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。     

部分响应连续相位调制信号在卫星移动信道中的误比特率性能分析

该文给出了组合卫星移动信道中采用差分相位检测(DPD)和最大比组合(MRC)的部分响应连续相位调制(PRCPM)信号的误比特率计算公式,并给出了有关数值计算结果。     

基于EXIT图的串行级联连续相位调制的外码设计

串行级联连续相位调制（SCCPM）系统可以大大地提高系统的功率利用率,这使得它在无线通信领域中得到广泛应用。给出了基于外信息传输（EXIT）图的SCCPM系统的收敛性能分析及外码设计,在CPM参数给定的情况下,通过EX IT图可以找出与该调制最匹配的外码。仿真结果表明：对于同一种调制不同外码的SCCPM系统,收敛的门限不同;收敛的门限越低,性能越好。     

自适应Turbo-QAM编码调制及其在 平坦Nakagami衰落信道的吞吐量性能

本文提出了一种通用的自适应编码调制系统吞吐量性能分析方法.基于各固定编码调制方式的误码率(BER)性能,使每种编码调制方案对应于一个信道平均信噪比(SNR)范围,再应用拉格朗日函数法得到使自适应编码调制系统吞吐量性能最大的信噪比转换门限,可得到系统的平均吞吐量性能.数值分析结果表明,相对于自适应M进制正交幅度调制(MQAM),自适应Turbo编码MQAM系统吞吐量性能有显著提高,并且该性能受瞬时误码率要求的影响较小.Nakagami信道中,在相同平均信道信噪比条件下,随着m的增大,系统吞吐量性能提高缓慢.     

基于维特比算法的连续相位调制信号解调研究

文中对连续相位调制信号的解调算法作了相关研究。阐述了如何在信号状态网格图的基础上应用维特比算法对信号进行解调,并分析了最大似然序列检测和基于判决反馈的减少状态序列检测这两种序列检测方法,仿真结果表明,基于判决反馈的减少状态序列检测能在几乎不损失误码性能的前提下大大减少解调运算量。     

连续相位调制系统盲速率接收技术

无线通信系统中速率自适应技术可适应无线信道条件变化,提高有效传输速率,是提升信道容量和无线传输灵活性的重要手段。针对传统通信系统速率自适应技术协议开销大、时延大、资源消耗大、速率切换不平滑的问题,提出了分段相位匹配接收的方式实现连续相位系统盲速率自适应接收,发送端可单方改变发送速率,同时在接收端实现速率盲检测。理论和仿真结果表明,连续相位调制系统盲速率接收技术具有时延低、资源消耗小且速率切换平滑的优势,特别适用于战术通信/数据链系统,工程实用性较强。     

基于模糊熵的连续相位调制识别算法

针对不同调制参数的多调制指数(Multi-h)连续相位调制(CPM)信号间识别问题,提出一种基于模糊熵的调制识别算法。模糊熵理论摒弃了近似熵中距离与数目的二值化相似性判断,提出利用隶属度函数判断相似性,可以更精确地描述时间序列的复杂度。算法分离接收信号的同相和正交分量并分别求其模糊熵,将求取的模糊熵作为分类特征送入支持向量机(SVM)进行分类,完成不同Multi-h CPM信号的调制识别。仿真实验结果表明,该算法在信噪比大于6 dB时,对不同调制指数集合的全响应矩形成形Multi-h CPM信号可以实现100%识别,且仅需较少符号数即可实现调制识别。     

基于椭圆球面波信号的连续相位调制及其频谱性能分析

椭圆球面波信号（PSWF）是时频域最佳能量聚集性信号,探索性地将PSWF信号应用于连续相位调制（CPM）技术,对基于椭圆球面波信号的CPM调制信号产生过程进行了描述;给出了采用自相关函数法对基于PSWF的CPM调制信号功率谱密度计算方法;结合数值计算、分析对比了最小频移键控、正弦频移键控、高斯最小频移键控以及基于高斯函数的CPM调制信号功率谱密度及其信号占用带宽等特性。数值计算结果表明椭圆球面波信号相比矩形脉冲、升余弦脉冲、高斯脉冲及（类）高斯脉冲作为CPM的基带调频信号,可以获得频谱性能、能量聚集性较好的CPM信号。     

连续相位调制信号的二阶循环平稳特性分析

连续相位调制(CPM)信号以其恒包络和优良的频谱特性在现代卫星通信和移动通信中越来越受到人们的重视,然而这一大类调制信号的循环平稳特性却较少有人关注。该文根据连续相位调制信号在不同调制指数下的基带循环谱,推导了其相应带通循环谱的表达式, 并对这些表达式的详细分析,得出了不同调制指数情况下循环频率与载频、码元宽度和峰值频偏之间的关系式。仿真实验证明这些结论是正确的。     

基于记忆因子的连续相位调制信号最大似然调制识别

为解决有记忆非线性的连续相位调制(CPM)信号调制方式识别精度低的问题,该文提出一种基于记忆因子的CPM信号最大似然调制识别新方法。该方法定义具有时齐马尔科夫性的映射符号,通过计算其后验概率构造记忆因子,进一步结合CPM分解和EM算法,推导出时间可分离,信道参数可估计的CPM信号似然函数。该调制识别方法所需符号数目少,适用信噪比范围广,识别CPM信号种类多且精度高,对相位误差鲁棒性强。仿真结果证明,当符号数目为200,信噪比为0 dB,相位误差任意时,该方法对8种CPM信号的识别率可达95%以上。     

基于循环谱的改进型二进制CPM信号符号速率估计

针对通信对抗领域中二进制连续相位调制(Continuous Phase Modulation,CPM)信号的符号速率盲估计问题,提出了一种基于循环谱和内插法的符号速率估计方法。该方法利用信号带宽对符号速率进行初步估计,以确定循环谱的计算区间和谱峰的搜索区间;接着采用一种新形式的基于单侧频移的离散频域平滑法来计算循环相关谱,并结合内插法对谱峰搜索结果进行校正,进一步提高符号速率的估计精度。理论分析结果表明,该方法在相同条件下可将栅栏效应的缝隙间隔缩小至原来的1/2。计算机仿真结果表明,在信噪比大于-3 dB时,同其他两种已有算法相比,该方法符号速率估计的归一化均方误差至少下降10-1。     

Analysis of capacity and coverage region for Rayleigh fading MIMO relay channel

In this paper, we consider Rayleigh fading MIMO relay channel with channel state information at the receivers. First, we extend the previously obtained results for the ergodic capacity of uncorrelated and semi‐correlated MIMO channels and derive closed‐form expressions for the capacity bounds of MIMO relay channel. Next, we study this channel from a new point of view, maximizing coverage region for a desired transmission rate, and investigate the optimal relay location in the sense of maximizing coverage region. However, in order to overcome the mathematical complexity in desired transmission rate analysis, because of the randomness of the multiple antenna channel matrices, we evaluate this rate by using an existing exact formula and also by an approximation we find in the high signal‐to‐noise ratio regime. Numerical results show a perfect match between the Monte Carlo simulations and the obtained analytical closed‐form expressions and also confirm the effectiveness of our approach in cooperative vehicular communication for determining optimal relay location at which the coverage region is maximum. Copyright © 2013 John Wiley & Sons, Ltd.     

分布式空频编码协同通信系统中基于导频辅助的频域信道估计算法

针对频率选择性衰落信道下的分布式空频编码协同通信系统,提出了基于导频辅助的各种频域信道估计算法,包括最小二乘、线性最小均方误差、低阶近似线性最小均方误差算法,并给出了相应的均方误差性能表达式.理论分析和仿真结果表明本文提出的信道估计算法在协同通信系统中具有很高的实用性和精确度.     

平坦慢衰落信道下基于HOS的PSK调制盲信道估计

提出一种基于符号高阶统计量（HOS, high-order statistics）的MPSK调制信道衰落系数盲估计算法。针对平坦慢衰落信道模型,首先分析了MPSK调制符号高阶统计量特征,证明了MPSK调制符号的M次方符号的值是唯一的,而当1≤M′相似文献   

GMSK信号在衰落信道中的频偏盲估计

对GMSK信号作线性近似，在此基础上提出衰落信道中估计GMSK信号频偏参数的算法，它适合于软件无线电接收机。该算法基于GMSK信号近似后二阶统计量的周期平稳特性，不需要前导字，不占用信号传输带宽，开环结构，计算量较小。在matlab6．0平台上对算法的估计性能进行了Monte Carlo仿真，并与其它算法作了比较，结果表明本文提出的算法是可行的。     

基于相位调制技术的可见光通信系统码间干扰识别研究

室内可见光通信系统的传输信道易受到多径效应产生严重码间干扰,降低通信质量,为此提出了相位调制技术的可见光通信系统码间干扰识别方法.通过构建可见光通信系统信道模型,针对信道光源之间在时域和频域上形成的重叠光信号在多径效应作用下,产生的码间干扰,利用位调制技术对系统信道展开均衡设计,并依照多径扩展统计限定码元速率均值,实现...     

Power allocation for AF relaying aided spatial modulation in the presence of imperfect channel state information

By combining Spatial modulation (SM) with cooperative communication, the diversity gain brought by cooperative relaying and high rate of SM can be obtained. In this paper, considering amplify-and-forward (AF) protocol, the performance of cooperative SM system with imperfect channel state information (CSI) over Rayleigh channel is analyzed. According to the performance analysis, the moment generating functions (MGFs) of effective signal-to-noise ratios (SNRs) are derived. With the MGFs, closed-form expressions of the error probability of antenna index detection and the error probability of symbol detection for imperfect CSI are achieved. Thereby, the approximate overall average bit error ratio (BER) is obtained, and these theoretical expressions include those under perfect CSI as special cases. Besides, the asymptotically approximate BER for large SNR is also derived. Based on this, a suboptimal power allocation (PA) scheme is developed, and the corresponding PA coefficients are attained by minimizing the asymptotical BER. As a result, closed-form PA can be attained for the system with multiple receive antennas. Computer simulations show that the theoretical BERs are close to the corresponding simulated results, which illustrates the effectiveness of the derived theoretical expressions. Compared with the conventional equal PA scheme, the proposed PA scheme enhances the BER performance efficiently.     

Performance analysis of cooperative diversity for two-way multi-relay system with channel estimation error

In this work, we consider an amplify-and-forward two-way multi-relay system for wireless communication and investigate the effect of channel estimation error on the error rate performance. With the derivation of effective signal-to-noise ratio at the transceiver and its probability density function, we can get approximate expression for average bit error rate. Simulation results are performed to verify the analytical results.     

协同通信系统中差分调制在Rayleigh衰落信道中的误码性能分析

根据源-中继-目的节点链路的等效信噪比模型,推导了检测传送和选择检测传送两种协议下目的节点瞬时信噪比的概率密度函数和特征函数,基于此推导了协同DMPSK调制近似误符号率的闭合表达式.推导结果不含积分表达式,方便计算,为系统设计和功率分配提供了理论基础.最后通过仿真验证了推导结果的正确性.     

Maximizing the data transmission rate of a cooperative relay system in an underwater acoustic channel

In this paper, we investigate the problem of maximizing the data transmission rate of a cooperative relay system in an underwater acoustic communication channel. With amplify‐and‐forward relaying and adaptive source transmission, we present optimal transmit signal power adaptation policies that maximize the data transmission rate, considering both frequency and time domains. The analysis takes into account a physical model of acoustic path loss and ambient noise power spectral density. Typical characteristics of underwater channel such as frequency‐dependent fading and time variations are also considered. Capacity bounds for channel state information (CSI) only at the receiver and CSI at both transmitter and receiver are presented. To maximize the data rate, we use the notion of an optimal bandwidth which corresponds to efficient allocation of signal power across the transmission bandwidth. Under the constraint of an average transmit power, the optimal transmit power adaptation policy is found to be ‘water‐pouring’ in frequency‐time domain, while the transmit power adaptation policy with a total power constraint is ‘water‐pouring’ in frequency domain. Results show that both frequency domain and frequency‐time domain power adaptation schemes provide much greater improvement in average data rate over that of the constant power case. Copyright © 2011 John Wiley & Sons, Ltd.