通过空间位置服务平台对位置服务领域中众多复杂的空间信息数据进行有效地整合和资源共享,可以为用户提供综合性的位置应用和服务.利用基于空间信息网格(spatial information grid ,SIG)的分布式思想对空间位置服务平台的架构进行了模...通过空间位置服务平台对位置服务领域中众多复杂的空间信息数据进行有效地整合和资源共享,可以为用户提供综合性的位置应用和服务.利用基于空间信息网格(spatial information grid ,SIG)的分布式思想对空间位置服务平台的架构进行了模型设计和技术实现,完成了地图数据和定位查询的分布式存储和检索.平台服务接口满足开放位置服务(openlocation service ,OpenLS)规范,利用XML进行信息编码,通过HTTP进行数据传输,介绍了相应的接口内容和调用示例.针对定位信息的更新和传递提出了一种新的基于Push的主动通知机制,提供与各种定位接口的数据转换和消息处理能力,高效地实现了位置应用和服务平台之间的消息传递.最后结合MAPGIS平台和CDMA手机定位技术进行了原型系统的实现,验证了平台理论模型和服务接口的可用性.展开更多
Software Defined Network (SDN) makes network management more flexible by separating control plane and data plane, centralized control and being programmable. Although, network measurement still remains in primary stag...Software Defined Network (SDN) makes network management more flexible by separating control plane and data plane, centralized control and being programmable. Although, network measurement still remains in primary stage in SDN, it has become an essential research field in SDN management. In this context, this paper presents a low-cost high-accuracy measurement framework to support various network measurement tasks, such as throughput, delay and packet loss rate. In this framework, we only measure per-flow edge switches (the first and the last switches). In addition, a new adaptive sampling algorithm is proposed to significantly improve measurement accuracy and decrease network overhead. Meanwhile, we consider a low-cost topology discovery approach into our framework instead of topology discovery currently implemented by SDN controller frameworks. In order to improve the accuracy of delay, we also join a time threshold value to adjust the time delay. Furthermore, we consider and analyze the balance between measurement overhead and accuracy in several aspects. Last, we utilize POX controller to implement the proposed measurement framework. The effectiveness of our solution is demonstrated through simulations in Mininet and Matlab.展开更多
Location-Based Services (LBS),an emerging new business based on smartphone and mobile networks,are becoming more and more popular.Most of these LBSs,however,only offer non-seamless indoor/outdoor applications and simp...Location-Based Services (LBS),an emerging new business based on smartphone and mobile networks,are becoming more and more popular.Most of these LBSs,however,only offer non-seamless indoor/outdoor applications and simple applications without giving stakeholders the chance to play an active role.Our specific aim is to solve these issues.This paper presents concepts to solve these issues by expanding the Open Location Services Interface Standard (OpenLS) to allow seamless indoor/outdoor positioning and to extend the content of the services to include information recommended by stakeholders.展开更多
文摘通过空间位置服务平台对位置服务领域中众多复杂的空间信息数据进行有效地整合和资源共享,可以为用户提供综合性的位置应用和服务.利用基于空间信息网格(spatial information grid ,SIG)的分布式思想对空间位置服务平台的架构进行了模型设计和技术实现,完成了地图数据和定位查询的分布式存储和检索.平台服务接口满足开放位置服务(openlocation service ,OpenLS)规范,利用XML进行信息编码,通过HTTP进行数据传输,介绍了相应的接口内容和调用示例.针对定位信息的更新和传递提出了一种新的基于Push的主动通知机制,提供与各种定位接口的数据转换和消息处理能力,高效地实现了位置应用和服务平台之间的消息传递.最后结合MAPGIS平台和CDMA手机定位技术进行了原型系统的实现,验证了平台理论模型和服务接口的可用性.
文摘Software Defined Network (SDN) makes network management more flexible by separating control plane and data plane, centralized control and being programmable. Although, network measurement still remains in primary stage in SDN, it has become an essential research field in SDN management. In this context, this paper presents a low-cost high-accuracy measurement framework to support various network measurement tasks, such as throughput, delay and packet loss rate. In this framework, we only measure per-flow edge switches (the first and the last switches). In addition, a new adaptive sampling algorithm is proposed to significantly improve measurement accuracy and decrease network overhead. Meanwhile, we consider a low-cost topology discovery approach into our framework instead of topology discovery currently implemented by SDN controller frameworks. In order to improve the accuracy of delay, we also join a time threshold value to adjust the time delay. Furthermore, we consider and analyze the balance between measurement overhead and accuracy in several aspects. Last, we utilize POX controller to implement the proposed measurement framework. The effectiveness of our solution is demonstrated through simulations in Mininet and Matlab.
文摘Location-Based Services (LBS),an emerging new business based on smartphone and mobile networks,are becoming more and more popular.Most of these LBSs,however,only offer non-seamless indoor/outdoor applications and simple applications without giving stakeholders the chance to play an active role.Our specific aim is to solve these issues.This paper presents concepts to solve these issues by expanding the Open Location Services Interface Standard (OpenLS) to allow seamless indoor/outdoor positioning and to extend the content of the services to include information recommended by stakeholders.
