Interference power statistics in ad-hoc and sensor networks

There exist accurate calculation methods for estimation of interference power sum statistics in fixed-topology wireless networks based on the log-normal shadowing radio model. Here we publish essential additions to these estimation methods to expand their use to sensor networks and ad-hoc networks with changing topology. In our calculations we take into account radio propagation conditions, density of nodes, size of the network, traffic load per node and MAC protocol characteristics. The accuracy of our calculation method is verified by simulations. We highlight the influence of MAC protocols on interference and show that an increase in network size or in node density does not necessarily lead into higher interference values. Our results can be deployed to estimate the network capacity. Ramin Hekmat received M.Sc. degree in electrical engineering from Delft University of Technology (TU Delft) in the Netherlands in 1990. He worked since then for several telecommunication companies in the Netherlands and the United States in Research and Development as well as managerial positions. In September 2005 he obtained Ph.D. degree for his work related to Ad-hoc Networks form TU Delft. Currently he is working as assistant professor in the faculty of Electrical Engineering, Mathematics and Computer Science of TU Delft. His prime research interest includes multi-user communication systems, wireless communications and peer-to-peer networks. Email: r.hekmat@ewi.tudelft.nl Mailing address: Delft University of Technology Electrical Engineering, Mathematics and Computer Science P.O. Box 5031 2600 GA Delft The Netherlands. Piet Van Mieghem has obtained the Master and Ph. D. in Electrical Engineering from the K.U.Leuven (Belgium) in 1987 and 1991, respectively. He has joined the Interuniversity Micro Electronic Center (IMEC) from 1987-1991. He was a visiting scientist at MIT, department of electrical engineering from 1992-1993. From 1993 to 1998, he was working in Alcatel Corporate Research Center in Antwerp where he has gained experience in performance analysis of ATM systems and network architectural concepts of both ATM networks (PNNI) and the Internet. Currently, he is full professor at Delft University of Technology with a chair in telecommunication networks. The main theme of the research is evolution of the Internet architecture towards a broadband and QoS-aware network. Email: p.vanmieghem@ewi.tudelft.nl Mailing address: Delft University of Technology Electrical Engineering, Mathematics and Computer Science P.O. Box 5031 2600 GA Delft The Netherlands.     

多线切割中切割线振动作用研究

在多线切割中砂浆有着极其重要的作用,不同的使用条件会直接影响切割晶片的几何参数。讨论了切割线在运动中的振动效果以及对切割产生的影响,通过试验及对高速摄像机拍摄照片的分析,得出不同砂浆携带方式极其在工作中的振动会直接影响到切割出晶片几何参数的结论。     

基于3G通信的软件无线电应用研究

软件无线电是第3代移动通信新技术的一个重要研究方向,它把硬件作为无线通信基本平台,主要依靠软件来完成接收系统的各项功能。为3G通信体制提供了一个开放的、模块化的系统结构。同时介绍了DSP技术和应用方案。     

500kW/380V国产钻机专用变频器的研制与应用

本文主要介绍国产钻机专用变频器的研制与应用。首先简要分析国外变频器在钻机应用中存在的缺点,并与国产变频器做了比较,论述了变频钻机的优点:随后解析原钻机控制系统中存在的问题,我们针对这种状况在大庆市石油管理局井下钻井公司的配合下对该油田钻机进行了变频改造;随后论述了该系统的技术改造方案。现场运行情况表明,该变频系统性能好,可靠性高,操作方便,其各项指标均达到了改造的预期效果。我们相信变频器在油田钻机上的成功应用将会有广阔的市场前景和发展潜力。     

Design of high-speed two-stage cascode-compensated operational amplifiers based on settling time and open-loop parameters

Settling behavior of operational amplifiers is of great importance in many applications. In this paper, an efficient methodology for the design of high-speed two-stage operational amplifiers based on settling time is proposed. Concerning the application of the operational amplifier, it specifies proper open-loop circuit parameters to obtain the desired settling time and closed-loop stability. As the effect of transfer function zeros has been taken into account, the proposed methodology becomes more accurate in achieving the desired specifications. Simulation results are presented to show the effectiveness of the methodology.     

FM HD Radio系统研究及覆盖干扰分析

我国目前尚未推出调频广播数字化标准,HD Radio是美国调幅/调频波段的数字广播标准并在美国本土和世界各国进行了测试和推广。本文主要介绍了FM HD Radio传输系统的相关技术及其传输性能,并结合一些国外实验室的测试结果讨论FM HD Radio的覆盖和干扰问题。     

水厂变频调速技术节能效果分析

本文分析和比较了南京市自来水公司下属五个水厂一、二级泵房内装设的水泵变频调速装置前后的运行数据,得出了变频调速技术在给水工程应用中的实际效果及适用性。     

频率抖动技术在开关电源EMC设计中的应用

文章先分析了开关电源的噪声产生原因,然后在研究频率抖动抗干扰理论和EMI测试仪器测试原理的基础上,提出频率抗干扰技术。最后结合某信息类产品的开关电源测试的频谱图,分析了频率抖动技术是如何减小EHI以及该技术本身可能带来的骚扰问题。     

OFDM系统中基于循环前缀的频偏估计算法

文章对几种常用的基于循环前缀(CP)的最大似然同步算法进行了分析,并对其频偏估计方差进行了比较;同时针对基于CP的同步算法在多径衰落信道下性能较差的情况,提出了一种改进的CP同步算法并进行了仿真,结果表明相比于原ML算法,文中算法在多径信道下可有效提高频偏估计性能.     

Steady-state analysis of a complex adaptive notch filter using modified gradient algorithm

Based on power spectral density (PSD) analytical technique, mean square error (MSE) (or variance) of the frequency estimate of a first-order complex adaptive IIR notch filter (ANF) using modified complex plain gradient (MCPG) algorithm is investigated in this paper. The steady-state expression for MSE is derived in closed form. A quantitative analysis for the estimation MSE has been carried out. It has been revealed that the MSE of frequency estimate is independent of an input frequency of a complex sinusoid. In addition, computer simulations are treated to corroborate the theoretical analysis and the relationships between MSE and system parameters are shown.