无线Mesh网络路由研究及设计

如何将高速IP接入延伸到"最后一公里"仍然是一个开放的、没有圆满解决方案的热点研究问题。无线Mesh网络技术由于其部署快速,资金投入小,易管理等特点,成为工业界力推的解决方案、学术界关注的研究热点。由于对WMN的特性界定模糊,网络资源管理、服务提供机制、QoS保证机制等的缺乏严重阻碍WMN的广泛部署。本文将给出WMN的一般定义描述,详细分析WMN的特性,对WMN的新路由协议的特点、分类和设计进行综述,为指导WMN路由协议的研究工作奠定基础。     

基于Mesh网络的工厂供气监测系统研究

本文介绍了工厂供气站使用过程中,基于Mesh网络和ZigBee技术的无线监测系统的设计思路、系统构成;分析了Mesh网络的结构特点,简要介绍了ZigBee技术并分析了如何实现各参数监测点与上位检测主机之间的数据通信;介绍了监测点的电路设计及系统程序设计流程。     

提高网络授时精度的Kalman滤波方法

在通信网络中传输标准时间往往受到时延很大的影响,造成精度不高.为了提高网络授时精度,提出一种基于卡尔曼滤波器的修正方法,将网络时延分解为固有延时、抖动时延、突发时延3个部分,利用Kalman滤波器减小抖动时延,利用跟踪门消除突发时延,从而使网络时延更加逼近固有时延,有利于提高授时精度.在MATLAB中运用SimEvents扩展模块,搭建一个端到端的计算机网络传输模型,验证了卡尔曼滤波对网络时延精度提高的效果,算法在稳定后,时延的估计值与测量值相比,精度可以提高大约100倍.在此基础上,利用LabVIEW设计了一个实时测试平台,嵌入MATLAB程序,实时获取通信网络时延并进行滤波处理.通过实际有线和无线网络测量的时延数据的验证,表明所提出的滤波修正方法的效果明显.     

一种分层无线传感器网络数据收集方法研究

无线传感器网络是资源受限的网络,而基于移动sink节点进行数据收集是提高网络性能的有效机制。我们研究了求解移动节点的调度的MES算法,提出了基于簇结构和移动sink节点调度相结合的分层数据收集算法,该算法基于簇结构计算移动sink节点移动路径。最后,通过仿真验证分析了该算法的性能,结果表明算法能在能量高效的前提下,显著提升网络时延等QoS性能,且对网络结构和应用环境具有良好的适应性。     

一种改进的分组帧时隙ALOHA算法

防碰撞算法是射频识别系统中提高标签识别效率的关键技术。为提高汽车防盗定位系统中多标签识别率,分析了现有ALOHA防碰撞算法存在时隙浪费、吞吐率低等缺点,提出了一种基于时间段分组的帧时隙ALOHA算法。该算法根据标签进入阅读器识别区内的时间顺序将标签分组,然后再使用帧时隙ALOHA算法对每组内的标签进行识别。仿真结果表明,相对现有的ALOHA算法,此方法能有效提高系统的吞吐率且稳定,减少时隙浪费,提高了汽车标签的识别率。     

一种无线传感器网络节点及其实现方法

为满足无线传感器网络不同应用的需求,结合无线传感器网络节点功耗低、可扩展性好、处理能力强等具体要求,提出了一种基于LPC2148和CC2420在2.4GHz频带下工作的无线传感器网络节点设计方案。节点采用了模块化的设计方法,文中阐述了节点各部分的硬件设计,分析了节点的布置及调度优化的原因,说明了节点间无线通信的实现过程。该方法构建一种无线传感器网络硬件平台,提高了性能,延长了使用寿命。     

全数字化M310核电机组DCS系统Mesh网络可靠性研究及应用

M310全数字化核电方家山机组在国内率先成功实施DCS一层网络拆分,本文从解决双机组数字化仪控系统相互影响出发,结合方家山机组DCS一层Mesh网络构架设计和跨机组通讯测试与应用,研究分析Mesh网络架构改变后数据通讯可靠性提升策略,可为同类型核电机组Mesh网络变更改造提供重要经验反馈和技术支持,亦可为全数字化核电机组DCS系统网络设计提供良好参考借鉴。     

无线多媒体Mesh网络容量感知路由优化研究

为了实现无线多媒体在高负载率业务下的资源预测和QoS优化,首先利用概率预测的容量感知模型探测MAC层的重传信息,动态感知无线链路的状态,实现高负载业务下的统计的信道容量概率预测.其次,利用跨层设计技术,基于链路状态和节点干扰的容量预测模型,提出一种基于位置的容量感知路由优化算法LCAR,实现统计的QoS网络资源预留以及分组转发,提高网络资源利用率.仿真结果表明,与现有的QoS路由优化方法相比,提出的算法可以降低无线网络的重传次数平均1～2次,提高无线网络的分组转发效率10％,平均改善网络的吞吐容量10％.     

无线传感器网络中一种改进的DV-HOP定位算法

在无线传感器网络中,节点定位技术占有非常重要的地位。为了提高节点定位精度,在研究和分析传统DV-HOP定位算法的基础上提出了一种改进算法。该改进算法中,每个信标节点通过分析实际距离和估计距离之间的误差,可进一步修正平均每跳距离;然后在未知节点坐标计算过程中引入二维双曲线定位算法代替传统的三边测量法,可减少节点计算误差。仿真结果表明,在无需增加额外的硬件设备的条件下,改进的DV-HOP算法与传统的DV-HOP算法相比,能够更加有效地提高节点的定位精度。     

一种无线传感器网络节点硬件结构设计

针对无线传感器网络实时监测和突发事件处理的应用需求,设计了无线传感器网络节点.节点采用超低功耗的MSP430F149单片机和具有多种工作模式的无线射频模块nRF905,采用了声音、磁性和加速度3种传感器,用于实现对环境数据的采集和目标信息的探测,同时通过蜂鸣器、麦克风以及音频信号的接收放大和解码电路实现节点间的测距.     

An improved mesh simplification method using additional attributes with optimal positioning

The use of highly detailed models is continuously increasing in computer-aided design (CAD) design and computer graphics field as the technology of range scanners advances. Real-time rendering and manipulating applications are also increasing to support applications in various areas such as collaborative design and scientific visualization. Although graphics hardware technology has been improved rapidly, more attributes such as color, material property, texture coordinate, and curvature are added to CAD models, and it becomes a challenge to handle and render such heavy models. Consequently, the models with complex mesh need to be approximated to improve the efficiency of rendering and manipulation and to reduce computation time. A considerable amount of work has been done regarding geometry preservation, but relatively little research has been performed to preserve both geometry and additional attributes. We present a feature sensitive simplification method using curvature color as an additional attribute. We also use curvature color filtering and optimal positioning methods after edge collapse to preserve feature more sensitively. Our method is applied to several models, and the performance is demonstrated by comparing it with other methods.     

Probabilistic dynamic distribution of wireless sensor networks with improved distribution method based on electromagnetism-like algorithm

Performance of the Wireless Sensor Networks (WSNs) depends significantly on coverage area which is determined via the effective dynamic distribution of sensors. Making mobile sensors’ dynamic distributions, which determines their positions within the network effectively, improves performances of WSNs by enabling sensors to form the coverage area more efficiently. In this paper, we initially propose the electromagnetism-like (EM) algorithm as the sensor distribution strategy to increase the coverage area of network after random distribution of sensors. Forming more effective coverage area by using mobile and stationary sensors and probabilistic detection model has been aimed by developing the Optimal Sensor Detection Algorithm that is based on the proposed EM algorithm (OSDA-EM). For this purpose, it has been thought that we would attain to more realistic results, with probabilistic detection model by forming the coverage area more effectively. Additionally, performance of the developed OSDA-EM algorithm has been compared with the Particle Swarm Optimization (PSO) and Artificial Bee Colony (ABC) algorithms which was previously used in the dynamic distribution of WSNs. Simulation results have shown that the developed OSDA-EM can be preferred in dynamic distribution of WSNs that performed with probabilistic detection model.     

一种改进粒子群的无线传感网络能量优化模型设计

针对传统无线路由算法节点选择存在很大的随机性,一旦选择边沿节点将造成长距离通信,从而降低通信效率的问题,设计了一种基于改进粒子群算法的能量优化模型.该模型利用改进粒子群算法对簇头选择进行优化,并综合考虑簇头能量、簇头传输距离、簇头分布等因素,设计新的适应度函数,从而在大范围内降低网络传输的能量损耗.此外还针对无线网络节点过早死的问题,提出一种基于最小能耗的单级跳和多级跳结合的通信方式,从而均衡整个无线网络能量,延长整个网络的寿命.最后通过仿真验证了模型的可行性.     

一种适用于WIA-PA网络的分层入侵检测方法

工业无线技术是满足工业应用高可靠、低能耗等特殊需求的一类无线传感器网络技术。针对WIA-PA(wireless net-works for industrial automation-process automation)工业无线网络的特点,分析了工业无线网络入侵检测的重要性,设计了一种基于全信道分析仪的分层WIA-PA网络入侵检测和安全数据处理架构,提出了一种适用于WIA-PA网络的分层入侵检测方法,在此基础上,设计并实现了基于WIA-PA的安全管理系统。测试表明,基于全信道分析仪的入侵分析系统能够有效检测网络入侵攻击,基于安全管理者的设备安全入网、密钥管理和安全服务能够在无线环境中得到较好的应用,有效地解决了工业无线网络内部资源受限的问题,提高了WIA-PA网络通信的安全性能。     

基于混合汇聚节点的无线传感器网络数据收集方法

在固定传感器网络中加入移动汇聚节点能降低整个网络的能量消耗、延长网络生存时间、增加网络容量。考虑网络中固定与移动汇聚节点共存的工作模式,提出了一种数据收集方法：在兼容网络原有固定汇聚节点模式的同时支持一个到多个移动汇聚节点,移动汇聚节点定期向其附近小范围内的传感器节点扩散自己的存在信息,传感器节点向离自己跳数最小的汇聚节点发送或者转发数据包。距离移动汇聚节点一跳的传感器节点通过应答-超时重传的方法来保证到移动汇聚节点的可靠数据传输。仿真研究表明：相对于传统固定传感器网络,使用该方法能够大幅度延长网络寿命(正常流量情况下延长600%以上,大流量情况下延长350%以上);在网络高负载时最高数据传输成功率能达到91%,比节点全静止时提高了8.3倍,最低数据传输延迟仅为46.5ms,比节点全静止时减小了92%。     

An improved cryo-jet freezing method

A new cryo-jet freezing apparatus is described that is easy to use and gives good results using a propane-butene mixture (3: 1). Our use of the freezer in the study of mouse spinal cord explant cultures is discussed. At the tissue surface, the quality of tissue preservation from freezing, followed by freeze substitution, rivals that of conventional electron microscopic methods. Certain intracellular structures are better visualized using our methods. There is no evidence of the tissue being distorted by the cryogen jet when the freezer is operated correctly. A new freeze substitution device is also discussed.     

无线传感器网络瓶颈节点判断及路由方法研究

针对无线传感器网络中存在的由于其失效导致网络节点割裂成互不连通的各部分的瓶颈节点问题,从一类准瓶颈节点角度出发,提出了基于节点间连通关系的聚类划分方法.在此基础上,建立了瓶颈节点的判断方法,进而从均衡节点能耗的角度,提出了基于最小跳数多路径选择的减轻准瓶颈节点和瓶颈节点影响的路由方法.仿真结果表明,应用这些方法的传感器网络,不仅能够有效的判断瓶颈节点,而且能够均衡准瓶颈节点和位于瓶颈节点前的汇聚节点的能耗,从而延长网络寿命.     

An improved Senarmont retardation analysis method

The phase difference between two plane polarized light rays whose electric field vectors (planes of polarization) are at right angles is often determined by Senarmont analysis. In this analysis, a quarter-wave plate whose vibration axes lie at an azimuth of ±45° to the planes of polarization of the two rays is inserted. The rotation of the analyser that leads to extinction is then determined by manual adjustment. This classical method has been significantly improved by, instead, measuring light intensities at thirty-two evenly spaced analyser angles which span 180° of analyser rotation. An unbiased estimate of the phase difference may then be extracted with high accuracy by analysis as a designed experiment. Of the several numerical analysis methods investigated, harmonic analysis is particularly attractive for routine use—especially with small computers. Iterative non-linear least-squares analysis on a mainframe computer was taken as the standard of numerical accuracy, against which direct algebraic solutions on a personal computer were evaluated. An ‘accuracy’ statistic (which measures the goodness-of-fit to the theoretical cosine function) has proven invaluable in assessing the validity of actual data. Data of exceptional quality are produced by the Leitz Jamin–Lebedeff optical system using intensities measured with a photodiode detector placed in the camera tube of the microscope. These data will support analysis to better than 0.0001° of analyser position, or <6×10^?7 periods. Since alignment of the optics with comparable accuracy is impossible, a method for accurately quantitating the contribution to the observed retardation that originates from within the optics, by performing the analysis on an air sample, has been devised.     

基于密度趋近的无线传感器网络故障恢复方法

无线传感器网络的应用已扩展到多个领域,常常工作在一些恶劣的环境下,例如战场、火灾等.有时候由于灾难性的破坏,导致整个网络同时被分割成很多孤立子区域.这些孤立区域彼此之间不连通,严重影响了网络的通信.提出了一种解决该类网络故障的方法.首先通过转置节点将失去连通的区域重新连接到最近的连通集,然后再将这些连通集连接起来,从而实现恢复网络连通性的目的.由于孤立子区域不知道彼此的存在,每个孤立区域需要派遣转置节点,通过级联移动方法加入到预定的连通集.采用密度趋近的方法对连通集进行划分,并用同样的方法将整个连通集划分成不同扇形区域,确保每个扇形区域都有负责相邻连通集的连通工作节点.新方法不仅避免了大规模地移动节点,也减少了节点的移动总距离,极大地节省了节点能量,延长了网络的生命周期.     

基于改进神经网络的移动机器人路径规划方法

通过分析基于神经网络的移动机器人路径规划的优缺点,指出该算法存在搜索区域过大,搜索具有盲目性,效率不高的问题和不足.针对此问题提出了3种优化该算法的方法:通过BP反向学习算法优化神经网络连接权值,来学习外部环境;采用组合光学探测器减小模拟退火算法搜索区域;陷入局部极小值时采用后退策略,跳出局部极小值.最后通过仿真实验具体实现了这两种算法,通过对比两种算法的有效性和收敛性,后一种算法较前一种有较大提高,证明了此算法应用到全局移动机器人路径规划中的有效性和正确性.