Turbo Trellis Coded Modulation with Enhanced Transition Metric over Rayleigh Fading Channels

This paper investigates the performance of a new Turbo Trellis Coded Modulation scheme over correlated flat fading channels with channel interleaving. The novelty of the scheme is based on the application of a new modified transition metric incorporated in the symbol-by-symbol MAP algorithm. We consider frequency non-selective, slow Rayleigh fading channels. Extensive simulation results together with EXIT chart analysis show that the proposed scheme achieves better performance compared to the conventional transition metric when channel state information is not available at the decoder. Kostas V. Koutsouvelis was born in Thessaloniki, Greece, on July 16,1970. He received the degree Diploma in Electrical Engineering from Aristotle University of Thessaloniki, Greece in 1996 and the Master degree in Satellite Communications Engineering from University of Surrey in 1997. From 1998 to 2003 he was involved in the development of V5.2 interface as a senior software designer in Intracom plc. In 2004 joined the research and development division of Hellenic Telecommunication Organization (OTE) and his also PhD candidate at Aristotle University of Thessaloniki working with Turbo codes and Turbo Coded Modulation. Christos E. Dimakiswasborn in Serres, Greece, on July 27, 1955.He received the degree Diploma in Electrical Engineering from the Aristotle University of Thessaloniki, Greece, in 1980. Working in the satellite communications and in the error correcting coding area he received his PhD degree in digital telecommunications from the Aristotle University of Thessaloniki, Greece, in 1994. In 1980 he joined the Department of Electrical Engineering, Telecommunications Division of the Aristotle University of Thessaloniki as a research fellow. Since 1997 he is a lecturer of digital communications at the same University. Presently, his research interests include digital modulations, coding theory, satellite and mobile communications and system simulation. Stamatis S. Kouris was born in Corfu, Greece. He received the degree of Doctor Engineer in Electrical Engineering from the University of Rome, Italy and the Diploma of Specialization in Telecommunications of the Instituto Superiore, University of Rome, in 1960 and 1963 respectively. In 1971 he was awarded the PhD Degree of the University of Edinburgh, UK. In the 1974 he was awarded a specialization Diploma in administration from the University of Pomona CA, USA. He is a member of the Technical Chamber of Greece, URSI, IRI and other organizations. Since 1964 he has been involved in research on radio-propagation, antennas and microwaves, working mainly at the Fondazione Bordoni, Italy, University of Edinburgh, UK and University of Thessaloniki, Greece. He has published several papers on radio-propagation, antennas, communication transmission and microwaves and millimeter-waves devices. In 1976 he joined with the Department of Electrical Engineering, School of Engineering Science, Aristotle University of Thessaloniki. He served as professor of telecommunications from 1978 to 2002. Since 2002 he is an emeritus professor.     

MIMO系统中空时分组编码的信道容量

在多输入多输出（MIMO）系统中，建立空时分组编码模型，在分析瑞利衰落下正交空时分组码接收信噪比的基础上，得到了正交空时分组编码信遗容量的表达式，并采用数值计算的方法对其进行分析论述，得出在接收天线数一定的情况下，增加发送天线数所能得到的信道容量的上界。同时，分析证明，在发送天线数一定时，正交空时分组编码信道容量随接收天线数的增加而增加。在接收天线数一定时，信遗容量也随着发送天线数的增加而增加，但当发送天线数增加到一定数量时容量的增加就变得不十分明显。     

适用于快速衰落信道的差分空时调制技术

介绍了适用于瑞利快变衰落信道不需信道参数估计的差分空时码研究进展。根据差分空时码的设计原理及性能标准,综合比较了现有方案的特点,揭示了这些方案之间的联系,并对差分空时码技术的应用前景进行了展望。     

空时格码迹准则在频选衰落信道下的证明

迹准则是当系统中发射与接收天线数之积较大时设计空时格码的准则,该准则最初是为平衰落信道而设计的。该文证明了迹准则在频选衰落信道下仍然成立,且仿真亦表明当信道为频选衰落时,迹准则意义下好码的性能优于其它码的性能。     

衰落信道下卷积码的软判决译码

本文将交织、信道输出软信息、信道特征软信息相结合,研究Rayleigh衰落信道下卷积码的Viterbi软判决译码,在利用和不利用信道状态信息(CSI)两种情况下给出软判决的支路度量计算公式和性能仿真结果,计算了卷积码的性能上界;研究了解调器输出量化门限(量化级数目、量化间距)对译码性能的影响.结果与硬判决译码及AWGN信道的相关结论进行了比较.     

具有不完全信道状态信息MIMO系统的优化设计

 本文研究了不完全信道状态信息(CSI)对多输入多输出(MIMO)系统容量的影响.基于平均功率和平均误码率的约束条件,我们提出了一种利用不完全CSI进行功率自适应调制的优化设计方案.根据Wishart矩阵的统计分布,我们导出了该系统容量的封闭表达式.研究结果表明:在具有不完全CSI的MIMO系统中,利用不完全CSI进行设计可以显著地提高系统的容量.     

Keyhole信道下正交空时分组码的性能分析

在某些MIMO（multiple—input multlple-output）衰落环境下，发射或者接收信号不相关，但是系统的信道容量依然很低，这种现象称之为Keyhole效应．本文针对Keyhole衰落MIMO信道，在任意的收发天线数目下，对正交空时分组码进行了性能分析，通过矩生成函数的分析方法，分析了Keyhole信道可以提供的分集增益，给出严格的封闭的符号错误概率表达式．并且针对收发天线数目不相等的情况，给出简洁的近似结果．在Keyhole衰落信道下的计算机仿真表明，，严格的分析结果与仿真结果一致，在高信噪比下，近似表达式也与仿真的结果吻合。     

Rayleigh衰落信道中分组码最大似然译码的性能

摆脱了传统代数译码方法,对分组码进行基于广义阵列码（ＧＡＣ）结构的网格译码（Ｔｒｅｌｌｉｓ ｄｅｃｏｄｉｎｇ）,研究了Ｒａｙｌｅｉｇｈ衰落信道中分组码与这种软判决最大似然译码方法相结合的性能。模拟结果显示。分组码采用网格译码,可为移动衰落信道带来显著的性能改善。     

基于双向逐幸存路径处理的空时格形码软判决自适应解码

本文提出一种针对TDMA下行链路的空时格形码自适应解码算法.为充分利用下行链路相邻时隙前导序列中的正交导引信号,该解码算法采用了双向逐幸存路径处理技术——正向处理利用基于当前时隙前导序列的自适应信道估计实现正向解码,并将软判决结果传递给反向处理模块;以正向软判决为先验知识,反向处理利用基于下一时隙前导序列的自适应信道估计实现反向解码,并将反向软判决作为最终结果输出.计算机仿真结果表明:在存在卷积外码的情况下,与基于最大似然序列检测的单向硬判决解码相比,基于所提出算法的软判决解码在多普勒频移小于60赫兹的时变信道中可提供1～2dB的增益.     

适用于串行级联结构的广义递归网格空时码设计

该文结合网格空时码(STTC)和分层空时码(BLAST)的优点,利用多个高码率卷积码,设计了一类适用于串行级联结构的广义递归STTC(G-RSTTC)。相比于传统以递归STTC为内码的串行级联空时码(SCSTC),其数据速率可随发送天线数增加而线性增加;相比于以BLAST为内码的SCSTC,基于G-RSTTC的SCSTC可获得更大的分集增益和编码增益。     

衰落信道下Turbo网格编码调制在图像传输中的性能研究

基于Turbo码和网格编码调制的特点,该文分析了TTCM的具体编译码方法,并分析比较了TTCM在8PSK调制下结合两种典型映射方案UP(Ungerboeck Partitioning),BP(BlockPartitioning)在Rayleigh信道中用于静态图像传输时的性能,给出了计算机仿真结果和评价图像传输质量的峰值信噪比(PSNR).     

MIMO系统中一种低复杂度联合检测算法

本文改进了概率数据辅助(probabilistic data association,PDA)算法,将其应用于MIMO(multiple-input multi- ple-output)系统中,并提出了一种partial-PDA LDPC联合检测算法,比PDA LDPC联合检测算法的计算复杂度更低。计算机仿真结果显示,partial-PDA LDPC联合检测算法能够取得非常接近于PDA LDPC联合检测算法的系统性能。     

The Code Design of the Space-time Trellis Codes with Dynamic Transmit Power Allocation

Space-time trellis codes (STTCs) have been shown to efficiently use transmit diversity to improve the error performance. In existing space-time trellis codes, the transmit power is equally distributed across all transmit antennas. However, this power allocation strategy is not optimum regarding the error performance. In this paper, we propose a design of space-time trellis codes with dynamic transmit power allocation (STTCs/DTPA), when partial channel state information (CSI) is available at the transmitter side. It is demonstrated that this new scheme can achieve a full diversity order and have much better error performance than the standard STTCs scheme, the existing STTCs/DTPA, and some other closed-loop transmit diversity schemes with partial CSI.     

空时编码在宽带无线接入系统空中接口中的应用

近年来 ,空时编码作为一种发送分集技术已引起人们广泛的关注。空时编码技术是一种把发送分集和编码相结合的技术 ,它能在不牺牲带宽的情况下提供好的性能。本文介绍了空时编码及其相关的概念 ,阐述了正交空时分组编码的编解码过程。本文还讨论了空时编码技术在固定宽带无线接入系统空中接口部分的应用。     

最大化瑞利熵的干扰对齐优化算法

干扰对齐技术常采用迭代的方法进行预编码矩阵与干扰抑制矩阵的设计,然而目前采用的迭代方法并不能做到完全的干扰对齐。针对这种情况,提出了一种新的干扰对齐优化算法,避开了反转信道的操作。该算法在最大化信干噪比算法的基础上加入完全干扰对齐的约束条件,将系统中各用户的所有干扰对齐约束条件进行奇异值分解,最终通过瑞利熵最大化的求解方法联合迭代求解发送侧的预编码矩阵与接收侧的干扰抑制矩阵。仿真结果表明,所提优化算法在较高信噪比时不同天线数下的和速率、不同迭代次数下的和速率等方面都优于原最大信干噪比算法。     

低信噪比下归零Turbo码码长及其帧同步识别

针对目前高斯消元法在归零Turbo码长、帧同步等参数识别过程存在容错性能低且计算复杂度高的缺点,该文提出一种低信噪比(SNR)下基于差分似然差(DLD)的识别算法。首先通过定义差分似然差的概念,利用归零Turbo码帧头两码元差分似然差为正值(“+”)的特性,构建分析矩阵实现码长的识别;其次,提出基于最小错误判决准则下的差分似然差“+”位置门限判决方法,完成帧同步;最后,从工程实际出发,遍历寄存器个数的可能值,实现码率、寄存器个数以及交织长度识别。仿真实验表明：所提算法对于归零Turbo码码长、帧同步等参数识别有效,差分似然差“+”位置分布与分析的数据结构特征一致,判决门限能够有效判断差分似然差“+”位置,同时,算法容错性能较强,在信噪比为–5 dB条件下,码长、帧同步等参数识别率能够达到90%以上,并且算法的复杂度远小于现有算法。     

采用两条支路分集接收的相关瑞利衰落信道容量

本文研究采用两条支路最大比合并(MRC)或选择合并(SC)分集接收的相关瑞利衰落信道理论容量推导恒定发射功率自适应M进制正交幅度调制(M-QAM)的频谱效率,并将它们与独立同分布瑞利信道理论容量进行比较,其结果对收发信机之间无视距分量路径、接收机上分集天线之间的距离小于半个波长的无线通信系统设计具有指导作用.     

基于MIMO的可见光通信中的信道均衡

针对基于多输入多输出(MIMO)的室内可见光通信(Visible-Light Communication,VLC)系统中存在的码间串扰(ISI)问题进行了分析,并提出了适用于MIMO可见光通信系统的信道均衡方案及实现方法.仿真实验结果表明,该方法可以有效降低MIMO可见光通信系统中的码间串扰的影响.     

状态网格图的LDPC码在OFDM系统中的应用

介绍了LDPC码的编译码技术,提出了一种新颖的2状态网格图译码算法,研究了该码在OFDM系统中的性能,对不同的译码算法进行了比较.仿真结果表明,LDPC码在OFDM基带传输系统中用2状态网格图对其译码能够更好的对错误码进行纠错,提高码字性能,信息传输速率会大大提高.     

An MMSE Decoding Algorithm without Matrix Inversion in QSTBC

The matrix inversion operation is needed in the MMSE decoding algorithm of orthogonal space-time block coding （OSTBC） proposed by Papadias and Foschini. In this paper, an minimum mean square error （MMSE） decoding algorithm without matrix inversion is proposed, by which the computational complexity can be reduced directly but the decoding performance is not affected.