An alternative coding for hydrofluorocarbons and their ethers

A shorter alternative to the ASHRAE code for HFC's and their ethers consists of unity for each fluorine and zero for hydrogens on each carbon. Ether oxygen positions are denoted E. Three additional rules ensure invariant codes. Flow charts illustrate how complex interconversion of the ASHRAE code with chemical formulae is compared with the directness of the new code which also conveys useful chemical information.     

循环陪集首集与Goppa码,Alternant码最小距离下限

文献１将求Ｇｏｐｐａ码，Ａｌｔｅｒｎａｎｔ码最小距离下限归结为求循环倍集首集Ａ中最小的比ｒ大的元Ｍ（ｒ）的问题。本文研究了Ａ中元所具有的特征，并得到了计算Ｍ（ｒ）的一个有用的方法。     

A forward‐only recursion algorithm for MAP decoding of linear block codes

The evolution of digital mobile communications along with the increase of integrated circuit complexity has resulted in frequent use of error control coding to protect information against transmission errors. Soft decision decoding offers better error performance compared to hard decision decoding but on the expense of decoding complexity. The maximum a posteriori (MAP) decoder is a decoding algorithm which processes soft information and aims at minimizing bit error probability. In this paper, a matrix approach is presented which analytically describes MAP decoding of linear block codes in an original domain and a corresponding spectral domain. The trellis‐based decoding approach belongs to the class of forward‐only recursion algorithms. It is applicable to high rate block codes with a moderate number of parity bits and allows a simple implementation in the spectral domain in terms of storage requirements and computational complexity. Especially, the required storage space can be significantly reduced compared to conventional BCJR‐based decoding algorithms. Copyright © 2002 John Wiley & Sons, Ltd.     

Design of Embedded Self-Testing Checkers for t-UED and BUED Codes

In this article we present a new method for designing self-testing checkers for t-UED and BUED codes. The main idea of this method is to map words of the considered code to words of a code of the same type in which the value of t or the number of check bits is reduced and repeating this with the obtained words until a parity code is obtained, or to translate the code words into words of a code for which such a mapping is possible. First we consider Borden codes for t = 2 ^k – 1, Bose, and Bose-Lin codes. The mapping operation is realized by averaging weights and check symbol values of the code words. The resulting checkers have a simple and regular structure. This structure is independent on the set of code words that is provided by the circuit under check. The checkers are very well suited for use as embedded checkers since they are self-testing with respect to single stuck-at faults under very weak assumptions. All three checker types can be tested with 2 or 3 code words. We also propose a novel approach to design checkers for Blaum codes that require much less code word tests than existing solutions.     

Adaptive Channel Estimation Aided Log-Map Turbo Decoder Implementation for DS-CDMA Based Mobile Systems

Practical implementation of convolutional turbo codec is impeded by the difficulty of real-time execution in high transmission rate communication systems due to high computational complexity, iterative block decoding structure, as well as the requirement of accurate on-line channel reliability estimation for maximum-likelihood decoding. Relying on innovative channel estimation techniques involving DS-CDMA specific noise/interference variance estimation and fading channel variation tracking, this paper provides a low-complexity all-digital design of an iterative SISO log-MAP turbo decoder for DS-CDMA based mobile communication systems. The issues of quantization and data flow in both pre-decoder processing module and iterative trellis decoding module are prudently addressed to ensure highly efficient hardware implementation. The efficient design strategies applied confine the decoding complexity while leading to an excellent performance within 0.2 dB of the software decoder.     

一种90°TCM旋转不变码的搜索算法及实现

概述了TCM旋转不变码的原理、设计思想及性能。并针对8psk调制介绍了一种90°旋转不变码的计算机搜索算法。对搜索出的旋转不变码进行了性能仿真。     

基于并元加性群的正交码发生器

将mn阶并元加性群G={0,1,2,…mn-1}的元依次作为位置的号码(m为素数),给出找出它的mn-1阶子群与陪集位置的简易方法,证明了矩阵的并元加性群扩大法,在此基础上给出正交码发生器的构造图,该编码器结构简单,使用方便,可产生足够多的编码,可用于同步多址CDMA通信中。     

COFDM系统性能模拟研究

介绍了COFDM的系统模型,并根据提出的系统模型,采用RS编码方式和不同调制方式对不同应用信道模 型下的误码率性能进行了仿真研究。     

AWGN信道下RA码译码算法研究

RA(Repeat-Accumulate)码是一种简单但非常重要的TLC(Turbo-Like Codes)码。本文首先介绍了RA码的Tanner图表示。然后重点分析研究并详细推导了RA码在加性高斯白噪声(AWGN)信道上的迭代译码算法。