Iterative multi-user detection and decoding for space-time block coding systems

1 Introduction Recently space–time coding (STC) techniques [1] are designed to combat fading in wireless links by utilizing multiple antenna systems, in which transmit diversity and coding gains can be exploited without sacrificing additional power and b…     

Soft-Decision Decoding of Punctured Convolutional Codes in Asynchronous-CDMA Communications Under Perfect Phase-Tracking Conditions

In this paper, the performance of punctured convolutional codes of short constraint lengths is discussed. The punctured codes are used to provide error protection to a particular user in an asynchronous CDMA system. A perfect phase reference is assumed to be available throughout this paper. A slow fading Rician channel is assumed. Maximum likelihood decoding through a Viterbi algorithm is used to decode the information symbols. Soft-decision decoding of punctured convolutional codes is considered in this paper. The upper bounds with Viterbi decoding are derived and plotted for the various punctured codes considered. The simulated results are found to agree very well with their upper and lower bounds.     

并行级联LDPC码译码迭代终止准则研究

提出了两种低复杂度的终止准则,以用于降低PCGC（并行级联Gallager码,parallel concatenated gallagercode）的译码器运算量.这两种准则通过观察边信息方差的改变情况,来判断是否终止译码器迭代.计算机仿真结果证明,这些终止准则可有效地降低译码器运算量,且不影响译码器误比特率性能.     

卫星通信协议中卷积码序列译码的计算机模拟

主要研究卫星通信协议IESS 309协议中的系统卷积码的编码及其序列译码的计算机模拟。用C语言实现了码率为1／2的36位的系统卷积码的编码，然后模拟高斯噪声信道生成一个Fano度量表，最后用Fano算法实现该卷积码的软判决序列译码，并进行了性能分析，为以后的工程应用打下一个良好的基础。     

卷积码维特比译码算法最佳反馈深度研究

卷积码可以用维特比算法作为译码算法,由于维特比译码器复杂度随着反馈深度的增长成指数倍增长,因而译码反馈深度对译码器的复杂度影响很大甚至可能无法实用,目前有些文献中仅给出了反馈深度的大致范围,但在硬件实现和性能仿真时无法确定一个具体的数值。通过在OFDM系统中运用卷积编码和维特比译码仿真分析发现,维特比译码器反馈深度为卷积码编码器存贮长度的5倍时,既可达到性能和硬件复杂度的良好折衷,又便于实际应用。     

网格编码调制在卫星高速数据传输中的应用

首先对网格编码调制(Trellis Coded Modulation,TCM)进行了系统概述,重点讨论了网格编码调制技术的基本特点、集合分割映射原理及Viterbi译码算法,并对TCM在AWGN信道中的性能进行了仿真,由此论证了网格编码调制技术在功率和带宽受限的卫星高速数据传输中的应用。     

基于单片机和PT2272的编码解码方法

以MCS 51单片机89C51和解码芯片PT2272 L4组成的编码解码器为例,介绍了解码芯片PT2272的特性,由89C51和PT2272组成的编码解码电路及其在实时控制网络中对PT2272 L4的数据通道寻址的编码,发码子程序的框图。说明这种编码解码方法的寻址空间大、速度快、可靠性高、价格低,特别适合于实时控制,有广泛的应用前景。     

Turbo MUD技术在TD-SCDMA系统中的应用

TD-SCDMA已成为第3代移动通信国际标准之一,它采用联合检测技术来抑制符号间干扰(ISI)和多址干扰(MAI)。介绍了Turbo多用户检测(MUD)技术在TD-SCDMA系统中的应用,该技术将Turbo迭代译码思想引入到联合检测,有机结合多用户检测和信道译码2种技术,通过在软MUD和软信道译码间多次进行迭代并及时交换软信息(如后验概率)来提高系统性能。研究表明,采用TurboMUD可使系统性能显著提高。     

RELAY ASSISTED TRANSMISSSION WITH BIT-INTERLEAVED CODED MODULATION

We investigate an adaptive cooperative protocol in a Two-Hop-Relay （THR） wireless system that combines the following： （1） adaptive relaying based on repetition coding; （2） single or two transmit antennas and one receive antenna configurations for all nodes, each using high order constellation; （3） Bit-Interleaved Coded Modulation （BICM）. We focus on a simple decoded relaying （i.e. no error correcting at a relay node） and simple signal quality thresholds for relaying. Then the impact of the two simple thresholds on the system performance is studied. Our results suggest that compared with the traditional scheme for direct transmission, the proposed scheme can increase average throughput in high spectral efficiency region with low implementation-cost at the relay.     

CSP封装Sn-3.5Ag焊点的热疲劳寿命预测

对芯片尺寸封装(CSP)中Sn-3.5Ag无铅焊点在热循环加速载荷下的热疲劳寿命进行了预测.首先利用ANSYS软件建立CSP封装的三维有限元对称模型,运用Anand本构模型描述Sn-3.5Ag无铅焊点的粘塑性材料特性;通过有限元模拟的方法分析了封装结构在热循环载荷下的变形及焊点的应力应变行为,并结合Darveaux疲劳寿命模型预测了无铅焊点的热疲劳寿命.