波束成形在TD-LTE-A系统中的性能优化

TD-LTE系统中的波束成形（Beam Forming）会受到收、发天线不对称性的影响。TD-LTE-Advanced（TD-LTE-A）系统中使用上行多天线发送可以解决天线不对称性的问题,因此需要对其分析以优化Beam Forming的性能。通过对上行多天线的信道状态信息（CSI）做特征值（SVD）分解,指出了Beam Forming对下行信噪比（SNR）的改善。针对Beam Forming模式下SNR和链路质量指示（CQI）的差异,提出了一种优化链路自适应的方法。数值仿真验证了优化后的TD-LTE-A相比TD-LTE的Beam Forming吞吐率最大提高了24%,其结论对商用TD-LTE网升级到TD-LTE-A具有显著价值。     

基于无速率码的遥感数据自适应传输技术

基于自适应编码调制的遥感数据传输方案实现了传输速率阶梯式换挡，但未能充分利用链路余量。为进一步提高遥感卫星数据传输过程中的频谱效率，提出了基于无速率码的遥感数据自适应传输技术。将无速率码与QPSK、8PSK、16QAM、64QAM调制方式结合，通过设定译码成功概率阈值得到离散信噪比下的最佳译码开销和最佳码率值。采用多项式拟合求得卫星过境期间码率值的变化情况，进而得到有效数据率变化曲线，实现了遥感卫星过境时段内有效数据率随仰角的无缝切换。通过求解有效数据率曲线的积分值，得到了采用联合译码算法的Raptor码在4种方案下的传输数据量。分析结果表明，与第二代数字卫星电视广播标准（DVB-S2）中的自适应编码调制方案相比，所提出的传输方案使传输数据量提高了10.29%~27.65%，且在信噪比低至-5 dB的情况下也可以进行数据自适应传输。     

多跳分集系统中一种新的基于无比率编码的跨层方案

研究了多跳分集系统中由于链路的不可靠传输直接应用实用网络编码存在差错的扩 散和传播问题。提出了一种新的基于无比率编码的跨层方案,该方案利用无比率编码的纠错 能力及实用网络编码码字随机特性,控制了输入链路的差错扩散和传播。结果表明,在满足 每条链路误包率一定的情况下,该方案获得了较好的差错性能。进一步分析了为了使每条 链路达到给定的误包率,无比率编码在不同信噪比下的冗余。     

宽带自适应MIMO-DFE空时接收机

设计了频率选择信道基于RLS算法的自适应判决反馈均衡MIMO-DFE空时接收机,由于这种接收机不需要信道识别,从而降低了接收机的复杂度。通过蒙特卡罗仿真评估了接收机在频率选择信道下的误符号率性能。仿真结果表明,在不加信道编码的情况下,该接收机在信噪比为 14dB时误符号率达到 10-3以下。     

时分双工系统波束赋形块长优化

提出了一种优化时分双工系统波束赋形块长的方案。在该系统中,由于上下行链路的 信道互易性,基站可以通过上行导频估计出当前时刻的信道状态信息,从而计算出下一时刻 的发射波束赋形向量或矩阵。当给定归一化导频开销时,不同的波束赋形块长对应不同的上 行信道估计误差和上下行传输时延,进而导致不同的系统性能。以块平均后验信噪比为目标 函数,推导出最优块长,它能同时最大化块平均后验信噪比和块遍历容量(上界)。仿真结果 验证了理论分析的正确性。     

一种基于纠缠交换的远程量子链路建立策略

提出一种以纠缠交换作为核心技术的远程量子链路建立策略,建立了基于链路状态矩阵的量子链路模型并分析了纠缠交换的实现和矩阵表示。提出了链路协议栈以及端到端的建立策略,分析了矩阵控制下的纠缠交换和纠缠纯化流程,计算得出了在基于自动重传请求(ARQ)协议经典信息辅助下的链路时延和吞吐量与节点数、误帧率、平均距离、操作成功率之间的定量关系。仿真结果表明：处于同一状态区间内的链路性能随节点数呈现出较为一致和平缓的变化;不同区间内的链路性能差异较为显著,在节点平均距离为1 km、经典信息误帧率为0、纠缠保真度为0.98的情况下,当节点数分别为32、33和34时,链路时延分别为1.0770 ms、1.0903 ms和1.6690 ms,链路吞吐量分别为0.9285 kb/s、0.9172 kb/s和0.5992 kb/s。     

多载波通信系统仿真中的EESM和MI-ESM方法

介绍了在OFDM系统仿真中链路级仿真和系统级仿真之间的映射方法，主要探讨了两种基于有效SINR映射的方法：指数有效SINR映射（EESM）和互信息有效SINR映射（MI—ESM）。着重阐述了这两种方法如何把多状态信道变成单状态信道以及为什么这种有效单SINR方法能够表示多个子载波SINR信道性能，同时也重点研究这两种方法的主要优缺点以及它们对RRM算法设计的影响。而且，也提及了如何去构建链路和系统级映射表（MCS，SINR，BLER）。     

一种基于双同步头的OFDM系统信噪比估计新方法

信噪比（SNR）是OFDM系统的一个重要的参数，在很多相关技术中得到了应用，如信 道估计、自适应解码、时间同步等。针对OFDM系统，设计了2个训练序列的同步头，选 取相邻4个子载波上的信号来进行噪声功率估计，并利用相邻信道频域相应的差值来抵消多 径和多普勒效应带来的信道衰落。仿真分析表明，此算法可以很好地适应时间和频域选择性 信道要求较高的环境，满足工程的要求。     

一种用于BICM-ID系统的新颖8APSK映射方案

为了能够通过高阶调制信号增加信道容量,提高编码增益和频谱效率,对8阶振幅移相键控(APSK)星座映射方案进行优化。基于欧氏距离设计准则提出一种新颖(2,6)-scheme 8APSK映射方案,并应用于联合准循环构造法构造的低密度奇偶校验(LDPC)(4 599,4 307)码的比特交织编码调制迭代译码（BICM-ID）系统中。信道容量仿真表明,所提方案在高、低信噪比区域都具有非常优越的互信息性能。误码率(BER)性能仿真表明,在BER为10^-7时,联合LDPC(4 599,4 307)码的(2,6)-scheme 8APSK映射方案较(4,4)-scheme 8APSK映射方案、8PSK调制的格雷(Gray)映射、集分割(SP)映射、半集分割(SSP)映射分别提高了约0.45 dB、1.10 dB、1.62 dB、2.13 dB的编码增益。外附信息转移(EXIT)图仿真说明,所提方案能够更早地打开译码通道,从而更早地通过迭代来实现无错译码。     

协同通信系统中差分调制在Rayleigh衰落信道中的误码性能分析

根据源-中继-目的节点链路的等效信噪比模型,推导了检测传送和选择检测传送两种 协议下目的节点瞬时信噪比的概率密度函数和特征函数,基于此推导了协同DMPSK调制近似 误符号率的闭合表达式。推导结果不含积分表达式,方便计算,为系统设计和功率分配提供 了理论基础。最后通过仿真验证了推导结果的正确性。     

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.