浅析京沪穗高速环网络保护方案

京沪穗环DWDM系统采用北电公司的LH1600G设备，由点对点的链型结构组成环状波分系统，用以承载SDH传输环网；SDH系统采用北电OPTera DX设备和华为10G设备，组成线路速率为10Gb／s的SDH传输环网。     

HDSL新技术的分析比较

xDSL是DSL(Digital Subscrlber Line)的统称，意即数字用户线路，是以铜电话线为传输介质的点对点传输技术。DSL技术在传统的电话网络(POTS)用户环路上支持对称和非对称传输模式，解决了经常发生在网络服务供应商和最终用户间的“最后一公里”的传输瓶颈问题。由于电话用户环路已经被大量铺设，如何充分利用现有的铜缆资源，通过铜质双绞线实现高速接入就成为业界的研究重点，     

高速公路外场监控图像传输方式浅析

介绍了目前高速公路外场监控图像传输最常用的3种方式,对3种方式的优缺点及其应用条件作了简要分析,并提出在选择图像传输方式上的个人见解。     

Free-riders impact on throughputs of peer-to-peer file-sharing systems

In a peer-to-peer file-sharing system, a free-rider is a node which downloads files from its peers but does not share files to other nodes. Analyzing the free-riders’ impact on system throughputs is essential in examining the performance of peer-to-peer file-sharing systems. We find that the free-riders’ impact largely depends on nodes behavior, including their online time and greed of downloading files. We extend an existing peer-to-peer system model and classify nodes according to their behavior. We focus on two peer-to-peer architectures: centralized indexing and distributed hash tables. We find that when the cooperators in a system are all greedy in downloading files, the system throughput has little room to increase while the cooperators throughput degrade badly with the increasing percent of greedy free-riders in the system. When all the cooperators are non-greedy with long average online time, the system throughput has much room to increase and the cooperators throughput degrade little with a high percent of greedy free-riders in the system. We also find that if a system can tolerate a high percent of greedy free-riders without suffering much throughput degradation, the system must contain some non-greedy cooperators that contribute great idle service capacity to the system. Foundation item: the National High Technology Research and Development Program (863) of China (No. 2007AA01Z457), and the Shanghai Science and Technology Development Funds (No. 07QA14033)     

白云机场至佛山专线开通

8月1日，白云机场至佛山专线正式开通，白云机场佛山城市候机楼同时启用。这是继开通珠海、东莞、中山、江门、深圳、顺德等珠三角线路后，白云机场又铺设的一条“点对点”长途客运专线。今后，佛山的旅客到白云机场乘机，可在白云机场佛山城市候机楼办理值机手续，然后便可轻松搭乘空港快线直达白云机场。