几种接收机在宽带相关信道下的性能分析

介绍了宽带相关MIMO信道模型。通过引入虚拟天线思想，窄带MIMO的空时信号处理算法可直接推广到宽带MIMO系统中。在发射端相关宽带信道下，对几种空时接收机做了仿真分析。计算机仿真结果表明：所有接收机的性能随相关系数的增大而性能下降，但在相关系数小于0．4时接收机的性能变化不大，MMSE-VBLAST接收机的性能最好，ZF-VBLAST与ZF、MMSE接收机相比在算法复杂度和性能上没有优势。     

多入多出(MIMO)分层空时码算法研究

概述了一种新的编码和信号处理技术—分层空时码(BLAST)的编解码算法,并比较了各自的优缺点。由于D-BLST的计算复杂度太大,重点分析了工程上具有实用价值的V-BLAST算法,文章的最后给出了仿真结果和结论。     

VBLAST在宽带空间相关信道下的性能分析

在宽带空间相关信道下,通过仿真分析、评估了VBLAST空时接收机的性能。仿真结果表明随着信道空间相关性的增大,系统的性能都有所下降;随着接收天线数的增加,信道相关性对系统的影响逐渐减小。     

垂直分层空时码的几种检测算法比较

垂直分层空时码（V-BLAST）是贝尔实验室提出的一种基于多入多出（MIMO）传输方式的空时码系统,其检测算法是MIMO系统的有效检测方法。首先介绍V-BLAST系统的信号模型,在此基础上应用不同的信号估计准则推导出不同的检测算法,最后通过仿真实验对各种算法的性能和优缺点进行了分析和比较。     

无线通信的新技术MIMO

多入多出(MIMO)技术是无线通信领域的重大突破,它充分开发空间资源,利用多天线实现多发多收,在无须增加频谱资源和天线发送功率的情况下,可以使信道容量成倍提高,还可以提高信道的可靠性,降低误码率,极大提高频谱利用率。文中介绍了MIMO技术,包括MIMO的优点、国内外对MIMO系统的主要研究方向及研究重点等。     

一种新型的非正交空时编码设计

空时分组码和BLAST系统是两种利用多发多收传输的典型的空时编码系统．但由于空时分组码受正交条件限制，传输效率得不到提高，而BLAST系统存在差错传播制约着误码率的下降．综合了这两种系统的优点，提出了一种非正交空时分组编码设计，并将其描述为空时分组BLAST系统、仿真结果表明，新系统在不同信道环境、不同调制方式和天线数目的情况下部具有良好性能，可以显著改善空时分组码和BLAST系统的性能。     

基于MIMO的垂直分层空时码检测算法

分层空时码(BLAST)是贝尔实验室提出的一种基于多入多出(MIMO)传输方式的空时码系统。本文着重研究了BLAST系统中一类垂直分层空时码的检测算法,依据信号模型,分析推导了基于迫零准则和最小均方误差准则的估计算法,并在此基础上采用了以上算法与判决反馈及最佳排序思想结合的方法,使系统的误码率性能得到了提高。最后通过仿真实验比较了各种算法的性能和特点,结果表明分层空时码用于无线通信具有极大优势。     

平坦信道下的MIMO信道估计误差分析

基于导频序列推导了频率平坦多输入多输出(MIMO)信道下的最小二乘信道估计(LS)误差;将信道估计误差等效为高斯噪声,推导了信道估计条件下系统的等效信噪比,提出了用系统的等效信噪比来分析和评估在信道估计误差条件下系统的误码性能;最后用等效信噪比的方法评估了ZF-V-BLAST算法在信道估计下的性能,结果表明和计算机仿真结果基本相吻合。     

无线通信领域中的MIMO与空时编码技术

提高频谱利用率是当前和今后无线通信的一个重要问题，多输入多输出(MIM0)和空时编码技术越来越引起人们的重视。介绍了MIMO系统及其D_BLAST和V_BLAST算法，并分别介绍了空时格码和空时分组码及其编码和解码方法。最后给出了MIMO与空时码的研究动态。     

V-BLAST算法在MIMO相关信道下的性能分析

文章给出一个MIMO相关信道模型,利用该模型,通过仿真分析研究了VBLAST算法在相关信道下MIMO系统 的性能。仿真结果表明,接收机的性能随信道相关性的增大而下降,但接收端的相关性对系统性能的影响大于发射端的相关 性对系统的影响。     

Performance of VBLAST Systems Based on Spatial Correlated MIMO Channels

1　Introduction　Recentinformationtheoryresultshaveshowntheenormouscapacitypotentialofwirelesscommunica tionsystemswithantennaarraysatboththetrans mitterandreceiver[1～ 3] .TheVBLASTarchitec ture[4～ 5] isonesuchapproach .VBLASTsystemstransmitparalleldatastreams,usingmultipleanten nas,simultaneouslyandinthesamefrequencyband .Withrichmultipathpropagation ,thesedif ferentstreamscanbeseparatedatthereceiverbe causeoftheirdistinctspatialsignatures.Inaflat fadingscatteringenvironmentwithindepen…     

Asymptotic Performance of Linear Receivers in MIMO Fading Channels

Linear receivers are an attractive low-complexity alternative to optimal processing for multiple-antenna multiple-input multiple-output (MIMO) communications. In this paper, we characterize the information-theoretic performance of MIMO linear receivers in two different asymptotic regimes. For fixed number of antennas, we investigate the limit of error probability in the high-signal-to noise-ratio (SNR) regime in terms of the diversity-multiplexing tradeoff (DMT). Following this, we characterize the error probability for fixed SNR in the regime of large (but finite) number of antennas.As far as the DMT is concerned, we report a negative result: we show that both linear zero-forcing (ZF) and linear minimum mean- square error (MMSE) receivers achieve the same DMT, which is largely suboptimal even in the case where outer coding and deAcircnot coding is performed across the antennas. We also provide an apAcircnot proximate quantitative analysis of the markedly different behavior of the MMSE and ZF receivers at finite rate and nonasymptotic SNR, and show that while the ZF receiver achieves poor diversity at any finite rate, the MMSE receiver error curve slope flattens out progressively, as the coding rate increases. When SNR is fixed and the number of antennas becomes large, we show that the mutual information at the output of an MMSE or ZF linear receiver has fluctuations that converge in distribution to a Gaussian random variable, whose mean and variance can be characterized in closed form. This analysis extends to the linear reAcircnot ceiver case a well-known result previously obtained for the optimal receiver. Simulations reveal that the asymptotic analysis captures accurately the outage behavior of systems even with a moderate number of antennas.     

基于MIMO系统的自适应无线链路方案

MIMO信道容量下降的主要原因是发射天线发出的信号在接收端形成的空间特征相似度太大造成的.有选择除去一些空间特征太为相似的天线能够有效的提高信道容量.为此本文提出了一种综合评估准则：波束形成矢量的范数.仿真结果表明,在发射天线总数相同的条件下,基于本文方法的选择效果逼近最大容量的选择效果.在自适应链路的实现中,发射天线的个数由接收性能最差信道的信噪比确定,能够保证在当时通信环境下最大的空间复用系数.     

空间相关信道下分布式MIMO系统中的STBC-VBLAST组合方案

在空间相关信道下分布式多输入多输出(D-MIMO)系统中,提出了一种新的空时分组编码(STBC)和垂直分层空时编码(VBLAST)组合方案.为充分利用D-MIMO系统的拓扑结构和空间相关信道的特性,在下行D-MI-MO系统的每个分布式天线(DA)簇内采用STBC,而在不同DA簇之间采用VBLAST.同时,为了降低系统复杂度并节省总发射功率,采用了基于最小传播路径衰落准则的天线选择方案.仿真结果证明,对比于传统VBLAST方式,所提出的STBC-VBLAST组合方案能显著降低系统误比特率(BER)并提高空间相关信道下BER性能的鲁棒性.因此,该组合方案是实现空间相关信道下D-MIMO系统下行分集与复用的折衷的一种有效方案.     

超宽带Rake接收机在密集多径信道下的性能

超宽带信号在室内环境中将经历密集多径传播,产生严重的时间弥敞。采用Rake接收是提高超宽带接收机性能的重要手段。该文针对采用BPSK调制的超宽带系统,推导出密集多径信道下Rake接收机的误码性能计算公式,揭示了Rake接收机性能与多径信道参数以及脉冲波形自相关系数之间的关系。针对典型信道模型和脉冲给出了计算实例。     

Performance Analysis of MIMO Based CDMA Code Acquisition Over Rayleigh Fading Channels

This paper proposes a new MIMO based CDMA code acquisition scheme. The pilot codes consist of a number of short Gold code sequences which are transmitted in parallel using a group of transmit antennas. Reception diversity is performed by multiple receive antennas at the receiver. Three different acquisition detection techniques are proposed and compared. Corresponding threshold optimizations are investigated as well. Detection and false alarm probabilities are derived in closed form based on the outputs of non-coherent matched filters. The acquisition performance is evaluated in terms of mean acquisition time (MAT) in Rayleigh fading environment. It is shown that the proposed MIMO acquisition scheme exhibits a much better MAT performance than the conventional single-antenna acquisition scheme. The results reveal that multiple receive antennas can be utilized to significantly reduce the MAT at the expense of receiver complexity increase. On the other hand, increasing the number of transmit antennas makes the MAT performance more robust in the presence of strong interference.     

Performance Analysis of Scheduling in Multiuser MIMO Systems with Zero-Forcing Receivers

Despite its low-complexity, the zero-forcing receiver is known to suffer from noise enhancement to restore the spatially multiplexed data in a single-user MI MO system. Nevertheless, in the multiuser system, the poor-channel avoidance property of the scheduling technique provides a natural way to overcome the drawback of noise enhancement (Heath et al., 2001). In this paper, we present an analytical framework to evaluate the performance of the zero-forcing receiver operating in the multiuser MIMO system with user scheduling. Using the order statistics technique, we derive closed-form expressions for the sum-rate capacity of the multiuser MIMO system that employs the simple spatial multiplexing at the transmitter and zero-forcing processing at the receiver with a number of scheduling algorithms. These closed-form expressions hold for an arbitrary finite number of users and facilitate efficient numerical evaluations for cases of practical interest. In addition, the tractable analysis provides insight into how the scheduling technique affects the performance of the multiuser MIMO system under scalar feedback and vector feedback. The results are also extended to the case of heterogonous users with unequal average SNR.     

Equalization Based Receivers for Wideband MIMO/BLAST Systems

This paper focuses on the usage of Equalization-Based receivers for Wideband Code-Division Multiple Access (WCDMA) Multiple Input, Multiple Output (MIMO) Bell Labs Layered Space Time (BLAST)-type systems. The main receivers on trial are the Zero-Forcing and Minimum Mean Square Error (MMSE) algorithm-based receivers and their variants, employing Parallel interference cancellation (PIC) and Iterative Partial Cancellation (IPC) schemes. To assess its performance in an existing system, the uncoded Universal Mobile Telecommunications System (UMTS) High-Speed Downlink Packet Access (HSDPA) standard was considered (using solely QPSK modulation) alongside the reference UMTS environments. The BER performance is assessed both by simulation and by semi-analytical processing.