基于超高速WLAN的MAC协议设计

为实现在无线局域网络中达到与有线千兆以太网相同的数据传输率,应用了OFDM和MIMO及信道绑定等技术．然而在超高速无线局域网络的设计中,物理层的高速需要更有效MAC协议配合才能获得真正性能的提高．分析了高速无线链路下原有RTS／CTS竞争机制的制约效应,得出高速WLAN需要采用全双工通信方式来提高系统吞吐量．提出了三种基于AP信道资源调度管理机制的解决方案,分析了各方案的特点,为超高速无线局域网络的MAC设计提供理论依据．     

Saturation throughput analysis of RTS/CTS scheme in an error-prone WLAN channel

In this paper, a new three-dimensional Markov model is proposed for the estimation of saturation throughput of RTS/CTS （request to send/clear to send） scheme in an error-prone wireless local area network （WLAN） channel. The model takes account of the effect of bit error on all the frames, and station short and long retry limits. Saturation throughput was re-analyzed using the new Markov model and numerical results closely matched those from simulation, confirming the accuracy of the new model. Evaluation of the influence of different parameters on throughput showed that the saturation throughput is sensitive to channel bit error rates and packet length, especially in high bit error conditions.     

A study on directional returns to scale

This paper investigates directional returns to scale (RTS) and illustrates this approach by studying biological institutes of the Chinese Academy of Sciences (CAS). Using the following input–output indicators are proposed: senior professional and technical staffs, middle level and junior professional and technical staffs, research expenditure on personnel salaries and other expenditures, SCI papers, high-quality papers, graduates training and intellectual properties, the paper uses the methods recently proposed by Yang to analyze the directional returns to scale and the effect of directional congestion of biological institutes in Chinese Academy of Sciences. Based on our analysis we come to the following findings: (1) we detect the regime of directional returns to scale (increasing, constant, decreasing) for each biological institute. This information can be used as the basis for decision-making about organizational adjustment; (2) congestion and directional congestion occurs in several biological institutes. In such cases the outputs of these institutes decrease when the inputs increase. Such institutes should analyze the underlying reason for the occurrence of congestion so that S&T resources can be used more efficiently.     

东莞轨道交通客流与投融资研究

掌握人口及其区域分布是客流量研究的出发点。文章利用作者前期对东莞的系统性人口研究成果探讨东莞城市轨道系统建设的可行性,对轨道交通客流量及建造与运营成本进行分析和测算。认为无论从构建珠三角城市群的角度及提升东莞整体竞争力而言还是东莞本身人口及自有力量而言,轨道交通建设都是可行的。     

OFDI反向技术溢出对我国经济增长的影响--基于对东盟的实证研究

采用2003-2010年我国对东盟9个国家①对外直接投资（OFDI）的面板数据,利用协整、误差修正模型、脉冲响应函数以及GLS方法,分析来自东盟的OFDI反向技术溢出对我国经济增长的影响。结果表明：（1）从短期、长期来看, OFDI反向技术溢出对我国经济增长有促进作用,但是影响大小尚不如FDI;（2）来自东盟的FDI能促进我国对东盟国家的OFDI,但是OFDI不能显著促进FDI的增加;（3）长期来看,OFDI与FDI对我国经济作用之间的差距有缩小的趋势,经济危机后这种趋势更为明显;（4）发达国家比发展中国家对我国经济影响更大。