网络组播的抖动测量技术的分析与实现

网络组播的延迟抖动极大的影响了其应用的整体性能,确定其延迟抖动的原因和位置至关重要,在R..Caceres等人提出的端到端基于组播的网络性能测试与分析法的基础上,对网络组播的延迟抖动从控制测试分组数和解决时间同步两个方面对测试算法进行了改进,从而使测试数据更准确、算法更加高效、适用.     

一种基于支持向量回归的互联网端到端延迟预测算法

互联网端到端延迟是指IP分组沿着互联网中一条确定路径进行传输的延迟,端到端延迟的精确预测是大量网络活动的基础,从网络协议设计到网络监测,再从确保端到端QoS性能到各种实时业务性能提升。提出一种新的端到端延迟的预测方法,主要贡献有:a)将互联网端到端延迟预测的问题转换为多元回归的预测问题,提出了基于多元回归的端到端延迟预测框架;b)采用支持向量回归SVR方法来求解端到端延迟的多元回归问题,提出了基于SVR的互联网端到端延迟预测算法。最后使用互联网采集的RTT数据来验证提出的算法,实验结果表明,提出的预测算法具有快速和精确特点,是一种适合实际应用的预测算法。     

多媒体信息网络中的性能测试

文中在R .caceres、F .LoPresti等提出的网络性能测试分析法基础上 ,利用多媒体信息传输网络的组播特性改进了该方法 ,避免了加重网络负载。     

WiFi-TSN低时延转换架构

无线网络与TSN(Time Sensitive Networking)的融合是目前工业界的关注点之一。传统的基于应用层软件的网关存在CPU利用率高、处理延迟长、性能差等缺点。因此提出了一种WiFi-TSN低时延转换架构,来实现WiFi网络与TSN网络的集成。该架构采用Verilog语言实现,通过硬件来保证通信信道之间可预测的延迟,能够在极短的时间内完成协议转换和协议数据的转发。采用Vivado EDA工具来完成电路的设计,并进行足量的仿真测试来评估电路的端到端延迟性能。     

基于随机网络演算的网络服务质量分析

为了提高网络的服务质量,提出一种基于随机网络演算的网络服务质量分析方法。首先推导出有效的端到端积压和时延边界,使到达流通过的节点数量呈线性增长;然后引入有效带宽和有效容量以延长到达流和服务进程的随机信息保留时间,可以更有效地计算端到端随机性能值;最后采用数据进行仿真实验,测试该方法的性能。结果表明,相对与其他网络服务质量分析方法,随机网络演算方法提高了网络的服务质量。     

ZigBee路由协议信标和非信标模式下的性能仿真比较

基于ZigBee协议开发无线抄表系统,并对系统的耗能、吞吐量、端端延迟和抖动等性能做了详尽分析.针对ZigBee协议中MAC层信标和非信标模式,对系统性能的影响做出仿真比较,为系统开发提供建设性的参考.用仿真工具NS-2构建了31个节点的树型网络.     

基于抖动测试的AFDX端到端延迟紧性修正

AFDX引入虚拟链路(Virtual Link)实现物理带宽资源的逻辑分隔。由于数据帧的异步到达和多路复用输出造成虚拟链路的时延抖动现象,并最终导致流量端到端延迟分析的不确定性。本文提出了一种基于抖动测试值的网络演算紧缩方法。通过分布式测试,获得虚拟链路在网络中的实际传输抖动,并以此为基础,建立了流量传输精确化模型,通过流量模型的逐级修正,使端到端延迟计算结果逐级精确化。通过将抖动实际值与理论分析结果相结合,提供了网络演算悲观度及其扩散影响度量的直观对比,提高了延迟计算的紧性。     

使用TTCN-3的端到端性能测试系统

介绍了网络端到端性能测试的基本概念和方法。在一致性测试框架上，使用TTCN-3测试语言，设计了端到端性能测试系统TTPerf。它的测试结构灵活，测试套开发方便。     

IP语音业务在仿真环境中的实施与性能测试

为了在仿真环境中实施IP语音业务并对其进行性能测试,提出了详细的仿真解决方案。设计一个小型企业网,部署了IP语音中的流量、QoS需求特征、呼叫分配等设计和工程问题。在满足QoS需求并为未来发展留出足够容量的基础上,实现了系统仿真。仿真系统产生不同数量的IP语音呼叫,获得了不同的IP流量和会话双方的端到端延迟,根据当前网络对流量的限制和用户对延迟的容忍度,从而成功地测算出现有网络可以支持的IP语音呼叫数量。仿真实验结果表明了IP语音业务在仿真环境中实施与验证的可行性和有效性。     

基于网络演算计算保证服务端到端延迟上界

归纳总结了网络演算,阐明了网络演算的两个基本工具——进入曲线和服务曲线,得出了服务曲线存在瓶颈效应、端到端延迟的理想与近似确定性上界、提供保证服务网络节点的服务曲线需求等结论,计算了服务曲线以速率等待时间及PGPS(packetizedgeneralizedprocessorsharing)形式表示的保证服务端到端延迟确定性上界.     

Energy-Efficient Cluster in Wireless Sensor Network Using Life Time Delay Clustering Algorithms

Through Wireless Sensor Networks (WSN) formation, industrial and academic communities have seen remarkable development in recent decades. One of the most common techniques to derive the best out of wireless sensor networks is to upgrade the operating group. The most important problem is the arrangement of optimal number of sensor nodes as clusters to discuss clustering method. In this method, new client nodes and dynamic methods are used to determine the optimal number of clusters and cluster heads which are to be better organized and proposed to classify each round. Parameters of effective energy use and the ability to decide the best method of attachments are included. The Problem coverage find change ability network route due to which traffic and delays keep the performance to be very high. A newer version of Gravity Analysis Algorithm (GAA) is used to solve this problem. This proposed new approach GAA is introduced to improve network lifetime, increase system energy efficiency and end delay performance. Simulation results show that modified GAA performance is better than other networks and it has more advanced Life Time Delay Clustering Algorithms-LTDCA protocols. The proposed method provides a set of data collection and increased throughput in wireless sensor networks.     

Probabilistic odd–even: an adaptive wormhole routing algorithm for 2D mesh network-on-chip

Wormhole routing is a popular routing technique used in network-on-chip. It is efficient but susceptible to deadlock, while deadlock will significantly degrade the network performance of NoC. Most existing adaptive wormhole routings avoid deadlock by reducing the degree of adaptiveness and thus sacrificing network performance. In this paper, we address both deadlock and network performance issues jointly, and propose a probabilistic odd–even (POE) routing algorithm that achieves the minimum packet delivery delay. The proposed POE dynamically adjusts the probabilities of constrained turns that may lead to deadlocks according to the current network conditions, and uses an efficient deadlock detection and recovery scheme when a deadlock happens. By adopting constrained turns adaptively to the network status, it not only reduces the frequency of deadlock and allows the network to be swiftly recovered when it occurs, but also greatly improves the degree of adaptiveness to obtain high network performance. Experimental results show that our method achieves a significant performance improvement both in terms of network throughput and average packet latency compared with the existing methods such as XY, odd–even, abacus turn model and fully adaptive routing algorithm while it only has moderate energy consumption.     

无线传感器网络中基于贝叶斯可变频的CSMA/CA算法研究

针对于在无线传感器网络中多个节点向Sink节点发送数据包造成的延时、丢包、碰撞检测、网络阻塞等问题,在802.15.4协议CSMA/CA算法的基础上提出了一种基于贝叶斯可变频的CSMA/CA算法(BVF-CSMA/CA)。该算法将贝叶斯估值得到的参数区间与CSMA/CA的碰撞检测机制相结合,使传感器节点发送的多数据包能正常与Sink节点实时通讯,采用这种算法减少了碰撞检测、节约了能耗、降低了网络通讯量、延长了网络的生命周期。本文通过使用NS2仿真工具模拟验证了该无线传感器网络的丢包率和能耗,实验结果表明,改进后的算法显著改善了这两个性能指标。     

基于通用PC架构的高精度网络时延测量方法

时延是准确测量时延抖动、带宽等网络性能指标的基础.目前的时延测量方法由于存在时钟误差和位置误差因而精度较差.提出一种改进的时延测量方法,以TSC(time stamp counter)寄存器取代系统时钟计时来消除测量的时钟误差,将时间戳记录位置由应用程序转移到网卡驱动来消除位置误差,极大地提高了时延测量精度.实验结果表明,与传统方法相比,不同包长度下,所提出的方法可降低测量误差21%～150%,且测量结果稳定,对系统吞吐量基本无影响.该方法基于通用PC架构,测量成本低,适于普遍采用.     

基于SASR的多路径协议SAMSR研究

比较和分析了自组网络中单路径与多路径的反应式路由协议,在SASR的基础上提出了一个新的多路径路由协议SAMSR。它通过记录重复的RREQ报文以获得更多网络拓扑信息,从而发现更多的可达路径,以及在收到重复的RREP报文后,发回重选报文RSEL保证路径间的节点不相干性。最后通过在NS-2平台上模拟考查其性能,表明SAMSR协议虽然增加了网络开销,但提高了分组抵达率,减少了端到端的路由时延。     

一种基于LWAP的IEEE 802.11平滑切换机制

IEEE 802.11网络中的BSS切换不可避免地产生丢包问题,这会造成网络性能严重下降,进而限制了移动环境下WLAN的广泛应用。为了降低切换过程中的丢包率,本文提出了一种在数据链路层、由无线链路事件触发的用户空间平滑切换机制,并且在基于嵌入式Linux平台的无线AP上进行了实现。大量的实验结果表明,在无需对当前IEEE 802.11协议进行改动的前提下,新切换机制可以保证在允许的时延范围内,较大地降低丢包率,提高网络性能,并且可以支持平滑漫游。改进的平滑切换机制独立于驱动,具有良好的可移植性,可以在现有AP上增量添加,而无需更改STA,降低了升级成本。     

基于推拉结合机制的P2P流媒体分发算法

随着流媒体直播应用的日益扩大,传统C/S（Client/Server）模式网络构架的服务器负载过重,导致QoS（Quality of Service）得不到保证,而P2P（Peer-to-Peer）网络具有负载均衡、可扩展性、容错性强等优点。目前P2P技术开始逐步走向成熟。大多数P2P流媒体数据分发采用Pull模式或Push模式,本文提出基于推拉结合机制的P2P流媒体分发算法,通过仿真实验,从系统开销、端到端延迟等方面对两者进行了性能对比。实验结果表明,该推拉结合机制有效的降低了数据块传输时延,并且在很大程度上避免了数据块的重复推送,降低了数据冗余。     

一种基于节点交换的DHT优化方法

分布式哈希表(DHT)存在逻辑拓扑与实际网络拓扑不匹配的问题,造成查询操作时延过大.针对该问题,提出一种基于节点交换的DHT优化方法,通过对DHT节点逻辑位置的调整,改善DHT的查找性能.使用地标聚类方法对节点进行分类,物理位置相近的节点属于同一个地标聚类区,采用地理布局的思想,使DHT覆盖网络逻辑拓扑与底层物理拓扑尽...     

Energy and delay optimized contention for wireless sensor networks

In wireless sensor network (WSN) studies, the main objective is minimizing the energy consumption so that the lifetime is maximized under the limited battery capacity constraints. Additionally, in most event-driven WSN applications, the end-to-end delay, and hence, the medium access delay should be minimized. Majority of the WSN MAC protocols are contention-based wherein contention window size setting involves an important trade-off between the collision probability and idle listening durations in contentions where both are aimed to be lowered for efficient network operation. In this paper, the energy optimizing and the delay optimizing contention window sizes are derived as a function of the number of contending nodes. For this purpose, we present separate analyses for the contention delay and for the energy consumed which are verified with detailed simulations. In order to obtain close to optimal performance values in a distributed manner, we propose a method for estimating the number of contending nodes since the individual wireless sensor nodes do not have this information readily. Simulations of an event-driven WSN application verify that the proposed method successfully improve both delay and energy efficiency of the contention-based medium access. The end-to-end network performance is also investigated by employing a geographical routing protocol. Results show that using the heuristic method proposed that use the optimum contention window size analyses presented, the overall network performance can be improved without incurring any overhead to the system.