多入多出超宽带信道建模与仿真

在IEEE802.15.3a超宽带(UWB)信道模型的基础上,利用平行波近似理论,根据天线阵列的结构和多径的传播方向,提出了一种新的多入多出(MIMO)超宽带统计信道模型。各个子信道的多径幅度、相位和波达时间被引入了信道模型。子信道的信道特征参数满足超宽带信道的特征。实际测量的统计结果表明,波离角(AOD)和波达角(AOA)服从拉普拉斯分布。空间相关性、信道容量和天线间距、角度扩展之间的关系表明,该信道模型满足实际的空间相关统计特性。该模型对MIMOUWB系统的研究具有重要意义。     

基于3种典型天线阵列的3D MIMO Kronecker信道建模

在传统的二维多输入多输出(two dimensional multiple input multiple output, 2D MIMO)信道模型基础上,引入仰角因子研究三维多输入多输出(three dimensional MIMO, 3D MIMO)信道模型。推导出基于均匀线形阵列(uniform linear array, ULA)、均匀圆形阵列(uniform circular array, UCA)和均匀矩形阵列(uniform rectangle array, URA)的3D MIMO Kronecker信道模型,并进一步讨论了信号离开角和到达角分别服从高斯分布、拉普拉斯分布和VMF(Von Mises Fisher)分布时的信道模型。仿真结果表明,当信号空间角度服从VMF分布时所建信道模型容量最大,在该角度分布下基于ULA信道模型的容量优于UCA和URA。     

Novel antenna selection algorithm based on Tanimoto similarity

A new antenna selection algorithm for multiple input multiple output （MIMO） wireless systems is proposed. The modified Tanimoto coefficient is used to compare the similarity of the rows/columns of the channel matrix. Based on the calculated similarity, the proposed algorithm chooses the antenna subset, which has the maximum product of dissimilarity and Frobenius norm. The proposed algorithm requires low computational complexity as to the optimal selection but with comparative outage capacity and average signal to noise ratio （SNR） performance. It can improve both the outage capacity and the average SNR as compared to random selection. The simulation results are shown to validate our algorithm.     

一种基于时频对偶特性的空频多普勒OFDM编码方案

基于时频对偶特性,提出了时变Doppler衰落信道下空频多普勒OFDM(Orthogonal Frequency Division Multiplexing)编码的一种新方案。在时变信道Doppler基扩展(BEM,Basis Expansion Model)模型的基础上,利用时频对偶性及循环矩阵的对角化处理,实现了时变Doppler衰落信道的线性化变换。通过OFDM调制,利用矩阵分块方法对OFDM子载频分块并按块进行复正交编码设计,实现了一般性MIMO系统中的空频多普勒OFDM编码。采用前端星座预处理与空频多普勒OFDM编码级联的方法,从而实现了包括信道Doppler分集在内的系统全分集增益。理论分析及实验仿真表明,新编码方案能稳健有效地对抗信道Doppler衰落,具有更高的频带利用率及更低的误比特率。     

互耦效应对MIMO/SA多天线系统信道容量的影响

多输入多输出/智能天线（multiple input multiple output/smart antenna, MIMO/SA）系统是4G的关键技术之一,多天线的互耦效应是影响MIMO/SA多天线系统性能的主要问题。建立了MIMO与SA相结合的多天线系统模型,推导了互耦效应影响下空间相关系数和信道容量的表达式|通过电磁场数值计算和蒙特卡罗方法仿真MIMO/SA多天线系统的各态历经信道容量。结果表明：在典型的角度谱分布下改变天线间距,考虑互耦效应的信道容量围绕无互耦效应时的信道容量上下振荡|基站天线阵列间距增大信道容量持续增大,移动台天线阵列间距增大到0.5倍波长后信道容量基本保持不变|互耦效应增大信道的空域相关性,从而降低信道容量。     

非理想反馈MIMO信道发射功率的信息论分析

研究了发射端只有非理想信道状态信息反馈的单用户多输入多输出(MIMO)无线通信系统的最优发送策略。当发射端具有信道协方差矩阵信息时,使得平均信道容量达到最大的发射方向和信道状态协方差反馈矩阵的特征矢量相一致,而相应的发射天线上的最优功率分配则难以解析获得。通过研究舒尔-凹函数的性质,对平均信道容量函数进行理论分析,并推导了输入协方差矩阵特征值分布达到信道容量的最优条件,以此探究发射天线上的最优功率分配方案。数值结果验证了上述结论的正确性。     

Lattice-reduction-aided MMSE precoding for correlated MIMO channels and performance analysis

The lattice-reduction (LR) has been developed to improve the performance of the zero-forcing (ZF) precoder in multiple input multiple output (MIMO) systems. Under the assumptions of uncorrelated flat fading channel model and perfect channel state information at the transmitter (CSIT), an LR-aided ZF precoder is able to collect the full transmit diversity. With the complex LenstraLenstra-Lova′sz (LLL) algorithm and limited feedforward structure, an LR-aided linear minimum-mean-square-error (LMMSE) precoder for spatial correlated MIMO channels and imperfect CSIT is proposed to achieve lower bit error rate (BER). Assuming a time division duplexing (TDD) MIMO system, correlated block flat fading channel and LMMSE uplink channel estimator, it is proved that the proposed LR-aided LMMSE precoder can also obtain the full transmit diversity through an analytical approach. Furthermore, the simulation results show that with the quadrature phase shift keying (QPSK) modulation at the transmitter, the uncoded and coded BERs of the LR-aided LMMSE precoder are lower than that of the traditional LMMSE precoder respectively when E b / N0 is greater than 10 dB and 12 dB at all correlation coefficients.     

大规模MIMO中继系统基于LoS的等增益传输方案

在中继分布大规模多输入多输出天线阵列情况下,对莱斯衰落环境中的双向放大转发多对中继系统进行了探讨。为了能有效减轻信道估计负担、提高频谱利用率,首先提出了一个只基于视距(line-of-sight, LoS)分量的线性传输方案。该方案采用实现复杂度低的等增益合并与等增益传输相结合的中继处理。然后分别推导了该方案无功率缩放和有功率缩放情况下的渐近可达速率闭式表达式。与传统的基于全部信道状态信息的线性传输方案比较,该方案更宜在LoS分量较强的情况下得到应用。     

一种MIMO收发天线联合选择算法

在MIMO系统中天线选择可以增加系统容量,并能有效地降低MIMO系统的复杂度和射频电路成本。仿真实验表明天线在发送接收两端不同的分配方式影响信道容量,发现了一种信道容量角度的最佳天线分配方式。针对收发天线选择的需求,设计了一种可获得较大信道容量的简单算法。该算法没有矩阵运算,计算复杂度低。仿真实验表明该算法和最优算法非常贴近,优于只有接收天线选择时的最优算法。     

Channel capacity of multiple-input multiple-output systems with transmit and receive correlation

In order to investigate the impact of channel model parameters on the channel capacity of a multipleinput multiple-output （MIMO） system, a novel method is proposed to explore the channel capacity under Rayleigh fiat fading with correlated transmit and receive antennas. The optimal transmitting direction which can achieve maximum channel capacity is derived using random matrices theory. In addition, the closed-form expression for the channel capacity of MIMO systems is given by utilizing the properties of Wishart distribution when SNR is high. Computer simulation results show that the channel capacity is maximized when the antenna spacing increases to a certain point, and furthermore, the larger the scattering angle is, the more quickly the channel capacity converges to its maximum. At high SNR （〉12 dB）, the estimation of capacity is close to its true wlue. And, when the same array configuration is adopted both at the transmitter and the receiver, the UCA yields higher channel capacity than ULA.     

空时MIMO无线通信系统随机信道模型的仿真研究与实现

对智能天线、空间分集和MIMO OFDM等多天线技术的信道传输特征进行了分析,提出了一种用于第三代及多天线MIMO无线通信系统的信道模型。该信道模型不仅涉及到接收信号的功率水平分布和多普勒频移,还考虑了信道衰落系数间的相关性以及智能天线阵列的几何分布和到达角度等特性。用3GPP通信协议基于Matlab实现了一个完整的MIMO信道仿真器。最后,通过实验验证了不同无线通信环境下MIMO模拟的信道容量与Shan non理论容量的一致性,从而说明了该仿真器的有效性和实用性。     

基于不完全信道信息的MIMO双向中继系统线性预编码算法#br#

针对配置两个通信节点的多输入多输出双向中继系统,提出一种基于不完全信道状态信息的预编码设计方案,该方案综合考虑信道估计误差与信道反馈延迟的情况。在中继发射功率受限的条件下,以最小均方误差为准则设计以预编码矩阵为变量的优化问题,提出矩阵分解和联合迭代两种线性预编码算法。矩阵分解法通过矩阵分解推导得到中继矩阵的闭式解;联合迭代法利用迭代算法交替迭代来联合优化预编码矩阵和接收端处理矩阵,直到算法收敛数。仿真结果表明,随着信噪比由0到25 dB逐渐增大,与现有方案相比,矩阵分解法能有效地降低系统的误比特率,联合迭代法能获得最佳的系统性能提升。     

双基地MIMO雷达参数辨识性分析

与传统的相控阵雷达不同，多输入多输出(multiple input multiple output， MIMO)雷达可以发射彼此正交的信号来形成独立信道，通过将各信道内的目标雷达反射截面积(radar cross section, RCS)进行平均可以有效抑制目标衰落，进而提高其参数辨识性能。根据给出的双基地MIMO雷达系统模型，对系统最多可分辨和定位目标的数目进行分析，并给出理论证明。分析表明，利用目标反射系数的非相关特性，双基地MIMO雷达最多可有效分辨和定位收发阵元数的乘积减1个目标。仿真实验证明了结论的正确性。     

Hybrid pilots assisted channel estimation algorithm for MIMO-OFDM systems

Abstract: A hybrid pilots assisted channel estimation algorithm for multiple input multiple output (MIMO) orthogonal frequency division multiplexing (OFDM) systems under low signal-to-noise ratio (SNR) and arbitrary Doppler spread scenarios is proposed. Motivated by the dissatisfactory performance of the optimal pilots (OPs) designed under static channels over multiple OFDM symbols imposed by fast fading channels, the proposed scheme first assumes that the virtual pilot tones superimposed at data locations over specific subcarriers are transmitted from all antennas, then the virtual received pilot signals at the corresponding locations can be obtained by making full use of the time and frequency domain correlations of the frequency responses of the time varying dispersive fading channels and the received signals at pilot subcarriers, finally the channel parameters are derived from the combination of the real and virtual received pilot signals over one OFDM symbol based on least square (LS) criterion. Simulation results illustrate that the proposed method is insensitive to Doppler spread and can effectively ameliorate the mean square error (MSE) floor inherent to the previous method, meanwhile its performance outmatches that of OPs at low SNR region under static channels.     

注意力机制CNN的毫米波大规模MIMO系统信道估计算法

在室外光线追踪通信场景下,针对毫米波大规模多输入多输出(multiple input multiple output,MI-MO)信道具有稀疏特性、系统受噪声因素影响导致信道估计精度低的问题,提出一种基于图像去噪的注意力机制卷积神经网络信道估计方法.首先,设定参数产生模拟真实环境的数据集,将所产生的信道矩阵看作二维图像...     

密集小小区莱斯衰落CoMP预编码及分时反馈的设计

密集小小区场景存在很强的视线传输(line-of-sight,LOS)成份,传统基于瑞利衰落的多点协作预编码码本性能将受到限制,同时密集小小区环境下非视线传输(non-line-of-sight, NLOS)成分将更加复杂需要频繁地进行反馈。因此提出一种针对密集小小区莱斯信道的码本设计方案,充分利用LOS和NLOS成分,并结合慢速移动场景的信道特点采用差分码本的形式,在不增加码本空间的基础上提高了实际的码本量化能力。同时设计了一种长短周期相结合的分时反馈方案,对不同莱斯因子的信道场景提供更灵活的支持。     

MIMO-STBC子载波资源分配算法研究

正交频分多址是一种无线环境下的高速传输技术,适合在多径传播和多普勒频移的无线移动信道中传输高速数据。在对与多天线STBC等效的单发单收模型进行研究的基础上,提出了一种适用于MIMO-STBC系统自适应优化的子载波资源分配算法,将复杂的分集增益指标转换为直观的SNR指标,明确表示出接收机SNR与信道相关矩阵之间的关系。仿真实验表明,该算法进一步提高了频谱效率与系统性能。     

矿井巷道的MIMO无线信道建模与性能仿真

矿井巷道电波传播环境非常复杂,建立MIMO无线信道模型有助于将无线通信技术应用到煤矿井下。针对矿井巷道中MIMO无线传输环境,提出一种随机独立的MIMO信道,然后根据矿井巷道的富散射环境,对该信道矩阵进行修正,建立了两种空间相关的MIMO信道模型。文章对包含完全独立路径的瑞利信道模型的奇异值和信道容量进行了分析比较,并对不同信道模型下的系统性能进行了仿真。仿真结果与文献的实测结果对比说明建立的模型不失一般性。

Abstract：

The radio propagation situation is very complex in mine laneway,so it is important to establish an efficient MIMO channel model for applying wireless communication technology to coal underground.A stochastic MIMO channel model was proposed firstly based on wireless propagation environment in mine tunnel,and then two spatial correlative channel models were established through correcting channel matrices based on abundant scatter environment.The singular values and the channel capacity obtained with a Rayleigh channel model were compared,and system performance of different channel models were simulated.The simulation results indicate that the established channel models are feasible by comparing with measurements results.     

基于STBC的双层预编码MIMO系统

提出一种结合空时分组码(space-time block coding, STBC)与双层预编码的方法。建立了基于STBC的双层预编码多输入多输出(multiple input multiple output, MIMO)系统模型,给出了预编码赋形权矢量的构造方法,利用预编码形成的两个虚拟子信道同时传输两个数据流,同时结合Alamouti STBC构成混合编码,带来分集增益;针对STBC双层预编码系统设计了一种低复杂度的译码方法。理论和仿真结果表明,新系统可以同时带来分集增益和复用增益,有效提高系统信道容量,与通常的MIMO系统相比,误码性能得到明显改善。     

基于Barzilai-Borwein迭代的低复杂度大规模MIMO信号检测算法

在大规模多输入多输出系统中,最小均方误差(minimum mean square error, MMSE)算法能达到接近最优的线性信号检测性能,但是MMSE算法需要复杂的矩阵求逆运算,这限制了该算法的应用。为了降低运算复杂度,改进MMSE算法,利用Barzilai Borwein(BB)迭代算法来避免矩阵求逆运算,提出了结构简单的BB迭代信号检测算法,且基于信道硬化特性进一步优化了迭代初始解以加快算法的收敛速度。理论和仿真结果表明,所提出的BB迭代算法的性能优于最近提出的Neumann级数展开算法,而其复杂度相比截短阶数i=3的Neumann级数展开算法减少了一个数量级;且该算法收敛速度较快,在给定初始值的条件下,通过简单的几次迭代,能够快速接近MMSE算法的检测性能。