernet as a data acquisition network. Network calculus theory, which has been successfully applied to assess the real-time performance of packet-switched networks, is used to analyze the networks. To properly describe the activity of switches, a novel approach of modeling data flows into or out of switches is addressed. Based on our model, a concisely analytical expression of the maximal end-to-end delay in line topology switched Ethernet is derived. Finally, the relative simulation results are demonstrated. These results agree well with the analytical results, and thus they validate the data flow modeling techniques.