V-BLAST系统中一种简单的发射功率分配方案

采用发射功率分配方案可以有效地提高V-BLAST系统的性能。一方面,采用注水发射功率分配方案,可以有效地提高系统容量,另一方面,采用合理的发射功率分配方案,可以在固定数据速率时,改善误码率性能。本文针对第二种应用,给出了一种基于等信干噪比的发射功率分配方案,计算复杂度低,需要的反馈信令少,而且该功率分配方案与调制方式和检测算法无关。通过对MMSE串行干扰抵消和MMSE软干扰抵消检测算法仿真验证,其性能远好于不采用发射功率分配方案,同时接近基于拉格朗日极值法的功率分配方案性能。     

一种软输入软输出的迭代检测算法研究

MIMO技术在LTE-Advanced系统中扮演了重要角色,在不增加系统带宽和发射功率的前提下可极大提升系统的容量与性能,被认为是无线通信领域的重大技术突破之一。信号检测技术对整个MIMO系统的性能起着至关重要的作用,也是当前研究的热点。文章针对目前广泛采用的基于MMSE处理准则的MIMO信号检测方法提出一种以MMSESIC为核心的迭代译码检测算法方案,并与MMSE软检测算法和ML软检测两种算法进行对比分析,结果证明该迭代算法是很有吸引力的检测技术。     

频率选择性信道下空间相关MIMO的迭代检测技术

给出了一种频率选择性信道下空间相关MIMO的系统模型,其发送端采用准循环系统RA码,接收端采用一种对空间相关和非相关信道均适用的软干扰消除迭代检测算法.该算法首先采用基于最小均方误差检测(MMSE)的滑动窗口模型进行干扰消除,然后采用多天线联合最大似然检测(ML)以得到软信息,再将得到的软信息传递到译码器译码并输出发送比特的软信息作为下一次迭代的先验信息,即完成一次迭代.此模型能够取得比较好的误码率性能(BER),其改进方案既增加了发送端的调制域分集,性能又有提升.作为比较,基于软干扰消除的逐天线MMSE迭代检测的方案(ABA SC/MMSE)性能很差.仿真结果也证明了以上观点.     

一种新颖的低复杂度MIMO—BICM迭代接收机设计

本文提出了一种用于多入多出（MIMO）比特交织编码调制（BICM）系统的低复杂度迭代接收机方案．该方案在第一次迭代中采用线性最小均方误差（MMSE）滤波，而在随后的迭代中采用一种低复杂度MMSE结合软干扰消除（SIC）的算法来抑制残余干扰和噪声．该算法通过将软干扰消除后的残余干扰和噪声的各分量近似为不相关的随机变量，使得在MMSE滤波时不必矩阵求逆，从而大大降低了计算复杂度．仿真证实该方案可以获得和传统的基于MMSE结合SIC的方案几乎相同的性能。     

基于MSK和LT码的联合迭代译码算法

传统的简单级联编码调制系统在译码时会造成软信息损失.提出了一种基于MSK和LT码的联合软迭代译码算法,设计了算法的系统模型.利用LT码的软译码和MSK调制的SISO算法,进行联合软迭代译码,提高了编码调制系统的性能.仿真结果表明:在误码率为10-4时,提出的算法比传统的简单级联编码调制算法约有1.5 dB的编码增益.     

FSO MIMO系统中分层空时码检测算法

多输入多输出(MIMO)系统可以有效提高频谱效率和系统容量。基于MIMO系统重点研究了无线光通信垂直分层空时系统(V-BLAST)检测算法。首先分析了最大似然、线性迫零、最小均方误差以及排序干扰抵消等典型的传统检测算法,基于OOK调制和4PPM调制对采用不同检测算法的系统差错性能进行了仿真对比,最后对Turbo码与BLAST技术相结合构成的新系统采用了软输入软输出(SISO)迭代检测译码方案。仿真结果表明,分层空时检测算法中性能最优的是ML,其次是SISO-MAP,ZF算法性能最差;Turbo-BLAST系统可以有效提高无线光通信系统的抗干扰性能。     

具有低复杂度的 LDPC 已编码非相干酉空时调制系统设计简

提出一种克服无线信道瑞利衰落和高斯白噪声干扰的非相干编码调制MIMO系统方案。纠错码采用IEEE 802.16e中的非规则QC-LDPC码,非相干调制采用基于三角函数的酉空时调制(SC-USTM)。在接收端,推导出SC-USTM的最大后验概率（MAP）解调算法;为了降低复杂度,构造了SC-USTM的双解调器方案;为了改善双解调的性能,在置信传播（BP）迭代解码器和MAP解调器之间引入了迭代反馈机制。仿真实验表明LDPC已编码SC-USTM的MIMO系统比未编码USTM的MIMO系统在 误码率时,性能改善15~17 dB,并且整个系统具有较低的计算复杂度。     

频率选择性快衰落信道中的MIMO—OFDM系统检测算法研究

当MIMO—OFDM（Multiple Input Multiple Output-Orthogonal Frequency Division Multiplexing）系统工作于频率选择性快衰落信道时，子载波正交性会受到破坏从而引入子载波间干扰（Inter-Cartier Interference：ICI）．ICI的存在将严重降低那些传统的用于检测准静止频率选择性衰落信道下MIMO—OFDM的检测算法的性能．本文将Schniter针对SISO（Sinsle Inputsingle Output）OFDM系统提出的最优线性预处理扩展到MIMO—OFDM系统，基于这个信号模型推广了基于最小均方误差滤波的迭代软判决干扰抵消（Minimum Mean Square Errorfiltering based Iterative Soft Decision Interference Cancellation：MMSE—ISDIC）逐符号检测算法，同时提出一种基于准最大后验概率准则的迭代软判决干扰抵消（quasi—maximum A postefiofi probability based ISDIC：quasi—MAP-ISDIC）联合检测算法．仿真结果表明在本文考虑的系统参数设定下这两种检测算法的性能均优于文献[8]中算法的性能，其中quasi．MAP-ISDIC检测算法能够获得接近基于理想ICI抵消的MAP检测算法的性能。     

基于LDPC编码的MIM0系统迭代接收机研究

研究了基于LDPC编码无线MIMO通信系统中的软输出最小均方误差干扰抵消迭代(MMSE PIC)检测算法.针对初次迭代检测时PIC输出的后验比特对数似然比(LLR)不可靠的问题,利用MMSE滤波器输出的高斯近似表示,给出了基于后验概率估计的迭代干扰抵消检测算法,以提高检测器输出的编码比特对数似然比的可靠性.仿真结果表明:改进的检测算法优于现有算法.     

基于Kaczmarz迭代的大规模MIMO系统低复杂度软输出信号检测

大规模MIMO系统上行链路中,最小均方误差（MMSE）算法能获得接近最优的线性检测性能,但是涉及复杂度较高的矩阵求逆运算.本文基于Kaczmarz迭代提出一种低复杂度软输出信号检测算法,在算法实现中避免了矩阵求逆运算,将实现复杂度由O（K³）降为O（K²）.同时,引入了最优松弛参数进一步加快算法收敛,最后给出了两种用于信道译码的LLR的近似计算方法.仿真结果表明：所提出的Kaczmarz迭代软输出信号检测算法经过两到三次简单的迭代即可较快地收敛,并达到接近MMSE检测算法的误码率性能的水平,其性能与复杂度均优于基于矩阵近似求逆的一类检测算法.     

Low Complexity Iterative ICI Cancellation and Equalization for OFDM Systems Over Doubly Selective Channels

In this paper, a low complexity iterative intercarrier interference (ICI) cancellation and equalization technique is proposed for use in OFDM systems over doubly selective channels. In the iterative parallel interference cancellation/minimum mean square error (PIC/MMSE) detector has a high complexity and a restriction on the structure which can not remove the ICI in the initial stage. Therefore, an error propagation occurs due to the ICI regenerated by the incorrect output of soft-input soft-output (SISO) decoder. In order to reduce the error propagation, an MMSE detector based on the successive interference cancellation (SIC) is used in the initial stage. The low complexity MMSE detector is also derived to minimize the error propagation by quantifying the decision error before SISO decoding. In the first iteration, simulation results show that the proposed scheme outperforms the conventional PIC/MMSE scheme by about 3 dB at bit error rate $({rm BER})=1times 10^{-3}$ while maintaining the equivalent computational complexity. In the subsequent iteration, it is possible to cancel the ICI out in the received signals by the aid of soft log-likelihood ratio (LLR) fed from the SISO decoder. Converting the LLR to the decision error probability, the error covariance matrix is obtained more accurately. As a result, the error propagation can be effectively reduced by dealing with only the dominant components, when considering decision errors. Finally, simulation results show that the proposed scheme outperforms the conventional PIC/MMSE scheme.      

双迭代级联译码的Turbo V-BLAST结构

垂直贝尔实验室分层空时(V-BLAST)方案能有效提高系统的信道容量而成为研究的热点。但多发送天线造成了接收信号的空间干扰,这严重造成了误比特(误帧)系统性能的下降。在接收端,采用了迫零(Zero-forcing)排序的迭代混合干扰消除(Hybird Interference Cancellation,HIC)算法,相比迫零排序的串行干扰消除(Serial Interference Cancellation,SIC)算法,在降低复杂度的同时提高系统性能。干扰消除后的软信息经过Turbo迭代译码,得到的硬判决信息可以反馈回到V-BLAST的迭代ZF-HIC干扰检测,进行系统级联迭代。因此,文中的Turbo V-BLAST结构具有双迭代级联的多迭代环特征。仿真证明能很大程度上改进系统的BER和FER,是一种理想的系统结构。     

BLIND MULTIUSER DETECTION FOR V-BLAST CODED MULTICARRIER CDMA SYSTEM

Focusing on the space-time coded multiuser mobile communication systems in the frequencyselective fading environment, this paper proposes a Vertical Bell labs LAyered Space-Time （V-BLAST） coded Multicarrier Code-Division Multiple-Access （MC-CDMA） scheme and its blind channel identification algorithm. This algorithm employs an ESPRIT-like method and the singular value decomposition, and the channels between every transmit antenna of every user and every receive antenna of the base station are blindly estimated with a closed-form solution. Based on it, an equivalent Minimum Mean-Squared Error （MMSE） time-domain multiuser detector is derived. Moreover, the proposed scheme exploits the precoding in the transmitter in order to eliminate the constraint of more receive antennas than transmit ones, required by most conventional V-BLAST codec schemes. Computer simulation results demonstrate the validity of this proposed scheme.     

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。     

Low complexity per-antenna rate and power control approach for closed-loop V-BLAST

Previous studies have shown that per-antenna rate and power control can greatly increase the data throughput of vertical Bell Labs layered space-time (V-BLAST), while an extra transmit antenna selection can provide additional diversity advantage. We combine the transmit antenna selection with power and rate control for each antenna. We derive a simple criterion for minimum bit-error rate (BER) or minimum total transmit power when the data throughput is constant over time. Zero-forcing and zero-forcing successive interference cancellation detections are considered. For practical implementation, we also present a fast algorithm that gives near-optimal performance with very low complexity. Simulation results show that the proposed closed-loop BLAST outperforms the open-loop V-BLAST significantly in terms of BER performance, especially when the antennas exhibit strong fading correlations.     

Novel decoding of square QAM modulated mimo systems based on turbo multiuser detection

By introducing the bit-level multi-stream coded Layered Space-Time （LST） transmitter along with a novel iterative MultiStage Decoding （MSD） at the receiver, the paper shows how to achieve the near-capacity performance of the Multiple-Input Multiple-Output （MIMO） systems with square Quadrature Amplitude Modulation （QAM）. In the proposed iterative MSD scheme, the detection at each stage is equivalent to multiuser detection of synchronous Code Division Multiple Access （CDMA） multiuser systems with the aid of the binary representation of the transmitted symbols. Therefore, the optimal Soft-Input Soft-Output （SISO） multiuser detection and low-complexity SISO multiuser detection can be utilized herein. And the proposed scheme with low-complexity SISO multiuser detection has polynomial complexity in the number of transmit antennas M, the number of receive antennas N, and the number of bits per constellation point Me. Simulation results demonstrate that the proposed scheme has similar Bit Error Rate （BER） performance to that of the known Iterative Tree Search （ITS） detection.     

Precoding and decoding design for two-way MIMO AF multiple-relay system

In this paper, a joint precoding and decoding design scheme is proposed for two-way Multiple-Input Multiple-Output (MIMO) multiple-relay system. The precoding and decoding matrices are jointly optimized based on Minimum Mean-Square-Error (MMSE) criteria under transmit power constraints. The optimization problem is solved by using a convergent iterative algorithm which includes four sub-problems. It is shown that due to the difficulty of the block diagonal nature of the relay precoding matrix, sub-problem two cannot be solved with existing methods. It is then solved by converting sub-problem two into a convex optimization problem and a simplified method is proposed to reduce the computational complexity. Simulation results show that the proposed scheme can achieve lower Bit Error Rate (BER) and larger sum rate than other schemes. Furthermore, the BER and the sum rate performance can be improved by increasing the number of antennas for the same number of relays or increasing the number of relays for the same number of antennas.     

Transmit power allocation for a modified V-BLAST system

In this letter, we present a modification of Vertical Bell Laboratories Layered Space-Time (V-BLAST), and propose an effective transmit power allocation (TPA) scheme for the modified system. The proposed TPA scheme minimizes the uncoded bit-error rate (BER) averaged over all detection stages, and requires small feedback overhead. Simulation results show that the modified V-BLAST system with the proposed TPA scheme provides a significant reduction in the uncoded BER compared with the conventional V-BLAST system. When the minimum mean-square error ing is adopted, the modified V-BLAST system is found to achieve the uncoded BER performance comparable to that of the maximum-likelihood detection for the conventional V-BLAST architecture.     

分布式MIMO的Turbo检测算法

当信道码为卷积码时,针对V-BLAST类空时码的分布式MIMO,该文提出了两种迭代检测算法:最大似然迭代接收机及一种低复杂度的迭代检测接收机。最大似然迭代检测接收机的复杂度为O(2MTSlogM),低复杂度的迭代检测接收机的复杂度为 O(M2TM2RS2M) 。在准静态、单径瑞利衰落信道中,对低复杂度的迭代检测接收机的误码率性能进行了计算机仿真验证,与非迭代的迫零检测相比,低复杂度的迭代检测接收机节约比特信噪比约7.5dB;在相同的误码率下,迭代6次与迭代1次相比,可节约3dB的比特信噪比;随着迭代次数的增加,迭代效果越来越小。