CPM编码调制发展前景

连续相位调制（CPM）技术是一类恒包络的数字调制技术,CPM信号的恒包络这一特性使它们对于非线性信道和衰落信道具有很强的抵抗性．特别适用于卫星通信和移动无线通信信道。与PSK调制方式相比,CPM调制系统不仅能够提供较高的频谱效率,而且具有一定的编码增益,这是因为接收器可以利用相位成型滤波器引入的记忆特性。CPM调制系统可以分解为一个连续相位编码器（CPE）和一个无记忆调制器（MM）的级联,因此出现了多种卷积码与CPM结合的调制方案,例如串行级联连续相位调制、基于环的串行级联连续相位调制、实用的连续相位调制、卷积编码器与扩展信道编码器的串行级联,等等。其中,基于环的串行级联连续相位调制具有很好的性能,在交织增益、自由距离、误码平层和收敛门限可能成为未来连续相位编码调制系统的发展方向。     

Rayleigh衰落信道中多级编码调制的不等错误保护

本文研究了Rayleigh衰落信道中以信道容量规则为设计准则的多级编码调制系统的不等错误保护性能的实现及其改进.在详细分析了多级编码调制的不等错误保护原理的基础上,设计了一种针对8ASK调制的非均匀信号星座.理论分析与计算机仿真均表明,非均匀信号星座的设计能够增强多级编码调制系统的不等错误保护能力,在不展宽频带的前提下有效地提高Rayleigh衰落环境下数字通信系统的传输质量.     

高速移动Rayleigh信道下的相位调制OFDM系统

高速移动的Rayleigh信道会使得传输信号的频谱发生Doppler扩展。本文对存在Doppler扩展的OFDM系统进行子载波干扰的理论分析，并针对高速Rayleigh信道对误码率造成的影响进行了基带仿真。仿真结果证实，相位调制OFDM系统在存在Doppler扩展的Rayleigh信道条件下的性能可以用单载波相位调制系统在慢衰落条件下的误码率理论值来近似；即使在移动台高速移动的情况下，实际中的Doppler扩展并不会使相位调制OFDM系统的误码率出现地板效应，所以相位调制OFDM系统比较适合高速移动的Ravleigh信道条件下的高速数据传输。     

在Rayleigh衰落信道中结合迭代多级译码和交织技术的多级编码调制方案

在基于“信道容量规则”的多级编码系统中采用交织技术与迭代多级译码相结合的方法，进一步提高其在Rayle曲衰落信道中的系统性能。     

采用预判决信息的LDPC码编码调制方案性能研究

低密度奇偶校验(LDPC)码是Turbo码以外另一种性能接近香农限的好码.本文将LDPC码与比特交织编码调制(BICM)相结合,首先给出了在不使用传统解调器与译码器之间迭代的情况下8PSK调制方案在AWGN信道和Rayleigh衰落信道中的性能(简称为无迭代方案).然后提出了一种新的接收端解决方案:首先对接收符号进行预判决,判决信息被用来调整解调器,从而在一定程度上弥补了不使用解调器与译码器之间迭代所造成的性能损失,并且相对于无迭代方案接收端复杂度几乎没有变化,但性能却有所提高.这说明原有比特度量产生方法并不是最佳的,该文使用预判决信息的方案给出了一个改善的思路.通过仿真结果可以得到结论:使用本文所提出的方案在AWGN信道和Rayleigh衰落信道中都可以在不增加复杂度的情况下提高性能.     

基于平均频谱效率的自适应编码调制优化设计

自适应编码调制(ACM)技术能够很好地改善无线信道的频谱利用率.文中提出了一种基于平均频谱效率的自适应调制编码系统的优化方案,运用该方案,ACM系统需要数量很少的优化编码,使吞吐量接近于AWGN信道容量.     

自适应格状编码调制

介绍了多维格状编码调制（MTCM）及其自适应格状编码调制的设计方法,并模拟了固定码率TCM与自适应TCM在衰落信道中的误码性能。     

相位调制的多用户OFDM-FH通信系统性能分析

 本文研究一种高效的通信方式,即相位调制的OFDM-FH通信系统。为了提高衰落信道下系统误码率性能,接收端采用最大比合并的分集接收技术。利用特征函数方法,推导该系统在加性高斯白噪声信道和瑞利衰落信道时系统误码率性能。给出误比特率与跳频频点数 ,OFDM子载波数N和用户数 等参数之间的关系。理论分析和仿真实验结果表明,在相同参数条件下,基于相位键控调制的OFDM-FH多址接入系统与其它OFDM-FH通信系统比较,具有系统频带宽度占用少、误比特率低等优势。     

衰落信道下Turbo网格编码调制在图像传输中的性能研究

基于Turbo码和网格编码调制的特点,该文分析了TTCM的具体编译码方法,并分析比较了TTCM在8PSK调制下结合两种典型映射方案UP(Ungerboeck Partitioning),BP(BlockPartitioning)在Rayleigh信道中用于静态图像传输时的性能,给出了计算机仿真结果和评价图像传输质量的峰值信噪比(PSNR).     

基于TCM的LDPC高效编码调制系统性能

为了缓解频带有效性与功率有效性的矛盾,提出了将低密度校验码与网格编码调制相结合的系统方案,其中在网格编码调制中采用了递归系统卷积码进行编码,以实现基于对数似然比的软译码方法,以此构造低密度校验码与网格编码调制相结合的编译码系统。分析了该系统在加性高斯白噪声干扰和瑞利信道下的性能和信道信息对于系统性能的影响。仿真结果表明,该系统能够有效地在频谱利用率和码字性能之间达到折衷,可以在一定程度上缓解矛盾。     

Maximum-likelihood Block Detection for CPM Signals

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On the bit error probability of QAM modulation

This paper presents some closed-form bit error probability expressions for coherent demodulation of both Gray coded and differentially decoded Gray coded QAM modulations in nonfading and frequency nonselective Rayleigh fading channels. These results demonstrate that as QAM constellation sizes get larger the BEP degradation due to differential encoding and decoding becomes negligible.     

Optimization of an OFDM Rayleigh fading system

An OFDM cellular system operating in a Rayleigh fading environment is described and its spectral efficiency is estimated in terms of the theoretically achievable average channel capacity (in the Shannon sense) per user. The analysis covers the operation over a downlink cellular time‐varying link and leads to a simple novel closed‐form expression for the optimal number of individual OFDM subcarriers, based on the maximization of the achieved spectral efficiency. Copyright © 2006 John Wiley & Sons, Ltd.     

CPM信号的微积分解调算法分析

连续相位调制（Continuous Phase Modulation）是一类包络恒定且相位连续的调制方式,具有很高的带宽和功率利用率,优良的包络和相位特性使其适用于空间通信。在分析CPM信号的模型基础上,研究了基于微积分的代数运算方法来完成对CPM信号的解调,该方法几乎不需要任何的先验信息和参数信息就能实现信号的盲解调,目的能够降低接收机的复杂度,是一种优秀的CPM信号解调方式。     

利用限幅器改善Rayleigh衰落信道中Turbo乘积编码PSAM系统的性能

该文研究了 Rayleigh衰落信道中 Turbo乘积编码辅助符号调制(TPC-PSAM)系统的性能并提出一种利用软信息限幅来改善的 TPC-PSAM性能的新方法,通过对不同的 Rayleigh衰落信道中 TPC-PSAM系统的性能仿真,结果表明在 10-4误比特率下,这种新方法对 TPC-PSAM的性能有5～8dB的改善。     

Optimal SIR for an hybrid cellular DS/SFH CDMA system

A hybrid direct‐sequence/slow frequency hopping code‐division multiple‐access (DS/SFH CDMA) system operating in a Rayleigh fading environment is described and its spectral efficiency is estimated in terms of the theoretically achievable average channel capacity (in the sense of information theory) per user. The analysis covers the operation over a broadcast cellular time‐varying link and leads to a simple novel closed‐form expression for the optimal average spread signal‐to‐interference power ratio (SIR) received by each user based on the maximization of the achieved spectral efficiency. Copyright © 2007 John Wiley & Sons, Ltd.     

微波通信中连续相位调制的非相干检测算法

提出了一种适合微波通信传输使用的多进制连续相位信号的频偏校正2码元差分检测算法.该算法利用2码元差分信息提取分支度量,进行维特比检测.同时利用判决反馈对微波通信中的载波频偏进行校正.通过对接收信号的复指数分解,分支度量的计算量得到了很大的简化.仿真结果表明,该算法的性能优于1码元差分检测.当接收信号存在载波频偏时,该算法仍然具有较好的检测性能.     

A ZCZ‐CDMA system with BFSK modulation

A quasi‐timing synchronous code division multiple access (CDMA) system called ZCZ‐CDMA, which uses a set of sequences with a zero‐correlation zone called ZCZ code as a spreading code, is useful for short‐range wireless communications because of its excellent properties such as co‐channel interference‐free performance, simplified hardware design, and low transmit power as well as fast frame synchronization capability. In this paper, a ZCZ‐CDMA system with binary frequency‐shift keying (BFSK) modulation called BFSK‐ZCZ‐CDMA is proposed. This system is characterized by using a pair of balanced ZCZ codes for spreading and transmitting the two spread components over the respective keying carrier frequencies. Its bit error rate performance, compared with those of existing BPSK‐ZCZ‐CDMA, ASK‐ZCZ‐CDMA, and CDMA systems using the other spreading codes, is evaluated in theory and simulation. The bit error rate performance of the three ZCZ‐CDMA systems over additive white Gaussian noise and Rayleigh fading channels are formulated. It is proved that BFSK‐ZCZ‐CDMA is much more robust in anti‐fading performance and low transmit power in such an environment that fading distributions on the keying frequencies are independent mutually. Fading versus frequency characteristics are also investigated. Copyright © 2012 John Wiley & Sons, Ltd.     

Average channel capacity for Rayleigh fading spread spectrum MIMO systems

In this paper, a novel approach to the problem of estimating the average channel capacity (in the Shannon sense) assigned to each user of a spread spectrum (SS) multiple‐input multiple‐output (MIMO) system operating in a Rayleigh fading environment, is presented. The analysis leads to a closed‐form expression which fully conforms to the upper bound of the channel capacity value of a non‐fading AWGN channel when the transmitted signal bandwidth tends to infinity proving the validity of the described analysis. Copyright © 2006 John Wiley & Sons, Ltd.