Single tone jamming elimination scheme of multicarrier spread spectrum system

The proposed scheme is based on Discrete Fourier Transform (DFT) domain processing. The key technology of this scheme is jamming parameters‘ accurate estimation and jamming reconstruction. Compared with the “threshold exciser”scheme.the proposed scheme can eliminate more jamming energy on the whole frequency band with the minimum loss of useful signal energy. As shown in the research and simulation, the proposed scheme is much better than the “threshold exciser” scheme, especially in the case of high power jamming whereas the “threshold exciser” scheme might be invalid.     

基于频率调制的多载波Chirp信号雷达通信一体化研究

为了减少电子战平台的体积和电磁干扰,一种有效的途径就是实现雷达与通信的一体化.该文针对雷达通信一体化信号设计中存在的不兼容和互干扰问题,根据信号能量共享的原则,提出了基于频分准正交多载波Chirp 信号的雷达通信一体化波形及其相应的系统实现方法.并采用宽带模糊函数对多载波一体化信号特性进行了详细分析,进一步研究了一体化信号的处理过程以及其系统性能.在均衡子载波准正交性和通信频谱效率下,通过理论分析和仿真结果表明在多载波频谱重叠率为20％的情况下,一体化信号能够满足雷达的常规探测,并且具有较低的误码特性.     

最佳相位的多载波QAM

对FPGA实现多载波QAM进行了研究,提出最佳相位的多载波调制算法以提高各路子载波的输出功率,并设计出高精度、低复杂度的DDFS以实现符合最佳相位关系的子载波合成.仿真及测量结果表明,最佳相位的多载波QAM具有更优的输出信号质量和更少的逻辑资源消耗.     

Performance analysis of wavelet packet multirate multicarrier multicode CDMA for wireless multimedia communications

Different kinds of Multirate (MR) communication systems, such as multicode (MCD) scheme and variable spreading length (VSL) schemes, have been considered for accommodating information sources with different data rates in Multicarrier code-division multiple access (MC-CDMA). In this paper, we propose the use of MCD scheme for MR services in MC/MCD-CDMA system that employs wavelet packets (WPs) as subcarriers. The bit error rate (BER) performance for the system was investigated by means of analytical methods and numerical results in a slow fading frequency selective Nakagami channel. The performance analysis includes the effects of diversity techniques, channel intensity profile, diversity order and fading parameter. Also, the effects of different service rates and number of users in each service rate were investigated. The performance of the system was compared to that of MC/MCD-CDMA based on sinusoidal carrier. Results reveal that BER performance is proportional to the service rate and our proposed system outperform the other system.     

基于小波包的多载波技术

首先比较基于3种小波调制的多载波技术的优劣，波包调制（WPM）无论在多速率分配还是在抗干扰方面都要优于多尺度调制（MSM）和M频带小波调制（MWM）。然后，引入双正交小波作为了载波的基函数，仿真它在AWGN信道和平坦瑞利落信道下的性能并对结果进行分析，引入双正交小波是系统实用化的关键一步。     

带有天线阵列的多载波DS-CDMA系统的性能分析

本论文提出了一个多载波DS-CDMA的下行空时接收机结构并且分析了它的性能，对于每一个载波，首先进行最优波束形成。再经过传统的RAKE合并，并比较了多天线接收机和单天线的接收机的性能。仿真结果表明，使用天线阵列，多径干扰和多用户干扰可以被有效的抑制，因而其系统容量远远高于单天线系统。     

On the performance of a stochastic gradient-based decorrelation algorithm for multiuser multicarrier CDMA

A stochastic gradient-based decorrelation is suggested for separation of an unknown linear mixture of signals. It is shown that while the decorrelation algorithm is similar in cost to the LMS algorithm, its rate of convergence is significantly faster making it more attractive for signal separation. Analysis of the decorrelator algorithm shows that the faster speed of convergence is a consequence of the eigenvalues spread associated with the decorrelation problem, which is smaller than the spread associated with the corresponding mean square problem. Operation of the algorithm is illustrated as an adaptive multiuser detector in a multiple carrier CDMA system.This work was supported in part by a grant from ROME Air Development Center, AFSC, Griffiss Air Force Base, NY, under contract F30602-93-C-0118.     

Saw chirp filter technology for satellite on-board processing applications

Market growth in the area of thin route satellite communications services has led to consideration of non-traditional system architectures requiring sophisticated on-board processing functions. Surface acoustic wave (SAW) technology exists today which can provide implementation of key on-board processing subsystems by using multicarrier demodulators. This paper presents a review of this signal processing technology, along with a brief review of dispersive SAW device technology as applied to the implementation of multicarrier demodulators for on-board signal processing.     

A Time-Frequency Well-localized Pulse for Multiple Carrier Transmission

In multicarrier transmission schemes, the essential requirement on the elementary pulse or envelope function is the orthogonality with its time-frequency shifted versions. However, the time and frequency dispersion of the mobile radio channel leads to the loss of orthogonality which produces intersymbol interference (ISI) and interchannel interference (ICI). Therefore, another requirement on the elementary pulse has to be imposed: the good localization in time and frequency. Based on the characteristics of the mobile radio channel, we design a new pulse to minimize ICI and ISI.     

基于优化多带复小波的多载波CDMA及反向链路性能

在分析多载波码分多址的原理基础上,利用优化生成的多带复小波,提出了一种基于优化多带复小波的多载波CDMA系统反向链路模型,并采用基于多天线的空间分集合并(SDC)技术进一步完善所提系统.该系统可利用优化多带复小波的优良特性来避免通常多载波CDMA由于插入循环前缀所带来的频谱效率的下降,在此基础上我们研究了所提系统采用空间分集合并技术时在瑞利衰落信道下的反向链路性能;给出相应的误比特率分析.理论分析和仿真结果表明采用基于最大比合并的SDC技术可显著提高所提系统抗空间衰落和各种干扰的能力,而且基于SDC技术的所提系统要好于同样基于SDC技术的通常多载波CDMA系统和基于实小波包的多载波CDMA系统.