通信信号处理的新技术——空时编码

多天线系统是第3代甚至未来的第4代无线移动通信中极具前途的一种技术。在论述多天线系统的信息论基础上,详细论述了将发射分集与编码相结合而产生的空时码技术,包括系统模型、空时分组码编译码方法和空时格码的星座图及性能仿真对比曲线,并指出了空时码技术的最新发展动态。     

V-BLAST的次优译码

在瑞利信道环境下V—BLAST系统的容量远远高于单天线系统。这是近年来V—BLATS系统成为研究热点的原因．针对如何实现这种高容量的V-BLAST系统，人们提出了多种解决方法．但由于有大量的求伪逆，迫零和排序计算，使得复杂度很高以至于难以实现．本文从一个全新的角度来解决V-BLAST的译码问题．文中所提出的方案是基于Greville递归求伪逆算法．利用G reville算法中的递归特性，将迫零向量的获取融合在求伪逆的过程中．仿真结果表明，本文的算法可以达到接近Golden算法的性能，但是复杂度大大降低。     

MIMO-OFDM系统中空时码性能分析

空时码技术可以提高数据的传输速率、频谱利用率和传输质量,在无线通信系统中得到了广泛的关注和研究。基于此对MIMO-OFDM系统中空时码的误码性能进行了研究和分析。在瑞利衰落信道下,比较了Alam-outi码和V-BLAST码的误码性能,以及联合Turbo码的空时码系统的性能。     

空时编码技术的研究

在第三代移动通信系统中,空时编码是抗信道衰落和提高系统容量的一种新的编码方式。本文介绍了三种主要的技术方案:分层空时码(BLAST),空时格码(STTC)和空时分组码(STBC)。     

空时码及其在移动通信中的应用

总结了空时码的分类，分析了各类空时码的性能特点和在移动通信中的应用，并对其研究方向和发展前景进行了探讨。     

Woven卷积码对级联空时格码性能的改善

Woven卷积码采用特殊的“编织”方式，将内码解码器的错误以某种形式分散开来，这种结构使其获得良好的纠错性能。本文研究与Woven卷积码级联方式改善空时格码的性能，首先针对级联方式选取合适的STCM(Space-Time Trellis Codes)，并提出具体级联方案，最后对非级联STCM系统和以Woven卷积码为外码的级联系统在衰落信道下的性能进行了比较，结果证明了采用Woven卷积码的级联STCM可以获得理想的性能。     

一种基于线性星座预编码和坐标交织的空时频发射方案

为获得存在多径衰落的MIMO-OFDM系统中高速率传输方案，给出了一种基于线形星座预编码和坐标交织的速率为1的简单空时频分组码．该传输方案通过线性星座预编码来获得频率分集增益，通过坐标交织变换来获得传输速率为1，且能适当改善系统的误码性能．仿真结果表明，与传统的结合空时码的OFDM系统相比，该方案能获得更大的分集增益、更高的频谱效率和更好的误码性能．在误码率为10^-2的未加信道编码的条件，本文方案与传统方案相比，至少能够提供约4dB的性能增益．若在接收端采用MMSE等线性接收方案，本文方案的计算复杂度并没有明显的增加。     

一种改进的空时Turbo网格码Log-MAP译码算法

提出应用于多天线系统的空时编码是未来无线移动通信中极具前途的一种技术.文中在详细论述了空时Turbo 网格码的基础上,针对Log-MAP译码提出了优化方案.仿真结果表明, 新的算法在大大降低译码复杂度的同时较好地保持了译码性能, 使其非常接近Log-MAP 算法的译码性能,同时也非常有利于硬件实现.     

空时编码中的BLAST分析

分层空时编码技术是近几年来通信领域新兴的研究方向,它主要用于解决高速无线通信下行传输问题。主要从分层空时编码的技术原理、设计准则及一种典型的译码算法入手,全面地分析了BLAST的特点,并通过仿真对几种典型的译码算法的性能进行了对比。最后对目前的研究动态做了简要的介绍。     

第三代移动通信中的空时编码技术

空时编码技术是一种有效提高无线通信系统容量的技术,在它的发展过程中产生了4种主要的技术方案:分层空时码(BLAST)、空时格码(STTC)、空时分组码(STBC)和酉空时码(USTC)。本文主要对这四种空时码的基本原理进行阐述,并对各种空时码类型的优缺点进行比较,最后讨论了空时码技术在第三代移动通信中的应用情况。     

多层空时编码方案的MIMO-OFDM系统研究

结合STBC和VBLAST混合编码结构的优点,提出将块分组编码应用于MIMO-OFDM系统.在发射端数据流分成两层输入块分组编码器后进行OFDM调制,在接收端,采用MMSE干扰抑制算法译码.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.     

垂直分层空时码的MAP检测器及其神经网络实现

该文基于最大后验概率准则,给出了垂直分层空时码的最佳检测箅法。算法对接收到的符号矢量的符号分量进行逐个地判决以使误符号率最小。同时还详细说明了径向基函数神经网络可以完全等价于最大后验概率检测算法,由于神经网络的硬件可实现性,本文提出的算法是可能在实际中应用的。     

Interference suppressing for cellular MIMO system based on turbo receiver

Space-Time Coding （STC）, which combines channel coding, modulation, and multiple transmit antennas, is a powerful scheme to achieve higher data rates and combat fading in wireless systems, in this paper, we propose a soil/cancellation turbo equalization scheme to suppress Co-Channel Interference （CCI） in STC systems. The simulation results show that the proposed method significantly improves the system＇s ability of interference suppression, while preserving the space-time structure.     

An Efficient Scheme to Achieve Differential Unitary Space‐Time Modulation on MIMO‐OFDM Systems

Differential unitary space‐time modulation (DUSTM) has emerged as a promising technique to obtain spatial diversity without intractable channel estimation. This paper presents a study of the application of DUSTM on multiple‐input multiple‐output orthogonal frequency division multiplexing (MIMO‐OFDM) systems with frequency‐selective fading channels. From the view of a correlation analysis between subcarriers of OFDM, we obtain the maximum achievable diversity of DUSTM on MIMO‐OFDM systems. Moreover, an efficient implementation strategy based on subcarrier reconstruction is proposed, which transmits all the signals of one signal matrix in one OFDM transmission and performs differential processing between two adjacent OFDM blocks. The proposed method is capable of obtaining both spatial and multipath diversity while reducing the effect of time variation of channels to a minimum. The performance improvement is confirmed by simulation results.     

Enhanced Multi-Antenna Technologies on OFDM for Future Mobile Communication Systems

Various types of multi-antenna techniques have been discussed to realize high speed data transmission in mobile communication systems. Those multiple antenna systems obtain space diversity gain by utilizing multi-paths as independent channels from transmitter and receiver. One important issue to utilize the powerful diversity gains of those multi-antenna technologies is how to create independent channels between transmitter and receiver. Almost all of conventional multi-antenna technologies have been discussed with assuming that there is not any correlation among channels between transmitter and receiver. However in realistic world this assumption is not always true and the correlation among channels becomes very high. This high correlation drastically degrades the performance of those multi-antenna technologies. In this paper we present an enhanced transmission diversity method to solve the problem of high correlation among channels. The following contents of this paper mainly focus on the Space Time Turbo Coding in OFDM systems, however the concept of the presented method can be adopted in various types of multi-antenna systems. This revised version was published online in August 2006 with corrections to the Cover Date.     

光码分多址的多脉冲检测解码器

提出一种新的光码分多址解码器 ,该解码器基于多脉冲检测 ,能充分利用信号的能量进行解码 ,并且 ,其结构与复杂性也完全独立于对系统中其他用户扩频序列的掌握和系统中的用户数 ,具有较好的可实现性。     

Improved Design Criterion for Space‐Frequency Trellis Codes over MIMO‐OFDM Systems

In this paper, we discuss the design problem and the robustness of space‐frequency trellis codes (SFTCs) for multiple input multiple output, orthogonal frequency division multiplexing (MIMO‐OFDM) systems. We find that the channel constructed by the consecutive subcarriers of an OFDM block is a correlated fading channel with the regular correlation function of the number and time delay of the multipaths. By introducing the first‐order auto‐regressive model, we decompose the correlated fading channel into two independent components: a slow fading channel and a fast fading channel. Therefore, the design problem of SFTCs is converted into the joint design in both slow fading and fast fading channels. We present an improved design criterion for SFTCs. We also show that the SFTCs designed according to our criterion are robust against the multipath time delays. Simulation results are provided to confirm our theoretic analysis.     

Block‐wise Alamouti schemes for OQAM‐OFDM systems with complex orthogonality

Offset quadrature amplitude modulation‐based orthogonal frequency division multiplexing (OFDM) systems cannot be directly combined with the Alamouti code because of the intrinsic imaginary interference. In this paper, we propose a block‐wise space‐frequency block coding (SFBC) scheme and a block‐wise space‐time block coding (STBC) scheme for offset quadrature amplitude modulation‐based OFDM systems, which achieve bit error rate performances that are close to OFDM systems. The proposed schemes satisfy the orthogonality condition of the Alamouti code in the complex field with guard band/intervals. To improve the spectral efficiency of the block‐wise SFBC scheme, we also consider the case without the guard band. It is observed that only the two innermost subcarriers do not satisfy the complex orthogonality condition when the guard band is removed. Then, a simple equalization scheme is proposed to independently equalize the two innermost subcarriers. Simulation results show that the block‐wise SFBC scheme works well under channels with mild‐to‐moderate frequency selectivity, and the block‐wise (STBC ) scheme suffers less than 1 dB loss under severe frequency selective channels at the bit error rate of 10 ^− 3, when only a simple one tap zero‐forcing equalizer is employed. Copyright © 2016 John Wiley & Sons, Ltd.     

基于多脉冲检测的光CDMA解码器

本文提出一种新的光ＣＤＭＡ解码器－基于多脉冲检测的光ＣＤＭＡ解码器,并对其解码性能与传统的相关解码器进行对比分析。     

长电缆数字化传输系统的可靠性设计

纠错编码被广泛应用在各种数字通讯、数字广播和数据存储系统中。随着单片机、DSP和FPGA等器件的快速发展,越来越容易在各种通用硬件平台上实现纠错编码。在长电缆的地震数据数字化传输中,采用单片机和FPGA实现Reed Solomon编码和交织编码,保证恶劣传输条件下可靠的高速数据传输,就此传输系统的功能结构以及编解码方案做简要介绍。