移动通信中V-BLAST系统及其检测算法研究

提高移动通信系统的容量是提高移动通信系统性能的目标之一。空时编码技术可以在一定衰落环境下提供高质量的编码符号,从而提高系统容量,因而在无线通信中得到了广泛的关注。贝尔实验室提出的垂直分层空时码系统(V-BLAST)是移动通信的一项重要技术,因其传输速率和频谱利用率都较高,已经开始在实际系统中应用。基于此,笔者主要研究垂直分层空时码系统的模型构成和常用检测算法,并对各种检测算法的特点和性能进行分析,在此基础上对算法进行改进,将传统的定序干扰消除算法和极大似然相结合,对改进算法进行仿真。     

一种快衰落下正交空时分组码的译码

准静态衰落信道下正交空时分组码MIMO系统的一种简单最大似然检测算法性能接近于最大似然检测算法．但在实际时变信道干扰下，性能表现较差。本文分析提出了在多个发送和接收天线下能有效消除时变信道对简单最大似然检测算法产生干扰的算法改进。计算机仿真表明，针对时变信道下的正交空时分组码MIMO系统，该译码算法性能实现简单、计算复杂度低，性能接近最大似然检测算法。     

非确定性MIMO系统的K-Best检测算法研究

研究无线信道优化问题,由于非确定性MIMO系统的信道矩阵行不满秩特性,导致MMSE-GDFE左预处理后引入了强干扰,使得传统K-Best算法产生了误码平层效应.为了消除误码平层效应,提出部分最大似然和K-Best结合算法,并在初始检测的强干扰区域利用部分最大似然算法获得局部最优解,降低强干扰对系统的影响消除误码平层效应,进而在局部最优解的基础上利用K-Best算法完成剩余符号的检测.保证MIMO检测器的软输出特性.仿真结果表明算法消除了传统K-Best算法中的误码平层效应,保证了检测的可靠性.     

MIMO-MC-CDMA系统分层空时非线性预编码

针对垂直分层空时方案（VBLAST）传统检测存在误层传输效应及复杂度高的问题,提出了一种多用户MIMO-MC-CDMA下行链路系统中基于QR分解的VBLAST非线性模代数预编码算法,该算法首先采用QR分解获得预编码矩阵,然后在发射端MC-CDMA子载波信道间进行非线性模代数THP预编码,可以有效地消除分层空时码的误层传输效应。在接收端采用迫零与最小均方误差准则,降低了下行接收机的复杂度。仿真结果表明,提出的算法比传统检测算法有效改善了系统的误码性能。     

基于V-BLAST的MIMO无线通信系统性能分析

重点对多输入多输出（MIMO）无线通信系统的信道模型、空时分组码（Alamouti）以及垂直分层空时码（V-BLAST）空间复用技术进行了仿真分析.首先利用MATLAB在信道建模中实现了基于瑞利环境下的信道容量仿真图,同时仿真并分析了天线相关性对信道容量的影响;然后进行了Alamouti方案和最大比接收合并（MRRC）之间的仿真分析;最后对V-BLAST系统中的线性检测（ZF）算法和最小均方误差（MMSE）算法做了仿真比较,从而得出V-BLAST系统优于非V-BLAST体系下的误码性能.     

一种高效的QMC检测算法

基于垂直分层空时码的MIMO-OFDM系统提出一种高效的QMC检测算法,该算法对信道矩阵进行一次排序QR分解,对最先检测的信号层采用ML-OSIC算法,用M算法检测中间的信号层,逐层增加保留值M以提高算法有效性,利用串行干扰消除检测余下的信号层。与QRD-M算法相比,QMC检测算法能降低计算复杂度。仿真结果表明,该算法以更低的计算复杂度获得更接近最大似然检测的性能,取得性能与复杂度之间的折中更理想。     

瑞利衰落MIMO信道下的检测算法研究

垂直分层空时码技术是提高无线信道数据传输速率的一种十分有效的方法.瑞利慢衰落MIMO信道下,MMSE检测算法能够很好的抑制信息流之间的干扰和噪卢的增强.针对瑞利快衰落MIMO信道.依据信号模型,应用多元统计分析、串行干扰消除及最佳排序相结合的方法,给出了一种逐符号检测的MMSE-OSIC检测算法,使系统的误码性能得到了提高.仿真实验结果表明,在快、慢衰落MIMO信道条件下,SSMMSE-OSIC检测算法与MMSE-OSIC检测算法,能够有效的改善各自适用系统的误码性能,提高频带利用率.     

下行LTE系统中基于格点减少辅助检测算法

LTE系统采用MIMO作为核心技术,需要良好的信号检测算法在接收端将发射信号尽可能无误地检测出来. 为了提高复杂环境中信号检测的性能,给出基于信道矩阵分解的格点减少预处理算法,可在一定程度上降低线性处理过程对噪声的放大. 现有基于格点减少技术的检测算法,虽然可以有效地提高MIMO系统的误比特率性能,但其检测性能与最优的ML算法相比仍然存在差距. 笔者在ML遍历搜索的思想和V-BLAST检测算法基础上结合格点减少技术,提出一种基于格点减少辅助分层检测算法. 仿真结果表明,在下行LTE系统中采用改进的格点减少辅助分层检测算法能够显著提高M IMO 系统的误码性能,检测性能近似最大似然算法.     

空间发射相关信道下的空时码性能

根据类空时码和类空时码不同的特点,研究了衰落信道的空间发射相关性对空时编码性能的影响,并分别给出发射相关条件下两类空时码的最大似然译码规则及其成对错误概率,通过仿真分析揭示了发射相关对两类空时码性能的影响。发射相关的存在会恶化空时码的误码性能,并且恶化的程度随着相关性的增强而增大,然而某些情况下,在低信噪比时,发射相关会起到改善误码性能的有益作用。空时码在发射相关条件下的性能将直接影响到空时码的实际应用。     

多天线阵列中基于矩阵求逆的BLAST和准正交STBC结合的HARQ算法的研究

提出了多天线阵列中基于BLAST和准正交STBC结合的HARQ算法,并采用低复杂度的矩阵求逆方法进行解码.推荐的算法不是如传统的ARQ算法那样重传同样的信号,而是将数据组成准正交空时码发射矩阵,重传的时候传输发射矩阵的下一行,并和以前传输数据联合进行空时码解码.所以推荐的算法可以额外获得空时码的分集增益,而在信道条件好和信噪比高时,由于没有重传的发生而可以获得BLAST的复用增益.对于部分发射矩阵联合空时码解码,本文提出了采用矩阵求逆的解码算法.仿真表明该算法和最大似然算法的性能相近而复杂度下降很多.本算法结合了BLAST和STBC以及HARQ的优势并采用了低复杂度的矩阵求逆算法,是一个既能够提高系统传输速率也能够提高系统抗干扰性能的HARQ方案.特别是本算法在所有接收天线数大于等于发射天线数的多天线阵列中有很强的实用性.     

LTE系统基于格基约减辅助V-BLAST算法

LTE作为以OFDM-MIMO为主要技术特征的第四代移动通信,它的终端信号检测实现比较困难,这就需要一种性能好、复杂度低的检测算法来实现。格基约减是一种在接收端对信道矩阵进行预处理,可以消除子信道间干扰和抑制噪声的增强。本文在已有的格基约减ELLL算法的基础上,提出一种限制条件更为宽松的对角格约减算法(DR)。该算法的计算复杂度要低于ELLL算法。在该算法的基础上,结合传统V-BLAST和K-best算法思想,给出了一种基于格基约减辅助的V-BLAST算法。仿真结果表明,在LTE系统中该算法能够在复杂度较低的情况下,性能更接近ML算法。     

Multiple symbol differential detection based on sphere decoding for unitary space-time modulation

Recently, a multiple symbol differential (MSD) sphere decoding (SD) algorithm for unitary space-time modulation over quasi-static channel has been proved to achieve the performance of maximum-likelihood (ML) detection with relatively low complexity. However, an error floor occurs if the algorithm is applied over rapid-fading channels. Based on the assumption of continuous fading, a multiple symbol differential automatic sphere decoding (MSDASD) algorithm is developed by incorporating a recursive form of an ML metric into automatic SD (ASD) algorithm. Furthermore, two algorithms, termed as MSD approximate ASD (MSDAASD) and MSD pruning ASD (MSDPASD), are proposed to reduce computational complexity and the number of comparisons, respectively. Compared with the existing typical algorithms, i.e., multiple symbol differential feedback detection (MS-DFD) and noncoherent sequence detection (NSD), the performance of the proposed algorithms is much superior to that of MS-DFD and a little inferior to that of NSD, while the complexity is lower than that of MS-DFD in most cases and significantly lower than that of NSD. Supported by the National Basic Research Program of China (973 Program) (Grant No. 2009CB320403), and the National Defense Pre-research Project of the 11th Five-Year-Plan of China (Grant No. 1060741001020102)     

长期演进系统中一种低复杂度球形译码算法

在长期演进(LTE)系统中,球形译码算法拥有接近于最大似然(ML)的误码率(BER)性能。针对在16QAM和64QAM等高阶调制情况下球形译码算法计算复杂度和所需硬件资源的急剧增加,提出了一种调整符号搜索策略的改进型球形译码算法。该算法在不同的检测层采用特定的符号搜索方案,并结合一种基于信噪比的动态调整半径方法。在无线瑞利信道环境下,对各种球形译码算法进行了仿真。仿真结果表明,提出的改进型算法基本保持传统球形译码算法较低的BER性能,同时还有效地降低了计算复杂度和硬件实现复杂度。     

Performance analysis of uplink MIMO MC-CDMA systems based on linear zero-forcing V-BLAST algorithm

A structure was proposed for multiple-input-multiple-output multicarrier code divi- sion multiple access （MIMO MC-CDMA） uplink transmission system. Linear zero- forcing V-BLAST （ZF V-BLAST） algorithm and maximum ratio combining （MRC） scheme was applied to the receivers. The average bit error rate （BER） expression was derived on condition that the number of receive antennas was larger than that of transmit antennas and it was verified by simulations. Numerical results show that the number of transmit and receive antennas, as well as the number of sub- carriers, all exert significant effects on the BER performance. The space diversity and frequency diversity show different abilities to improve the BER performance. The MIMO MC-CDMA system based on linear ZF V-BLAST algorithm is capable of achieving better BER performance than that of the conventional MC-CDMA system by reducing the number of transmit antennas or increasing the number of receive antennas.     

新的基于仿射投影算法的盲多用户检测器

多径衰落信道下的盲自适应多用户检测算法的运算复杂度通常都比较大,将基于仿射投影算法的盲多用户检测器与RAKE分集技术相结合,提出了一种盲自适应接收算法。该接收算法平衡了收敛速度和计算复杂度之间的矛盾,具有相对较好的收敛性能及较小的运算复杂度。通过模拟实验比较了几种算法的收敛、跟踪及误码性能,结果表明该方法具有明显的整体优势。     

A novel adaptive V-BLAST algorithm based on subspace tracking and Hermitian matrix perturbation theorem

A novel vertical Bell laboratories layered space-time(V-BLAST)system with adaptive successive interference cancellation(SIC)detector based on subspace tracking(SST)and Hermitian matrix perturbation theorem is proposed in this paper,and the corresponding optimal symbol detection order operation is obtained.Moreover,asymptotic limit theorems for the detectors are established.The final simulation results verify that the symbol error probability(SEP)performance,the immunity to channel estimation errors and the algorithm convergence rate are superior to that of the conventional V-BLAST detection algorithm when channel estimation errors exist.     

Computationally efficient near-optimal combined antenna selection algorithms for V-BLAST systems

The Vertical Bell Laboratories Layer Space–Time (V-BLAST) system using ordered successive interference cancellation (OSIC) detection is a popular system architecture featuring high data rate and moderate computational complexity. The performance of the V-BLAST system can be further improved by exploiting the diversity and closed-loop gain provided by the technique of combined antenna selection (CAS). In this paper, we investigate the design of CAS algorithms with a goal to minimize the system?s error rate. As the error rate of a system varies dramatically with the transceiver architecture, the proposed CAS algorithms explicitly take the VBLAST detection structure into account. Despite the optimal CAS can be achieved by exhaustively searching all the transmit and receive antenna subsets, the applicability of this brute-force approach is excessively limited due to its huge computational complexity. To this end, we propose two computationally efficient CAS algorithms by implementing a greedy strategy incrementally or decrementally to fully exploit the recursive structure of mean-square-error matrices between consecutive V-BLAST detection stages. Near optimal error rate performance can therefore be obtained with significantly lower complexity as verified by the extensive computer simulations.     

基于移动信标和DOA的声阵列网络自定位机制

研究了面向声阵列网络的自定位问题,提出了三种基于移动信标和波达方向(DOA)的最大似然自定位机制:基本最大似然估计(BML)、具有声信号传播延时补偿功能的最大似然估计(PCML)和基于二次计算的最大似然估计(RML).研究了声信号传播延时效应,并采用PCML和RML对此进行了补偿.详细分析了信标移动速度、DOA误差和信...     

A low-complexity hybrid algorithm based on particle swarm and ant colony optimization for large-MIMO detection

With rapid increase in demand for higher data rates, multiple-input multiple-output (MIMO) wireless communication systems are getting increased research attention because of their high capacity achieving capability. However, the practical implementation of MIMO systems rely on the computational complexity incurred in detection of the transmitted information symbols. The minimum bit error rate performance (BER) can be achieved by using maximum likelihood (ML) search based detection, but it is computationally impractical when number of transmit antennas increases. In this paper, we present a low-complexity hybrid algorithm (HA) to solve the symbol vector detection problem in large-MIMO systems. The proposed algorithm is inspired from the two well known bio-inspired optimization algorithms namely, particle swarm optimization (PSO) algorithm and ant colony optimization (ACO) algorithm. In the proposed algorithm, we devise a new probabilistic search approach which combines the distance based search of ants in ACO algorithm and the velocity based search of particles in PSO algorithm. The motivation behind using the hybrid of ACO and PSO is to avoid premature convergence to a local solution and to improve the convergence rate. Simulation results show that the proposed algorithm outperforms the popular minimum mean squared error (MMSE) algorithm and the existing ACO algorithms in terms of BER performance while achieve a near ML performance which makes the algorithm suitable for reliable detection in large-MIMO systems. Furthermore, a faster convergence to achieve a target BER is observed which results in reduction in computational efforts.