MIMO系统的波束形成技术研究及其仿真

概述了智能天线中的波束形成技术和MIMO系统中空时分组码原理,基于传统的最小均方(LMS)算法和MI-MO系统中空时分组码,研究分析了两者相结合的可行性。     

STBC-VBLAST混合系统中基于GMD算法的预编码方案

为了获得最大信道容量,采用几何均值分解（GMD）将MIMO信道分解为若干相互独立且具有相同增益的并行子信道,从而使调制解调和编解码过程得到简化,在容量和差错率之间取得折中。将该方法与VBLAST接收机结合起来,在高信噪比下可以获得接近ML接收机的性能。为此,提出将GMD算法应用于STBC-VBLAST混合系统中VBLAST部分,仿真结果表明,该算法能够使混合系统的性能得以极大提高。     

Blind adaptive receiver for uplink multiuser massive MIMO systems

Herein, we consider uplink multiuser massive multiple‐input multiple‐output systems when multiple users transmit information symbols to a base station (BS) by applying simple space‐time block coding (STBC). At the BS receiver, two detection filters for each user are used to detect the STBC information symbols. One of these filters is for odd‐indexed symbols and the other for even‐indexed symbols. Using constrained output variance metric minimization, we first derive a special relation between the closed‐form optimal solutions for the two detection filters. Then, using the derived special relation, we propose a new blind adaptive algorithm for implementing the minimum output variance‐based optimal filters. In the proposed adaptive algorithm, filter weight vectors are updated only in the region satisfying the special relation. Through a theoretical analysis of the convergence speed and a computer simulation, we demonstrate that the proposed scheme exhibits faster convergence speed and lower steady‐state bit error rate than the conventional scheme.     

短波单载波空时分组码的频域均衡研究

短波通信受多径衰落、干扰复杂等影响严重。空时分组码(Space Time Block Code,STBC)技术在无需增加频谱资源和天线发射功率的前提下,可以利用多输入多输出(Multiple-Input Multiple-Output,MIMO)信道提供的分集增益提升传输可靠性。分析短波MIMO研究现状,提出短波单载波STBC频域均衡(Frequency-Domain Equalization,FDE)系统架构,针对短波信道引入的码间干扰研究MIMO MMSE-FDE均衡技术,并将单载波STBC频域均衡与时域均衡及短波现有波形进行仿真对比。仿真结果表明,相较于短波现有波形,单载波STBC频域均衡系统的可靠性有较大幅度提升,且性能与STBC时域均衡接近,但计算复杂度远低于STBC时域均衡。     

基于Ka频段的自适应MIMO调制算法

这里研究了一种应用于Ka频段卫星通信信道的自适应多输入多输出(MIMO,multiple-Input multiple-Out-put)调制算法,不同于一般Ka频段卫星通信的信道衰减补偿算法,该算法主要是能根据不同天气条件,利用MIMO系统的接收信噪比自适应的转换调制方式,以维持一定的目标比特率为目标,从而获取较高的系统吞吐量。仿真结果表明,该算法能有效应对Ka频段固定卫星通信信道下的严重信道衰落,兼顾系统性能和频谱效率,得到较高的吞吐量。     

一种用于CDMA下行链路的空时编码盲多用户检测

提出了一种适用于下行链路的盲多用户检测器,在下行链路的接收方只需进行简单解码和盲多用户检测就可以获得同采用多天线接收相同的效果。仿真结果表明当加入空时编码和盲多用户检测后对移动接收方南误码率有提高。     

BER Performance of Cooperative Transmission for the Uplink of TDD‐CDMA Systems

In time division duplex (TDD) code division multiple access (CDMA) systems, chip‐synchronous transmission in the uplink is obtainable, thus leading to free multiple access interference in flat Rayleigh fading channels plus additive white Gaussian noise. This motivates us to develop a novel cooperative transmission strategy that allows single‐antenna devices to benefit from spatial diversity using orthogonal signature sequences. The proposed cooperation is applicable to many digital modulation methods and achieves the fullest diversity level, low implementation complexity, and a full data rate. Closed‐form bit‐error‐rate expressions were also derived and compared to simulation results in order to evaluate its validity. A variety of numerical results demonstrated the cooperation's superiority over single transmission under the same transmit power constraint.     

密钥生成与管理系统

本论文是关于密钥生成及管理的软件。密钥生成的算法采用RSA算法,密钥的管理采用数据库技术来实现。在密钥生成的过程中,利用费马小定理判定素数并且生成大素数,利用欧几里德算法生成私钥。     

多副接收天线下的差分空时分组码系统分析

差分空时分组编码(DSTBC:Differential Space-Time Block Code)由于接收端不需要进行信道估计,可大大简化接收机复杂度,但是现有的研究大都集中在单天线接收。文章详细分析了DSTBC在多天线接收条件下的编码、调制和解调.仿真结果表明,多接收天线的DSTBC系统比单接收天线的STBC(Space-Time Block Code)系统,性能更为优越。通过比较可看出,在静止情况下或者中速移动但信道条件比较好的情况下,DSTBC系统完全可以作为STBC系统的替代。     

Performance analysis of MIMO systems with multiuser diversity

In this paper, we present a comprehensive performance analysis for multiple‐input multiple‐output (MIMO) systems with multiuser diversity over Rayleigh fading channels. We derive exact closed‐form expressions of the outage probability and the average bit error rate (BER) for different MIMO schemes, including the selective combining (SC), maximum ratio combining (MRC) and space‐time block codes (STBC). We also provide the explicit upper bounds on the BER performance. Finally, the mathematical formalism is verified by numeric results that study the interaction between the antenna diversity and the multiuser diversity. It is observed that the system performance is deteriorated as the number of transmit antennas increases in multiuser scenario, which is unlike the case in single‐user systems. Copyright © 2007 John Wiley & Sons, Ltd.