基于混沌扩频CDMA的伽利略卫星定位系统编码技术

在伽利略系统中编码技术日益重要。文章在将混沌扩频技术应用到伽利略系统中后,对系统的信道特性进行了探讨,特别是利用混沌扩频的优秀随机性和正交性对系统进行了信道仿真。仿真结果表明信道衰减小于-40 dB,满足CDMA2000协议规范,从而简化了传统CDMA系统PN码产生的复杂性,统一了信号源和信道编码的混沌序列的使用。这种将混沌扩频CDMA技术代替传统PN序列的方法在伽利略系统中的应用具有实用性和可行性。     

基于自适应神经网络的光伏输出功率预测

文中提出了一种基于不同拓扑结构的自适应神经网络(ANN)预测光伏输出功率的方法,建立了一个与数据采集系统协同工作的天气监测系统,利用三种不同类型的自适应神经网络进行功率输出预测。为了研究气候变化对发电量的影响,使用天气数据(气温、太阳辐照度和风速)以及两个测试光伏电池板历史功率输出数据对ANN进行了训练。通过将模型预测值与功率输出测量数据进行比较,计算结果验证了所提方法对短期功率输出预测问题的适用性,并确定了最佳拓扑结构。     

基于PL3200的CDMA扩频电力线载波通信系统设计

介绍CDMA扩频通信的基本原理、PL3200型SoC的结构及其载波通信功能模块,提出一种基于PL3200的CDMA扩频电力线载波通信系统的设计方案.     

Novel spatial spread spectrum based fiber optic CDMA networks forimage transmission

Novel code division multiple access (CDMA) fiber optic networks based on spatial frequency spread spectrum for image transmissions are proposed. Two key technologies are the parallel fiber optic transmission of spatially encoded images and parallel access to image data through optical spatial encoding and decoding. The temporal signature sequences used in conventional time-domain CDMA are replaced by two-dimensional (2-D) signature patterns to encode and decode binary image pixels. This enables the fully parallel access and transmission of images. The fundamental rules and methodology to construct optical orthogonal signature patterns (OOSP) are presented. Furthermore, it is shown that the all-optical implementation of the proposed system is feasible by utilizing optically addressable spatial light modulators in both the spatial encoder and the decoder along with multicore fibers as the parallel image transmission medium. The predicted overall throughput can reach 10 Tb/s     

基于光克尔效应的时间分辨荧光光谱测试系统

基于光克尔效应的时间分辨光谱测试技术主要用来研究发荧光的物质在受到激光照射时所表现出的瞬态行为信息。其主要思想是以空间函数来代替光学的响应时间函数,而其响应时间是通过两束光脉冲的相对时间差体现的。我们通过控制光学延迟可以控制两束光脉冲的时间差,并最终得到荧光物质受到激发光照射时表现出的瞬态行为信息。本文设计了一套基于光克尔效应的时间分辨光谱测试系统,其中光学延迟的软件控制系统由c#语言开发而来,通过控制直线精密滑台来实现光学延迟的控制。同时,考虑到样品的不同区域可能具有不同的性质,本文同时设计了一套由易语言开发的、能控制样品移动的软件控制系统,主要通过控制二维滑台来实现。     

基于CPLD的功率输出自测试及保护技术研究

机载供电系统中存在大量的功率接触器和继电器,在驱动这些装置时,如果电路中的瞬态电流过大,将损坏机载计算机本身及后级控制电路.本文设计并实现了一种基于CPLD的功率输出自测试及短路保护技术,由硬件分立元器件和可编程逻辑器件代替DSP处理器,无需软件参与,完全由硬件实现功率驱动和过流保护,使其具有非常高的可靠性和安全性,性能大大优于传统控制开关.     

基于MLP神经网络的铝电解槽出铝量预测

铝电解生产是一个大延迟、多变量耦合和非线性的过程.铝电解槽每天的出铝量往往是根据多年积累的经验制定的,目前为止还没有一个准确的计算方案.根据电解槽的各个状态参数进行相关性分析,其中电解质水平、铝水平、槽温、分子比变化等一些列参数对出铝量的影响相对较大.本文将从操控系统得到的各参数数据集分为测试集、训练集,利用机器学习框架搭建MLP神经网络日出铝量模型,通过模型得到预测值和真实值进行对比,对误差曲线进行了分析.     

基于多子波的CDMA系统

将多子波的分析滤波器、预处理以及平衡化等方面的最新研究成果应用于通信领域,提出了多子波码分多址(MW-CDMA)通信系统的理论框架。在MW-CDMA中,系统首先将接收信号投影到相互正交的子波空间上,然后在各子波空间中进行多用户解调。理论分析系和仿真结果表明,这种系统可以很好地抑制多址干扰和环境噪声。同时也为减少解码的计算量提供了新的思路。     

基于OFDM的多载波CDMA系统的研究

MC—CDNA系统是将CDNA和OFDM技术的优点结合在一起的多址方案。首先介绍了OFDM的基本原理，并据此给出MC—CDNA系统的模型，通过对MC—CDNA和DS—CDNA的性能比较，MC—CDNA能提供更高的系统容量，结构更简单，抗干扰性更强，更适用于未来移动通信的需要。     

An analytic approach for CDMA output of feedforward power amplifier

In this paper, a novel method is introduced to predict the Code-Division Multiple-Access (CDMA) output spectrum of an RF power amplifier linearized with feedforward technique based on transfer function. In this method, an RF power amplifier is modeled mathematically by nonlinear complex envelope transfer function based on AM-AM and AM-PM distortion diagrams. Using this model, analytic expressions of CDMA output spectrum of power amplifier is calculated. Having mathematical model of RF power amplifier leads to derive analytic expressions for InterModulation (IM) products in feedforward amplifier. Based on these expressions, IM products are related to nonlinear complex envelope transfer function of feedforward amplifier. Then, CDMA output spectrum of feedforward linearization technique is predicted. The loops imbalances in feedforward technique are considered in analysis. Finally, the results of derived expressions in MATLAB software are compared with ADS simulations results and good agreements were achieved. Employing this method gives insight for feedforward analysis and loops imbalances effects in feedforward amplifier for CDMA applications.     

CDMA蜂窝网频谱规划方案的比较分析

本文建议了CDMA蜂窝网频谱规划的两种方案,频率复用系数分别为K=4/3与K=3.文中以纯语音业务为例讨论了不同频谱规划之间的区别.仿真结果显示目前所普遍采用的K=4/3的频谱规划方案并非最佳选择,当小区之间移动终端分布不均匀时,K=3的频谱规划方案在小区容量方面优于K=4/3的规划方案.     

Synchronous CDMA based on the cyclical translations of a CAZAC sequence

A new scheme of synchronous CDMA is introduced in the paper. The new scheme is based on a code made by all the cyclical translations of a basic sequence having constant amplitude and white discrete spectrum. Such a code is proposed here for the first time as a code for CDMA. According to the proposed scheme, a cyclic prefix is appended to the multiplexed signal. The proposed scheme has a property that none of the known CDMA schemes has: in a multipath environment, it allows multiuser interference to become cyclic intersymbol interference. Noticeably, the memory of the finite state machine that describes the ISI model is equal to memory of the multipath channel. The main advantage of our proposed scheme is that optimal and suboptimal detectors can be obtained from detectors proposed in the past for the ISI channel, which are much easier to implement than conventional multiuser detectors of classical CDMA schemes. Another advantage of our scheme is that it leads naturally to a signal processing architecture similar to that of OFDM systems, hence based on the efficient FFT/IFFT algorithm.     

CO激光器的输出频谱特性

本文报导了CO激光器的输出频谱特性，指出CO激光谱线是单纵模，调谐腔长，振荡频率在增益剖面上扫描，调谐范围为C/2L。     

基于视觉掩盖的码分多址水印算法

本文提出了基于视觉掩盖的的码分多址水印算法,利用视觉掩盖在小波变换域完成水印的嵌入.采用水印估计的方法提取水印信号,实现了不需要原始图像完全恢复出水印信号的水印盲检测,进一步提高了数字产品版权认定的可靠性.     

DCT域的数字指纹CDMA扩频追踪

以DCT变换为基础,结合了数字图像JPEG压缩和通信CDMA技术的特点,提出了一种基于双DCT变换、扩频技术的二维数字指纹追踪算法。通过像素值和DCT系数两种平均合谋方式攻击和追踪性能分析验证,该追踪方案能够有效抵抗多用户合谋和抗JPEG压缩,同时具有较高的峰值信噪比和良好的追踪特性。     

Design of spread spectrum multicode CDMA transport architecture formultimedia services

We investigate a new application of the well-known spread spectrum code division multiple access (SS-CDMA) techniques to multimedia services related to the development of the next-generation wireless mobile networks interconnecting with a wireline ATM-based broadband network. Such services allow users to share novel multimedia applications without any geographical restrictions. However, since the mobile radio channel has a fixed limited bandwidth, the traditional SS-CDMA system may not be sufficient to accommodate the variable bit rate (VBR) multimedia services requested by multiple mobile users simultaneously. Moreover, the traffic load at the base station can change dynamically due to the time-varying throughput requirement of these requested multimedia services. To tackle this difficulty, a multicode CDMA (MC-CDMA) technique is proposed to provide multirate multimedia services by varying the number of spreading codes assigned to each user in order to meet its throughput requirement. In MC-CDMA, a spreading code can be used to transmit information at a basic bit rate. Users (video or data) who need higher transmission rates can use multiple codes in parallel. Meanwhile, the maximum available number of codes in the MC-CDMA system is still limited. Hence, a cost-effective dynamic code allocation scheme has then been proposed to dynamically assign an appropriate number of codes to each user for achieving the maximum resource utilization for multiuser multimedia services via the mobile radio channel. Finally, a number of real multimedia titles generated from the well-known MacroMind Director are conducted to evaluate performance     

On the output spectrum of unlocked driven oscillators

A method is given to determine the components of the signal of an unlocked driven oscillator. The phase modulation signal, which perturbs the free oscillation, is expanded in a Fourier series.     

基于ESD测试的无线电网络抗SSDF攻击协作频谱感知方案

针对认知无线电网络中协作频谱感知容易遭受数据伪造攻击的问题,提出一种基于检验统计和极端学生化偏差检验法的协作频谱感知方案。首先,将差分进化算法与加权增益合并软决策融合方法相结合,形成一种高效的节点决策融合机制。然后,在协作感知中,根据节点的软决策数据,利用检验统计消除故障认知节点。最后,利用提出的改进型ESD检验法消除恶意认知节点,从而形成全局决策。仿真结果表明,该方案在协作感知中能够有效过滤SSDF攻击数据,具有较低的误检测率。     

基于FHT似然比检验的CRN协作频谱感知方案

针对认知无线电网络中由于噪声功率不确定性而影响频谱检测性能的问题,提出了一种基于模糊似然比检验的协作频谱检测方法。首先,将每个次用户(SU)中的噪声不确定性均建模为模糊假设检验(FHT);然后,在FHT上利用似然比检验构建带有阈值的模糊能量检测器,该阈值依赖于噪声功率不确定性边界;最后,在融合中心结合SU的局部硬决策并做出最终决策,从而检测主用户是否存在。通过Monte Carlo模拟受试者ROC曲线及检测概率/SNR曲线验证了本文方法的有效性,仿真结果表明,相比其他几种较新的能量检测器,本文方法获得了更好的检测性能。     

Dynamic spectrum access based on interruptible spectrum leasing

Dynamic spectrum access (DSA) based on interruptible spectrum leasing allows secondary users (SUs) to lease a licensed, but idle, spectrum that is owned by primary users (PUs) on condition that the PUs preempt the access to the leased spectrum. This paper considers a DSA scenario where the SUs opportunistically use the primary spectrum in addition to their own band and the PUs use their own band regardless of the opportunistic access. This operating scenario can contribute to leverage the spectrum utilization by exploiting underutilized spectrum resources, but involves a problem that the SUs may be forced to interrupt on-going services in response to the PUs?? reclamation of the leased spectrum. In this paper, we address the optimal call admission control (CAC) problem in order to coordinate the DSA based on interruptible spectrum leasing by considering the tradeoff between the additional spectrum use and the penalty on the service interruption. To this end, we adopt the profit of the secondary wireless service provider as a cost function of the CAC policy in a market mechanism manner. The optimization problem is modeled as a profit maximization problem, and a linear programming (LP) formulation of the semi-Markov decision process approach is provided. Through the simulation results, we analyze the LP solution of the optimal CAC for the leasing based DSA and demonstrate that the proposed CAC policy judiciously uses the access opportunities of the SUs considering the service interruption.