GSM直放站覆盖区串话问题分析

GSM直放站覆盖区内通话出现的串话问题,往往被认为是因直放站覆盖所导致.文章试图对移动通信串话的原因进行分析,探讨直放站覆盖区串话现象与直放站的应用有无必然联系.     

多模移动通信基站电源线干扰测试的研究

针对移动通信基站电源线干扰现象,分析干扰信号的类型,把AC、DC线路干扰信号分别划分为8类和9类,设计了基站整机电源系统进行抗干扰能力的测试方法及测试装置。测试结果表明,抗干扰测试装置能够保证基站在多种注入式干扰或耦合干扰的情况下正常运行,验证了基站在过压、短时中断等应力环境下的工作能力,并保证基站在雷击等干扰下不被损坏,提高了对基站输入端口的抗干扰能力。     

无线传感器网络中带消息恢复机制的PBC广播认证协议

为了在无线传感器网络(WSN)中保证安全等级的情况下最小化通信和计算成本,提出了一种带消息恢复机制的基于配对密码学的广播认证协议。该机制不需要同时传输原始签名信息和新生成的签名信息,认证/消息恢复过程能自动恢复原始签名信息。首先初始化系统,基站产生系统参数;然后用户从基站获取密钥,访问WSN;最后当用户需要广播消息给WSN时,用户使用包含消息恢复机制的身份签名(IBS)协议写下签名消息,生成签名后进行消息广播。实验性能分析表明,与IMBAS和IDBAS相比,本文协议的广播消息大小分别减少了30%和22.3%,在112比特位安全等级,总能耗至少减少30%左右,在80比特位安全等级至少可降低15%的总能耗。     

GSM网串话问题分析及处理

移动网串话问题在网络中时有发生,引起串话的环节很多,本文不仅对常见串话问题如接线错误、数据配置错误等进行了分析,还重点对空口串话进行了分析,并结合实际处理案例提出了解决建议。     

CDMA蜂窝网移动台测试

CDMA蜂窝网是一种新型的数字蜂窝体制，它和传统模拟蜂窝系统，GSM、TDMA等数字系统有很大的不同，因此，对CDMA蜂窝网基站、移动台等设备的测试亦有很大区别。惠普公司开发的HP8924C等测试仪表可完成CDMA蜂窝网移动台的测试，HP8921A综合测试仪配合HP83203B适配器完成CDMA蜂窝网基站的测试。在此重点探讨CDMA蜂窝网移动台的测试内容和方法。一、CDM移动台测试概述CDMA系统有许多独特的测试要求，如，CDMA的宽带传输系统允许纠错码用于所有话音数据比特，其处理增益加强了CDMA对传输差错的承受度，CDMA的新凋制格式需…     

基于双光反馈垂直腔面发射激光器获取双路高速物理随机数研究

提出基于双光反馈下垂直腔面发射激光器(VCSELs) 输出的正交偏振分量混沌振荡来同时获取两 路物理随机数(PRN)的方案,数值分析了不同反馈强度下所获取的最终比特序列的随机性能 。研究结果表明,通 过选择合适的反馈参量可使VCSELs中两个偏振分量均呈现混沌振荡;其输出的两路混沌信号 作为熵源, 经8位模数转换器(ADC)量化、比特序列按位反转、异或(XOR)运算和m bit最低有效位(m-LSBs) 截 取等后续处理后可得到最终比特序列;采用美国国家标准技术研究所(NIST)提供的NIST special publication 800-22统计测试套件对基于不同反馈强度下 所产生的 混沌信号熵源所获取的最终比特序列的性能进行测试,初步确定了获取可通过NIST speical publication 800-22统计测试的两路随机数所需的反馈强 度的范围。     

在微蜂窝码分多址小区的上行链路实现比特同步的设想

本文信为在微蜂窝小区的结构下，即蜂窝小区的半径在１００ｍ到２００ｍ时，可由小区基站发出比特同步信息，小区内的各手持机根据接收到的比特同步信息，实现上行链路的比特同频通信。     

高速数字用户线传输设备——HDSL

HDSL（高比特率数字用户环路）是按照CCITTG．703、G．823建议设计和制造的，它采用了2B1Q编码、高速自适应数字滤波及先进的信号处理技术来均衡全部频段上的线路损耗，消除噪音及串话，使用户环路的两对常规铜芯电缆能以2．048Mbit／s的速度双向传输数字信号，这特别适用于GSM900MHz的基站的扩容和公用网络的接入。其应用见图1。HDSL通过置于环路两端的收发信机，采用2B1Q线路码、自适应滤波和回波抑制技术来实现宽带高速数据传输，其结构框图如图2所示。HDSL采用2B1Q线路码，连续2个二进制比特经编码转换后，变为1个四进制模…     

在微蜂窝码分多址小区的上行链路实现比特同步的设想

本文认为在微蜂窝小区的结构下,即蜂窝小区的半径在100m到200m时,可由小区基站发出比特同步信息,小区内的各手持机根据接收到的比特同步信息,实现上行链路的比特同步通信。本文的分析和计算表明,同步通信可显著地降低误码率。     

HP GSM系统基站安装及维护测试

GSM基站测试可分为两部分考虑,即基站安装测试及基站日常维护测试。 安装测试通常由基站制造商完成。在安装阶段,基站尚未提供服务(Abis尚未与基站控制器相连)。故这类测试属于中断业务测试。测试内容包括指标参数测试和功能测试。     

Precoder Partitioning in Closed-loop MIMO Systems

We study unitary precoding for multistream MIMO systems with partial channel state information at the transmitter. We introduce a quantization scheme in which the full space of non-equivalent precoding matrices is partitioned into Grassmannian and orthogonalization parts. The Grassmannian part is used for maximizing the power after precoding and the orthogonalization part is used for removing cross talk between the data streams. We show that orthogonalization improves the attainable capacity when the receiver is linear. We give a parametrization for the non-equivalent orhogonalization matrices and a metric which measures the orthogonality of the transmission. Optimal orthogonalization codebooks for two-stream transmission are presented. When feedback is limited, the optimal partitioning of feedback bits between Grassmannian and orthogonalization parts becomes an issue. In correlated scenarios, the number of feedback bits may be significantly reduced by investing bits into the orthogonalization part.     

Comparative investigations of DWDM transmission system with PMD for different orthogonally modulated signals at 80 Gb/s

Polarization mode dispersion (PMD) has become one of the major limiting factors for high‐bit‐rate optical transmission systems. This paper evaluates the performance of dense wavelength division multiplexed (DWDM) system with PMD at 80 Gb/s in the presence of Kerr‐nonlinear effects. Orthogonally modulated signals have been investigated and compared for tolerance against PMD in a DWDM transmission system with direct detection receivers. The optimized combinations of orthogonal polarization (OP) with carrier‐suppressed return‐to‐zero (CSRZ) and CSRZ differential‐phase‐shift‐keying signals are shown to improve PMD tolerance over high bit rates and long transmission lengths. Improved performance greater than 4 dB is observed for CSRZ modulated signal with OP because of less channel cross talk and reduced power transfer between adjacent bits over different PMD values. The numerical results demonstrate that our proposed orthogonally modulated signals perform better with lesser complex direct detection receivers. Copyright © 2015 John Wiley & Sons, Ltd.     

高阻p型硅大面积四象限探测器的研制

采用PIN结构,研制出高阻p型硅大面积四象限探测器。详细介绍了器件结构设计和制作工艺。对器件响应时间、象限串扰、暗电流和响应度等参数进行了计算与分析。实验结果表明,器件响应度达到0.45A/W（λ=1.06μm）,暗电流小于50nA（Vr=135V）,象限间串扰低于2.5%。     

VXI在红外探测器有效面积测试中的应用

介绍基于VXI总线的红外小光点自动测试系统,这套系统能够精确测试红外探测器 有效面积,还可以用于测试红外探测器的空间响应及串音测试。     

信道串扰对多信道混沌通信的影响

构建了基于垂直腔面发射激光器(VCSELs)的多信道全光混沌通信系统模型,通过描述其特性的数率方程,研究了信道串扰对系统混沌同步及解码性能的影响。在数值模拟中,使用一个改进型的参数——相似指数作为参考标准来评价同步性能。结果表明,相对注入强度越小,信道间隔越大,系统同步的性能越好;双信道系统的同步质量相比主从式单信道系统会有明显下降,而进一步增加信道数量,同步品质并不发生显著改变。以2.5Gb/s伪随机数字调制下的混沌掩藏方式为例,分析了不同信道条件下系统解码性能。在同步质量足够高时,信号可以得到较好的恢复。     

Cross‐talk Cancellation Algorithm for 3D Sound Reproduction

If the right and left signals of a binaural sound recording are reproduced through loudspeakers instead of a headphone, they are inevitably mixed during their transmission to the ears of the listener. This degrades the desired realism in the sound reproduction system, which is commonly called ‘cross‐talk.’ A ‘cross‐talk canceler’ that filters binaural signals before they are sent to the sound sources is needed to prevent cross‐talk. A cross‐talk canceler equalizes the resulting sound around the listener's ears as if the original binaural signal sound is reproduced next to the ears of listener. A cross‐talk canceler is also a solution to the problem—how binaural sound is distributed to more than 2 channels that drive sound sources. This paper presents an effective way of building a cross‐talk canceler in which geometric information, including locations of the listener and multiple loudspeakers, is divided into angular information and distance information. The presented method makes a database in an off‐line way using an adaptive filtering technique and Head Related Transfer Functions. Though the database is mainly concerned about the situation where loudspeakers are located on a standard radius from the listener, it can be used for general radius cases after a distance compensation process, which requires a small amount of computation. Issues related to inverting a system to build a cross‐talk canceler are discussed and numerical results explaining the preferred configuration of a sound reproduction system for stereo loudspeakers are presented.     

Design of a self-routing frequency division multiple access(SR-FDMA) network using an optical ring filter with or without gain as arouter

Self-routing frequency division multiple access (SR-FDMA) network with ASK coherent detection and dual ring topology is proposed. The router, which employs the optical ring filter, is used as a means for selecting the desired channel carrier and at the same time as a bypass of the other channel carriers. The channel capacity and the carrier-to-noise ratio are investigated with the consideration of cross talk and power budget penalty. We find that there exists an optimum coupling coefficient of the transceiver coupler and a trade-off in selecting channel number and data rate. The results show that the router with gain can suppress the cross talk, compensate the power budget penalty, and largely increase the channel number. Therefore, with this router, a self-routing, high-density FDMA network is feasible     

5类电缆性能测试的基本指标

结构化布线工程的最后一步是对布线系统的测试和评估，电缆的性能测试经常被忽视，基本指标有：近端串扰，综合近端串扰，衰减串扰比，等效远端串扰，综合等效远端串扰，回波损耗，延迟抖动等。     

低频太赫兹准目标雷达散射截面的实验研究

以研究太赫兹雷达散射截面的特性为目的,选用所搭建低频太赫兹雷达测试系统,并借助于标准目标法开展了有关太赫兹雷达粗糙铝盘散射截面的实验研究工作.实验结果表明:在小角度散射中太赫兹雷达散射截面随散射角的增大变化比较明显,在散射角超过5后太赫兹雷达散射截面随散射角的变化趋向缓慢,但当散射角超过12后探测信号的强度已衰减到无法测量,在太赫兹雷达散射截面的测试中没有出现微波雷达散射截面的大小随散射角的变化而剧烈振荡的现象;将测试结果与同尺寸微波、激光雷达散射截面的结果进行了对比,得到结论:在0附近太赫兹雷达散射截面的数值比同尺寸微波雷达散射截面的数值要小两个数量级,但比同尺寸激光雷达散射截面的数值要高一个数量级.     

基于高速PCB电路的信号完整性分析与设计

在高速数字信号系统中,信号在传输线上传输的质量一直被工程师们广为关注.文章以系统中传输线上的串扰为例,突出了信号完整性分析在系统设计过程中的重要性,同时系统阐述了串扰形成的原因以及影响它的主要因素,最后结合数值仿真分析,得出了串扰问题的一些结论,并总结归纳了解决串扰问题的具体方法.