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RESEARCH ON A SOFT-DECISION ITERATIVE DECODING OF A LINEAR BLOCK CODE

线性分组码软决策迭代译码研究

基本信息

批准号：
06650416
负责人：
KASAMI Tadao
金额：
$ 1.28万
依托单位：
Nara Institute of Science and Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1994
资助国家：
日本
起止时间：
1994 至 1995
项目状态：
已结题

项目摘要

In this research, we investigate the following two types of soft-decision suboptimum decoding of a linear block code.(a) Generalized closest coset decoding for a decomposable code : For a code C of length n, C is said to be decomposable if C is the direct sum of C_1 and C_2 of length n. For this type of decomposable codes, we propose a new suboptimum closest coset decoding scheme shown below. Let C'_2 be a supercode of C_2 which is independent from C_1. The following is a kind of closest coset decoding of C.Let z be the received unquantized n-tuple. (1) Decode z into a codeword in C_1 + C'_2 by maximum likelihood decoding. Let u + v be the decoded codeword in C_1 + C'_2, where u*C_1 and V*C'_2. (2) Decode z into a codeword in C_2 + {u}, a translate of C_2, by maximum likelihood decoding. Let u+v denote the decoded codeword, which is the output of the overall decoding. This suboptimum decoding scheme is a generalization of the multi-stage decoding scheme for multi-level modulation codes … More and the closest coset decoding scheme for codes with the |u|u+v|-structure proposed by Hemmati.We investigate the evaluation method of the block error probability of a decomposable block code for the above decoding scheme over an AWGN channel. For some specific example codes, we evaluate the block error probability and the decoding complexity.(b) Iterative decoding : Consider the following iterative decoding scheme : First generate an initial candidate codeword by a relatively less complex decoding a algorithm, such as a hard-decision algebraic decoding. Then iterate that we find more likely codeword around the current candidate codeword by searching by using a minimum weight subtrellis diagram around the current candidate codeword, until we can't find more likely codeword, neither the candidate codeword pass a test of optimality.For this type of iterative decoding, we derive the least stringent sufficient condition that the available information on the code is restricted to (i) the minimum weight and a few small weights and (ii) for a given positive integer h, h or fewer already generated candidate codewords. We also derive a sufficient condition on the optimality under the same assumption as above, except that the condition (i) is changed to (i') complete knowledge of the weight profile of a code is known. We evaluate the average reduction of number of decoding iterations for some Reed-Muller codes over an AWGN channel.We also present a new soft-decision iterative decoding algorithm based on searching by using a minimum weight subtrellis diagram. We show the block error probablity and the decoding complexity for some Reed-Muller codes over an AWGN channel for the proposed decoding. Less

本文研究了线性分组码的两种软判决次优译码：(A)可分解码的广义最近陪集译码：对于长度为n的码C，如果C是长度为n的C_1和C_2的直和，则称C是可分解的。对于这类可分解码，我们提出了一种新的次优最近陪集译码方案，如下所示。设C‘2是独立于C_1的C_2的超码。下面是C的一种最接近陪集译码。设z是接收到的未量化n元组。(1)通过最大似然译码将z译码为C_1+C‘_2中的码字。设u+v是C_1+C‘_2中的译码码字，其中u*C_1和V*C’_2。(2)通过最大似然译码将z译码为C_2+{u}中的码字。设u+v表示解码的码字，其是整体解码的输出。该次优译码方案是多级调制码…的多级译码方案的推广提出了一种最接近陪集译码的|u|u+v|-结构码译码方案，研究了该译码方案在AWGN信道下可分解分组码的误块率的评估方法。对于一些具体的示例码，我们评估了误块率和译码复杂度。(B)迭代译码：考虑以下迭代译码方案：首先通过一种相对较简单的译码算法来生成初始候选码字，例如硬判决代数译码。然后利用当前候选码字周围的最小权子格图进行搜索，迭代找到当前候选码字周围更有可能的码字，直到找不到更可能的码字，候选码字都没有通过最优测试，对于这种迭代译码，我们得到了最不严格的充分条件，即关于码的可用信息被限制在(I)最小权重和几个小权重，(Ii)对于给定的正整数h，h或更少已经生成的候选码字。在与上述相同的假设下，我们还得到了最优性的一个充分条件，只是条件(I)改为(i‘)已知码的重量分布的完全知识。评估了AWGN信道下某些Reed-Muller码译码迭代次数的平均减少，并利用最小权子网格图提出了一种新的基于搜索的软判决迭代译码算法。在AWGN信道下，我们给出了一些Reed-Muller码的误块率和译码复杂度。较少