基于多项式遍历和码字相关的Turbo码盲识别

针对1/n码率Turbo码的盲识别问题,提出了一种基于多项式遍历和码字相关的检测识别方法。该方法首先对码字序列进行分组,利用分组验证的方法对数据中的卷积码进行快速检测,进而识别出Turbo码的码率;然后,利用欧几里得算法对Turbo码的分量编码器a的参数进行识别,进而通过对编码器b的遍历,恢复出伪随机交织序列;最后,通过与信息序列的码字相关,验证编码器b的参数是否正确,同时利用相关谱峰值所在位置识别交织器参数,实现了Turbo码的全部参数估计。仿真实验验证了该算法的有效性。对算法的误码适应能力进行的仿真分析表明,该方法能够在较高误码率条件下实现Turbo码的检测与识别。     

直升机卫星通信系统中Turbo码外交织器设计与仿真

在直升机卫星通信系统（HSCS）中,如何克服由于旋翼遮挡导致的系统性能恶化是一个亟需解决的关键问题。旋翼遮挡相当于对码字信息的成片删除,通过分析删余Turbo码中删余矩阵的设计准则,首先对Turbo码的编码结构进行改进,并提出了一种适用于直升机旋翼遮挡环境下的交织器。它满足以下特性：将删除均匀分散在整个码字序列中,变突发错误为随机错误;码字中每个信息位与其对应的2比特校验位中最多只删1位;与被删比特组相邻的两个比特组保留;删除部分中以信息位-校验位1-校验位2的模式循环,这些特性保证了删除信息的可靠恢复。最后对不同遮挡比例下新型交织器与传统交织器进行仿真比较,结果表明采用新型交织器改善了数据传输的误码率(BER)性能,提高了HSCS系统的可靠性。     

帧长可配置Turbo码编译码器的设计与实现

针对固定帧长Turbo码灵活性和适应性差的缺点,提出了一种帧长可配置的Turbo码编 译码器的FPGA实现方案,可以由用户根据数字通信参数设计要求自行改变交织深度, 以使译码性能与信息速率达到最佳平衡。采用“自上而下”的设计思想和“自下而上” 的实现流程相结合的方法,对Turbo码编译码系统进行模块化设计,优化调试后下载配置到X ilinx公司的Virtex-2 Pro系列中。测试结果表明,该设计具有良好的移植性和通用性,为T urbo码在不同环境下的应用建立了统一平台。     

归零Turbo码参数的盲识别

针对归零Turbo码码率、码组起点、交织起点、交织长度参数识别问题，首先引入矩阵秩量比的概念，推导出适用于归零Turbo码矩阵秩量比下限，提出了基于秩量比判决门限的码长识别算法；其次，遍历一交织帧输出码元，找出最小秩量比对应的位置，实现交织起点和码组起点的识别；然后，依靠完整的交织帧输出数据，利用分析矩阵实现码率与分量编码器中寄存器个数识别；最后，由以上识别的参数计算出交织长度。仿真结果表明：在信噪比为5 dB时，单靠信息序列，各部分的识别概率能达到80%以上；在交织长度为100时，提出的识别算法与传统算法相比，性能相近，识别时间大约缩短为原来的1/3。     

一种高效的Turbo码硬件实现算法

针对Turbo码译码实现中硬件消耗、时延和纠错性能之间的矛盾，对Turbo码硬件实现中的译码算法进行了优化研究，提出了一种基于MAX-Log-MAP算法的高效Turbo码硬件实现算法。实验表明，本文所实现的Turbo码是硬件消耗与译码性能的良好折衷。     

Turbo码译码性能与循环迭代次数探讨

Turbo码中独有的循环迭代结构是Turbo码具有良好的译码性能的一个重要原因。本文重点探讨了循环迭代次数对Turbo码译码性能的影响。并对探讨结果进行了计算机仿真 ,模拟出信噪比 -误比特率曲线。     

低信噪比下随机交织器识别

针对Turbo码随机交织器参数识别问题,充分利用信道截获数据的软判决信息,提出了一种基于对数符合度的交织映射关系识别算法。该算法从计算总的编码方程成立概率出发,定义了能很好衡量概率大小的对数符合度概念,极大地简化了计算复杂度,使得计算量仅与截获码块数目和交织长度的平方有关,计算方式仅为大小比较与符号提取;再利用正确交织位置能够使总的编码方程成立的概率达到最大这一特性,依次实现各个位置的交织关系的识别。与现有算法相比,所提算法识别性能稍差,但计算复杂度更低。仿真结果表明,在信噪比为0 dB、交织长度为200时,仅需要截获码块数目为500,其正确识别率就能达到100%。     

Turbo码解码过程中的加权算法

本文通过调整迭代解码过程中系统位接收值的加权系数，提出了一种Turbo码加权迭代解码算法。该算法改变了迭代运算后Turbo码解码器输出软值中系统位接收值信息和它的外部估计信息的比重，使Turbo码无论在低信噪比或是在高信噪比时均具有优良的纠错性能。仿真结果显示，采用Turbo码加权迭代解码算法，不仅能提高Turbo码的收敛速度，而且能进一步降低Turbo码解码时的地板值，使Turbo码的比特误码率在高、低信噪比时都能够得到进一步改善。     

基于劳伦多项式的LAS码构造及性能分析

对基于Hadamard矩阵的LA码和基于劳伦多项式（Laurent Polynomial）的LS码的生成 及相关特性进行研究,从占空比、相关特性、零干扰窗长度、码字总数等方面仿真分析了LA S码的性能,并结合实际应用,理论分析了LAS-CDMA系统与传统CDMA系统的归一化容量,仿 真比较了LAS码和Gold序列在准同步CDMA系统中的误码性能。仿真和理论分析表明：LAS码具 有均匀的零干扰窗（Interference Free Window,IFW）特性;不同主码的互相关函数IFW附 近存在较小的副峰,多址干扰较小;在准同步移动通信系统中,LAS-CDMA抗多址干扰性能 明显优于传统CDMA系统,使用 LAS码比使用Gold序列有更好的误码性能。     

一种基于快跳频技术的多载波CDMA系统

为进一步提高多载波CDMA系统的频带效率与抗干扰能力，提出了一种跳频多址技术结合多载波调制的传输方案，利用跳频技术将部分子载波传输与随机交织引入到多载波传输系统中，给出了系统实现的模型，并对该传输方案的系统带宽和误码性能进行了分析。理论分析与仿真结果表明：与以往的多载波CDMA系统相比，所建议系统的结构简单，性能优异，消除了已有系统中峰均功率比高和远近效应等问题，具有较强的抗多址干扰与窄带干扰的能力，并能有效地抗信道中突发错误的能力。     

Brown＇s Blossom in Britain-China

The overall strategic relationship between U.K. and China is ＂better than ever＂, China- Britain relations have maintained good momentum, with increased high-level exchanges and the reinforcement of strategic mutual trust, with more room for growth in the future.     

Challenge and Opportunity Go Hand in Hand——What Global Economic Agitation Brings to the China's Economy?

Domino effects of the global finance agitation As the origin of the subprime crisis,US financial institutions lost USS45 billion last year,accounted for over half of the total US,EU & Japan loss.Since January 15th,Chtigroup released its financial statement of the 4th quarter,showing a net deficit of USS9.83 billion,which marked the hisoric high of its quarterly deficit.     

Sinosteel：Extraordinary Moves in Industry Chess

Among the Fortune 500 firms,more and more images from China emerge out.On the 2008 list,Sinosteel Corporation,a landmark group of China industries quietly squeezes into the candidate line.As the largest steel service ＆ trade enterprise,its sales reached at RMB 111.24 billion,with a year-on-year increase of 83.03 percent,and the profit grew by 180.03 percent.On the Sinosteel 2008 Work Meeting,the president Huang Tianwen uttered,＂In the coming year,we will work for US$20 billion sales,and look forward to getting a position in Fortune 500 firms for ourselves.＂     

Walk Through Unusual Five Years—— An Exhibitor＇s Canton Fair Course

When the 103rd Canton Fair is approaching, an old friend of Canton Fair, Li Ying from Jiangsu prov-ince recollected his past five years＇ experiences to the grand trade meeting. Each year is special, with some unforgettable memories colored by the year.     

Jean-Pierre Duprieu： Willing to Be A Legate of Sino-French Business

Estaing, former French president, Valery Giscard d＇Estaing attended Sino-French Economic Seminar held in Shanghai in early April and said that the world center has shifted from the west to the east with many European and US companies entering into Asia, and China has the ability to play an important role in the world stage. Estaing, naming himself＂French Confucian＂, then said in Chinese that a cook-group includes 10 people in ancient Chinese soldier system and the cook is in charge of cooking for them. And people who belong to the same cook are actually ＂Partners＂.     

China''''s Stock Market Wave

The annual meeting of the World Economy Forum was held in Davos,a little town in Switzerland,on January 23rd to the 27th this year,with the theme"the Power fo Collaborative Innovation",over 2500 celebrates from ture political and cconomic circles of more than 80 countries and challengred logether to talk about the future of the global economy in 2008,A Forum for the problems and challenges that face whole world,some of the keywords which drew attention during the event were:the U.S.subprime mortgage crisis,soaring energy prices,the economic slowdown in the U.S.ermerging economic bodies,authority funds and the general unpredictable nature of the global economy.     

Trade Promotion from Neighborhood

If you are considering to trade with companies in Japan or expanding your .business to Japan, we are ready to help from the very beginning.＂ You will find this greeting at the first sight on the Chinese website of Japan External Trade Organization （JETRO）. JETRO has committed itself in delivering highly efficient and quality services to meet the demand of internal and external customs including Japanese companies, hence winning a good reputation in the international trade arena. In recent years, with its priority in advancing business cooperation in South and East Asia, JETRO has made great achievement in promoting trade between China and Japan. Therefore, China＇s Foreign Trade interviewed Mr. Yoichi Maine, Deputy Director General of JETRO BEIJING.     

Auto Parts Market Potential Coming into Surface

Looking at the increasingly fierce competition in the world auto market. global automobile manufacturing industry, taking Europe, the U.S. and Japan as representatives, is gradually forming a new type of relationship, mutual cooperation between whole vehicle and parts manufacturers. We can clearly see that auto parts manufacturers have become independent from the whole vehicle manufacturing companies, which means that the former structure of auto industry has greatly changed, and a new relationship,     

Domino Effect on Electricity and Coal Prices

In the middle of last December, the key purchase contracts for coal used in power generation in 2008 were signed, reflecting a demand for more than 1.085 billion tons. It is important to note that the country＇s five biggest power producers, China Huaneng Group, China Guodian Corporation, China Power Investment Corporation, China Huadian Corporation and China Datang Corporation, had settled on the prices on their purchase contracts, and they are expected to consume 290 million tons of coal for generating electricity,     

Slimmed May Day Holiday

Last November the State Council of China decided to renew its holiday system by reducing the seven-day May Day holiday to three days and introducing three new one-day public holidays, namely the Qingming Festival, Dragon Boat Festival and Moon Festival. By doing so, the three golden-week holidays that were introduced in 1999, namely the Spring Festival, May Day and National Day, could be better distributed.