基于SIP的无线网络移动性管理研究

为了使移动设备能在无线IP网络中无缝漫游,无线IP网络必须要能提供有效的移动性管理来支持终端的移动性。基于SIP提出了一种新的应用层移动性管理方案,和已有的移动性管理方案相比,它既支持实时业务的快速切换,减少了切换时的延迟和丢包,也支持非实时业务,而且实现和部署起来比较简单方便。     

基于SIP的无线网络移动性管理研究

为了使移动设备能在无线IP网络中无缝漫游，无线IP网络必须要能提供有效的移动性管理来支持终端的移动性。基于SIP提出了一种新的应用层移动性管理方案，和已有的移动性管理方案相比，它既支持实时业务的快速切换，减少了切换时的延迟和丢包．也支持非实时业务，而且实现和部署起来比较简单方便。     

An agent infrastructure for on-demand processing of remote-sensing archives

Advances in data collection techniques and database technologies, such as remote sensing and satellite telemetry, have led to the collection of huge amounts of data distributed among large databases and heterogeneous remote sites. Intelligent and automatic processing of the distributed data and efficiently supporting scientific collaboration between both professional and casual users is a highly demanding task. It is also particularly challenging when the system must cope with active data that is processed on-demand. These requirements have generated an urgent need for more advanced software infrastructure to create, maintain, evolve, and federate these active digital libraries of scientific data. Traditional models of distributed computing are inadequate to support such complex applications. As part of the ongoing Synthetic Aperture Radar Atlas (SARA) Digital Library project, the research presented here proposes a collaborating mobile agent approach to on-demand processing of remote sensing data. The approach, which is based on autonomous data processing and enables different image analysis algorithms to be wrapped as mobile agents, is expected to be an improvement over the static CGI-based interface and inefficient information discovery that are currently used by SARA. We discuss the agent-based infrastructure we have developed. The SARA system allows users to dispatch their compute-intensive jobs as mobile agents. Since the agents can be programmed to satisfy their specific goals, even if they move and lose contact with their creators they can survive intermittent or unreliable network connections. During their lifetime, the agents can also move themselves autonomously from one server to another for load balancing, and to enhance data locality and fault tolerance. The SARA system relies on XML to support agent communications on clusters of servers. Although the examples presented are based mainly on the SARA system, the proposed techniques are applicable to other active archives. In particular, we believe the proposed agent design can be used to dynamically configure distributed parallel computing resources and automatically integrate data analysis in remote sensing systems.     

A hierarchical, agent-based service oriented architecture for smart environments

Service Oriented Architectures, which allow for the integration of different subsystems and of applications running on different devices and platforms, may be very suitable to solve the problem of service personalization in large smart environments like cities, where the number of potential users and potentially available services is rapidly growing. Taking this into account, we have designed an agent-based service oriented architecture for smart spaces. Two of the greatest challenges in the design of such a solution are providing effective device, service and context federation and composition mechanisms and handling user mobility. For the first challenge, we have designed a hierarchical architecture and developed a set of inheritance, aggregation and access mechanisms for devices, services and context. To handle user mobility, we have followed three different strategies, using stationary, mobile or nomadic agents. In this paper, we describe the main aspects of our architecture and perform an experimental evaluation to determine the advantages and drawbacks of the different strategies.     

一种新型非交互移动代理路径检测协议

移动代理目前广泛应用于分布式并行计算、网络信息搜索、电子商务等领域,但安全问题一直是阻碍其发展的重要原因。结合身份密码学知识和洋葱路由工作原理提出了一种新型的非交互式移动代理路径检测协议,检测过程中无需双方协商,既节省了网络带宽,又加快了加解密速度。基于身份的加密也避免了公钥基础设施中身份证书的复杂管理,提高了系统运作效率。     

High level MANET protocol: Enhancing the communication support for mobile collaborative work

Mobile collaborative activities involve on-demand interactions among nomad users. Unavailability of communication support in the physical scenario where users are located cannot be a limitation to carry out such collaboration instances. Mobile workers can take advantage of the communication capability embedded in their mobile devices in order to create communication channels between them. The Mobile Ad-hoc Networks (MANET) are infrastructures that can be used to support the nomad users' activities. However, these networks have a short communication threshold; therefore, they need to include a routing protocol as part of its infrastructure to allow mobile workers to collaborate when they are not physically close. This paper presents an application level routing protocol that was designed to support nomad workers performing mobile collaborative activities. The protocol, named High Level MANET Protocol (HLMP), provides several automatic services that are required by mobile collaborative systems. Some of these services are the automatic MANET formation, peer detection and messages routing. HLMP has been implemented in a mobile communication infrastructure and used in several mobile groupware systems.     

MANET能量与其他网络性能平衡路由协议

提出了一种网络性能平衡估价函数,该函数考虑了节点通信过程中的通信信息,包括节点已成功传送的数据包数、掉包数、已发送的控制包数、路由发起次数、路由总跳数以及节点的剩余能量。基于该函数,设计了一种基于能量和其他网络性能参数平衡的路由协议——BEOP,该协议通过在网络中选择平衡估价函数值小于给定阈值的节点作为路由节点,从而得到一条网络性能较优的传输路径。仿真结果表明,该协议能够很好地平衡网络性能,与DSR、MBCR协议相比,BEOP协议在网络平均时延、平均吞吐量、控制开销、丢包率、包成功发送率及网络生存时间等性能上都有较好的改善。     

一种可实现高精度时间同步的数据传输方法

KM2A探测器阵列是高海拔宇宙线观测站(LHAASO)的主体探测器阵列之一,近7000个探测器平均分布在1.3 km 2的实验范围内。针对大面积分布式布局的高能物理实验中读出电子学系统的时间同步和数据传输问题,提出一种可实现高精度时间同步的数据传输方法。借助TCP/IP协议栈和White Rabbit时钟同步技术融合时钟网络与数据网络,TCP/IP协议栈在仅保留PC通信协议的基础上,无需增加额外硬件,即可实现高效可靠的数据传输和高精度时钟同步。测试结果表明,该方法可以实现探测器阵列内LHAASO KM2A读出电子学插件间时间同步精度优于1 ns,同时保证了数据传输的可靠性。