简述扩频通信技术

随着信息时代的到来,个人通信、GPS定位、3G网络、4G网络的不断普及和升级,人们与扩频技术的距离悄然间已相互渗透。为了提高通信质量和网络速度,对信息传输的研究是必经之路,这里,就信息传输中一个新颖而又重要的技术——扩频技术进行浅要分析与论述。     

无线扩频技术的比较研究

通过对无线扩频技术的比较研究,指出了直接扩频技术和跳频技术各自的长处和不足,为在无线通信系统、第三代移动通信宽带、CDMA系统或无线局域网等系统中正确的选择和应用扩频技术提供一些参考。     

无线扩频技术的比较研究

通过对无线扩频技术的比较研究 ,指出了直接扩频技术和跳频技术各自的长处和不足 ,为在无线通信系统、第三代移动通信宽带CDMA系统或无线局域网等系统中正确的选择和应用扩频技术提供—些参考。     

个人通信中的扩频技术

在个人通信中,必然会遇到频谱共享、通信安全、传播环境和多径干扰等复杂技术难题,而扩频通信技术是同时解决这些问题又可提供多种信息服务的良策。本文主要讨论扩频技术基础以及扩频技术在个人通信中的应用。     

扩频技术及其应用

扩频技术是充分利用有限频谱资源,提高无线信息传输效率的一种新技术,文章介绍了扩频通信工作原理及其系统模型,详细阐述了扩频通信的两种主要技术:直接序列扩频和跳频扩频,解释其工作原理,并将这二者的性能进行比较。另外介绍了扩频与数字水印技术的结合,利用扩频原理的数字水印技术具有很高的健壮性和安全性。     

多码直接序列扩频技术（MC-DSSS）在无线接入中的应用

直接序列扩频(DSSS)技术是当今人们所熟知的扩频技术之一。它是二战期间开发的，最初的用途是为军事通信提供安全保障。直接序列扩频技术将窄带信息信号扩展成宽带噪声信号。这种技术使敌人很难探测到信号。即便探测到信号，如果不知道正确的编码，也不可能将噪声信号重新汇编成原始的信号。     

无线扩频通信技术及其在银行业的应用研究

阐述分析了无线通信的数据调制与扩频、直接扩频系统、频率跳跃扩频系统,以及无线局域网标准,详细研究分析了扩展频通讯系统的应用,特别是在银行业的应用。     

多码直接序列扩频技术(MC-DSSS)在无线接入的应用

该文首先对直接序列扩频技术进行了概述,接着对直接序列扩频系统的处理增益及直接序列扩频技术和多径问题进行了阐述,最后分析了直接序列扩频与窄带相比的优点及多码直接序列扩频技术(MC-DSSS)。     

扩频技术在移动通信中的应用

简介扩频技术原理、特点、应用以及ＣＤＭＡ。     

移动通信系统的抗干扰技术

我国移动通信发展迅速，随之而来的是空间频谱日益拥挤，容易引起相互间的干扰，本文简要叙述了几种目前常用的移动通信通信设备抗干扰技术，探讨了抗干扰技术的发展趋势。     

Enhanced Resource Blocks Management in D2D based Communication for 5G Networks

D2D based communication holds a promising future for 5G networks as they are efficient and can yield high data rates, good signal to noise interference ratio, improved resource-block uploading time, minimized delay from one end to the other and conserved power for transmission. The traditional system of cellular type contains cell edge clients who need a larger resource blocks count as well as time to upload data. Hence the quality of service will be reduced. The relay scheme in the proposal for cooperative type D2D networks is pivoted on the value of channel gain as well as transmission link distance. For bringing down the resource blocks’ count as well as uploading time, the paper is proposing a capable scheme of selection of relays that employs communication of D2D in the situations of uplinking. To begin with, in a cell modeling is done. It contains D2D pairs of multiple types as well as cellular clients. Next, the analysis related to issues of allocating resources as well as control of power is done. In order to lessen the resource blocks as well as their uploading time, the paper in proposal suggests a better blocks management mechanism that uses D2D based communication. Simulated output infers that the method in the proposal is superior to the present methods as far as time to upload contents; resource blocks, SINR, throughput as well as rates of data and Energy Consumption are concerned. Added to that, the stated method conserves 43% of the Energy Consumption of the network clients and while doing that the time to upload the contents is not affected.

     

桐乡市广电IP城域网系统配置优化探析

以CISCO系列交换设备组网为例,着重从生成树优化、OSPF路由优化、系统管理VLAN设置、网络时间校准以及设备配置标准模板等方面,简述了中小型广电IP城域网系统配置的优化思路以及几个参考实例。     

10-GHz ultralow-noise optical sampling stream from a semiconductordiode ring laser

We report, what is to our knowledge, the lowest-noise pulsetrain produced to date with an actively mode-locked external-cavity semiconductor diode laser. Operating characteristics at 10 GHz include dispersion-compensated pulsewidths as short as 1.2 ps, amplitude noise as low as 0.12% rms, and residual phase noise as low as 43-fs rms. Potential application of such a laser in a next-generation optical analog-to-digital converter would theoretically provide as much as 8.6 bits of resolution, while sampling a 5-GHz waveform at the Nyquist frequency     

MIMO systems with full and reduced hardware complexity

MIMO (multiple-input-multiple-output) systems propose enormous gains in the capacity of wireless systems without requiring more spectral resources. This paper first gives an overview of the use of MIMO for diversity and spatial multiplexing, and the use of channel state information in MIMO systems. It then explores the use of antenna selection as a means for the reduction of the hardware complexity. It is shown that the performance in a spatial-multiplexing application is almost as good as that of full-complexity systems as long as the number of RF chains is at least as large as the number of data streams.     

基于不经意传输的拓扑隐藏广播协议设

为了保护消息广播中节点关系、地理位置等敏感信息,将高效的NTRU(Number Theory Re―search Unit)公钥加密算法与不经意传输协议相结合,通过引入不可信的第三方以保证广播的中间过程无法被任意节点所获知,从而实现了隐藏网络拓扑结构的目标.该协议可认为是拓扑隐藏广播的具体实现,解决了现有概念性方案中尚未涉及的秘钥重构、相邻节点身份隐藏及网络动态变化等问题.安全性分析表明,在半诚实攻击模型下该方案能够保证网络中任何一部分节点被攻破均不会导致其他节点拓扑信息泄露.此外,通过与相关概念性协议进行实验对比分析,该方案除安全性外还可充分体现计算、通信开销与节点平均度数无关的优势.     

Mechanical Derivation of Fused Multiply–Add Algorithms for Linear Transforms

Several computer architectures offer fused multiply-add (FMA), also called multiply-and-accumulate (MAC) instructions, that are as fast as a single addition or multiplication. For the efficient implementation of linear transforms, such as the discrete Fourier transform or discrete cosine transforms, this poses a challenge to algorithm developers as standard transform algorithms have to be manipulated into FMA algorithms that make optimal use of FMA instructions. We present a general method to convert any transform algorithm into an FMA algorithm. The method works with both algorithms given as directed acyclic graphs (DAGs) and algorithms given as structured matrix factorizations. We prove bounds on the efficiency of the method. In particular, we show that it removes all single multiplications except at most as many as the transform has outputs. We implemented the DAG-based version of the method and show that we can generate many of the best-known hand-derived FMA algorithms from the literature as well as a few novel FMA algorithms.     

基于中红外DFB-ICL的氨气传感器设计

氨气是主要恶臭物质之一,为了实现工业环境污染源中氨气排放的连续监测,研制了中红外激光气体传感器,与传统近红外氨气传感器受干扰气体影响较大不同的是,该传感器采用中红外分布反馈结构的带间级联激光器(distributed feedback inter-band cascade laser, DFB-ICL)为光源,工作波长在3 μm附近,避免了水和CO2干扰气体的影响,同时以空芯光波导（芯径1 mm、长度5 m）做气体池,采用自制多通道数字锁相放大器,同时解调1f和2f谐波信号,实现免校准测量,获得了传感器的梯度实验结果,线性度高达0.99917,不确定度高达0.9%。Allan方差评价结果显示其稳定性非常出色,在最佳积分时间167 s时,本传感器的检测限低至9.7 ppb。     

Characterization of mass-transported p-substrate GaInAsP/InPburied-heterostructure lasers with analytical solutions for electricaland thermal resistances

Studies have been carried out to evaluate mass-transported p-substrate GaInAsP/InP buried-heterostructure lasers, which have a number of potential advantages over the more conventional n-substrate lasers. Devices have been fabricated with series resistances as low as 3 Ω, in good agreement with the p-substrate spreading resistance calculated using conformal mapping. A further development of this theory yields simple formulas of thermal resistances of heat generated both in the active region and in the p-InP. The presently fabricated p-substrate lasers also showed CW threshold currents as low as 4.5 mA, differential quantum efficiencies as high as 34% per facet, output powers as high as 33 mW per facet, and a maximum total electrical-to-optical power conversion efficiency of 36%     

板线平衡器在八木天线中的应用

文中提出了用于八木天线的新型馈电结构———板线平衡器。给出了详细的板线平衡器和八木天线的设计过程及仿真和试验结果。在仿真设计的基础上制作了试验模型,并对其进行了测量。实验结果表明：板线平衡器具有设计灵活、耐高功率等特点。该天线既可当常规天线使用又可作为高功率宽频带阵列天线单元。     

基于FPGA的并行数据转SPI接口设计

在进行不同设备间的数据传输时,最基本的要求是连线尽可能少、数据传输速率尽可能快、误码率尽可能低。对此进行了并行数据转换为串行数据的接口电路研究,提出了同步并行传输速率的n倍改进SPI传输方案。其特点是传输速率高、时钟独立、可与并行接口端和SPI串行接口端进行双向通信。测试结果显示系统达到预定功能,其接口电路的实现方法可为数据的高速接口提供新的借鉴。