改进的MIMO系统球译码检测算法

针对球译码检测算法的搜索半径影响着其算法复杂度的问题,提出一种改进算法.改进算法对球译码检测算法的搜索半径乘上一个常量压缩因子,且在每层搜索中削减噪声因子的影响.通过缩减搜索球半径、缩小搜索范围实现算法复杂度的降低.仿真结果显示:在信噪比低于10 dB时,改进算法比传统球译码检测算法计算复杂度平均降低18％左右,同时误码性能损失较小.     

基于MIMO OFDM系统的一种低复杂度球型译码检测算法*

在已知的多输入多输出(MIMO)及正交频分复用(OFDM)系统的信号检测算法中,球型译码检测算法的译码性能十分接近于性能最优的最大似然检测算法,并且其译码复杂度有很大的降低,但其会受到译码半径的影响。普通的球型译码检测算法,信道噪声对算法的译码半径影响较大,为了降低信道噪声对译码半径的影响度,提出了一种新型的球型译码检测算法,该算法在译码初始半径分别根据两种不同的情况作出选择。仿真结果显示,其选择的译码半径受噪声的影响极小,达到了降低译码复杂度的目的。总体而言,新型的球型译码检测算法极大地降低了译码复杂度     

MIMO系统中一种新的时变信道跟踪方法

该文提出了时变平坦：豪落信道环境下多输入多输出（MIMO）通信系统中一种新的基于递归最小二乘法（RLS）的带干扰对消的信道跟踪方法（RLS—IC）。该方法将每个数据子流上的进行信道跟踪的滤波器等效为一个加长的新的滤波器,并把已解出的子流数据作为新的输入参数,应用RLS算法自适应调整新的信道跟踪滤波器参数。仿真结果表明,该文提出的带干扰对消的信道跟踪方法可以更好地跟踪信道变化,节省训练序列开销,同时比已有的递归最小二乘方法能提供更好的误符号率（SER）性能。     

多符号差分检测的低复杂度球形译码设计

在多符号差分检测系统中,深度优先的球形译码是一种典型的次优的检测算法。然而从复杂度角度来说,它仍有较高的计算复杂度,且存在流水线和并行操作困难等缺点。针对这些问题,目前主要从两个方面对该算法进行改进：一是通过选择合适的约束半径来降低复杂度;二是与K-Best（M）算法结合来解决并行操作问题。主要研究前者,并在现有的理论基础上,提出了两种半径选择方法,即线性半径和非线性半径。仿真结果表明,两种半径约束下的球形译码在复杂度上低于最大似然检测却同时能保证它们的性能损失小于0.5 dB。     

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。     

多用户MIMO系统的低复杂度天线选择算法

块对角化是一种用于多用户MIMO系统下行链路的预编码方案,它可以完全消除多用户间的干扰。论文就是针对采用块对角化预编码的多用户MIMO下行链路,基于信道F-范数提出一种新的次优天线选择算法。该算法计算复杂度较低。仿真结果显示,其系统容量接近采用最优算法的系统容量。     

多用户MIMO系统中的一种低复杂度用户选择算法

联合块对角化和几何均值分解(BD-GMD)是一种用于下行多用户多输入多输出(MU-MIMO)系统的预编码方案。在信噪比(SNR)较高的情况下,此方案在信道吞吐量和误符号率(SER)两方面都是渐进最优的。但是,在BD-GMD方案中,发射和接收天线的数量限制了能同时通信的用户数。在一个拥有大量用户的下行MU-MIMO系统中,为了使得系统总的吞吐量最大,基站必须从大量的用户中选出一个用户子集,同时对他们进行服务。采用穷尽搜索算法能得到最优的用户子集,但这种方法所需要的计算量太大。因此,提出了一种次最优但是计算复杂度较低的用户选择算法,用于采用BD-GMD方案的下行MU-MIMO系统。此算法具有随用户数变化的线性复杂度,另外,仿真结果显示,其总的吞吐量大致能达到采用穷尽搜索算法所获得的系统总吞吐量的95%。     

基于可靠性度量排序的λ-广义球形解码算法

针对欠定多输入多输出(MIMO)系统中信道矩阵非满秩的问题,提出基于可靠性度量排序的λ-广义球形解码(λ-GSD)算法。该算法将信道矩阵直接转换成满秩矩阵,然后采用基于可靠性度量的排序策略,将排序后由最小均方误差算法得到的次优解作为λ-广义球形解码算法的初始值,减小了初始搜索半径,同时对球形解码算法搜索半径的收缩进行了指数收敛加速处理。仿真结果表明,所提算法同最大似然检测算法和原λ-GSD算法相比较,能获得相同的误符号率性能,而平均运算时间比原λ-GSD算法有明显降低。     

一种低复杂度高性能的MIMO系统自适应检测算法

如何克服发射信号的重叠和码间干扰是MIMO系统信号检测技术面临的关键问题。信号检测算法的性能优劣是影响MIMO技术能否真正适于实际应用的关键因素。结合MLD算法高性能和MMSE-SIC算法低复杂的优点,对Hybrid算法进行了改进,提出了一种基于信道最大/最小特征值的自适应混合检测算法。该算法重新定义了自适应系数,并通过信道矩阵特征值的特性,自适应控制三种子混合算法检测数据流时的百分比,以达到更高的检测效率。仿真结果表明：无论信道在何种复杂环境下,该算法具有与MLD算法几乎相同的误码性能,计算复杂度也有很大的改善。     

A modified Guruswami-Sudan algorithm for decoding Reed-Solomon codes

We tighten a key estimate, which dictates the computational complexity of Guruswami-Sudan algorithm, on the lower bound of the degrees of freedom, and then propose a modified decoding algorithm for Reed-Solomon codes beyond half the minimum distance. The computational complexity of the modified algorithm is lower than the Guruswami-Sudan algorithm for the medium to high rate Reed-Solomon codes, and has the same asymptotic complexity as the algorithm proposed by Wu. Besides we also claim that our modified algorithm outperforms Wu's algorithm to some extent.     

Parallel sphere detector algorithm providing optimal MIMO detection on massively parallel architectures

Multiple‐input multiple‐output (MIMO) systems have attracted considerable attention in wireless communications because they offer a significant increase in data throughput and link coverage without additional bandwidth requirement or increased transmit power. The price that has to be paid is the increased complexity of hardware components and algorithms. The sphere detector (SD) algorithm solves the problem of maximum likelihood (ML) detection for MIMO channels by significantly reducing the search space of possible solutions. The main drawback of the SD algorithm is in its sequential nature, consequently, running it on massively parallel architectures (MPAs) is very inefficient. In order to overcome the drawbacks of the SD algorithm, a new parallel sphere detector (PSD) algorithm is proposed. It implements a novel hybrid tree search method, where the algorithm parallelism is assured by the efficient combination of depth‐first search and breadth‐first search algorithms. A path metric‐based parallel sorting is employed at each intermediate stage. The PSD algorithm is able to adjust its memory requirements and extent of parallelism to fit a wide range of parallel architectures. Mapping details for MPAs are proposed by giving the details of thread dependent, highly parallel building blocks of the algorithm. Based on the building blocks proposed, a mapping to general‐purpose graphics processing unit is provided, and its performance is evaluated. In order to achieve high‐throughput, several levels of parallelism are introduced, and different scheduling strategies are considered. Copyright © 2015 John Wiley & Sons, Ltd.     

MIMO雷达对高速运动目标搜索策略研究

高速运动目标,是现代雷达探测中遇到的一种新情况。针对海军相控阵雷达对海上空中高速运动目标的探测,推导了多元阵列的MIMO雷达探测概率的计算公式,在此基础上,计算了距离单元内目标探测概率,并比较了正交信号模式下与有向波束模式下MIMO雷达对高速运动目标探测概率。研究表明,对于高速运动目标,使用有向波束探测模式,在相同的信噪比下可以达到更高的探测效率。     

基于合作似然检测和球形译码的多用户多输入输出多跳中继系统

针对多输入输出(MIMO)系统在传输数据过程中的误码率(BER)和信道容量优化问题,提出一种基于合作似然检测和球形译码的多用户MIMO多跳中继系统。首先,该系统构建二阶协作的MIMO中继系统模型对信道数据的中继传输过程以及路径损耗、阴影衰落情况进行分析;接着,通过球形译码来推导出等效的最大似然规则进行对数正态阴影衰落检测;最后提出最大调和平均信道功率选择策略,基于相关性链路度量和最大信道功率阈值为用户选择误码率更小的接入链路,从而改善多用户MIMO系统的性能。实验仿真结果显示,与基于互信息最大化的多用户MIMO多跳中继系统以及基于解码转发和多入多出技术正交空时分组编码(STBC)的中继系统相比,该系统在数据传输过程中的平均比特误码率分别降低了27.4%和32.6%,平均信道容量分别提高了9.5%和12.7%,因此在减少误码率和提高信道容量上具有较好的效果。     

多用户MIMO系统下行收发联合设计

提出了一种改进的基于最小和均方误差(TMMSE)准则的MIMO系统下行链路收发联合设计算法,该算法通过迭代求解预编码和解码矩阵。相比于已有算法,充分利用了信道状态信息,借鉴BD算法的思想优化了迭代初值的选取。将求解Lagrange乘子的过程由非线性转化为线性,获得了Lagrange乘子的解析解,并使计算结果更加精确。仿真结果表明,该算法获得了更快的收敛速度,系统的误码性能得到显著提升,同时算法的计算复杂度明显降低。     

多用户MIMO系统低复杂度收发联合波束成形方案

基于多用户多输入多输出(MIMO)有限反馈系统提出了一种收发联合波束成形方法。该方法在发送端采用每个用户酉速率控制(PU2RC)波束成形技术,在接收端采用基于信干噪比(SINR)最大化的天线合并算法。天线合并算法利用用户SINR的广义Rayleigh熵特性寻找最佳的天线合并矢量。仿真结果表明,该方法能充分利用信道信息,不仅改善了传统PU2RC系统的和速率性能,相对于已有的迫零(ZF)联合波束成形方法,对信道状态信息的量化误差的敏感性更低,用户选择算法的复杂度更低,且低速率反馈条件下和速率性能更优。     

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)     

基于离散粒子群优化的多用户MIMO用户选择*

为了在降低计算复杂度的同时获得良好的性能,给出了一种基于离散粒子群优化的多用户MIMO用户选择方法.该方法基于sum-MSE预编码,所支持的用户数目取决于接收方的子流数之和,改变了传统的用户选择方法支持的用户接收天线数之和不大于发送天线数的限制.当移动台子流个数小于接收天线数时,所研究的用户选择方法可以增加同时服务的用户个数,获得更高的系统和容量.仿真结果表明,该方法能够在系统性能和复杂度之间进行良好的折中.     

Stable adaptive fuzzy control for MIMO nonlinear systems

In this paper, an indirect adaptive fuzzy control scheme is presented for a class of multi-input and multi-output (MIMO) nonlinear systems whose dynamics are poorly understood. Within this scheme, fuzzy systems are employed to approximate the plant’s unknown dynamics. In order to overcome the controller singularity problem, the estimated gain matrix is decomposed into the product of one diagonal matrix and two orthogonal matrices, a robustifying control term is used to compensate for the lumped errors, and all parameter adaptive laws and robustifying control term are derived based on Lyapunov stability analysis. The proposed scheme guarantees that all the signals in the resulting closed-loop system are uniformly ultimately bounded (UUB). Moreover, the tracking errors can be made small enough if the designed parameter is chosen to be sufficiently large. A simulation example is used to demonstrate the effectiveness of the proposed control scheme.     

Improved adaptive fuzzy control for MIMO nonlinear time-delay systems

This paper presents an improved observer-based indirect adaptive fuzzy control scheme for multiinput-multioutput (MIMO) nonlinear time-delay systems.The control scheme synthesizes adaptive fuzzy control with adaptive fuzzy identification.An observer is designed to observe the system state,and an identifier is developed to identify the unknown parts of the system.The update laws for parameters utilize two types of errors in the adaptive time-delay fuzzy logic systems,the observation error and the identification error.Performance analysis proves the superiority of the update laws in terms of faster and improved tracking and parameter convergence.Simulation results of two-link manipulator demonstrate the effectiveness of the improved control scheme.     

Order evaluation to new elementary operation approach for MIMO multidimensional systems

A new elementary operation approach (NEOA) for Roesser model realisation of multi-input and multi-output (MIMO) multidimensional (n-D) systems has been recently proposed, which can generate a lowest possible realisation but requires trying different processing manners for various possible realisations with different structures and orders. This paper develops two kinds of novel order evaluation methods and the corresponding algorithms for the realisation procedures A and B of the NEOA, respectively, such that the best processing manner for the lowest possible realisation can be determined with much less computational complexity. These new results enable us, for the first time, to know exactly the order of a realisation before actually conducting the realisation, and thus provide us a novel and high-efficiency way to explore the lowest possible realisation problem for MIMO n-D systems. Examples are given throughout this paper to illustrate the main idea as well as effectiveness of the proposed methods.