基于独立分量分析的多天线空时盲接收方案

将独立分量分析(ICA)技术应用于无线通信环境中,通过分析空时分组码(STBC)和垂直-贝尔实验室分层空时(V-BLAST)的本质结构,建立了多种适用于ICA的特定通信系统模型,并以此实现了对发射信号的盲检测,从而代替了基于信道估计的传统接收方法.理论分析表明,ICA盲接收技术的应用可以有效提高系统对信道估计错误的顽健性和系统设计的灵活性.仿真结果验证了所提方案的有效性,并对算法实现的复杂度和收敛特性进行了分析.     

基于独立分量分析的正交空时分组编码盲检测方案

通过在不同天线发射的信号之间引入时域和空域信息,正交空时分组编码(OSTBC)可以获得发射分集增益,而且可以在不牺牲带宽的情况下获得更高的编码增益。但是其译码却需要精确的信道状态信息(CSI),因此,信道信息估计的准确性严重影响系统的性能。基于独立分量分析(ICA)的盲源分离(BSS)技术可以在不进行信道估计的情况下对发射信号实现有效检测。通过利用OSTBC的正交特性,提出了2种基于ICA的盲检测方案,同时,一些基于信道估计的检测算法也被用来进行性能比较。瑞利衰落信道下的仿真结果表明,2种新方案均具有较好的系统适应性和误码率性能。     

波束空时分组编码的ICA盲检测方案

理论研究已经证明,结合波束形成和空时分组编码的混合系统与传统的单纯使用波束发射或空时编码的方案相比具有很大的性能提高;传统的译码方案是借助接收端的信道估计来实现的,它需要知道准确的信道状态信息(CSI)。但如果信道估计不易实现,则系统性能将受很大影响。独立分量分析(ICA)作为一种经典的盲信号分离技术可以在不进行信道估计的情况下对发射信号实现有效检测。本文针对接收端的信号结构提出了一种基于ICA的正交检测方案;并通过仿真将新方案与传统方案进行了性能比较。仿真结果表明,新方案具有较好的系统适应性和误码率特性。     

波束空时分组码系统中一种基于ICA的正交检测方案

结合波束形成和空时分组编码的混合系统与传统的单波束发射以及单空时编码发射分集方案相比可以大大提高链路性能;传统的译码方案通常以接收端能够获取精确的信道状态信息为前提;但是对于某些特定的通信环境,这种前提条件通常很难满足.独立分量分析(ICA)技术可以在不进行信道估计的情况下对发射信号实现有效检测.本文针对接收端的信号结构提出了一种基于ICA的正交检测方案;并通过仿真将新方案与传统方案进行了性能比较,仿真结果表明,新方案具有较好的系统适应性和误码率特性.     

垂直分层空时编码的直接解码和盲信道估计算法

提出了适合垂直分层空时编码结构的盲信号检测和信道估计算法,在发射端进行了预编码,并利用一种类ESPRIT算法进行了盲信号检测和信道估计。与已提出的绝大多数垂直分层空时编码结构的信号检测和信道估计算法不同,去掉了接收天线数必须大于发射天线数这一约束。计算机仿真结果显示所提出的盲信号检测和信道估计算法与非盲算法几乎有相同的性能。     

OFDM-MIMO系统中发射分集和信道估计技术研究

文章研究了OFDM-MIMO系统中的循环延迟分集（CDD）,以及基于Alamouti的空时分组编码（STBC）与空频分组编码（SFBC）,针对发射分集方案所必须知道的信道信息,对两种信道估计方法,即最小二乘（LS）＋线性插值与最小均方误差（MMSE）插值进行了研究。通过链路仿真还给出了以上分集方案在不同信道条件下的性能曲线,此外,对两种信道估计方法的误帧率做了统计。结果表明,CDD结合信道编译码可获得分集增益,有效对抗无线信道的衰落性。STBC,SFBC在不需要外码的情况下便可获得较大分集增益,且分别适用于频率选择性衰落与时间选择性衰落信道。而MMSE估计可以获得较为理想的误帧率,为分集方案提供较准确的信道参数以提高系统的可靠性。     

基于SP-LCCMA的STBC MC-CDMA系统盲信道估计

研究了空时编码多载波码分多址系统（STBC MC—CDMA）盲信道估计技术。根据信道位于信号子空间的特点,提出基于信号子空间投影线性约束恒模算法（SP—LCCMA）的盲信道估计,避免了噪声子空间信道估计的缺点,将估计信道应用于STBC MC—CDMA系统多用户检测。仿真结果表明,提出算法的收敛速度和信干噪比（SINR）性能优于一般恒模算法。     

STBC MC-DS-CDMA系统基于子空间信道盲估计的多用户检测

该文提出了一种空时分组码(STBC)多载波(MC)DS-CDMA(STBC MC-DS-CDMA)系统结构,并通过在STBC MC-DS-CDMA下构造的统一的信号模型,实现了系统上行链路基于子空间的信道盲估计,仿真结果表明了方法行之有效。基于信道估计的结果进一步实现了系统最小均方差(MMSE)多用户检测,使系统的BER性能得到很大提高。     

分组空时块码系统中的排序最大信噪比检测算法

提出并比较了应用于分组空时块码（G—STBC）系统中两种不同信道模型的排序最大信噪比（MaxSNR）检测算法。该系统在发端对发射天线分组，每组进行独立的空时块码编码；在收端应用排序最大信噪比算法进行检测。由于空时块码提供了额外的时域约束，所以可以利用这个约束对信道模型进行变换，得到一个等效信道模型，然后再使用排序MaxSNR检测；当然也可以直接利用原有的信道模型，即非等效信道模型进行检测。仿真结果表明：当接收天线数不少于发射天线数的一半时，采用等效信道模型下的排序MaxSNR算法，系统的误码曲线就能保持陡降性；并且在收发天线数相同时，其性能总是优于非等效信道模型。     

STBC块传输系统中的一种新型分集合并算法

该文在二发一收的空时分组码(STBC)单载波块传输系统中,提出一种空时和多径分集合并接收算法。通过基于STBC的单载波频域均衡(STBC-SC-FDE)算法得到对发送信号的估计,以此和信道状态信息(CSI)分离接收信号中的各多径分量,对各多径分量分别采用STBC合并,最后再将各多径分量的合并输出结果按照最大比(MRC)的方式进行合并,从而实现空时二维RAKE接收。该算法在较低的计算复杂度情况下,可以同时获得发射分集和多径分集,Monte Carlo仿真验证了该算法的性能。     

Multidimensional Blind Separation Using Higher-Order Statistics: Application to Non-Cooperative STBC Systems

Blindly separating the intercepted signals is a challenging problem in non-cooperative multiple input multiple output systems in association with space–time block code (STBC) where channel state information and coding matrix are unavailable. To our knowledge, there is no report on dealing with this problem in literature. In this paper, the STBC systems are represented with an independent component analysis (ICA) model by merging the channel and coding matrices as virtual channel matrix. Analysis shows that the source signals are of group-wise independence and the condition of mutual independence can not be satisfied for ordinary ICA algorithms when specific modulations are employed. A new multidimensional ICA algorithm is proposed to separate the intercepted signals in this case by jointly block-diagonalizing (JBD) the cumulant matrices. In this paper, JBD is achieved by a 2-step optimization algorithm and a contrast function is derived from the JBD criterion to remove the additional permutation ambiguity with explicit mathematical explanations. The convergence of the new method is guaranteed. Compared with the ICA-based channel estimation methods, simulations show that the new algorithm, which does not introduce additional ambiguities, achieves better performance with faster convergence in a non-cooperative scenario.     

A new subspace method for blind estimation of selective MIMO‐STBC channels

In this paper, a new technique for the blind estimation of frequency and/or time‐selective multiple‐input multiple‐output (MIMO) channels under space‐time block coding (STBC) transmissions is presented. The proposed method relies on a basis expansion model (BEM) of the MIMO channel, which reduces the number of parameters to be estimated, and includes many practical STBC‐based transmission scenarios, such as STBC‐orthogonal frequency division multiplexing (OFDM), space‐frequency block coding (SFBC), time‐reversal STBC, and time‐varying STBC encoded systems. Inspired by the unconstrained blind maximum likelihood (UML) decoder, the proposed criterion is a subspace method that efficiently exploits all the information provided by the STBC structure, as well as by the reduced‐rank representation of the MIMO channel. The method, which is independent of the specific signal constellation, is able to blindly recover the MIMO channel within a small number of available blocks at the receiver side. In fact, for some particular cases of interest such as orthogonal STBC‐OFDM schemes, the proposed technique blindly identifies the channel using just one data block. The complexity of the proposed approach reduces to the solution of a generalized eigenvalue (GEV) problem and its computational cost is linear in the number of sub‐channels. An identifiability analysis and some numerical examples illustrating the performance of the proposed algorithm are also provided. Copyright © 2009 John Wiley & Sons, Ltd.     

MC‐CDMA MIMO systems with quasi‐orthogonal space–time block codes: Channel estimation and multiuser detection

This paper investigates blind channel estimation and multiuser detection for quasi‐synchronous multi‐carrier code‐division multiple‐access (MC‐CDMA) multiple‐input multiple‐output (MIMO) systems with quasi‐orthogonal space–time block codes (QO‐STBC). Subspace‐based blind channel estimation is proposed by considering a QO‐STBC scheme that involves four transmit antennas and multiple receive antennas. Based on the first‐order perturbation theory, the mean square error of the channel estimation is derived. With the estimated channel coefficients, we employ minimum output energy and eigenspace receivers for symbol detection. Using the QO‐STBC coding property, the weight analyses are performed to reduce the computational complexity of the system. In addition, the forward–backward averaging technique is presented to enhance the performance of multiuser detection. Numerical simulations are given to demonstrate the superiority of the proposed channel estimation methods and symbol detection techniques. Copyright © 2011 John Wiley & Sons, Ltd.     

A general scheme for equalization of space-time block-coded systems with unknown CSI

Recently, space-time block codes (STBCs) have gained much attention as an effective transmit diversity technique to increase the capacity of wireless communication systems. In this paper, we consider a general technique for direct equalization of space-time block-coding systems with unknown channel state information (CSI). This technique is suitable for several existing hybrid STBC schemes, such as STBC/orthogonal-frequency-division multiplexing (STBC-OFDM) and STBC/code-division multiple access (STBC-CDMA). We show that by exploiting the redundancy in the structure of STBC, a zero-forcing equalizer can be constructed without channel estimation. The conditions for the identifiability of the zero-forcing equalizer are also derived to ensure correct equalization. To further improve the performance of the proposed method, a new iterative algorithm is developed by incorporating the finite alphabet property of information symbols. Simulation results show that the proposed algorithms can outperform comparative schemes in most simulation conditions.     

Performance Comparison of MIMO-STBC Systems with Adaptive Semiblind Channel Estimation Scheme

Wireless communication is now a part of everyday life in the urban areas. Wireless LAN is mostly utilized communication system as an example. These wireless devices are data rate and range limited, for which the scientists are spending great efforts on finding ways to overcome these limitations. Multi input multi output (MIMO) antenna systems are the example through which these limitations have been reduced upto great extent which provides multilayer beamforming, diversity, and spatial multiplexing. Analysis of adaptive semiblind channel estimation scheme for MIMO antenna array systems with different code rate space time block coding (STBC) has been performed using the adaptive pilot assisted modulation scheme proposed earlier. Semi blind channel estimation method provides the best trade-off in terms of bandwidth overhead, computational complexity and latency. The result after using MIMO systems shows higher data rate and longer transmit range without any requirement of additional bandwidth or transmit power. This paper presents the detailed analysis of diversity coding techniques using MIMO antenna systems. Different STBC schemes have been explored and analyzed with the different code rate STBC using MATLAB environment and the simulated results have been compared in the semiblind environment which shows the improvement even in highly correlated antenna arrays, and is found close to the condition when channel state information is known to the channel.     

一种适用多种空时编码方案的MIMO自编码器通信系统

为提升现有端到端通信系统的适应性与信道估计的准确性,提出了一种适用于多种空时编码方案的多输入多输出(Multiple-Input Multiple-Output,MIMO)自编码器通信系统.该系统将基于卷积神经网络的自编码器引入到MIMO系统中,并结合信道估计网络实现信道均衡,通过端到端的学习方式实现各种空时编码方案下...