小波包跳频通信系统的性能分析

介绍了将小波包调制（WPM）技术与跳频技术相结合的高效通信方式,即小波包跳频（WPM-FH）通信系统。利用特征函数法分析和推导了系统在高斯信道、瑞利衰落信道下的误码性能,给出了用户数,跳频点数及子信道数与系统性能之间的关系。理论分析和实验仿真表明,该系统不仅保持了小波包调制技术的优点,提高了频谱利用率,且具有较好的抗多径衰落和抗干扰能力,较好地改善了通信系统性能。同时,为了进一步改善多径衰落对系统性能的影响,在接收端加入了自适应均衡技术,实验结果表明系统性能得到了一定的提高。      

基于小波的变换域通信系统抗干扰性能研究

变换域通信系统通过信道估计在变换域设计信号波形避开干扰,它没有采用载波调制,而是用一个类似噪声的基函数进行信息调制。对高斯白噪声信道下的取不同门限值的基于小波的变换域通信系统与DSSS的抗干扰性能作了比较分析,仿真结果表明基于小波的变换域通信系统相比于DSSS在单音、多音、线性调频、10%部分带宽干扰下误码率平均改进约10dB,在70%部分带宽干扰下误码率平均改进约5dB,并对基于小波的变换域通信系统门限值的选取给出了建议。     

基于复小波包基函数调制的跳频多址通信系统

该文给出了一种生成复数小波包基函数的方法，提出了一种基于复小波包基函数调制的跳频多址通信系统的模型。该系统在多径衰落时变信道下采用判决反馈均衡器接收的性能与基于实小波包基函数调制的同类系统相比有明显改善，且通过采用空间分集接收，可显著提高系统的误码率性能。该系统易于支持多速率话音和数据业务，具有频谱利用率高，抗单音干扰能力较强和保密性高等优点。     

基于小波变换/小波包变换的多载波调制技术

小波/小波包在通信系统中的应用是近年来一个新的研究领域,而基于小波/小波包变换的多载波调制技术是其中一大研究热点。由于小波/小波包基函数具有良好的正交性与时频局域性等特点,基于小波/小波包变换的多载波调制技术,能够有效地提高通信系统性能。本文介绍了当前几种主要的基于小波/小波包变换的多载波调制方案,分析了这些方案的性能特点及发展趋势,并与其他方案进行了比较。     

多小波分形调制理论及其性能分析

该文提出正交多小波分形调制理论,计算了理论功率谱密度和二进数据下的误码率。多小波分形调制在各尺度能够提供更多的子频带,为更多用户服务,具有更高的频带利用率。仿真了其在加性高斯信道、Rayleigh信道和多径信道下的误码率,并利用多小波周期自相关函数分析了系统抗多径干扰能力,更进一步,根据多小波周期自相关函数的过零点数对多小波函数进行正交时移重叠,提高了系统数据速率。     

多径信道下MPSK信号的调制分类算法

针对多径信道中MPSK信号的调制分类问题,提出一种新的基于小波变换的分类算法.算法所用的小波变换相位信息特征对平坦衰落信道具有衰落不变性,对频率选择性衰落信道也具有很强的抗多径能力.与已有方法相比,新算法极大地降低了对多径信道冲激响应模式的限制,更具有普适性.理论分析和计算机仿真试验都证明了新分类算法的稳健性和有效性.     

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。     

甚低频信道小波调制方式研究

针对目前甚低频通信抗干扰能力,抗截获能力不理想问题,提出了甚低频通信系统的小波调制方式,该调制方式是将数据源经过逆小波变换发送信号,加入噪声后再经过小波变换在接收端接收,最后在接收端把接收信号同发送信号,得出其误码率。小波调制具有冗余度高、抗干扰性能强的特点。同时小波调制信号的时域波形类似于噪声,便于隐藏在噪声中传输,提高了系统的抗截获能力。与传统的频移键控(Frequency-shift Keying,FSK)调制比较,在3次联合估计下,小波调制方式的抗干扰能力优于传统的FSK调制方式。通过对甚低频通信系统进行仿真,验证了该算法的有效性。     

MFSK调制方式在极低速通信中的性能分析

MFSK调制方式是一种常用的恒包络调制方式,其非相干解调时具有较强的抗衰落能力以及抗频偏能力,尤其适合于极低速通信。针对极低速通信,重点仿真分析了不同阶数MFSK调制方式恒参信道下的误码性能,以及基于短时傅里叶变换的8FSK变参信道下的解调性能,最后给出了适合于极低速通信保障的FSK调制波形设计方案,通过验证说明了MFSK在极低速通信中具有工程应用价值。     

基于小波分组调制的多码多载波跳频通信系统分析

介绍了一种将多码调制、小波分组调制以及跳频技术相结合的高效通信方式——小波分组多码多载波跳频通信系统.推导了系统在Nakagami-m衰落信道下的误码性能,给出了用户数、小波分组类型、小波分组滤波器长度以及跳频点数与系统性能之间的关系.理论分析与数值计算表明:增加小波分组滤波器长度可以有效降低系统误码率,但不同小波分组类型对系统性能的影响不大;跳频技术的引入不仅增加了系统的安全性,同时也可有效降低多址干扰对系统性能的影响,提高了系统的可靠性.     

Performance analysis of fractal modulation transmission over fast-fading wireless channels

Fractal modulation schemes have been under investigation for signal transmission over time-varying channels because of their advantages in data transmission at different frequency bands. This also allows efficient reception when channel conditions are varying by selecting the optimal frequency/time resolution based on the current channel condition. We present a performance analysis of fractal modulation transmission over Rician fast-fading channels in the presence of AWGN. A quadrature transmission scheme is simulated and compared, in terms of error robustness, to a QAM transmission system. Other papers analysing fractal modulation system performance do not consider time-varying channels, which are important as they represent the main configuration for communication systems based on this modulation technique. The novelty of our paper lies in the comparison of a fractal modulation system to a QAM one (core of the OFDM modulation technology, extensively used in broadcasting) using a testbed simulation environment where additive noise and fast fading are considered as typical error sources for transmission over wireless channels. Several wavelet families for a fractal modulation scheme have been considered and performance for each one measured; results reported show the effectiveness of the fractal modulation paradigm and confirm its effective utilization in data broadcasting.     

基于小波和分形理论的调制信号特征提取方法研究

本文针对通信信号这种非平稳的、信噪比(SNR)变化范围较大的信号,应用小波分析和分形理论,提出了有效的特征提取方法,所提取的分形特征包含了区别不同调制类型所需的幅度、频率和相位等主要信息。同时这种特征具有较好的抗干扰特性,基于这种特征的分类器的设计简单、高效。计算机模拟结果表明此方法的有效性。     

Emerging applications of multirate signal processing and waveletsin digital communications

Multirate systems and filter banks have traditionally played an important role in source coding and compression for contemporary communication applications, and many of the key design issues in such applications have been extensively explored. We review developments on the comparatively less explored role of multirate filter banks and wavelets in channel coding and modulation for some important classes of channels. Some representative examples of emerging potential applications are described. One involves the use of highly dispersive, broadband multirate systems for wireless multiuser communication (spread spectrum CDMA) in the presence of fading due to time-varying multipath. Another is the wavelet-based diversity strategy referred to as “fractal modulation” for use with unpredictable communication links and in broadcast applications with user-selectable quality of service. A final example involves multitone (multicarrier) modulation systems based on multirate filter banks and fast lapped transforms for use on channels subject to severe intersymbol and narrowband interference. Collectively, these constitute intriguing, interrelated paradigms within an increasingly broad and active area of research     

基于粒子群支持向量机的通信信号调制识别算法

为了解决大部分通信信号调制识别方法计算量大和分类器训练困难问题,提出一种基于粒子群(PSO)支持向量机(SVM)的调制识别方法.将小波理论与调制信号的瞬时特征、高阶累积量以及分形理论相结合,得到一种混合模式特征向量,并利用粒子群支持向量机对2ASK,4ASK,2PSK,4PSK,8PSK,2FSK,4FSK,8FSK,...     

改进型Sierpinski分形微带天线仿真

将HFSS高频仿真软件对不同张角下的二阶Sierpinski分形天线进行仿真,得到不同情况下的回波损耗参数和方向图。Sierpinski分形天线具有多频段的特性,由其自相似分形结构决定。在一定角度下的二阶Sierpinski分形天线具有双频特性,可以广泛应用于卫星通信和移动通信。     

Communication emitter individual identification based on 3D-Hibert energy spectrum and multi-scale fractal features

For communication emitter identification,a novel method based on Hilbert-Huang transform (HHT) and multi-scale fractal features was proposed.First,the time frequency energy spectrum was derived via HHT,which was called a complicated curved surface in the three-dimension space,namely,3D-Hilbert energy spectrum.Then,the differential box dimension and the multi-fractal dimension was extracted to compose the feature vector under multi-scale segmentation using fractal theory.Finally,communication emitter individual identification was obtained using the two dimensions of features above and the support vector machine (SVM).Moreover,the novel method was compared with two existing methods to identify simulated and actual signals with different and the same modulation modes,respectively.Results show that the identification rate of the novel method is higher than that of the two other methods.The features extracted by the novel method have high stability,sufficiency,and identifiability,also outweigh the negative effects of the change of signal-to-noise ratio and the number of training samples and emitters.     

基于分数布朗特征的低分辨雷达目标分类

低分辨雷达目标的JEM效应不仅体现在对目标回波的频率调制上,还体现在幅度调制上,以上2种调试特征是互补的关系,综合运用2种调制特征将会改善低分辨雷达对飞机目标的分类与识别能力。分数布朗运动模型是一种可以用来描述自然界中随机分形的统计模型,文中提出将分数布朗运动模型用于反映回波幅度的不规则程度或起伏程度,以及回波幅度起伏的快慢,分别提取回波时域和频域的分数布朗分形维,再采用支持向量机分类器进行分类,很好地将直升机与民航机2类目标区分开来。实测数据表明,综合分类正确率大于85!。     

高阶累积量和分形理论在信号调制识别中的应用研究

提出了将信号高阶累积量和分形盒维数相结合的特征提取方法。信号高阶累积量特征具有良好的抗噪性能,被广泛应用于调制识别。2ASK和BPSK的高阶累积量、以及2FSK,4FSK,8FSK的高阶累积量相等,使得只提取信号高阶累积量不足以区分信号。针对这一问题,引入信号的分形盒维数,提取信号的高阶累积量和分形盒维数构成联合特征参数,构建级联神经网络分类器,对信号进一步进行分类。对2ASK, 4ASK, BPSK, 4PSK, 2FSK, 4FSK, 16QAM七种信号进行了仿真,结果表明,该方法提取的特征参数计算复杂度低,具有较好的抗噪性能。在信噪比不低于5dB、测试样本数不少于200的条件下,正确识别率达到了85%以上。      

Transmission Performance Simulation Study Evaluation for High Speed Radio Over Fiber Communication Systems

Radio over fiber communication system technology modulation techniques are presented in this study in order to enhance the performance behavior of optical fiber communication systems. The proposed modulation techniques used to meet this aim mainly consist from a mixture of traditional modulation technologies. The proposed modulation technologies include merging modulation techniques such as pulse amplitude frequency modulation, quadrature amplitude frequency modulation, differential phase shift keying amplitude modulation, offset quadrature phase shift keying amplitude modulation and frequency phase modulation are applied on different optical communication system models. The different types of modulation techniques are illustrated and discriminated in current research paper that provides measured quantities details that namely received power, maximum Q-factor and minimum bit error rate regarding to simulation results. Optiwave Simulation Version 13 software is the basic tool which is used to study proposed models.

     

紫外光通信中调制技术研究

紫外光通信是无线光通信的一种,它是利用紫外光在大气中的散射来进行信息传输的一种新型通信模式。然而,紫外光通信的调制解调技术是整个系统的关键难点。在详细阐述紫外光单散射信道模型的基础上,分析了开关键控(OOK)和脉冲位置调制(PPM)的调制结构,并在紫外光单散射信道模型中对上述两种调制技术进行了比较。结果表明:PPM调制技术在误码率性能及信息传输速率上都要优于OOK调制技术,并且随着PPM调制阶数的增加,这种优势会更加的明显。