SIR Weighting Combining Diversity Using Matched Filter for Personal Communication Systems

We propose a novel SIR weighting postdetection combining diversity scheme with a new accurate SIR estimation method. The SIR is estimated and used as the weighting factor to compensate severe cochannel interference, one of the most important issues for PCS in terms of frequency utilization. Theimprovement offered by the proposal depends on SIR estimation accuracy.The SIR is, in this paper, estimated by a matched filter where theauto-correlation between received signal and unique word is calculated. Computer simulationsconfirm that the SIR of each diversity branch can be estimated easily andaccuratelyby the proposed SIR estimation method. The proposed diversity scheme achievesaperformance very close to that of ideal SINR weighting diversity underRayleighfading with severe cochannel interference. When average SIR = 10 dB and thenumber of branches(L)=4, the proposed diversity scheme lowers the requiredE_b/N₀ by 5 dB at BER = 1×10^-3compared to conventional maximal ratio combining diversity. This paper alsopresentsthe unique word length required to realize adequate performance, i.e.,robustnessagainst high-pitch Rayleigh fading.     

Study on multiple receiver systems in non-line-of-sight ultraviolet communication systems

In this article, multiple receiver effects in a non-line-of-sight （NLOS） ultraviolet （UV） communication system is studied. The idea of using multiple receivers for diversity reception is known as a practical, effective and widely applied technique in wireless communications. The current approach is to use multiple antennas at the receiver in order to improve the quality of the received signal. A method of modeling and simulation is proposed to depict the principle and feasibility of the multiple receiver adopted in UV communication. The study provides an insight to the channel characteristics and achievable capabilities of ultraviolet communication systems with multiple receivers. It provides guidelines for practical system design with discussions on trade off between the receiver gain and the additional cost.     

高性能同步数字传输/光纤网络芯片组

文中介绍了一种2．5Gbps同步数字传输／光纤网络（SDH／SONET）芯片组。发送器由MAX3890（合路器、时钟发生器）和MAX3867（激光驱动器）组成,总随机抖动仅为3．4psRMS,MAX3890可提供2．5Gbps时钟给MAX3867的输入锁定,用于数据信号的再定时,使MAX3867成为仅有的系统性抖动源,典型的系统性抖动≤50psRMS。接收器由MAX3866（TIA）、MAX3875（时种及数据恢复）和MAX3885（分路器）组成,总随机抖动仅4．6psRMS系统性抖动约为20psRMS。该芯片组对于ITU／Bellcore关于2．5Gbps SDH/SONET抖动规范有显著的设计裕量。     

卫星地球站射频单元型号核准项目及测试方法浅析

本文介绍了我国卫星地球站的发展现状,说明了卫星地球站射频单元型号核准的检测项目,并详细阐述了各个项目的测试方法。     

A MC-CDMA Mobile Communication System Employing Pre-Rake and Transmit Diversity

In this paper, a multi-carrier code division multiple access (MC-CDMA) downlink mobile communication system employing pre-rake and dual transmit diversity is proposed. It combines high spectral efficiency with an immunity to channel dispersion and fading. It also ensures small size, cost and power consumption of the terminal. Theoretical and simulation results for the system under consideration are obtained. Depicted results show appreciable improvements of the proposed system over those previously known.Emad K. Al-Hussaini received his B.Sc degree in Electrical Communication Engineering from Ain-Shams University, Cairo, Egypt, in 1964 and his M.Sc and Ph.D. degrees from Cairo University, Giza, Egypt, in 1974 and 1977, respectively. From 1964 to 1970, he was with the General Egyptian Aeroorganization. Since 1970, he has been with the Department of Electronics and Communications, Faculty of Engineering, Cairo University, and is currently professor there. He was a research fellow at Imperial College, London, UK, and at the Moore School of Electrical Engineering, University of Pennsylvania, Philadelphia, PA, USA, in the academic years 1976/1977 and 1981/1982, respectively. In 1990, he received the Egyptian national encouragement award for outstanding engineering research. He has written several papers for technical international journals and conferences. His research interests include signal processing, fading channel communication, modulation, and cellular mobile radio systems. Dr Al-Hussaini is a senior member of IEEE. He is listed in Marquis Whos Who in the World and in the IBC (International Biographical Center, Cambridge) for outstanding people of the 20th century.Hebat-Allah M.Mourad received her B.Sc, M.Sc and Ph.D degrees in Electrical Communication Engineering from Cairo University, Egypt, in 1983, 1987 and 1994 respectively. Since 1983 she has been with the Electronics and Communications Department, Faculty of Engineering Cairo University and is currently associate professor there. Her research interests include mobile communications, satellite communications and optical fiber communications.Fatma A. Newagy received her B.Sc and M.Sc degrees in electrical communication engineering from Cairo University, Egypt in 1998 and 2002 respectively. Since 1999, she has been a research assistant with the Department of Electronics and Communications, Faculty of Engineering, Cairo University. She is pursuing her Ph.D. there. Her research interests include mobile communications and modulation techniques for spread spectrum and wireless communications.     

相关瑞利信道下差分空时检测协同分集方案

本文提出了一种采用分布式差分空时分组编码和检测的协同分集方案,在不需要信道状态信息(CSI)的情况下可以实现满分集和全速率发射,并推导了相关瑞利信道下该方案误码率(BER)性能上限的解析表达式。传统的差分空时分组编码对整个码块进行差分,而协同分集下的任何一个协同用户进行差分编码时都不知道整个码块的信息。本文所提出的差分BPSK调制方案,通过将两协同用户的信息分别被调制到相互正交的实轴和虚轴上,从而将码块的联合差分转化为各用户独立差分。分析了在协同用户间不同的信道状态信息(CSI)和协同用户到接收用户不同的CSI情况下本文所提出发射方案的性能。仿真结果表明本文所提出的方案获得了明显的分集增益,同时也较好的吻合了理论分析的结果。     

空间相关信道下基于线性星座的预编码技术

文中首先介绍基于MIM0系统的开环预编码技术,重点讨论如何采用线性星座预编码(LCP)方法对多天线系统进行预处理,使多天线系统获得较高的分集增益与编码增益.然后,对LCP预编码系统在空间相关信道下的差错性能作深入分析,分别对弱相关信道与强相关信道两种不同情况下的LCP预编码性能展开详细讨论.最后,用MATLAB软件进行仿真试验,将经过酉星座旋转处理的预编码系统与V-BLAST多天线传输系统作比较,得出不同相关信道下预编码系统的比特差错概率,并验证相应结论.     

IEEE 802.11自组网中基于能量控制的RTS/CTS机制

基于IEEES02.11协议的无线网络,受无线通信环境以及节点位置的影响较为明显.特别在节点较为密集的时候,MAC层的RTS/CTS机制将会严重的影响信号的空间复用度.通过研究影响数据正确接受的干扰范围与传输距离之间的关系,提出一种通过调节节点的传输功率,从而提高数据传输的空问复用度的算法.仿真的结果验证了这种算法能够明显提高网络的吞吐量.     

The Inequality Between Two Distributions: Applications to the Analysis of Diversity Data

A new measure called diversity difference is proposed for the inequality of a pair of distributions. The diversity difference measure satisfies eight properties of a measure of inequality. This measure is simple to calculate and provides easily interpreted results.Existing inequality measures examine the distribution of a single variable whose data are arranged in a monotonic order. The new measure can employ multiple variables and does not require each to be monotonic but can be used if the data happen to be monotonic. The pair of distributions is useful for organizational diversity data because one of the distributions represents the actual proportions of employees in any class or set of classes and the other distribution is the benchmark or anchoring distribution. Data from the measure can be displayed in diversity difference trees for quick interpretation.The diversity difference measure can be arranged to define a Lorenz curve. An example with three classes (gender, race, and age) is employed to provide examples of the measure, the resulting Lorenz curve, and the disparity ratio.     

跨层级性别多样性变量在工作满意度和离职意图之间的调节作用

本研究在国外研究的基础上,将不同职务层级的性别多样性变量引入离职意图的前因变量模型中,并检验了多样性变量对于工作满意度和离职意图之间的调节效应。在对298个样本做回归分析后,发现了高层管理者和中层管理者性别多样性变量对离职意图的显著影响作用,以及基层管理者和上级性别多样性变量对于工作满意度和离职意图的调节作用。