利用遗传算法构造QC-LDPC码

考虑到围长(girth)对低密度奇偶校验（LDPC）码的影响,提出了一种利用遗传算法构造大girth的准循环LDPC(QC-LDPC)码的新方法。该方法借助于计算机搜索,多次运用遗传算法,分步提高girth,在得到大girth 的同时,构造出具有准循环结构的LDPC码。分析发现,该构造方法的复杂度与码长成线性关系。仿真结果表明：在误码率(BER)为10-6时,新方法构造的QC-LDPC码比基于欧式几何构造方法、Gallager和Mackay构造法分别获得约0.15 dB、0.5 dB和0.2 dB的净编码增益(NCG),且因具有准循环结构更易于存储和硬件实现。     

一种改进的基于中国剩余定理的QC-LDPC码构造方法

为增大QC-LDPC码围长的同时减少码中包含的短环,提高其纠错性能,提出了一种基于中国剩余定理（CRT）的QC-LDPC码改进联合构造方法。该方法将设计围长为g的长码长的QC-LDPC码的问题简化为设计一个围长为g的短分量码的问题,然后通过对其余分量码校验矩阵的列块进行适当置换,使得构造出的QC-LDPC码具有更少的短环和更优的性能,更适于可靠性要求较高的通信系统。仿真结果表明,与已有的CRT联合构造方法设计的QC-LDPC码相比,新方法构造的QC-LDPC码具有更少的短环,在误码率为10-6时获得了1.2 dB的编码增益。     

双中继协作通信的功率分配改进方案

为克服信息处于深度衰落情况下单中继协作困难,减少多中继协作目的端信号处理的复杂度,给出了双中继节点参与协作通信的功率分配方案。两个中继节点分别采用放大转发(AF)、译码转发(DF)以及混合译码放大转发(HDAF) 3种协作方式进行通信。在满足一定的中断概率和节点功率限制情况下,利用MATLAB软件中的Fmincon优化函数,得到了各节点的最小发射功率。数值分析表明,在相同条件下,两个中继节点采用HDAF协作方式比采用AF协作方式、DF协作方式消耗的系统总功率分别少4～9 dBm、0.5～1 dBm,最大限度地节约了系统功率的消耗。     

利用域间映射的多元QC-LDPC码构造

通过定义有限域间的映射关系,提出了一种低复杂度的多元准循环奇偶校验码（QC-LDPC）的构造方法。利用这种方法可将较高阶数有限域的校验矩阵映射到指定的较低有限域上,且能保持原矩阵的结构性与稀疏特性。所构造的多元LDPC码不仅具有较低的译码复杂度且具有准循环特性,在硬件上也易于用移位寄存器实现。在高斯白噪声（AWGN）信道下的仿真结果表明,所构造的多元QC-LDPC码具有良好的编译码性能。当误码率为10-6时,码率为0.765的QC-LDPC码在目标域GF(8)上能获得0.2 dB的性能增益。     

基于改进EASI算法的DS-CDMA信息码与伪码盲估计

针对直扩序列码分多址(DS-CDMA)系统多用户检测的问题,提出 了一种基于性能指标（PI）变步长EASI算法信息码与伪码盲估计的算法。该算法在比较盲源 分离（BSS）和DS-CDMA系统模型的基础上,用自适应的方法估 计混合矩阵进而估计出伪码,并利用分离矩阵分离观测信号从而估计出信息码。另外,该算 法利用PI值来调整步长,使算法收敛速度和稳定性能达到一个理想平衡点。实验结果显示, 该算法具有很好的抗多址干扰(MAI)的能力,伪码和信息码的误码率分别在-10 dB和0 dB时达到10－2以下;对不同用户数,5 dB时所有扩频码被完全正确检测 的概率几乎都在80%以上。     

一种低迭代次数的极化码置信传播译码算法

针对置信传播（Belief Propagation,BP）译码算法在迭代次数较多时吞吐量和译码时延性能提升受限的问题,提出了一种低迭代次数的极化码BP译码算法,通过采用比特翻转和子信道冻结的方式,降低译码过程中的迭代次数。仿真结果表明,相对于传统极化码BP译码算法（设置最大迭代次数为40次）,所提算法在信噪比为3 dB时可将平均迭代次数减少约53%,处理单元平均计算次数减少约68%。该算法所带来的低时延和低功耗效益可运用在对功耗要求较高的大规模机器类型通信,以及对时延要求较高的超可靠低延迟通信等5G场景下的极化码译码中。     

单中继多用户MIMO系统中继预编码新方案

针对单中继多用户多输入多输出(MIMO)通信系统中用户间干扰问题,提出了一种可以有效抑 制用户 间干扰的中继接收和预编码方案。该方案在中继端对信号进行迫零（ZF）接收,利用最大化 信漏噪比（SLNR）准则设计中继端预编码向量,并针对难以获得最优解的情况,利用迭代解 出次优解。仿真结果表明,与中继端ZF预编码相比, SLNR预编码更好地抑制了用户间干扰 ,相同和速率性能下,基站发送端功率比ZF预编码减少4 dB,具有实用价值。     

认知FrFT域通信系统及其抗干扰性能分析

为了增强无线通信系统的抗干扰能力,设计了一种认知FrFT(分数傅里叶变换)域通信系统（ CFrFTDCS ）,在变换域通信系统中采用分数傅里叶变换,并与认知无线电技术结合,给出了系统的结 构框图和工作原理,分析了系统的抗干扰性能。计算机仿真结果表明,CFrFTDCS具有较强的 抗 干扰能力,针对单音干扰、窄带干扰和Chirp干扰,CFrFTDCS的平均误码率性能比直接序列 扩频（DSSS）通信系统分别改善了约15.70 dB、13.29 dB和13.79 dB,比传统 的变换域通信系统（TDCS）分别改善了约0.18 dB、0.23 dB和3.63 dB。     

利用双正交小波变换优化G3-PLC系统性能

为了提高G3-PLC(G3-Power Line Communication)在复杂信道环境下通信的可靠性，提出了基于双正交小波变换的正交频分复用（Discrete Wavelet Transform-Orthogonal Frequency Division Multiplexing,DWT-OFDM）。通过双正交小波变换减小复杂信道环境下G3-PLC通信系统中OFDM载波间干扰，并通过合理减少循环前缀，优化传输效率，降低峰均比。在DWT-OFDM的G3-PLC系统中，通过不同小波基性能分析与对比，利用bior6.8双正交小波基进行系统性能优化。将DWT-OFDM的G3-PLC系统在实际电力线噪声库环境下进行实验分析，仿真结果表明，在平均误码率为10-3量级时，性能有5 dB左右提升，通信效率由40%提高至54%；结合限幅法，峰均比由11 dB降低至8 dB，通信性能极大优于基于FFT-OFDM的G3-PLC系统。     

基于中国剩余定理和贪婪算法扩展的QC-LDPC码

在缩短阵列码的基础上运用中国剩余定理（CRT）和贪婪算法提出了一种新颖的大围长、码长更加灵活的QC-LDPC构造方法,且所构造的码字的校验矩阵采用楼梯矩阵循环置换而成。与传统CRT构造方法相比,只需已知一个分量码——缩短阵列码,同时新构造QC-LDPC码码长与码率选择比较灵活,围长更大,如果围长一样,则使最短环数量尽可能地少。仿真分析表明：在误码率为10-6时,在相同码率和码长的条件下,利用所提出的构造方法所构造的girth-8(4,k)QC-LDPC码在加性高斯白噪声(AWGN)和瑞利衰落信道中分别与缩短阵列码相比可获得约1.2 dB和2.0 dB的净编码增益,与CRT码相比分别改善了0.3 dB和0.7 dB的净编码增益,且性能与Gallager随机码性能相似但编码复杂度大大降低。     

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.     

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.     

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,     

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＂.