对WLAN无线网络规划及优化技术的分析

经过理论分析和OPNET仿真比较所提出的针对WLAN无线接入网络的规划从传播预测及覆盖设计方面研究覆盖规划、分析研究基于DCF协议的容量规划以及干扰分析和信道优化配置等方法,能有效的降低数据包的碰撞概率,从而降低了时延,增加了系统吞吐率、和网络容量.提出的基于RTS/CTS机制改进的退避算法是对基于CSMA/CA协议的DCF性能的分析和改进,并得出的饱和条件下系统归一化吞吐率、丢包率、网络延时等性能,以此指标用来指导实际吞吐量的估算和网络容量规划.     

WLAN无线网络规划及优化技术研究

针对WLAN无线接入网络的规划方法,分别从传播预测及覆盖设计方面研究覆盖规划、分析研究基于DCF协议的容量规划以及干扰分析和信道优化配置等。其中容量规划部分采用已有退避窗口机制(BEB)的二维马尔可夫模型,对基于CSMA/CA协议的DCF性能进行分析并改进。提出了基于RTS/CTS机制改进的退避算法,得出了饱和条件下系统归一化吞吐率、丢包率、网络延时等性能,以指导实际吞吐量的估算和网络容量规划。经过理论分析和OPNET仿真比较,所提出的新算法降低了数据包的碰撞概率,从而降低了时延,增加了系统吞吐率,进而增加了网络容量。     

TCP在WLAN中的性能提高与分析

IEEE 802.11被用于支持无线以太网(WLAN)中的分组传输.分布式协调功能(DCF)是IEEE 802.11的MAC协议的基本方式.为提高传输控制协议(TCP)在WLAN上的性能,本文提出了DCF+,并引入了分析模型对DCF及DCF+在WLAN上的吞吐量性能进行分析.建模及仿真结果表明本文提出的DCF+可以提高TCP在WLAN上的性能.     

瑞利信道下802．11DCF性能分析及仿真

文章对于Peter P.Pham提出的有限负载备件下二维马尔可夫链的分析模型进行了改进,推导出了IEEE802.11 DCF的吞吐率与饱和程度的关系。仿真了不同因素：节点数,传输速率、数据包长度对于IEEE802．11DCF性能的影响。仿真结果表明：在瑞利信道下,网络处于非饱和状态时,吞吐性能受到几种因素的综合作用。在大多数情况下,RTS／CTS接入方式的性能都优于基冬接入方式。     

全业务运营下宽带无线接入网络建设纵横谈

在全业务运营环境下,移动互联网业务正在成为市场发展的主要抓手。宽带无线接入作为移动互联网的关键环节正面临诸多技术、经济问题。WLAN和Femto是当前重要的宽带无线接入技术,通过对两种技术的比较以及系统、覆盖总体方案的设计,从频率规划和扰码规划、无线接入点选择、网络性能测试等不同角度对WLAN和Femto网络建设中的重要问题进行分析,最后对我国宽带无线接入网建设中需注意的问题给出简要结论。     

基于PWLAN GPF的QoS性能分析与仿真

基于IEEE802.11协议中PCF/DCF技术,在无线局域网(WLAN)中,介绍了GPF的系统结构和数据帧格式等。分别对基于IEEE802.11b媒体接入控制(MAC)协议、基于IEEE802.11e媒体接入控制(MAC)协议以及基于业务划分Qos的GPF仿真的时间参数和接入原则等进行了说明。在PWLAN的3种测试环境下,对802.11b、802.11e、GPF协议的整体性能进行了仿真,并对其结果进行了分析。     

多小区无线局域网的系统吞吐率估计算法

在多小区无线局域网(Wireless Local Area Networks,WLAN)中,由于存在小区间接入访问点同频干扰,以及小区间同频用户干扰,其系统性能与单小区网络具有很大不同。本文提出了支持多种用户传输速率共存、支持用户非均匀分布的多小区WLAN系统吞吐率估计算法。通过对多小区WLAN巾接入访问点的布置、信道的配置进行仿真,结果表明即使在存在小区间同频干扰的情况下,估计算法也能得到满意的吞吐率估计结果。     

一种关联SNR的停等DCF优化方案

针对IEEE 802.11的DCF(Distributed Coordination Function)效率较低的问题,提出了一种结合速率控制的改进方案——停等DCF及其性能分析模型.速率控制使用自适应调制编码技术给出了可调节业务BER(Bit Error Rate)的SNR(Signal to Noise Ratio)门限确定算法;设置暂停信道接入的最低SNR门限,可减少传输错误,并降低接入冲突;调节BER,可在信道时间、冲突概率和误帧率间达到优化折中,使系统吞吐率最大.分析和仿真说明了模式是准确的,停等DCF有效地克服了DCF缺乏丢包区分机制的问题,实现了跨层的性能优化.     

基于Markov过程的WLAN最佳退避窗口研究

IEEE 802.11被用来支持无线局域网(WLAN)中的分组传输,而分布式协调功能(DCF)是802.11的MAC层协议的基本方式,本文采用Markov过程研究分析了MAC层移动站点竞争发送权的过程,探讨了在大用户量的情况下,通过调整退避窗口的参数来提高WLAN的系统吞吐量。     

通用可组合安全的WLAN Mesh网络可信接入认证协议

现有的WLAN Mesh网络接入协议和可信网络接入协议在性能和安全性方面不能很好的满足WLAN Mesh网络可信接入的要求.针对这一情况,提出了一种高效的可证明安全的WLAN Mesh网络可信接入协议MN-TAP,该协议仅需4轮交互就能实现访问请求者,策略执行点和策略决策点三者之间的用户认证和密钥确认,同时在第一轮交互中就实现了策略决策点对访问请求者平台身份的认证和平台完整性的校验,提高了协议执行的效率,降低了服务器端的负载.利用通用可组合安全模型对新协议进行了安全性证明,并对协议性能进行了对比分析.结果表明:新协议达到通用可组合安全,且与现有协议相比性能优势明显.     

Technology innovation and process integrations for sub-100nm gate patterning

This paper presents a brief overview of the Applied Centura(R)DPS(R)system,configured with silicon etch DPS Ⅱ chamber, with emphasis on discussing tuning capability for CD uniformity control. It also presents the studies of etch process chemistry and film integration impact for an overall successful gate patterning development. Discussions will focus on resolutions to key issues, such as CD uniformity, line-edge roughness, and multilayer film etching integration.     

White organic light-emitting devices based on fac tris（2- phenylpyridine） iridium sensitized 5,6,11,12-tetraphenylnap -hthacene

We have fabricated the white organic light-emitting devices （WOLEDs） based on 4,4＇ -bis（2,2 -diphenyl vinyl）-1,1＇ - biphenyl （DPVBi） and phosphorescence sensitized 5,6,11,12,-tetraphenylnaphthacene （rubrene）. The device structure is ITO/2T-NATA （20 nm）/NPBX （20 nm）/CBP： x%Ir（ppy）3：0.5% rubrene （8 nm）/NPBX （5 nm）/DPVBi （30 nm）/Alq（30 nm）/LiF（0.5 nm）/A1. In the devices, DPVBi acts as a blue light-emitting layer, the rubrene is sensitized by a phosphorescent material, fac tris （2-phenylpyridine） iridium [Ir（ppy）3], acts as a yellow light-emitting layer, and N,N＇ -bis- （1-naphthyl）- N,N＇ -diphenyl -1, 1＇ -biphenyl-4,4＇ -diamine （NPBX） acts as a hole transporting and exciton blocker layer, respectively. When the concentration of Ir （PPY）3 is 6wt%, the maximum luminance is 24960 cd/m^2 at an applied voltage of 15 V, and the maximum luminous efficiency is 5.17 cd/A at an applied voltage of 8 V.     

Complete approach to automatic identification and subpixel center location for ellipse feature

To meet the need of automatic image features extraction with high precision in visual inspection, a complete approach to automatic identification and sub-pixel center location for similar-ellipse feature is proposed. In the method, the feature area is identified automatically based on the edge attribute, and the sub-pixel center location is accomplished with the leastsquare algorithm. It shows that the method is valid, practical, and has high precision by experiment. Meanwhile this method can meet the need of instrumentation of visual inspection because of easy realization and without man-machine interaction.     

小角度扩展相关性近似算法分析

本论文提出一种在多天线MIMO信道相关性建模中小角度扩展近似理论算法,并应用于分析MIMO系统性能。分析中分别对三种不同角能量分布情况下的空间相关性研发快速近似计算法,并同时提出双模(Bi-Modal)角能量分布情况下的近似运算。通过分析这些新方法的近似效率,可以得到计算简单、复杂度低、而且符合实际的MIMO相关信道矩阵,对系统级的快速高效计算法的研究和系统级的评估以及误差分析具有重要的意义。     

Curved crystal spectrometer for the measurement of X-ray lines from laser-produced plasmas

In order to diagnose the laser-produced plasmas, a focusing curved crystal spectrometer has been developed for measuring the X-ray lines radiated from a laser-produced plasmas. The design is based on the fact that the ray emitted from a source located at one focus of an ellipse will converge on the other focus by the reflection of the elliptical surface. The focal length and the eccentricity of the ellipse are 1350 mm and 0.9586, respectively. The spectrometer can be used to measure the X- ray lines in the wavelength range of 0.2-0.37 nm, and a LiF crystal （200） （2d = 0.4027 nm） is used as dispersive element covering Bragg angle from 30° to 67.5°. The spectrometer was tested on Shengnang- Ⅱ which can deliver laser energy of 60-80 J/pulse and the laser wavelength is 0.35 μm. Photographs of spectra including the 1 s2p ^1P1-1s^2 ^1S0 resonance line（w）, the 1s2p ^3P2-1s^2 1S0 magnetic quadrupole line（x）, the 1s2p ^3P1-1 s^2 ^1S0 intercombination lines（y）, the 1 s2p ^3S~1-1 s^2 ^1S0 forbidden line（z） in helium-like Ti Ⅹ Ⅺ and the 1 s2s2p ^2P3/2-1 s622s ^2S1/2 line（q） in lithium-like Ti Ⅹ Ⅹhave been recorded with a X-ray CCD camera. The experimental result shows that the wavelength resolution（λ/△ 2） is above 1000 and the elliptical crystal spectrometer is suitable for X-ray spectroscopy.     

Preparation and Characterization of TaN ALD Precursors

High purity organic-tantalum precursors for thin film ALD TaN were synthesized and characterized.Vapor pressure and thermal stability of these precursors were studied.From the vapor pressure analysis,it was found that TBTEMT has a higher vapor pressure than any other published liquid TaN precursor,including TBTDET,TAITMATA,and IPTDET.Thermal stability of the alkyl groups on the precursors was investigated using a 1H NMR technique.The results indicated that the tertbutylimino group is the most stable group on TBTDET and TBTEMT as compared to the dialkylamido groups.Thermal stability of TaN precursors decreased in the following order:TBTDET ＞ PDMAT ＞ TBTEMT.In conclusion,precursor vapor pressure and thermal stability were tuned by making slight variations in the ligand sphere around the metal center.     

A Versatile Mixed-Signal Pin Approach for Cost-Effective Test of Automotive ICs

Integrated circuits (ICs) intended for increasingly sophisticated automotive applications bring unique test demands. Advanced ICs for applications such as highly integrated automatic braking system (ABS) and airbag controllers combine high voltage digital channels, significant VI demands and precise timing capability. Along with continued missioncritical reliability concerns, the trend toward higher voltage operation and increased device integration requires specialized test capabilities able to extend across the wide operating ranges found in automotive applications. Among these capabilities, automotive test requirements increasingly dictate a need for a cost-effective versatile mixed-signal pin electronics with very high data rates reaching up to 50MHz with a voltage swing of-2 V to +28 V.     

Electronic Structure of Semiconductor Nanocrystals

This paper reviews our recent development of the use of the large-scale pseudopotential method to calculate the electronic structure of semiconductor nanocrystals, such as quantum dots and wires, which often contain tens of thousands of atoms. The calculated size-dependent exciton energies and absorption spectra of quantum dots and wires are in good agreement with experiments. We show that the electronic structure of a nanocrystal can be tuned not only by its size,but also by its shape. Finally,we show that defect properties in quantum dots can be significantly different from those in bulk semiconductors.     

Critical Stage Rule-Based Real Time Dispatch（RTD）System in Highly-Mixed-Products （HMP） FAB

An improving utilization and efficiency of critical equipments in semiconductor wafer fabrication facilities are concerned. Semiconductor manufacturing FAB is one of the most complicated and cost sensitive environments. A good dispatching tool will make big difference in equipment utilization and FAB output as a whole. The equipment in this paper is In-Line DUV Scanner. There are many factors impacting utilization and output on this equipment group. In HMP environment one of the issues is changing of reticule in this area and idle counts due to load unbalance between equipments. Here we'll introduce a rule-based RTD system which aiming at decreasing the number of recipe change and idle counts among a group of scanner equipment in a high-mixed-products FAB.     

Optical vibration and deviation measurement of rotating machine parts

It is of interest to get appropriate information about the dynamic behaviour of rotating machinery parts in service. This paper presents an approach of optical vibration and deviation measurement of such parts. Essential of this method is an image derotator combined with a high speed camera or a laser doppler vibrometer （LDV）.