基于ETX模块接口扩展基板电路的实现

ETX（Embedded Tecnology Extended）模块具有完整的PC功能和高效的CPU性能。通过扩展ETX模块的各种外设功能,实现的标准扩展接口有IDE、CF卡、VGA、USB、串口等扩展电路,使ETX广泛应用于各种控制领域。     

无线Mesh网络的新型建模方法研究

对无线Mesh网络准确建模是开展Mesh网络各项研究的基础,基于传统802.11协议模型来分析Mesh网络性能会导致较大的偏差。提出了一种适用于无线Mesh网络的新型模型用以计算网络饱和状态下性能参数的理论值,如丢包率、节点发送概率等,性能分析和仿真结果表明,该方法更能精确地评估无线Mesh网性能。同时在此基础上给出了路由判据ETX理论值的计算方法,该方法可用来预测ETX值而无需实测,从而有效的减少了测量误差和带宽消耗。     

无线Ad Hoc网络中可靠路由的研究

改进了ETX算法,提出了将动态ACK算法与改进的ETX算法相结合的新的链路状况监测算法,以便在选路时忽略质量不好的链路。建议了一种从中间节点开始恢复的备用路由机制以便在链路断时能快速恢复,取代了笔者之前提出的QDSR基于源节点的备用路由机制。NS2仿真实验结果表明,在节点移动速度较小的较大规模移动Ad Hoc网络中,改进后的算法明显减少了路由错误,并且减少了路由发生错误后重新找到一条路径所需要的平均时间。     

HWMP协议的路径选择参数的研究与改进

混合无线网格协议中的路径选择参数过于注重考虑不同网络间路径选择操作的兼容性,而没有很好地考虑到802.11s中各条链路类型的差异对路径选择操作的影响。针对该问题,同时考虑到802.11s支持多速率通讯的要求,在传统WCETT的基础上提出了一种新的路径选择参数计算方案。最后,进行了仿真实验,结果表明：新的路径选择参数有助于提高网络吞吐量,降低丢包率。因此,该参数对于优化基于802.11的无线网格网的路径选择,提高网络性能是行之有效的。     

基于状态转移的机会路由算法研究

现有机会路由算法采用与传统无线路由相似的转发机制,为每个节点指定全局度量值或下一跳节点集合。该文首先通过反例指出转发机制不能总获得最优的性能,进而提出从状态转移的角度研究机会路由过程,将不同已接收到的节点集合视为不同的状态,并将路由过程看作由不同状态组成的马尔科夫链。随后建立了相应的路由算法模型,该模型能够揭示路由过程的本质特征,可适用于多播与多冲突域场景。在此基础上提出了基于状态转移的最佳机会路由算法(Shortest Opportunistic Routing, SOR),证明了其在多播与多冲突域场景下可获得最小期望传输次数(Expected Transmission Count, ETX)代价。仿真结果表明了SOR算法的有效性,其性能优于已有算法。SOR算法可应用于多跳无线网络的最优机会路由策略选择,计算给定拓扑下可获得的最小端到端ETX代价。     

基于CPCI总线CPU主控模块的设计与实现

在一些恶劣环境和军事应用环境条件下,所应用的计算机比普通商用计算机具有更高、更严的要求,提出基于CPCI总线的CPU主控模块设计方案。该方案严格遵守CPCI规范,利用高性能、低功耗、集成度高的ETXPM模块实现通用计算机的主板功能,采用TI公司的PCI2050B桥电路作为CPCI的接口模块,实现了多级总线扩展结构。该设计方案简化了设计,节省了30％的研制费用,缩短了1／2的研制周期。该模块已经通过舰载的应用测试,在-40．85℃的环境下,系统工作稳定,各接口应用正常,达到了该项目的技术指标要求。     

a high-throughput path metric for multi-hop wireless routing

This paper presents the expected transmission count metric (ETX), which finds high-throughput paths on multi-hop wireless networks. ETX minimizes the expected total number of packet transmissions (including retransmissions) required to successfully deliver a packet to the ultimate destination. The ETX metric incorporates the effects of link loss ratios, asymmetry in the loss ratios between the two directions of each link, and interference among the successive links of a path. In contrast, the minimum hop-count metric chooses arbitrarily among the different paths of the same minimum length, regardless of the often large differences in throughput among those paths, and ignoring the possibility that a longer path might offer higher throughput.This paper describes the design and implementation of ETX as a metric for the DSDV and DSR routing protocols, as well as modifications to DSDV and DSR which allow them to use ETX. Measurements taken from a 29-node 802.11b test-bed demonstrate the poor performance of minimum hop-count, illustrate the causes of that poor performance, and confirm that ETX improves performance. For long paths the throughput improvement is often a factor of two or more, suggesting that ETX will become more useful as networks grow larger and paths become longer.This research was supported by grants from NTT Corporation under the NTT-MIT collaboration, and by MIT’s Project Oxygen.Douglas De Couto received his Ph.D. in Computer Science from MIT in June 2004 for work in multi-hop wireless routing. He was a member of MIT’s Computer Science and Artificial Laboratory. He also received his S.B. and M.Eng. degrees in Computer Science and Electrical Engineering from MIT, in 1998. His research interests include multi-hop wireless networks, sensor and embedded networks, and applications of GPS. E-mail: decouto@csail.mit.eduDaniel Aguayo is a graduate student in MIT’s EECS department and a member of MIT’s Computer Science and Artificial Intelligence Laboratory. He received an S.B. in Computer Science and Electrical Engineering from MIT in 2001, and an M.Eng. in 2002. His research interests are focused on multi-hop wireless networks. E-mail: aguayo@csail.mit.eduJohn Bicket is a graduate student in MIT’s EECS department and a member of MIT’s Computer Science and Artificial Intelligence Laboratory. He received a B.S. from Cornell University. His research interests include multi-hop rooftop 802.11 networks and device drivers. E-mail: jbicket@csail.mit.eduRobert Morris is an associate professor in MIT’s EECS department and a member of MIT’s Computer Science and Artificial Intelligence Laboratory. He received a Ph.D. from Harvard University for work on modeling and controlling data networks with large numbers of competing connections. He co-founded Viaweb, an e-commerce hosting service. His current interests include routing in multi-hop rooftop 802.11 networks, modular software-based routers, distributed hash tables, and peer-to-peer file storage. He has received a Sloan Fellowship, an NSF Career award, and the ITT Career Development Chair at MIT. E-mail: rtm@csail.mit.edu     

基于XPE的变尺度级联随机共振系统研究

随机共振作为一种新颖的信号处理手段在各个领域得到了广泛应用,在随机共振的基础上讨论了级联随机共振的构成方式,采用模拟电路的形式对其进行实现,并基于该电路构成嵌入式变尺度级联随机共振系统.此系统硬件采用ETX技术,可以对CPU主板功能进行全新整合,软件上通过定制XPE操作和采用EWF技术,加强了系统的稳定性,同时变尺度算法和最佳级联随机共振判断程序在系统中的移植可以使之在较高频率的场合准确应用.最后给出了应用实例,验证了该系统对信号提取的准确性.     

基于ETX模块的PCI高速数据传输卡的设计与实现

介绍了ETX模块、PCI总线及PCI9054芯片，研究了在ETX系统中如何使用芯片PCI9054具体设计和实现高速数据传输功能。