应用DT-MLWDF降低下一代铁路通信业务的丢包率

针对目前铁路通信系统丢包问题,采用最大权重优先算法和最大权重时延优先算法对延时改进,提出基于延时吞吐量算法(DT-MLWDF),找出接近阈值的最大度量业务;然后利用比例算法均衡最大度量业务的吞吐量和数据传输,降低业务丢包率,解决车地实时性(RT)和非实时性业务(NRT)数据的同步传输问题。以往调度算法侧重于商业LTE技术,改进算法是在铁路通信系统中的应用。仿真结果显示,在阈值范围内增加时延,可以有效地降低丢包率。     

面向数据中心网络的分布式负载均衡网关架构

为满足数据中心网络在高并发量、低尾延时等性能上的需求,提出一种面向数据中心网络的分布式负载均衡网关架构。该新型网关架构主要包括资源池化汇聚算法、优先调度算法和动态负载均衡算法等3个核心算法模型。基于该架构,借助现场可编程门阵列(FPGA)实现智能网关的整体设计。通过第三方测试,基于分布式负载均衡网关架构的智能网关可针对数据包的关键信息实现灵活、可扩展的负载均衡,线速可达9.4 Gbps(不丢包),线速为10 Gbps的丢包率约5%,端口时延为2 μs。与通用的负载均衡方案(软件负载均衡与硬件负载均衡)相比,分布式负载均衡网关架构采用基于数据包优先调度的负载均衡策略和硬件存储资源智能“池化”的流量管理,保障了数据中心网络系统中百万级数据流的高效分发,提升高并发量、低时延应用的性能。在面向百万条并发情况下,网络链路响应尾延时小于60 ms。     

基于优先级的OBS核心节点性能研究

设计了基于业务优先级的光突发交换核心节点模型,采用多级光纤延迟线的光缓存来提高交换网络的性能.交换节点在4个端口8条波长(4×8核心交换结构)的情况下,当光纤延迟线基本延迟单元为50μs、级数为8,负载为0.8时,丢包率小于0.01;为了满足不同业务服务质量的要求,将数据包按优先级划分,采用基于优先级的插空算法(VFPP),在相同缓存配置条件下使高优先级数据的丢包率降低到以下,在高负载下平均时延小于不区分优先级的情况.     

软件定义卫星光网络蚁群优化波长路由技术

针对卫星光网络中网络拓扑动态时变和业务类型多样化的问题,研究了在软件定义网络架构下保障服务质量的路由技术,提出了一种基于多业务的卫星光网络蚁群优化波长路由算法。通过改进蚁群算法的启发函数,将波长空闲率、时延、时延抖动、丢包率作为蚂蚁选路的重要依据,为业务选择了满足多种服务质量的最优路径;采用分组波长分配方法对不同等级的业务进行了区分服务,为不同业务分配了不同的波长集。仿真结果表明:与CL-ACRWA算法和Dijkstra算法相比,降低了卫星光网络的平均时延、平均时延抖动、平均丢包率,提高了波长利用率,同时也降低了高优先级业务的网络拥塞概率。     

基于QoS付费业务的LTE下行跨层分组调度算法

准4G网络（LTE）即将商用会给人们带来更多的方便,以至于大量用户在日常生活中使用更多的QoS业务,这样系统会出现了拥塞和调度不够合理的情况,影响了高优先级业务的丢包率、时延和公平性。通过对LTE下行跨层分组调度各种算法的研究分析,从时延、丢包率、吞吐量和公平性等因素入手,在原有的比例公平性调度算法（PF）上进行改进,加入了补偿因子和付费权重值,使得改进型跨层调度算法,在吞吐量有一定提高的情况下,有效地降低了高优先级业务的丢包率和时延,并确保了高优先级业务的公平性。     

IEEE 802.16中改进的QoS动态分层调度算法设计

WiMAX(IEEE802.16)为每个节点提供实时业务和非实时业务,并对不同的业务提出了QoS保证服务。调度算法是WiMAX为分类业务提供QoS保证的重要技术。本文提出一种用于WiMAX系统PMP模式下的动态调整优先级的分层调度算法DAPQ,DAPQ算法由基站(BS)和用户站(SS)共同实现,为不同优先级的业务流动态分配带宽,可以为系统提供更好的公平性,并有效的减少时延。仿真结果表明,本文提出的算法在一定程度上降低了rtPS业务的时延和丢包率。     

软件定义网络中面向时延和负载的多控制器放置策略

在多控制器管理的软件定义网络(SDN)中,时延和负载是控制器放置问题(CPP)要考虑的重要因素。该文以降低控制器之间的传播时延、流请求的传播时延和排队时延、均衡控制器间负载为目标,提出一种控制器放置及动态调整的策略,其中包括用于初始控制器放置的负载均衡算法(BCRA)和遗传算法(GA),用于动态调整控制器负载的在线调整算法(ADOA)。以上算法均考虑网络连通性。仿真结果表明:在初始控制器放置时,在保证流请求的传播时延、排队时延和控制器传播时延较低的情况下,BCRA部署在中小型网络中时,其负载均衡性能与GA相近且优于k-center和k-means算法;GA部署在大型网络中时,与BCRA, k-center和k-means算法相比,使得负载均衡率平均提高了49.7%。在动态情况下,与现有动态调整算法相比,ADOA可以保证较低排队时延和运行时间的同时,仍能使负载均衡参数小于1.54。     

M—DCF：在单区网中实现QoS的媒体访问协议

本文结合IP通信的特点,提出了一种适用于WLAN单区网的改进型媒体访问控制协议M-DCF,并进行了计算机仿真。仿真结果表明,M-DCF可以降低系统总的丢包率,话音业务的丢包率,降低话音帧的时延,从而保证话音业务的服务质量,同时也降低了数据帧的时延。     

基于选择性迭代的KSP低轨卫星负载均衡路由方法

低轨卫星(Low Earth Orbit,LEO)系统具有传输时延低、路径损耗小和运行周期短的特点,但大规模卫星部署和地面业务非均匀性的特点,导致卫星网络局部拥塞和局部空闲,为优化卫星网络全局负载均衡和回避拥塞问题,文章提出一种基于选择性迭代的K最短路径算法(Selective Iteration of K Shortest Paths,SI-KSP)。与传统K最短路径方法相比,所提的SI-KSP负载均衡路由方法网络吞吐量增加且丢包率大幅下降;与CA-KSP方法相比,所提方法网络吞吐量相近但丢包率和平均时延均降低。该文所提方法能实现根据全局负载情况选择路径分布,有效避免链路拥塞,达到更优化的负载均衡效果。     

支持业务均衡的OBS网络分布式回退偏射路由算法

突发竞争是引起光突发交换(OBS)网络丢包的主要因素之一,而作为一种有效的突发竞争解决方法的偏射路由,因其对光缓存器的性能和数量要求较低而备受关注。然而,现有偏射路由算法忽略了偏射业务对偏射路径上原有业务的影响以及业务被偏射后自身的成功传输率,同时也忽略由偏射引起的偏置时间不够的问题,致使OBS网络整体丢包率较高。为此,本文提出了一种支持业务均衡的分布式回退偏射路由算法(DBDF-LB),基本思路在于:从全网业务均衡出发,根据网络状态信息分布式的为偏射业务选择一条丢包率最小、跳数最短的路径;然后通过回退机制,利用网络资源来缓存突发包,从而补偿由偏射引起的额外偏置时间。与典型的最短路径偏射算法(SPDF)相比,DBDF-LB能有效降低丢包率约23~50%,而成功传输突发包所经历的平均跳数增加不到1跳。     

Development of the readout system for waveguide multilayer optical card

Waveguide multilayer optical card （WMOC） is a novel storage device of three-dimensional optical information. An advanced readout system fitting for the WMOC is introduced in this paper. The hardware mainly consists of the light source for reading, WMOC, motorized stages addressing unit, microscope imaging unit, CCD detecting unit and PC controlling ＆ processing unit. The movement of the precision motorized stage is controlled by the computer through Visual Basic （VB） language in software. A control panel is also designed to get the layer address and the page address through which the position of the motorized stages can be changed. The WMOC readout system is easy to manage and the readout result is directly displayed on computer monitor.     

Nanoimprint Lithography -A Next Generation High Volume Lithography Technique

IntroductionNanoimprint Lithography is a well-acknowl-edged low cost, high resolution, large area pattern-ing process. It includes the most promising methods,high-pressure hot embossing lithography (HEL) [2],UV-cured imprinting (UV-NIL) [3] and micro contactprinting (m-CP, MCP) [4]. Curing of the imprintedstructures is either done by subsequent UV-lightexposure in the case of UV-NIL or by cooling downbelow the glass transition temperature of the ther-moplastic material in case of HEL…     

Collinear phase-matching study of terahertz-wave generation via difference frequency mixed in GaAs and Inp

The collinearly phase-matching condition of terahertz-wave generation via difference frequency mixed in GaAs and InP is theoretically studied. In collinear phase-matching, the optimum phase-matching wave hands of these two crystals are calculated. The optimum phase-matching wave bands in GaAs and lnP are 0.95-1.38μm and 0.7-0.96μm respectively. The influence of the wavelength choice of the pump wave on the coherent length in THz-wave tuning is also discussed. The influence of the temperature alteration on the phase-matching and the temperature tuning properties in GaAs crystal are calculated and analyzed. It can serve for the following experiments as a theoretical evidence and a reference as well.     

Effects of the alloy compositions on the phonon-polaritons in ternary mixed crystals

Composition dependence of bulk and surface phonon-polaritons in ternary mixed crystals are studied in the framework of the modified random-element-isodisplacement model and the Bom-Huang approximation. The numerical results for Several Ⅱ - Ⅵ and Ⅲ- Ⅴ compound systems are performed, and the polariton frequencies as functions of the compositions for ternary mixed crystals AlxGa1-xAs, GaPxAS1-x, ZnSxSe1-x, GaAsxSb1-x, GaxIn1-xP, and ZnxCd1-xS as examples are given and discussed. The results show that the dependence of the energies of two branches of bulk phonon-polaritons which have phonon-like characteristics, and surface phonon-polaritons on the compositions of ternary mixed crystals are nonlinear and different from those of the corresponding binary systems.     

Influence of PVK ： NPB hole transporting layer on the characteristics of organic light-emitting devices

A doping system consisting of NPB and PVK is employed as a composite hole transporting layer （CHTL）. By adjusting the component ratio of the doping system, a series of devices with different concentration proportion of PVK ： NPB are constracted. The result shows that doping concentration of NPB enhances the competence of hole transporting ability, and modifies the recombination region of charge as well as affects the surface morphology of doped film. Optimum device with a maximum brightness of 7852 cd/m^2 and a power efficiency of 1.75 lm/W has been obtained by choosing a concentration proportion of PVK ： NPB at 1：3.     

New insert layer structure OLEDs

An insert layer structure organic electroluminescent device（OLED） based on a new luminescent material （Zn（salen）） is fabricated. The configuration of the device is ITO/CuPc/NPD/Zn（salen）/Liq/LiF/A1/CuPc/NPD/Zn（salen）/Liq/LiF/A1. Effective insert electrode layers comprising LiF（1nm）/Al（5 nm） are used as a single semitransparent mirror, and bilayer cathode LiF（1 nm）/A1（100 nm） is used as a reflecting mirror. The two mirrors form a Fabry-Perot microcavity and two emissive units. The maximum brightness and luminous efficiency reach 674 cd/m^2 and 2.652 cd/A, respectively, which are 2.1 and 3.7 times higher than the conventional device, respectively. The superior brightness and luminous efficiency over conventional single-unit devices are attributed to microcavity effect.     

Analysis of error performance on Turbo coded FDPIM

Due to variable symbol length of digital pulse interval modulation（DPIM）, it is difficult to analyze the error performances of Turbo coded DPIM. To solve this problem, a fixed-length digital pulse interval modulation（FDPIM） method is provided. The FDPIM modulation structure is introduced. The packet error rates of uncoded FDPIM are analyzed and compared with that of DPIM. Bit error rates of Turbo coded FDPIM are simulated based on three kinds of analytical models under weak turbulence channel. The results show that packet error rate of uncoded FDPIM is inferior to that of uncoded DPIM. However, FDPIM is easy to be implemented and easy to be combined, with Turbo code for soft-decision because of its fixed length. Besides, the introduction of Turbo code in this modulation can decrease the average power about 10 dBm, which means that it can improve the error performance of the system effectively.     

A method for calculating the center position of collimated light

It is a key problem to accurately calculate beam spots＇ center of measuring the warp by using a collimated laser. A new method, named double geometrical center method （DGCM）, is put forward for the first time. In this method, a plane wave perpendicularly irradiates an aperture stop, and a charge couple device （CCD） is employed to receive the diffraction-beam spots, then the geometrical centers of the fast and the second diffraction-beam spots are calculated respectively, and their mean value is regarded as the center of datum beam. In face of such adverse instances as laser intension distributing defectively, part of the image being saturated, this method can still work well. What＇s more, this method can detect whether an unacceptable error exits in the courses of image receiving, processing and calculating. The experimental results indicate the precision of this method is high.     

Cost-effective test solutions for smart card and other integrated flash applications

From its emergence in the late 1980s as a lower cost alternative to early EEPROM technologies, flash memory has evolved to higher densities and speedsand rapidly growing acceptance in mobile applications.In the process, flash memory devices have placed increased test requirements on manufacturers. Today, as flash device test grows in importance in China, manufacturers face growing pressure for reduced cost-oftest, increased throughput and greater return on investment for test equipment. At the same time, the move to integrated flash packages for contactless smart card applications adds a significant further challenge to manufacturers seeking rapid, low-cost test.     

An improved parallel thinning algorithm with two subiterations

The parallel thinning algorithm with two subiterations is improved in this paper. By analyzing the notions of connected components and passes, a conclusion is drawn that the number of passes and the number of eight-connected components are equal. Then the expression of the number of eight-connected components is obtained which replaces the old one in the algorithm. And a reserving condition is proposed by experiments, which alleviates the excess deletion where a diagonal line and a beeline intersect. The experimental results demonstrate that the thinned curve is almost located in the middle of the original curve connectivelv with single pixel width and the processing speed is high.