室内分布发射天线STBC系统的发射天线位置优化

该文针对室内环境下分布发射天线STBC系统,在考虑了路径损耗、阴影衰落和莱斯衰落的基础上推导了室内的平均误符号率(AASER),通过使室内的平均误符号率最小得到了优化的发射天线位置。理论分析表明最优的发射天线位置与房间的长、宽、高以及移动台的高度有关。仿真结果验证了理论分析的正确性。     

基于ZigBee的公交信息系统研究与实现

提出利用ZigBee技术开发的城市公共交通信息平台系统结构方案,通过采用自组织传感器网络,解决了目前公共交通信息实时传送的问题。系统采用TI/Chipcon公司的CC2430和CC2431芯片,利用无线通信模块与上位机通信,实现对公交车辆运行信息、到站信息、车辆状况的智能监控与管理。     

基于分块和滑动窗口的车牌定位方法

车牌定位是车牌识别系统的关键环节.提出了一种利用分块和滑动窗口快速定位车牌的新方法.首先,进行垂直边缘的检测;然后利用分块和滑动窗口的方法进行搜索,产生车牌候选区域;最后经过判别得到车牌区域,并对边界加以调整.实验结果证明这种算法具有定位准确、效率高、适应性强的特点.     

自适应渐消UKF算法及其在仅测角被动定位中的应用

针对仅测角被动定位受多径、镜像和干扰源影响,噪声无法准确建模,传统EKF及其改进滤波算法容易发散的问题,将自适应渐消因子引入UKF算法中,调整滤波增益以及状态误差协方差矩阵,提出一种自适应渐消UKF算法,给出了具体的计算流程。仿真了不同雷达诱饵布置干扰下滤波算法的稳定性。仿真结果表明,与传统的EKF以及自适应渐消EKF算法相比,该算法收敛速度更快,稳定性更好。     

基于连续相位调制的协同分集系统在平坦衰落信道下的容量分析

连续相位调制(CPM)由于其相位连续和恒包络,可以使用低成本的非线性功率放大器,且CPM信号有近于1的峰均功率比,在放大器处产生的能量消耗小,从而解决协同系统中移动终端的成本和能量受限问题。本文针对平坦衰落信道下的CPM协同通信系统,研究了可表征系统容量下界的对称信息率(SIR)。分析和数值结果表明,协同CPM系统与单入单出CPM系统相比,能获得更大的信道容量,同时还拥有更低的中断概率。进一步地,以最大化系统遍历容量为目标,在考虑路径损耗的条件下,对系统的最优中继位置问题进行了讨论。分析和数值结果表明,对比中继位置在对称中点的系统,最优中继位置系统的信道容量获得明显提升。进一步,研究了信道估计误差和SNR估计误差对CPM协同通信系统的容量的影响。     

基于模糊PID控制的PCB微钻检测系统

PCB微钻的检测需要对微钻的运动轨迹进行精密的控制,这里在直线电机驱动的模型下进行研究分析。通过建立直线伺服电动机推针机构的系统仿真模型,详细分析了模糊PID算法以及数学模型。分别用传统的PID控制与模糊PID控制,对推针装置的推针过程进行了仿真。结果表明,模糊PID控制器能较好地实现微钻的位置跟踪,使其按照预定的运动轨迹运动,提高了检测的精度。     

Location Management in PCS Networks by Caching Two-Level Forwarding-Pointers

One of the challenging tasks in Personal Communication Services (PCS) is to efficiently maintain the location of PCS subscribers who move from one region to another (hereafter called mobile users). When a mobile user receives a call, the network has to quickly determine its current location. The existing location management scheme suffers from high signaling traffic in locating the mobile users. Two-level forwarding pointer scheme has been proposed from per-user forwarding pointer scheme to reduce the cost of signaling traffic. In this paper, we enhance the two-level forwarding pointer scheme. When a mobile user moves from its current Registered Area (RA), which is served by Mobile Switching Center (MSC), to another RA the local switch that acts as a parent of those two MSCs maintains this movement in its memory (hereafter called cache entry). A cache entry is used to locate rapidly the mobile user instead of querying the Home Location Register (HLR) and waiting for its reply. HLR is centralized in the network and far away from the mobile users so that the signaling traffic crossing it is expensive. Sometimes the cache entry may be failed to reach the mobile user then a two-level forwarding pointers will be created from the corresponding Visitor Location Register (VLR), attached to its MSC, through a correct path to locate the mobile user. Thus, there is a saving in cost of querying the underlying HLR. The analytical results indicate that such proposal efficiently reduces the signaling traffic cost for all values of Call to Mobility Ratio (CMR), this is especially considerable when CMR ≥1, without any increase in the call setup delay. Salah M. Ramadan (samohra@yahoo.com) received the BS and MS degrees from Computers Engineering Department, Al-Azhar University, Cairo, Egypt, in 1995 and 2002, respectively. From 2002, he was a Ph.D. student in Computers Engineering Department at Al-Azhar University and is currently pursuing the Ph.D. degree, where he is a research assistant in the Wireless Networks Branch. His research interests include traffic management in ATM networks, routing protocols, mobility management in PCS networks, and mobile computing. He is currently an instructor in Cisco Academy, Egypt. Ahmed M. El-Sherbini (Sherbini@mcit.gov.eg) received the Ph.D. in Electrical and Communication Engineering, Case Western University, U.S.A. March 1983 and M.Sc. in Communication Engineering, Cairo University, Giza, Egypt, June 1980. (M. Sc. Research Studies at the Ecole Nationale Superieure des Telecommunications (ENST), Paris, France). He is the Director, National Telecommunication Institute – Ministry of Communications and Information Technology, Egypt and Professor of Electrical and Communication Engineering Dept. Faculty of Engineering, Cairo University, Egypt. M. I. Marie received his B.Sc., M.Sc. and Ph.D. in electronic and communication engineering from Cairo University on 1972, 1981, 1985, respectively. Now he is a professor of communications at Computer and System Engineering department Al-Azhar University, Cairo, Egypt. His fields of interest includes digital communication, computer networks and protocols development. M. Zaki (azhar@mailer.scu.eun.eg) is the professor of software engineering, Computer and System Engineering Department, Faculty of Engineering, Al-Azhar University at Cairo. He received his B.Sc. and M.Sc. degrees in electrical engineering from Cairo University in 1968 and 1973 respectively. He received his Ph.D. degrees in computer engineering from Warsaw Technical University, Poland in 1977. His fields of interest include artificial intelligence, soft computing, and distributed system.     

一种快速跟踪的单站无源定位算法

在单站无源定位与跟踪中，扩展卡尔曼滤波算法对初始值依赖性较强，在观测方程非线性较强时收敛速度和稳定性无法满足要求，因此文中提出了一种优先估计慢变化参量的定位跟踪算法，通过仿真比较验证了该算法具有较好的收敛速度和稳定性，具有对滤波初始值的依赖性小的优点。     

基于UWB无线网络的定位算法研究

UWB（超宽带）技术作为一种新型的短距无线通信系统，在室内定位技术中越来越受到重视．文中分析了TOA和TDOA等传统定位算法，介绍了一种新的基于RTT的简单异步算法和一种基于TTOA的定位算法，最后给出了各个算法优缺点的比较结果．     

基于静止、准静止双星TDOA／FDOA无源定位算法

针对由静止卫星、准静止卫星构成的无源定位系统，该文研究了利用到达时间差／到达频率差（TDOA／FDOA）联合对地球表面固定辐射源的无源定位算法。与迭代搜索法相比，该算法不需要初值，不用迭代运算，仅仅需要解4次多项式方程，因此该算法更有效。文中推导了定位方程的求解算法，分析了多项式方程的多根情况，并提出了相应的解决办法；最后进行了蒙特卡罗仿真，仿真结果表明该算法具有适应能力强、定位精度高的优点。