可信的反馈声誉保护协作频谱感知软判决算法

协作频谱感知中信任机制的引入,起到了抑制恶意用户频谱感知数据伪造(SSDF)攻击行为的作用。然而,数据融合中心不加区分地接收协作感知结束后的反馈信息,为恶意用户带来了实施“掺沙子”攻击的机会。恶意用户向数据融合中心反馈错误的主用户频谱状态,使信任机制不能得出准确的信任值。为此,提出了一种基于反馈声誉的信任机制,考虑反馈中的个体性特征,引入反馈声誉的思想来量化认知用户信任值。同时,将信任值量化结果用于权重经典软判决算法——序贯概率比检测(SPRT)算法,消除SSDF恶意用户参与软判决数据融合的影响,形成可信序贯概率比检测算法(FSPRT)。仿真结果表明FSPRT算法的性能优于传统SPRT算法,能有效降低网络信任值计算误差,并保持较好的感知性能。     

抗SSDF攻击的EWSPRT协作频谱感知方案

比较了认知无线电网络中几种典型的协作感知方案在篡改感知数据(SSDF)攻击条件下的感知 性能,并提出了一种增强型加权序贯检 测（EWSPRT）协作方案。在该方案中,各次用户首先通过能量检测得到2 bit本地决策 ,然后 收集其它协作用户的感知结果进行决策融合和最终判决,并依据历史观测信息动态更新各协 作用户的融合权重;利用改进的信任度更新算法能使恶意用户的融合权重更快地降低,从而 有效地减少SSDF攻击对协作过程的影响。Monte-Carlo仿真结果表明,与传统方案相比,EWS PRT方案能够更有效地抵抗SSDF攻击。     

一种基于覆盖表融合的移动群智感知协作算法

在集中性较高的感知区域中，移动群智感知网络节点在无控制的模式下，容易产生感知数据冗余度大幅升高的问题，降低了网络感知质量。针对这种情况，首先对感知区域进行时空域划分，并对感知过程进行建模;然后引入单元格充足感知覆盖概念，设计了一种基于覆盖表信息融合的移动节点协作感知数据收集算法。实验仿真表明，相较于原始感知模式和本地控制模式，该算法能大幅消除感知冗余数据，从而提高感知网络的数据质量，同时节约移动节点代价。     

一种基于无线电环境地图的路由优化机制

设计认知无线网络路由算法时,需要兼顾主用户保护与路由性能两个方面。为了提高认知无线网络中次用户之间路由的端到端性能,提出了基于无线电环境地图的路由优化机制,该机制中无线电环境地图能够为次用户提供主用户保护有关的无线电环境数据。首先,无线电环境地图根据次用户的数据请求将各授权频段的可用概率与功率控制相关信息反馈到该次用户;其次,次用户可以计算出与上一跳次用户之间的链路稳定性以及传输时延;最后,目的次用户通过计算每条路由的端到端吞吐量的期望值,然后选取期望值最大的一条路由。仿真结果表明,该路由机制在平均分组投递率、平均端到端吞吐量、平均端到端时延方面均优于对比路由算法。     

基于信誉模型的无线传感器网络恶意节点识别方法

无线传感器经常工作于开放外部环境中,如何识别恶意节点对保证无线传感器网络安全高效工作有重要意义。建立无线传感器网络的信誉评测模型,引入贝叶斯公式计算信誉,最后经过拟合分析得到节点的信誉服从Beta分布,通过节点之间彼此交换信誉信息,计算直接信誉和间接信誉的整合之后的信任值与信任阈值进行比较判断节点是否为恶意节点。仿真结果表明该模型在小型无线传感器网络中对恶意节点具有较高的捕捉率。     

基于压缩感知和最小二乘的分布式协作频谱感知

针对认知无线电(CR)集中式频谱感知算法对融合中心要求高，而且对节点失效的容忍性也不高等缺点，提出了一种基于压缩感知的分布式多节点协作算法。认知无线电网络中每个CR节点在接收信号频谱后，首先根据压缩采样理论在本地获取压缩采样测量值，然后利用l1范数约束的最小二乘算法在本节点估计频谱，把在此节点估计的频谱传给下一相邻节点，以此进行迭代优化直到算法收敛。理论分析和仿真结果表明，所提算法不仅计算复杂度低，收敛速度快，而且精确重构性能好，可靠性较高。     

基于可信度计算的分布式共识合作感知算法

对于分布式的认知无线网络,由于不存在融合中心节点,次级用户节点之间的合作感知往往 采用信息交互的渠道进行,其中一种基于共识合作的感知机制受到广泛的研究,但这种机制 在鲁棒性方面存在一定的缺陷,当恶意节点存在时,其错误信息将影响局部的感知判决结果 ,为此,提出一种基于感知节点可信度的共识合作感知机制。在该机制中,各节点对邻居节 点的可信度进行计算,并把计算出的可信度值发送给其他节点,通过对各节点可信度的累加 计算,最终计算出各节点的可信度,各节点以此决定是否与其邻居节点合作以及如何合作。 仿真结果证明,在恶意节点存在的情况下,该算法在感知性能和收敛速度上都较未改进算法 有不同程度的提升,减轻了不可靠节点对合作感知结果的影响。     

LAT模型中基于次用户权值优化的频谱感知

全双工认知无线电LAT（Listen-and-Talk）模型因自干扰消除不完全而使得频谱感知能力下降。为提升频谱感知性能，提出了LAT模型下基于次用户加权的协作式频谱感知方法，分别研究了决策融合和数据融合下次用户最优权值的算法。求解最优权值时利用了凸优化方法，在处理非凸问题时利用了序列规划的方法，得到了较好的优化结果。仿真实验表明，在加权融合机制下的LAT模型得到了趋近于传统LBT（Listen-before-Talk）模型的频谱感知能力。     

利用压缩测量值的非重构宽带频谱感知

为了解决在认知无线电(CR)宽带系统中快速精确分析数据并实现频谱感知的技术难题,对非重构压缩频谱检测进行了研究。提出了一种利用压缩测量值的非重构宽带频谱感知算法,推导分析了虚警概率和检测概率的封闭表达式。该算法利用离散余弦变换（DCT）矩阵的能量压缩特性观测得到主用户能量压缩信息,并利用新型压缩检测器对压缩信息进行判决。仿真表明,所提算法降低了计算复杂度,提供了比传统的能量检测器和压缩检测器更好的工作特性。     

随机共振在认知无线电频谱感知中应用的最新研究进展

频谱感知是认知无线电网络的一项关键技术。低信噪比（SNR）环境下频谱检测的性能会大 幅降低,而随机共振（SR）能 有效提高信号信噪比,所以将其应用到频谱感知中,能增强认知用户对主用户（PU）的检测 性能。〖JP2〗首先介绍了随机共振在认知无线电频谱感知中应用的最新研究进展,包括随 机共振在 本地感知中（如能量检测、协方差矩阵频谱感知、循环平稳特征检测）及协作感知中的应用 ,然后指出了随机共振在认知无线电频谱感知中还有待解决的问题,并提出了下一步的研究 方向。     

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＂.