基于广义ABBA空时分组码的OFDM系统

采用准正交设计的空时分组码虽然可以达到速率为1,但是牺牲了部分分级增益。广义ABBA（GABBA,Generalized ABBA）空时分组码提出了一种改进型块状迭代准正交分组空时码（QOSTBC,Quasi-orthogonal Space-time Code）编码方式。此编码方式能提供全分集增益,并且满速率传输。克服原有正交分组空时码（OSTBC,Orthogonal Space-time Block Codes）在多天线（天线数大于2）、复信号时不能实现全速率传送的缺点。OFDM调制技术是抗多径效应的有效手段之一,两者相结合的MIMO-OFDM系统很好利用了时间、空间和频率三种分集,使系统达到很高的传输效率和频谱利用率。     

多发射与多接收天线系统盲自适应算法研究

提出了一种用于正交空时分组码(OSTBC:Orthogonal Space-Time Block Code)多发射天线多接收天线系统的盲自适应接收机.该方法主要利用了正交空时分组码的内在特性,给出了一个针对正交空时分组码多发射天线多接收天线系统的无约束代价函数,分析了该函数的全局最小值点.利用该无约束代价函数,通过投影逼近方法给出了递推最小二乘(RLS)自适应算法实现.仿真结果表明:该接收机可以很好的跟踪衰落信道的变化,在不利用导频信号的情况下很好的还原出原始的传输信号.     

两种闭环准正交空时分组码的设计

针对准正交空时分组码(QOSTBC)存在自干扰的特性,提出了两种基于部分反馈的闭环QOSTBC的设计方法,这两种反馈方法可以减小QOSTBC的自干扰,提高QOSTBC的误码性能。仿真和分析结果表明提出的方法在相同反馈信息下的性能优于天线混淆(TAS)准正交空时分组码,在系统性能相差不大(不超过0.5dB)的情况下所需的反馈信息远小于信道正交化空时分组码(CO-STBC),而且提出的方法具有较低的设备复杂性和较好的鲁棒性。     

适于匙孔信道的准正交极化空时分组码及性能分析

构建了一种适于匙孔信道的满码率极化准正交空时分组码以改善其误比特率性能,采用快速最大似然译码算法进行译码,并与匙孔信道的传统准正交空时分组码、单中继瑞利信道和单中继匙孔信道的极化准正交空时分组码分别进行误比特率的仿真和比较.结果表明:在相同SNR条件下,本文构建的分组码比传统准正交分组码具有更低的误比特率;与两种单中继极化准正交空时分组码相比,在SNR较高情况下本文分组码具有更好的性能.     

基于DSTBC-MC-CDMA的无线网络协同发射分集系统

协同分集(cooperative diversity)技术通过使网络中各单天线用户共享彼此天线,形成虚拟的多天线阵列来实现发射或接收分集,可以有效地提高系统性能。该文提出无线网络中频率选择性衰落信道环境下的一种基于分布式空时分组码(Distributed Space Time Block Code, DSTBC)和MC-CDMA的协同发射分集方案,并给出了系统实现。建立了误码模型,探讨了协同用户间的信道状态信息(CSI)对系统误码性能的影响,分析了误码性能的上限,并给出了仿真结果。结果表明,DSTBC-MC-CDMA系统相对于未协同的MC-CDMA系统,获得了明显的性能增益。     

基于分层结构的空时分组码

提出了一种新的空时编码方法,该方法结合了分层空时BLAST (Bell Layered Space Time)结构及空时分组码STBC (Space Time Block Code)的优点.采用在发射端对发射天线分组,对于每组进行独立的空时分组编码,而在接收端进行分组干扰抑制,并且用奇异值分解方法实现解码.该方法具有高于STBC的频谱利用率和码速率.仿真结果验证了该方法的抗衰落性能优于BLAST.     

一种新的准正交空时分组码的设计

根据正交设计理论,当发送天线数大于2时,不存在可以获得完全分集增益和全速率的复正交空时分组码.对空时分组码采用准正交设计,能够保证数据以全速率传输,但是会使其误码性能降低.文章在对准正交空时分组码(QOSTBC)结构研究的基础上,提出了一种全速率的四发射天线准正交空时分组码,并给出了基于最大似然译码方法.仿真结果表明,文章方案与已有典型的Jafarkhani准正交空时分组码相比,在高信噪比时有更好的误码性能.     

一种新的QO-GLSFTBC-OFDM技术

提出了一种可以使QOSTBC(Quasi-Orthogonal Space-Time Block Code)获得满分集增益的QO-GLSFTBC-OFDM (Group Layered Space-Frequency-Time Block Coded Orthogonal Frequency Division Multiplexing)技术,与基于星座图旋转的改进QOSTBC方法相比,本文提出的方法不扩大每个发射天线发送符号的星座图.从理论分析的结果可以看出,本文所提出的方法在保持QOSTBC满速率优点的前提下,可以同时获得满空间分集增益;而且编码和译码的过程都是基于线性处理的,计算简单.计算机仿真结果也证明了该方法的有效性.     

一种提高空时分组码低信噪比性能的方法

通过对空时分组码（Space-Time Block Code，STBC）在低信噪比时的成对差错概率（Pairwise Error Probability，PEP）的分析，提出了一种针对全分集准正交空时分组码（Quasi-Orthogonal Space-Time Block Code，QOSTBC）低信噪比性能的改进方法。该方法是利用分组码的码字差别矩阵的最大特征值所对应的特征向量，来提高空时分组码的性能。本文用严格的数学推导证明了该方法，并通过了仿真验证。     

准正交空时分组码性能仿真与分析

本文分析了传统的JafarkhaniQOSTBC（准正交空时分组码）和基于星座旋转的JafarkhaniQOSTBC的编、译码方案,并仿真了不同条件下OSTBC（正交空时分组码）、传统QOSTBC和基于星座旋转的QOSTBC的性能。仿真结果表明,在不增加译码复杂度的情况下,基于星座旋转的QOSTBC能够获得比传统QOSTBC更好的性能。     

A Noval RAR-QOSTBC Scheme with Linear Decoding for M-PSK Over Diverse Channels

The full rate can be attained by the conventional Quasi-Orthogonal Space–Time Block Codes (QO-STBC) with the downside of more decoding intricacy and less diversity gain. Grammian matrix of already existing QO-STBC scheme contains non-diagonal elements i.e. interference terms which are responsible for more computational load at the receiver. The non-diagonal elements causing interference while decoding process are eliminated from the grammian matrix by the use of RAR (reflection and rotation) operations on the detection matrix of already existing QO-STBC. Reflection and rotation QO-STBC (RAR-QOSTBC) scheme is proposed in this paper, which results in transformation of the grammian matrix into a diagonal matrix. Corresponding to the diagonal matrix, a new RAR-QOSTBC encoding matrix is generated. RAR-QOSTBC scheme enables to achieve more diversity gain as well as it reduces decoding intricacy at the receiver as comparison to the already existing QO-STBC method. Analysis has been performed for different levels of PSK modulation over two distinct channels (AWGN and Rayleigh) by changing the number of receive antennas. Simulation result shows a significant improvement in the BER performance because of the removal of non-slanting elements from the detection matrix.     

SVD iterative decision feedback demodulation and detection of coded space-time unitary differential modulation

A new suboptimal demodulator based on iterative decision feedback demodulation (DFD), and a singular value decomposition (SVD) for estimation of unitary matrices, is introduced. Noncoherent communication over the Rayleigh flat-fading channel with multiple transmit and receive antennas, where no channel state information (CSI) is available at the receiver is investigated. With four transmit antennas, codes achieving bit-error rate (BER) lower than 10/sup -4/ at bit energy over the noise spectral density ratio (E/sub b//N/sub o/) of -0.25 dB up to 3.5 dB, with coding rates of 1.6875 to 5.06 bits per channel use were found. The performance is compared to the mutual information upper bound of the capacity attaining isotropically random (IR) unitary transmit matrices. The codes achieve BER lower than 10/sup -4/ at E/sub b//N/sub o/ of 3.2 dB to 5.8 dB from this bound. System performance including the iterative DFD algorithm is compared to the one using Euclidean distance, as a reliability measure for demodulation . The DFD system presents a performance gain of up to 1.5 dB. Uncoded systems doing iterative DFD demodulation and idealized pilot sequence assisted modulation (PSAM) detection are compared. Iterative DFD introduces a gain of more than 1.2 dB. The coded system comprises a serial concatenation of turbo code and a unitary matrix differential modulation code. The receiver employs the high-performance coupled iterative decoding of the turbo code and the modulation code. Information-theoretic arguments are harnessed to form guidelines for code design and to evaluate performance of the iterative decoder.     

DSTBC Impulse Radios with Autocorrelation Receiver in ISI-Free UMD Channels

For transmitted-reference impulse radio, it has been experimentally shown that multiple transmit antennas can provide an energy boost in the received signal. Here, we propose a 2-transmit and Q-receive differential space-time block coded impulse radio with autocorrelation receiver. A mathematical model for predicting the system bit-error-rate (BER) performance is derived for intersymbol interference-free transmission over an ultra-wideband channel, and validated with computer simulated results. From the results, it is observed that in migrating from 1-transmit to 2-transmit antennas, a signal-to-noise ratio gain of 3 dB, 2 dB and 1 dB at BER = 10^-5 can be achieved, respectively, for the case of 1-, 2- and 4-receive antennas.     

基于迫零检测的异步V-BLAST最优发射功率分配

由于异步发射V-BLAST各路子流的符号在时间上未对齐,同步V-BLAST所采用的逐符号功率分配方法不再适用。针对这个问题,该文提出了一种以块平均误比特率为优化目标,逐符号块进行功率分配的方法。该方法首先计算每个符号的瞬时信噪比,然后求出异步符号块的平均误比特率,最后求解优化问题得到各天线的最优发射功率值。平坦瑞利衰落信道下的仿真表明:两发两收、BPSK调制、迫零检测的异步V-BLAST,误比特率为10-3时最优功率分配有2dB的性能改善。     

TPC-BASED STBC MULTIUSER DETECTION WITH LSE-RLS ALGORITHM

The Bit Error Rate （BER） performance of a Turbo Product Code （TPC） based Space-Time Block Coding （STBC） multiuser wireless system in the frequency-selective channels has been investigated. Both of the good error correcting capability of TPC and the large diversity gain of STBC can be achieved simultaneously. A Least Square Error-Recursive Least Square （LSE-RLS） algorithm is applied to estimate the channel and cancel the interference. Simulations show that the proposed system can obtain about 2.7dB gain in Es/N0 at the BER of 10^-3.     

分布式STBC-OFDM交织深度优化

该文在分布式发射天线场景下,考虑多径瑞利衰落信道,针对每个天线上分别采用交织分组子载波功率扩展的STBC-OFDM链路,提出了一种交织深度优化方法:根据分布式信道的多径数和多径时延,以最小化成对错误概率上界为目标,设置交织子载波分组的交织深度。在两发一收STBC, BPSK调制,由M.1225步行测试信道A, B组成的分布式场景下仿真,结果表明:当误比特率为10-5时,与传统方法相比,该文方法有1.5 dB的功率节省。     

基于预编码的全码率准正交空时分组码

针对传统八天线全码率准正交空时分组码解码复杂度高的问题,该文提出了两种基于预编码的传输方案。利用四天线正交码扩展得到新的八天线准正交码,结合两个反馈相位信息构成的预编码矩阵,使信道矩阵正交化,消除码间串扰,实现码元独立最大似然解码。发送端采用交织技术,进一步提高了性能,实现了双码元联合最大似然解码。和获得满分集增益的星座图旋转方案不同,预编码方案最大程度上减少了码间串扰,提高准正交码的性能。仿真结果表明,基于预编码的两种准正交码性能好于星座旋转准正交码,而且降低了解码复杂度。     

Combined turbo coding and unitary space-time modulation

Space-time coding is well understood for high data rate communications over wireless channels with perfect channel state information. On the other hand, channel coding for multiple transmit antennas when channel state information is unknown has only received limited attention. A new signaling scheme, named unitary space-time modulation, has been proposed for the latter case. In this paper, we consider the use of turbo coding together with unitary space-time modulation. We demonstrate that turbo coded space-time modulation systems are well suited to wireless communication systems when there is no channel state information, in the sense that the turbo coding improves the bit error rate (BER) performance of the system considerably. In particular, we observe that the turbo-coded system provides 10-15 dB coding gain at a BER of 10/sup -5/ compared to the unitary space-time modulation for various transmit and receive antenna diversity cases.     

异步V-BLAST中基于功率扩展的迭代并行干扰消除

在平坦瑞利衰落信道下,异步V-BLAST系统中,现有检测算法随信噪比提高误码率性能改善缓慢。为此,该文提出一种基于预处理矩阵的迭代检测算法:在发射端,通过预处理矩阵将发射信号扩展到整个数据帧上,以获取空时分集度;在接收端,采用低复杂的迭代并行干扰消除方法,由于在迭代过程中干扰重建基于预处理矩阵,所以上次迭代的检测误差被扩展,降低了迭代过程中的误差传播。仿真验证了所提方法的有效性,在8发4收场景下,误码率为10-3时,与现有串行干扰消除方法相比,带来了约7 dB信噪比增益。