VBLAST系统中检测技术的研究

首先研究VBLAST系统中几种经典串行干扰抵消算法(SIC),包括QR检测算法,ZF检测算法和MMSE检测算法.在此基础之上,分析和比较了一种改进的检测算法,改进算法主要采用最大似然检测(ML)和串行干扰抵消(SIC)相结合的方法,目标是有效的减少传播误差,从而以少量的复杂度换取误比特性能的提高.分析和仿真结果表明,与经典检测算法相比,改进算法能够很大程度改善系统的误比特率.     

VBLAST-OFDM系统中改进的QR分解检测算法

基于VBLAST-OFDM系统中传统QR分解算法,将最大似然和并行干扰消除的思想引入QR分解算法中,提出了对QR分解算法的改进方法,克服了传统QR分解算法检测性能差的缺点,运用QR分解从最后两层信号开始,等效为2收2发的MIMO系统。用最优算法检测判决后,回代到原QR分解算法检测余下层信号;或者依次并行消除已判决信号的影响,再进行下个等效MIMO系统的判决,直至所有信号检测完毕。仿真结果表明,本文改进的QR分解检测算法比传统的QR算法和迫零算法在误码性能上得到改善。     

混合STBC-VBLAST系统天线选择方案研究

研究表明MIMO系统中接收端SNR是一加权卡方随机变量,其权值为相应信道协方差逆阵的对角元素。为获得传输效率和传输可靠性间的折衷,利用协方差矩阵逆阵的对角元素,提出一种基于最小平均误码率（BER）的混合STBC-VBLAST发射天线选择方案。通过与传统无选择的VBLAST系统和有选择的VBLAST系统的BER和容量分别进行仿真比较,验证了所提混合STBC-VBLAST系统天线选择方案的优越性。     

Pilot Symbol Assisted Hybrid Detection for OFDM‐Based Spatial Multiplexing Systems

In this paper, we provide a new detection scheme for a pilot symbol assisted interference nulling and cancellation operation to reduce unexpected effects owing to parallel transmission in orthogonal frequency division multiplexing (OFDM)‐based spatial multiplexing systems. We have shown that the investigated OFDM vertical Bell laboratories layered space time (VBLAST) detection based on hybrid processing performs better than ordinary OFDM‐VBLAST detections based on serial processing and parallel processing, respectively.     

STBC与VBLAST联合编码方案研究

在多输入输出(Multiple-Input Multiple-Output,MIMO)系统中提出一种块分组编码与VBLAST的联合编码方案,该方案对最先检测的2层数据流采用块分组编码,其余层采用垂直分层空时码(Vertical Bell Layered Space-Time Code,VBLAST)的编码方式,MIMO系统同时具有了空时分组码(Space Time Block Code,STBC)可以降低误码率的优点与VBLAST能够提高系统容量的优点。块分组编码将数据符号按层分块后交叉通过不同的天线对发射,数据流之间产生了一定交织效果,使编码获得了更好的分集增益,在接收端结合QR分解的最大似然解码算法进行解码。仿真结果表明该联合编码方案与传统的Alamouti编码和VBLAST的联合编码方案相比误码率性能有较大改善。     

基于VBLAST的水声MIMO高速通信技术研究

为实现高速水下通信,提出了一种基于VBLAST（贝尔实验室垂直分层空时）编码的水声MIMO（多输入多输出）通信技术。该技术通过在发射端和接收端同时采用多个阵元进行多发多收,借助空间复用,可有效解决水下通信系统带宽资源缺乏的难题,使系统在不增加带宽的条件下成倍提高数据传输速率。在水声MIMO通信系统的接收端,提出采用带有二阶数字锁相环、基于自适应空时判决反馈均衡的相干解调技术。该技术可有效克服水声MIMO信道中的多径干扰及同频干扰,且能自适应跟踪信道变化。仿真及湖试结果证明了所提水声MIMO高速通信技术的良好性能。     

基于VBLAST—OFDM的平行循环迭代QR分解检测算法

论文提出了一种基于VBLAST—OFDM系统的平行循环迭代QR分解检测算法,称为P-IQRD算法。该算法主要克服循环迭代QR分解算法最先检测层性能差的缺点,将平行算法的思想引入到循环迭代QR分解算法中,进一步抑制了误码传播现象,有效提高了系统的检测性能。仿真结果表明,文中提出的P-IQRO算法比循环迭代QR分解算法、传统的平行算法、QR算法和迫零算法在误码性能上要好。     

Euclidean Geometry LDPC-VBLAST System Design and Performance Evaluation

Among popular multi-transmit and multi-receive antennas techniques, the VBLAST (Vertical Bell Laboratories Layered Space-Time) architecture has been shown to be a good solution for wireless communications applications that require the transmission of data at high rates. Recently, the application of efficient error correction coding schemes such as low density parity-check (LDPC) codes to systems with multi-transmit and multi-receive antennas has shown to significantly improve bit error rate performance. Although irregular LDPC codes with non-structure are quite popular due to the ease of constructing the parity check matrices and their very good error rate performance, the complexity of the encoder is high. Simple implementation of both encoder and decoder can be an asset in wireless communications applications. In this paper, we study the application of Euclidean geometry LDPC codes to the VBLAST system. We assess system performance using different code parameters and different numbers of antennas via Monte-Carlo simulation and show that the combination of Euclidean geometry LDPC codes and VBLAST can significantly improve bit error rate performance. We also show that interleaving data is necessary to improve performance of LDPC codes when a higher number of antennas is, used in order to mitigate the effect of error propagation. The simplicity of the implementation of both encoder and decoder makes Euclidean geometry LDPC codes with VBLAST system attractive and suitable for practical applications.     

一种多用户VBLAST MIMO系统快速非线性检测算法

提出了一种针对多用户CDMA VBLAST MIMO系统结构的快速非线性检测算法,该算法首先通过核方法将接收端多个天线收到的信号进行非线性映射,得到新的数据空间,然后对其进行加权求和得到输出信号,最后形成系统判决输出。为了避免直接矩阵求逆运算,权系数的求解采用递增方式进行,这将显著减小算法计算量和复杂性。仿真结果表明:提出的算法在误码率方面能够取得明显优于常规线性MMSE算法的性能,算法的有效性得到验证。     

OFDM系统的联合收发机设计

Orthogonal Frequency Division Multiplexing (OFDM) is an effective technique to deal with a frequency selective channel since it can convert the channel into some flat fading subchannels. However, very different output SNR values of the sub-channels will lead to poor bit error performance when a linear equalizer and Equal Bit Allocation (EBA) are adopted in OFDM systems. So, we proposed three novel nonlinear Joint Transceiver (JT) schemes based on Zero-Forcing (ZF) criterion and Minimum Mean Square Error (MMSE) criterion respectively, which can transform all subchannels of an OFDM system into subchannels with identical channel gain. Thus, EBA is equivalent to the Optimum Bit Allocation (OBA) for these subchannels. Numerical analysis helps us to obtain the theoretical approximate BER values of the JT scheme. Simulation results verify the numerical analysis and confirm that the performance of our proposed JT scheme greatly outperforms the traditional linear equalizer with EBA at moderate and high SNR values.