LDPC码在因子图上的构造及其译码

LDPC码是一种可以接近香农限的线性分组码，可通过稀疏奇偶校验矩阵来构造。也可以用因子图来构成。根据LDPC码的不同构成方法至今已提出了数种不同的译码方法。本文介绍了基于因子图的LDPC码的构造方法，分析了和一积(SPA)译码算法的基本原理，最后详细讨论了用SPA算法对LDPC码进行译码的过程。     

BIBD循环置换矩阵的多进制LDPC码构造

提出了基于均衡不完全区组设计（Balanced Incomplete Block Design,BIBD）的 多进制准循环LDPC（Low Density Parity Check）码代数构造方法。在该构造方法 中提出了广义多进制位置向量的概念,并根据广义多进制位置向量和BIBD法对指数矩阵进行 广义二维扩展,构造出具有循环置换子矩阵的多进制校验矩阵,由此得到girth不小于6的多 进制LDPC码。仿真结果表明,采用FFT-QSPA（基于快速傅里叶变换的多进制和积算法）对构 造出 的LDPC码进行译码,在AWGN信道下相比 于同参数的RS码来说可以取得明显的编码增益,并且优于多进制Mackay码。     

一种动态加权的LDPC译码方法

为了加快低密度奇偶校验（LDPC）码的译码速度，有效改善LDPC码的译码性能，针对校验节点更新过程中的对数似然比（LLR）值的大小，设计了一种LDPC码的动态加权译码方法。以IEEE 802.16e标准的奇偶校验矩阵为例，根据LLR值的变化规律，利用增长因子和抑制因子对和积译码算法和最小和译码算法进行动态加权。仿真结果显示，基于动态加权的译码方法相对于传统译码方法误码率都有明显改进，译码复杂度也有所降低。     

LDPC码的快速编码实现

LDPC码是一种定义在稀疏校验矩阵H上的线性分组码,矩阵H可以用称为Tanner图的二分图来表示。文中通过对快速编码的实现进行分析,给出了能够达到线性复杂度编码的码构造方法,同时分析采用这些方法构造的LDPC码在AWGN信道下的纠错性能不差于随机构造的LDPC码。     

比特级码率兼容多元LDPC码打孔算法

多元低密度奇偶校验（Non-binary Low-density Parity-check，NB-LDPC）码在中短码情况下性能优于传统二元LDPC码，更接近香农限。针对多元LDPC码码率兼容（Rate-compatible）的问题，提出了一种基于比特级的新型多元打孔算法。首先采用二进制镜像矩阵概念对多元校验矩阵进行映射处理，再根据变量节点的度分布选择合适的打孔节点，从而实现比特级多元LDPC码码率兼容的打孔方案。仿真结果证明与基于符号级的多元打孔算法相比，所提方案的误码率性能在各个码率分别有0.2~0.4 dB的增益。     

利用软解调序列的LDPC码闭集识别方法

为实现对包括低密度奇偶校验（LDPC）码在内的一系列“稀疏几何编码”的识别,基于软解调序列,设计和实现了一种闭集集合应用背景下的识别方法。以校验约束关系作为切入点,首先回顾了基于硬解调序列的传统识别策略;接着分析和推导了软解调序列所应满足的校验约束形式;通过引入后验校验对数似然比（CLLR）这一统计量,最终设计了相应识别算法。在事先给定先验编码集合的闭集应用模式下,仿真结果显示,算法明显占优,识别增益在低信噪比环境下可达2~6 dB。     

一种可快速编码的QC-LDPC码构造新方法

为解决LDPC码的编码复杂度问题,使其更易于硬件实现,提出了一种可快速编码的准 循环LDPC码构造方法。该方法以基于循环置换矩阵的准循环LDPC码为基础,通过适当的打孔 和行置换操作,使构造码的校验矩阵具有准双对角线结构,可利用校验矩阵直接进行快速编 码,有效降低了LDPC码的编码复杂度。仿真结果表明,与IEEE 802.16e中的LDPC码相比,新 方法构造的LDPC码在低编码复杂度的基础上获得了更好的纠错性能。     

基于PEG构造方法的不同码率LDPC码的性能研究

论文针对LDPC码校验矩阵的PEG构造方法进行了研究,并基于PEG构造方法对规则LDPC码的不同码率进行了性能仿真,得出结论：在低信噪比的情况下,低码率的LDPC码较高码率的LDPC码具有更优异的性能。     

一种基于本原多项式的LDPC构建新算法

在分析传统LDPC编码方式的基础上,提出一种基于本原多项式实现LDPC编码的新方 法。根据特定LDPC码长选择合适的本原多项式作为子矩阵,对子矩阵进行行列分解、组合, 最终构建LDPC码校验矩阵〖WTHX〗H〖WTBZ〗。仿真实验结果和工程应用证明：新算法构建 的LDPC码在恶 劣的通信环境下,误码率、误帧率优于传统Mackay-LDPC码,具有较好的性能。     

一种低复杂度的多元LDPC译码算法

针对多元低密度奇偶校验（LDPC）码译码复杂度高、时延大等问题，提出了一种基于硬信息的低复杂度多元LDPC译码算法。来自信道的接收信号在初始化时，先进行非均匀量化预处理。在迭代过程中，校验节点端只需传输单个比特的二进制硬可靠度信息至变量节点。在变量节点端，可靠度信息按比特位进行简单的累加和更新，无需任何的系数修正操作。同时，变量节点使用了全信息的方式将信息传输至与其相邻的校验节点。仿真结果显示，与基于比特可靠度（BRB）的多元LDPC译码算法相比，提出的算法在较低量化比特情况下，能获得约0.3 dB的译码性能增益，且译码复杂度更低。     

Universal Coverage, Pinpoint Illustration and Profound Impact HTC 2008 Intermedia Recommendation and Introduction Meeting

Holding 88 percent of train media resources across China, based on "Time Cube", on the 2008 Intermedia Recommendation and Introduction Meeting on December 19, 2007, HTC announced its high-profile strategy of tour marketing and tapping the immeasurable potentials on the train. Meanwhile, HTC officially launched its brand new product Olympic Train on the meeting, providing a fabulous platform for all the brands that are prepared to do a smart marketing on the occasion of 2008 Olympic Games.     

Market presence in China strengthened Network growth and Dual-Chinese-Hub Strategy More frequet Flyer Benefit——Air China and shanhai Airlines Join Star Alliance

In the end of 2007, Air China Limited (hereinafter "Air China") and Shanghai Airlines, formally joined Star Alliance at a ceremony held in the new Terminal Three at Beijing Capital International Airport. With the addition of the two Chinese airlines, Star Alliance now has 19 member carriers operating 17,000 daily flights to 897 destinations in 160 countries.     

A World of Love 2008 Music Grand Ceremony

Under the guidance of the theme slogan of the 29th Olympic Games - One World One Dream, with dream, love and dedication as its theme, the 2008 Music Grand Ceremony ＆ 1000 People Charity Concert on 100 days cotmtdown to Paralympic Gamesis officiaily launched on December 22, 2007. The 2008 Music Grand Ceremony is sponsored by China Disabled Persons＇ Federation, and co-hosted by National Paralympic Committee of China,     

MUYANG GROUP

With its headquarters in the historic city of Yangzhou,Jiangsu Muyang Group Co.,Ltd has since its founding in 1967 grown into a well-known group corporation whose activities cover research ＆ development,project design,manufacturing,installation and services in a multitude of industries including feed machinery and engineering,storage engineering,grain machinery and engineering,environmental protection,conveying equipment and automatic control systems.     

China''''s National Oil Reserve Center was Born

Aseries of events that occurred in October 2007, are rewriting the history of China's energy industry: November 3 an Energy Law Committee asked the public for suggestions on improvements; forty top experts came together to form the National Energy Expert Advisory Committee on November 6; and the National Oil Reserve Center (NORC)became the nerve centre of oil reserves on November 18. Yet, behind the progress of these recent activities remains the fact that international oil prices still hover around a very high price of US$ 90/barrel, and China's oil imports are close to accounting for half of its total oil reserves.     

2007 China Harbor Ten People

2007 China Harbor Ten People elected the entrepreneurs who contributed a lot to port economy and enterprises this year trough their talent management.These ten people embody their social responsibility,professional skills,creative ability,and charming personality.Bearing full confidence in China＇s port economy,the port entrepreneurs are brave enough to explore a brand new area,so as to promote harbor economic development. At the very beginning of 2008,China Shipping Website,Dalian Maritime University,and China Port and Shipping In- stitute jointly select the 2007 China Harbor Ten People,demonstrate port entrepreneurs＇ stunning minds,disclose their secrets to success,and providing abundant experiences to others in harbor development.The top ten people are various excellence during the ups and downs harbor development.     

Sony Style in China

Since the normalization of the diplomatic ties between China and ） Japan, the bilateral economic relations have deepened continually. According to the statistic of Japan, China passed U.S. to become Japan＇s top trade partner as well as is the second largest export market for Japan and is the largest import resource for Japan. Japan companies such as Mitsui, Sumitomo, Sony and Panasonic, have set the subsidiaries in China and explored their scales. This year 2008 marks the 30th anniversary of the signing of the ChinaJapan Treaty of Peace and Friendship.     

China''''s Import and Export of Textiles and Apparel in the Q1

China's textile and apparel industry suffered an unprecedented cold market for exports in the first quarter this year,the result of a few factors including: the appreciating RMB, decreasing export rebate rate,expanding influence of the U.S. subprime crisis, increasing costs of production and rising labor cost.     

Financial Services for Post-Quake Reconstruction

The May 12 earthquake in Sichuan caught Chinese people by surprise and took the nation＇s heart. While mourning the dead and searching for the missing, many services must be provided for the survivors in the wake of the earthquake. Available post-quake financial services have become an important part of the reconstruction effort in the disasterstricken areas of Sichuan province.     

The Frankenstein Syndrome: The Creation of Mega-Media Conglomerates and Ethical Modeling in Journalism

Aristotle saw ethics as a habit that is modeled and developed though practice. Shelly's Victor Frankenstein, though well intentioned in his goals, failed to model ethical behavior for his creation, abandoning it to its own recourse. Today we live in an era of unfettered mergers and acquisitions where once separate and independent media increasingly are concentrated under the control and leadership of the fictitious but legal personhood of a few conglomerated corporations. This paper will explore the impact of mega-media mergers on ethical modeling in journalism. It will diagram the behavioral context underlying the development of ethical habits, discuss leadership theory as it applies to management, and address the question of whether the creation of mega-media conglomerates will result in responsible corporate citizens or monsters who turn on their creators.