功率约束下的星地协作网络中断概率分析

针对星地协作网络，考虑中继节点转发卫星节点信号时会受发射功率和干扰功率约束，提出了一种基于中继节点与目的节点间链路最大信噪比准则来选择中继节点的放大转发部分中继选择策略。在卫星链路遭受阴影莱斯衰落和地面链路遭受瑞利衰落情况下，推导出系统中断概率下界的闭合表达式。仿真结果表明了理论分析的正确性，并展示了不同阴影莱斯信道参数、不同中继数目、不同功率约束对中断概率的影响。     

一种联合链路持续时间与平均速率的中继选择方法

针对中继系统中节点快速移动时采用传统中继选择方法造成系统可传输数据量较低 的问题,提出一种联合链路持续时间与平均速率的中继选择方法。该方法首先分析了系统采 用两跳传输及协作传输两种模式下的链路持续时间,分别给出了节点速度及相互之间距离满 足不同条件时的链路持续时间表达式,然后计算两种模式下的链路平均可达速率,最后基于 所提出的准则完成中继选择。仿真结果表明,与传统的中继选择方法相比,该方法可以使系 统获得更多的数据传输,同时具有较低的中断概率。     

同信道干扰下的中继网络性能分析

分析了两跳中继网络在同信道干扰下的中断概率。在中继网络中,源节点广播信号至所有的中继节点,此时同信道干扰在中继节点或者目的节点处被引入。中继节点采用解码转发策略转发源节点的信号,而目的节点采用最大比合并技术接收来自中继节点的信号。最终推导了各种干扰情形下系统中断概率的闭合表达式。仿真结果表明,解析曲线和蒙特卡洛仿真曲线非常吻合,而同信道干扰在某些场合会对系统性能造成较大影响。分析结果对中继网络的系统设计和参数设置都有一定的参考意义。     

认知选择协同分集任意信噪比中断概率的分析

选择中继已被证明是一种有效和实用的协作分集方法.但是,现有的分析主要集中在渐进高信噪比(SNR)区域,因此,研究认知选择协同分集系统任意信噪比的中断概率具有现实意义.推导了瑞利衰落信道选择中继协议的中断概率解析式,并进行了仿真.仿真结果表明,选择中继协议在任意信噪比情况下,增加中继节点可降低中断概率,而解码中继协议(DF)在低、中信噪比情况下不一定降低中断概率;同时,选择中继协议的中断性能和分集增益随频谱空穴检测能力的提高而增强.     

卫星网络的协作通信技术

分析了用于点对点和点对多点通信链路协同通信技术的使用。通过设计一个简单的中 继模型来分析多节点协作通信方式。运用放大转发、解码转发协作协议,分别计算比较了链 路 的效率和同步性,以通过不同的中继协议来仿真中断概率与频谱效率的理论性能。 仿真分析表明,完全功率分配比平均功率分配方法提高约3 dB的信噪比。     

结合全双工与协作干扰的无线网状网物理层安全策略

针对无线网状网中缺少窃听者先验知识不利场景中的安全连接问题,提出了一种结合全双工和协作干扰技术的物理层安全策略。利用全双工通信中的自干扰消除技术和协作干扰技术,提出的安全策略可有效劣化位于信息传播范围内包括潜伏在接收节点附近窃听者的接收性能。为保证信息的安全传输给出了协作干扰节点的选择方法,基于随机几何等数学方法导出了选定路径的安全连接概率表达式。性能分析和仿真结果表明,所提方法与仅基于全双工或协作干扰技术的方法相比,其安全性能有较大提升。     

一种基于混合智能算法的协作中继选择新方法

针对多用户多中继场景下协作通信系统的中继选择问题,提出了一种基于混合智能算法的协作中继选择新方法。不同于现有的为每个源节点分配一个中继节点的中继选择方法,新方法建立了为每个源节点分配一个或多个中继节点的优化模型,以最大化多用户多中继协作系统的最小接收信噪比为优化目标,采用结合了模拟退火与遗传算法的混合智能算法来搜寻中继选择问题的最优解。仿真结果表明,所提方法可显著提高目的端的接收信噪比,且算法具有较强的全局搜索和快速寻优能力。     

基于资源分配和功率控制的D2D中继选择

为优化蜂窝用户通信与设备直传（D2D）中继通信共存下的同频干扰问题，满足蜂窝用户容量要求，提出了一种基于能效的联合资源分配和功率控制的D2D中继选择算法。该算法首先对等效D2D中继链路进行资源分配，减小算法复杂度的同时使得D2D链路对蜂窝链路产生的干扰最小；然后以资源分配结果和功率控制算法为依据进行中继选择。该方案不仅考虑了D2D中继链路的能效问题，而且还同时考虑到了对蜂窝链路的干扰问题。通过仿真验证，所提算法不仅能有效提升D2D中继链路的能效值，同时降低了对蜂窝用户的干扰。     

基于深度强化学习的协作通信中继选择

协作通信是无线传感器网络(Wireless Sensor Network，WSN)实现数据可靠传输的关键技术，而协作通信技术的关键在于中继方案的选择。为此，提出了一种基于深度强化学习的协作通信中继选择算法(Deep Q-Learning Based Relay Selection Scheme,DQ-RSS)。首先，将WSN中具有中继选择的协作通信过程建模为马尔科夫决策过程，并采用Q学习在未知网络模型的情况下获取最佳中继选择策略；其次，针对高维状态空间下Q学习收敛时间长的问题，采用DQN(Deep-Q-Net)算法来加速Q学习的收敛。对比仿真实验结果表明，DQ-RSS在中断概率、系统容量和能耗方面均优于现有的中继选择方案，且能够有效节省收敛时间。     

认知中继网络中基于频谱感知的自适应功率控制策略

针对采用联合overlay和underlay频谱共享模式的认知中继网络,基于频谱感知结果和干扰信道条件,提出了自适应功率控制策略,从理论上分析了次用户的中断概率。通过Monte-Carlo仿真,与单一overlay或underlay频谱共享模式和固定功率控制方案下次用户的中断性能进行了比较。仿真结果表明,采用自适应功率控制方案,在相同中断概率条件下,次用户对主用户的干扰概率降低了70%~80%;在相同干扰概率条件下,次用户的中断概率降低了1~2个数量级,频谱共享性能得到了有效提高。     

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."     

Slowdown Trade Surplus Growth

According to Ma Kai＇s economic planning report submitted to the NPC session on March 5th,（Ma Kai is the Minister in charge of the National Development and Reform Commission）,the government has listed the slowdown in trade surplus growth and the steady expansion of external investment as major tasks for 2008.     

Ouyang Riping： A Hero Besides Entrepreneur

A bout fifty years ago. a baby＇s cry broke the sky of quietness, in a small and beautiful town of Hunan province, which surroundcd by green hills and clear water. Though his .birth brought his family great happiness and hope just as any new life, nobody knew that the little boy would get great achievement when he grow up. even start his business oversea, and earn international honor. Let＇s share with you the entrepreneur Ouyang Riping＇s story, which may insights thcsc people who want to succeed and complete oneself in favorite condition or adversity rather leave things to so-called fate.     

Belarus, A Chinese Fort in Europe

＂In recent years, we＇ve found increasing interest from Chinese investors in the Belarus economy. Please let China know, Belarus is always ready to be a true friend to China. We have built a fort in Europe for China,＂ the President of Belarus, Alexander Lukashenko told Zhou Xiaochuan, President of the Bank of China, during his visit to the capital of Minsk, on January 8th, he expressed his high praise and firm confidence in the development of Sino-Belarusian relations.     

What＇s Behind Spring Festival？

Similar to what the Christmas Day means for the westerners,the Spring Festival is the most important celebration for Chinese people.This big event according to Chinese traditional lunar calendar relaxes and pleases the whole country as the happiest gathering time of the year.National-wide crusade for going back home,too-difficult-to-get train tickets,generous family-going-out shopping,Miaohui laundering,New Year Eve reunion dinner,visiting friends and relatives,watching annual TV gala......each piece of clue reminds us of the smell of Chinese Spring Festival.     

KEY WDRDS for Foreign Investment in China

FDI(Foreign Direct Investment),a component of a country's national financlal accounts,is investment of foreign assets into domestic structures,equipment,and organizations.It does not include foreign investment into the stock markets,concession and subcontract.FDI iS thought to be more useful to a country than investments in the equity of its companies because equity investments are potentially "hot money"which can leave at the first sign of trouble,whereas FDI is durable and generally useful whether things go well or badly.     

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.     

Consumption, New Protagonist in 2007 GDP

Not long ago, the National Bureau of Statistics released its 2007 Macro Economy Index. Social consumption retail sales reached RMB 8.9 billion, increased by 16.8 percent over the previous year, or 3.1 percentage points higher; the whole investment in social fixed assets was valued RMB 13.7 billion, a year-on-year increase of 24.8 percent, that is 0.9 percentage points higher; and trade surplus amounted to RMB 24.7 billion, rising by 47.7 percent compared with the same period last year, 26.3 percentage points falling over the increasing speed last year. According to preliminary estimates, GDP for the year was RMB 24.67 trillion, up by 11.4 percent from the previous year,