一种AD9371宽带无线同步定时模块简化方法

在满带宽100 MHz条件下,AD9371的收、发采样频偏问题严重,不采用精确的同步定时模块时,在高斯白噪声信道下测试,误码率较调制误差公式erf值偏高。传统的Gardner定时同步算法虽能降低采样频偏,但Gardner算法的实现复杂度太高。针对这对性能和复杂度间的矛盾,给出了一种同步定时模块的现场可编程门阵列(Field Programmable Gate Array,FPGA)简化实现方法。简化后的Farrow滤波器的乘法器与原始的Farrow相比减少50%,环路滤波器占用FPGA资源和传输时延比原环路滤波器都减少了50%以上。将简化后的同步定时模块在AD9371板卡上进行测试,结果表明简化后的同步定时模块与传统的Gardner同步定时模块性能在-30 dBm时误码同时降低到零,性能完全一样,证明此种同步定时方法的等效简化切实有效。     

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。     

基于IEEE 802.11a标准的符号同步新算法

针对OFDM系统符号定时，采用了两种经典算法的结合一符号同步两步算法，提出符号同步低复杂度算法，并进行分析与仿真，结合频率偏移估计比较两种算法性能。仿真结果表明。该方案中的低复杂度算法的符号定时精度较高，且算法简单。     

一种适用于宽带短波通信OFDM系统符号定时同步的新方法

针对宽带短波通信正交频分复用（OFDM）系统,提出了一种不需要数据辅助的高效符号定时同步方法。该方法利用OFDM符号中的空载波不传输任何数据这一特性,通过最小化空载波上的数据能量来将符号定时点锁定在安全区域内,从而完成符号定时同步。该方法可以有效对抗多径效应,适用于短波通信系统。最后将该方法与Al-Dweik同步方案在宽带短波信道条件下进行了仿真对比,结果表明该方法有着更精确的符号定时同步性能,并且适用于各种星座图调制。     

OFDM系统的多符号改进算法

针对OFDM训练符号同步算法中存在的大采样数据而导致捕获时间过长的问题。提出了一种多符号改进算法。该算法应用对多个符号等间隔取样并共轭相乘累加的方法，在采用小数目的采样数据时就可以取得较好的性能，同时缩短了定时捕获时间，克服了原来算法中存在的问题。最后，仿真表明该算法的有效性。     

面向DVB-S2系统的最优相关间隔帧同步方法

针对卫星通信第二代卫星数字电视广播（Digital Video Broadcasting-Satellite 2,DVB-S2）系统中可变的编码调制方式和物理层帧长，以及接收机需要工作在低至-2 dB的信噪比条件的要求，提出了一种基于DVB-S2帧头结构的最优相关间隔相关检测和双阈值峰值检测帧同步方法，并采用状态机控制PLS（Physical Layer Signaling）码解码，通过解出帧头信息快速跟踪下一帧头位置。仿真结果表明，该方法性能明显优于传统的SOF+PLSC（Start of Frame and Physical Layer Signaling Code）算法，并且能够适用于低信噪比条件和可变的编码调制方式。     

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。     

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。     

宽带卫星通信中的ACM技术

采用自适应编码调制技术(ACM)的卫星数字视频广播新标准(DVB-S2)应用到宽带卫 星通信网中,将极大提升系统吞吐量,提供更丰富的交互式业务。从实际应用的角度,分析 了ACM的控制机制并提出其编码调制方案的简化方法。仿真结果表明,在几乎不影响系统性 能的前提下,该方案可以大幅降低ACM机制的复杂度。     

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.     

Like An Angel

The central bank of China has raised her deposit rate for 6 times,and deposit reserve rate for 16 times,since last year up to now,which resulted to a great suffer to those small and medium sized enterprises in finance collection.30 percent of China s small and medium sized enterprises have to be closed down, and 60 percent of them are because of finance problem.How to gather the fund is the biggest obstacle for China's enterprises to grow.     

Zhang Hao,Health of wealth

Contribution to the society Zhang Hao owns great opportunity to store intelligence and knowledge, in her early year.Zhang Hao was graduated from Economic Management Department of People's University in 1983 and later finished her study in Advanced Training Program of CEO of Chinese Direct Selling Enterprises in Peking University.