Turbo码与TCM编码调制技术研究

本文研究了Turbo码与网格编码调制(Trellis Coded Modulation,TCM)相结合的编码调制技术,给出了Turbo码与TCM相结合的调制方案,对Turbo码与TCM调制方案进行了计算机仿真,仿真结果表明,其性能要优于传统的采用卷积码的TCM调制。     

无线局域网中高效自适应编码调制技术

在高速无线局域网通信领域中，Turbo乘积码和自适应编码调制是两项关键技术。介绍了Turbo乘积码高效编码调制设计方案，研究了适应于高速无线数据传输的自适应策略算法，设计了基于Turbo乘积码的自适应编码调制方案，并实现了两项关键技术的结合。     

网格编码调制在无线信道下的应用

网格调制编码是将编码与调制相结合,利用信号集的冗余度来获取纠错能力.它通过增加系统设备复杂度解决了在不增加信道带宽、不降低有效信息传输速率的情况下获得明显的编码增益的问题,同时使系统的频带和功率利用率达到最佳.在无线信道下,对网格编码调制技术进行了研究,提出了基于无线信道的非对称调制信号集设计方案以及信号映射规则,进行了仿真.结果表明:在对称调制信号上,调制方式分别为4PSK和8PSK模式,编码器状态数增加相对于未编码时的BPSK和QPSK编码增益可以得到提高;非对称调制信号集相对于对称调制信号集可进一步改善编码增益.因此,网格编码技术可以在功率和频率受限的通信系统中得广泛的应用.     

调制编码技术分析与应用

通信对数据业务的需求越来越高,现代战争又越来越依赖高效、可靠的通信保障,实现恶劣环境下的高速率可靠通信是重点应用研究的方向。文中对比分析了目前几种流行的调制技术,分析了这些调制编码技术的特点,并结合通信应用,分析了OFDM调制与LDPC编码的应用价值。     

基于PLC通信的噪声特性及多载波调制技术研究

基于中压PLC通信的特点,对中压信道噪声特性进行了总结研究,并在Matlah下实现噪声仿真波形;对PLC通信上现有调制解调技术进行比较总结,应用Matlab编程实现了FSK调制解调,并在实现单载波FSK调制解调基础上,实现了多载波FSK调制解调。介绍了采用多载波调制技术实现数字信号传输的基本原理及其优点;从理论上分析总结了中压PLC信道及噪声特性,并结合均衡、编码,小波变换等技术,提出了进一步提高多载波调制系统性能的途径。     

水下通信中TCM的关键技术研究

网格编码调制技术克服了传统通信体制中调制与编码的分离独立设计而制约数字通信系统性能的缺陷;在分析TCM工作原理的基础上,介绍了其关键的组成部分,最后通过仿真比较了未编码4PSK调制解调技术与TCM技术的性能,仿真结果表明,在误码率相同的情况下,TCM技术比未编码4PSK要多出很可观的渐进编码增益,这在功率与带宽受限的水声信道中是很有意义的.     

无人机通信中的非对称物理层网络编码研究

物理层网络编码可以提高无线通信系统的性能。针对无人机组网通信的环境特点,建立了无人机组网通信中的非对称双向中继信道模型,研究了该模型中的物理层网络编码,提出了非对称多阶相移键控物理层网络编码方案,推导出该方案的中断概率、误码率等无人机组网通信系统的主要性能指标的理论表达式。通过实验,验证了所提出方案及其理论分析的正确性,分析了各种非对称相移键控调制方式下的系统性能,为物理层网络编码在无人机组网通信中的设计以及性能评估提供了理论依据。     

一种基于BICM-ID的物理层网络编码联合设计方案

基于迭代比特交织编码调制(BICM-ID)提出了一种物理层网络编码与编码调制技术联合设计方案。该方案将编码调制技术和物理层网络编码联合设计,提高了网络吞吐量,通过设计一种星座映射方案,增大欧氏距离,降低误码率。此外,由于译码器部分只采用了一个SISO译码模块,编码译码方式采用卷积码,使得译码复杂度大大降低。     

4D-8PSK-TCM的Matlab Simulink仿真

4D-8PSK-TCM是一种应用于地球卫星探测的高效率编码调制技术,在提高频带效率的基础上,仍然能获得较好的编码增益.本文介绍了基于Matlab Sireulink建立4D-8PSK-TCM的仿真模型,仿真了系统在不同量化比特情况下的误码性能曲线,分析得出了系统FPGA实现的最佳量化方案.     

在MIMO—OFDM系统实现自适应编码调制的算法

研究了信道质量和子载波调制方式、联合最优编码率和最佳调制方式与信道容量、频谱利用率的关系．提出一个使系统得到较高的频谱效率和信道容量的自适应编码调制算法。其中,系统的有效数据传输效率是根据信号干扰噪声比进行评估的。论证了MIMO—OFDM系统自适应编码调制算法,分析它的信道容量以及频谱效率,并进行仿真实验,给出算法的性能结果。     

两种LDPC译码算法在OFDM系统应用中的改进

低密度校验码是一种基于稀疏校验矩阵的线性码,此码性能接近Shannon限,并具有简单有效的迭代译码算法。大部分文献提到的LDPC迭代译码算法均基于BPSK调制,相对于MQAM／MPSK调制,BPSK调制频谱利用率太低。在未来的3G＋高速无线通信中,最广泛运用的物理层技术OFDM必然采用频谱利用率较高的多电平调制。因此。如何把LDPC码用于多电平调制下的OFDM是一个关键,将目前较为简化的基于二进制调制的两种译码算法作改进,也即扩展,使之能够应用到基于多进制调制的OFDM系统中．     

基于对偶原理构造三相电流型多电平逆变器拓扑

受三相逆变器拓扑图非平面性的制约,很难直接运用对偶原理实现三相电压型逆变器拓扑与三相电流型逆变器拓扑之间的相互转换。为充分利用三相电压型多电平逆变器的研究成果以便构造三相电流型多电平逆变器拓扑,文章探讨了针对三相电压型二电平逆变器的两种拓扑图平面化处理方法,并分析了用于构造三相电流型多电平逆变器拓扑的可行性。在三相飞跨电容箝位电压型多电平逆变器拓扑基础上,通过增加一个独立电压源获得其平面化的等效电路,并以此作为原始拓扑利用对偶原理提出了一种新型的三相电流型多电平逆变器拓扑。采用多载波SPWM技术对该类逆变器的正确性与合理性进行了仿真验证。     

光盘的调制编码技术

一、引言信息技术的发展对光盘系统的存储容量和数据传速率提出了越来越高的要求,调制编码技术对提高光盘容量和数据传速率有很大的作用。因此,对调制编码技术的研究具有很大的意义。     

A power conversion system for PMSG-based WECS operating with fully-controlled current-source converters

We propose a new power conversion system for a permanent magnet synchronous generator （PMSG） based grid-connected wind energy conversion system （WECS） operating with fully-controlled back-to-back current-source converters. On the generator side, two independent current-source rectifiers （CSRs） with space-vector pulse width modulation （SVPWM） are employed to regulate and stabilize DC-link currents. Between DC-link and the electrical grid, a direct-type three-phase five-level current-source inverter （CSI） is inserted as a buffer to regulate real and reactive power fed to the grid and thus adjusts the grid side power-factor. We also present a current-based maximum power point tracking （MPPT） scheme, which helps the generator extract the maximum power through closed-loop regulation of the generator speed. By applying the multilevel modulation and control strategies to the grid-side five-level CSI, a multilevel output current waveform with less distortion is produced, and the bulk requirement of the output capacitor filter to eliminate the harmonic current is reduced. All the proposed concepts are verified by simulation models built in a PSIM environment.     

基于NLM策略的模块化多电平换流器研究

介绍了模块化多电平换流器的拓扑结构和工作机制,建立MMC数学模型,将电容均压控制算法运用到不同调制策略中以实现电容电压的稳定.在Matlab-Simulink及RT-LAB半实物仿真平台下搭建7电平的逆变器仿真模型,验证最近电平逼近调制的优势.结果表明最近电平逼近调制策略下换流器运行正常,输出波形质量高、谐波含量少、子模块电容电压波动小,在电平数较高的应用场合中具有较大的优势;并证明了Matlab-Simulink和RT-LAB仿真结果的一致性以及RT-LAB仿真效率的高效性.     

High-performance emulation of hierarchical structures on hypercube supercomputers

The problem or emulating multilevel structures on hypercube supercomputers is studied in the paper. The frequently used pyramid belongs to the class of multilevel structures. Several algorithms have been published in the literature for the emulation of pyramids by hypercubes. The paper extends the most important of these algorithms to make them applicable for multilevel structures. Results for the Connection Machine system CM-2 with 16,384 processors are presented and comparative analysis of the new algorithms is carried out. It is shown that very often higher performance can be obtained for multilevel structures other than the pyramid.     

基于循环路径的级联多电平逆变器母线电容波动均衡控制系统

传统控制级联多电平逆变器的频率偏差较大，性能不稳定。为此，设计一种级联多电平逆变器母线电容波动均衡控制系统。在调频盲卷积开发平台的基础上，协调母线电容大数据采集器及均衡控制器的连接方式，完成新型系统的硬件运行环境搭建。利用线性聚类控制程序中的目标节点，移植调频盲卷积的协议栈及规划大数据的循环路径，完成新型系统的软件运行环境搭建，实现基于循环路径的级联多电平逆变器母线电容波动均衡控制系统的搭建。对比试验结果表明，与传统系统相比，应用均衡控制系统后，时域、频域调频波仿真波形的控制有效性均能达到65%以上。     

Using FPGA real time model for novel 33-level switched-capacitor multilevel inverter for PMSM drive

This research work focuses to put forward a novel inverter topology of multilevel voltage output. The presented topology is devised by means of switched-capacitor technique (SCT) and switched-capacitor cells count is decided by output levels quantity. In the technique introduced, SCT inverter is in a flexible configuration and has the capability to self-balance the capacitor's voltage with no use of auxiliary circuits what so ever. The topologies presented decrease power switches quantity, isolated dc power supplies, diodes, size and scheme budget when contrasted to similar traditional topologies. For instance, by the involvement of introduced SCMLI structure only 18 power switches were required for 33 levels of output voltage, power switch of 18 Body Diodes and voltage source of 1 dc. This inverter's working principle and anticipated modulation policies are offered, and investigation of power lose is also done. Lastly, the introduced multilevel inverter is assessed for its performance along with the experimental outcomes of the thirty three-level inverter. For permanent magnet synchronous motor (PMSM), multilevel drive is presented in this paper using FPGA (Field Programmable Gate Array) having SiC inverter. For power semiconductor devices, suitable alternate of Silicon (Si) is SiC MOSFET because of its superior material characteristics. So, in order to have accurate operation and achieve high frequency, presented a inverter using SiC MOSFET.     

A Hint Frequency Based Approach to Enhancing the I/O Performance of Multilevel Cache Storage Systems

With the enormous and increasing user demand, I/O performance is one of the primary considerations to build a data center. Several new technologies in data centers, such as tiered storage, prompt the widespread usage of multilevel cache techniques. In these storage systems, the upper level storage typically serves as a cache for the lower level, which forms a distributed multilevel cache system. However, although many excellent multilevel cache algorithms have been proposed to improve the I/O performance, they still have potential to be enhanced by investigating the history information of hints. To address this challenge, in this paper, we propose a novel hint frequency based approach (HFA), to improve the overall multilevel cache performance of storage systems. The main idea of HFA is using hint frequencies (the total number of demotions/promotions by employing demote/promote hints) to efficiently explore the valuable history information of data blocks among multiple levels. HFA can be applied with several popular multilevel cache algorithms, such as Demote, Promote and Hint-K. Simulation results show that, compared with original multilevel cache algorithms such as Demote, Promote and Hint-K, HFA can improve the I/O performance by up to 20% under different I/O workloads.     

基于多级神经元的神经网络及其在分类中的应用

为了提高前向神经网络的分类能力,该文将多级神经元扩展使用到多层感知器的输出层和隐含层中,并提出了量子神经网络的学习算法。通过一个实际的分类问题实验验证了该方法的有效性。实验表明,无论输出层或隐含采用多级神经元,都可以带来分类能力的提高。而当输出层采用多级神经元时,还可以导致连接的减少和训练速度的加快。