High speed decoding of the binary (47, 24, 11) quadratic residue code

An efficient table lookup decoding algorithm (TLDA) is presented to decode up to five possible errors in a binary systematic (47, 24, 11) quadratic residue (QR) code. The main idea of the TLDA is based on the weight of syndrome, the syndrome decoder together with a reduced-size lookup table (RSLT), and the shift-search method given by Reed et al. Thus, the size of the lookup table and computational complexity in a finite field can be significantly reduced. The memory size of the proposed condensed lookup table (CLT) consists of only 36.6 Kbytes and is only about 0.24% of the full lookup table (FLT) and 3.2% of the lookup up table given by Chen et al., respectively. These facts lead to significant reduction of computational time and the decoding complexity. A simulation result shows that the decoding speed of the proposed TLDA is much faster than all existing decoding algorithms. Moreover, it can be extended to decode all QR codes, including the class of the cyclic codes when the code length is moderate. The CLT makes this new decoding algorithm suitable for hardware or firmware implementations.     

C语言程序设计题自动评分算法的研究

目前主要的C语言上机考试系统程序设计题主要采用的是结果比对评分法,这种方法并不查看考生的程序内容,不能反映考生的真实水平并且有失公允。在比较结果的评分方法基础上,增加了修复编译评分与关键代码对比评分,使评分结果更加公正、准确,使评分结果更加接近于人工阅卷,具有很好的实用价值和应用前景。     

联合信源信道算术码研究

介绍联合信源信道算术码添加禁用符号的编码方法,以实例方式引入联合信源信道算术码的检错原理。综述联合信源信道算术码的检错时延分布、几何分布,分析各种解码方法、序列解码方法及其各种改进,研究基于有限状态机的解码方法与其他信道码构成的迭代式联合解码方法,并展望目前联合信源信道算术码研究存在的问题及其前景。     

SVC在无线信道传输中的非均衡差错保护

针对H.264的可伸缩视频编码扩展标准(SVC)在噪声信道中的传输,采用低密度奇偶校验码(LDPC)提出一种非均衡差错保护的方案。在所提的方案中,根据时间、分辨率和质量把原视频序列按重要性分成不同的层。由于不同层的数据对错误的敏感性不同,对其进行不同码率的LDPC信道编码,实现非均衡差错保护。根据视频流中每一帧不同层的PSNR增量不同,和不同信道码率下正确解码的概率不同,反复计算每一帧所有码率组合的PSNR增量值并找出最大组,从而进行信道编码并传输。实验表明,在相同的平均码率条件下,提出的方案相比其他方案的PSNR值增加了2.8 dB,更适合无线信道的传输。     

高速可配置RS纠删解码器的VLSI设计

目前对可配置纠错与删除(纠删)解码器研究较少。为此,采用性能优异的RS编码方法,提出一种高速可配置RS纠删解码器的超大规模集成电路(VLSI)架构,并详述可配置纠删BM模块的构成。该架构通过折叠技术,使解码器在保证高速的前提下降低硬件复杂度。通过0.18 μm工艺和Design Complier工具综合测试结果表明,与同类解码器研究相比,该解码器在硬件复杂度吞吐率和可配置性方面,均具有较大优势。     

基于LQI的WSN自适应差错控制方案

针对无线传感器网络(WSN)中信息传输误码率高和能量受限的问题,提出一种基于链路质量指示(LQI)的自适应差错控制方案。利用IEEE802.15.4协议的物理层规范为无线传感器网络提供精确的信道质量评估,根据LQI与误包率之间的数量关系,将信道质量非均匀地划分为8个等级,并选择8种BCH码与之对应,在节点通信过程中实时地选择最佳的BCH码作为纠错码。实验结果表明,该方案具有较高的能量效率,能够有效降低误包率。     

A Fast Algorithm for Adaptive Prefix Coding

In this paper we present a new algorithm for adaptive prefix coding. Our algorithm encodes a text S of m symbols in O(m) time, i.e., in O(1) amortized time per symbol. The length of the encoded string is bounded above by (H+1)m+O(nlog ² m) bits where n is the alphabet size and H is the entropy. This is the first algorithm that adaptively encodes a text in O(m) time and achieves an almost optimal bound on the encoding length in the worst case. Besides that, our algorithm does not depend on an explicit code tree traversal. A preliminary version of this paper appeared in the Proceedings of the 2006 IEEE International Symposium on Information Theory (ISIT 2006). M. Karpinski’s work partially supported by a DFG grant, Max-Planck Research Prize, and IST grant 14036 (RAND-APX). Y. Nekrich’s work partially supported by IST grant 14036 (RAND-APX).     

Coding with skew polynomial rings

In analogy to cyclic codes, we study linear codes over finite fields obtained from left ideals in a quotient ring of a (non-commutative) skew polynomial ring. The paper shows how existence and properties of such codes are linked to arithmetic properties of skew polynomials. This class of codes is a generalization of the θ-cyclic codes discussed in [Boucher, D., Geiselmann, W., Ulmer, F., 2007. Skew cyclic codes. Applied Algebra in Engineering, Communication and Computing 18, 379–389]. However θ-cyclic codes are powerful representatives of this family and we show that the dual of a θ-cyclic code is still θ-cyclic. Using Groebner bases, we compute all Euclidean and Hermitian self-dual θ-cyclic codes over of length less than 40, including a [36,18,11] Euclidean self-dual θ-cyclic code which improves the previously best known self-dual code of length 36 over .