一种新的SC—FDE系统粗定时同步算法

定时同步是单载波频域均衡(SC-FDE)系统的一项关键技术,其中的粗定时同步算法决定着同步收敛速度,由Schmidl和Cox提出的传统算法中出现的测度峰值平台影响着粗同步的精度与速度。通过训练符号格式的重新设计,利用其中4个相同部分良好的相关特性,提出了一种基于特殊训练符号的粗同步算法。仿真结果表明,在高斯白噪声信道和多径衰落信道条件下,新算法定时偏差估计的方差和均值接近于理论值,粗定时同步能够精确地完成,较好解决了测度峰值平台问题。     

叠加共轭对称训练序列的OFDM系统时频同步方法

针对正交频分复用（OFDM）系统对同步错误率和频率偏移敏感的问题,提出了一种叠加共轭对称训练序列的OFDM系统时间和频率同步方法。该同步方法将快速傅里叶逆变换（IFFT）调制后的序列构成具有共轭对称特性的训练序列,并叠加到OFDM数据符号上;在接收端,利用叠加训练序列和融合循环前缀信息来获取OFDM系统同步信息。理论分析和仿真表明：在信噪比为5 dB时,该同步算法定时同步正确概率已接近100%;在信噪比为4 dB时,频偏估计精度可以达到10-4;该同步算法不仅具有更好的同步性能,而且节省系统的有效带宽以及降低系统的计算法复杂度。     

一种新的定时和频偏联合估计算法

提出了一种新的正交频分复用(OFDM)系统定时和频率同步联合算法。该算法仅需要一 个训练符号就可以完成定时和频偏估计,额外开销量小,定时和频率同步的实现均在时域进 行,简化了同步实现的复杂度。由于使用自相关处理,定时同步对频率偏差具有较强的鲁棒 性。与以往的定时同步算法相比,该算法避免了定时平台和多峰值的出现,即使在非常低 的信噪比下,其定时测度都是一个尖脉冲。仿真结果表明,该算法能快速地实现定时和频率 同步。     

一种采用可变同步帧的OFDM符号定时同步算法

符号定时同步是正交频分复用（Orthogonal Frequency Division Multiplexing,OFDM）系统中最为关键的同步之一。针对现有的基于数据辅助类的同步算法中帧头存在持续时间长、抗噪声性能差和对载波频偏敏感等问题,提出了一种可变长度的同步帧结构,采用滑动差分相关算法完成符号定时同步。仿真结果表明,提出的同步帧结构持续时间短于一个OFDM符号周期,并且训练序列长度可以通过估算信噪比大小而灵活控制。同时,所提算法在归一化载波频偏为12（远远超过晶振的误差范围 ±10-5）的情况下正常工作;在高斯白噪声和多径衰落信道中都有较好的性能,且其流水线结构易于硬件实现。     

采用截断循环前缀的OFDM系统码元盲同步

为提高低信噪比下抗干扰能力,提出一种更加稳健的正交频分复用（OFDM）系统盲同步方案。所提方法不需要预先估计信噪比（SNR）信息,而是根据循环前缀（CP）和距离分析,进行定时偏移的盲估计。算法利用CP和对应码元尾部的相似性,在频域最小化码间距离。为减少计算复杂度,距离测量同样可在时域进行。为提高算法性能,剥离多径干扰,使用了截断CP技术。仿真结果表明,在SNR为0 dB时,算法依然可正确识别定时偏移位置,较以往基于CP的盲同步算法,所提方案在低信噪比下性能更加稳健。这使得所提算法更适合一些低SNR情况下的应用,如混合直接序列扩频技术的OFDM系统。     

一种改进的GFDM时频同步算法

针对广义频分复用（GFDM）系统对符号定时同步要求较高的问题,提出了一种新的基于前缀码的同步算法。在接收端,在获取粗略定时信息的基础上,利用前缀码前后两部分的相位差实现载波频偏估计,并对接收序列的频率偏移进行纠正,然后通过纠正后序列与已知发射前缀的互相关函数实现精确的符号定时估计。由于该前缀码具有共轭对称的特性,使其避免了“平顶效应”的出现。结合5G中低时延高可靠场景,在频率选择性信道中对其进行仿真,并通过均方误差对其性能进行了评估。理论分析及仿真结果表明,该算法相对于原算法具有更好的定时同步性能和更低的复杂度,提升了GFDM系统的整体性能。     

IEEE802.11a标准中OFDM系统的同步新算法

根据IEEE802．1la的数据分组结构，利用短训练序列时域响应的特点，对接收到的短训练序列进行窗口平移相关，由相关峰确定符号定时，并利用短训练序列进行粗频偏估计。仿真结果表明，该算法能有效地克服噪声及频偏的影响，定时准确，较好地消除了频偏。与其它文献提出的算法相比，具有定时准确、计算量小、频偏估计范围大的特点。     

适用于多速率高阶QAM的定时同步改进算法

针对速率可变的高阶正交幅度调制(QAM)信号定时同步问题，提出了一种基于Gardn er理论的定时同步改进算法。新算法改原有滤波器结构为两级插值级联优化结构来实现多速 率信号的定时同步，可独立于载波同步单独使用，比传统结构具有更强的普遍适用性。仿真 结果表明，该算法可以准确地对速率可变的128QAM信号进行同步。     

下一代演进移动通信系统主同步信道设计

为了解决下一代演进移动通信系统在异构网场景由于小区ID数量不足导致的小区ID模 糊问题及小区间干扰问题,提出了一种主同步信道和序列设计方法。其中主同步信道基于分 级和非分级的混合结构,主同步序列由具有恒包络零自相关特性的Bjrck序列的修正序列 组成。仿真结果表明,与IEEE802.16m系统相比,设计的主同步信道由于采用的序列具 有更 低的相关值和峰均比,在小区间干扰场景具有更小的误检测概率。     

LTE中一种改进的基于探测参考信号的定时估计算法

研究了LTE系统中探测参考信号(SRS)的定时同步方法。由于基本的滑动相关算法和传统的后向搜索算法不能有效地消除相关过程中旁瓣峰值的影响,不适用于SRS的定时同步。因此,针对SRS的时频结构特点,提出一种改进的后向搜索算法。该方法通过将本地序列与接收序列在时域上相关得到定时度量函数,并重新定义门限值,通过结合门限和新的搜索技术来确定第1径的位置,从而得到正确的定时采样点。仿真结果表明,所提方法的估计性能优于滑动相关算法和传统的后向搜索算法,有效地消除了旁瓣峰值的影响,提高了SRS的正确定时概率。相比传统的后向搜索算法,所提方法的估计性能提高了6倍左右。     

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,     

Public Financial Expenditure——A Reflection of the Livelihood Improvement

In recent years.China's public finance put social construction high on the agenda and attaches more importance on livelihood insurance and improvement.The 2003-2007 public financial expenditure reflects a fact that the government isputting more emphasis on livelihood andissues concerning the people.     

Voices from the MPC and CPPCC

"Crucial for economic growth.energy utilization has its role in all economic sectors and every aspect of people's daily life.Now we are in dire need of a new profession,namely energy manager.We not only need to have passion and responsibility,but also a scientific approach to conserve energy and cut emissions.APpropriate legislation should be in place.and a special profession should be introduced to ensure the implementation of these laws and regulations."