This paper presents a novel real-time routing protocol, called CBRR, with less energy consumption for wireless sensor networks (WSNs). End-to-End real-time requirements are fulfilled with speed or delay constraint at ...This paper presents a novel real-time routing protocol, called CBRR, with less energy consumption for wireless sensor networks (WSNs). End-to-End real-time requirements are fulfilled with speed or delay constraint at each hop through integrating the contention and neighbor table mechanisms. More precisely, CBRR maintains a neighbor table via the contention mechanism being dependent on wireless broadcast instead of beacons. Comprehensive simulations show that CBRR can not only achieve higher performance in static networks, but also work well for dynamic networks.展开更多
The data acquisition stations and the data processing center of the Science and Application Center for Lunar and Deep-space Exploration (SACLuDE) are located at different geographical sites. They respectively have the...The data acquisition stations and the data processing center of the Science and Application Center for Lunar and Deep-space Exploration (SACLuDE) are located at different geographical sites. They respectively have their own local networks and interconnect with each other through access to the core data network. This paper describes the clock drift in the computer and other networked devices building up the infrastructure of the above local networks. The network time variance of the stochastic model is also estimated. The poor precision of network synchronization will bring about potential hazards to the network operation and application running in the networks, which is clarified in the present paper. At the end of the paper, a cost-effective and feasible solution is proposed based on the Global Position System (GPS) and the Network Time Protocol (NTP).展开更多
The authors propose a new persistent transmission based real time Ethernet MAC protocol that provides a predictable upper bound for the delivery delay of real time frames. Moreover, it is compatible with the protocol ...The authors propose a new persistent transmission based real time Ethernet MAC protocol that provides a predictable upper bound for the delivery delay of real time frames. Moreover, it is compatible with the protocol used by the existing Ethernet controllers for conventional datagram traffic and thus standard Ethernet stations can be used in the system without any modification. The paper describes the protocol in detail and analyses the maximum delivery delay for real time traffic and the efficiency of the channel.展开更多
Coverage holes often appear in wireless sensor networks due to sensor failure or the inheritance of sensor＇s random distribution. In the hybrid model, mobile sensors in the network are acquired to heal coverage holes...Coverage holes often appear in wireless sensor networks due to sensor failure or the inheritance of sensor＇s random distribution. In the hybrid model, mobile sensors in the network are acquired to heal coverage holes by their mobifity. When multiple coverage holes appear in the sensor network and each of them has a time requirement （in which the coverage hole has to be healed）, conflicts for the requests of the same mobile sensor may arise. A distributed multiple mobile sensor schedufing protocol （DMS） is proposed in this paper to solve this problem by finding mobile sensors in the time response zone defined by the time requirement of each coverage hole. Simulation results show that DMS can well schedule the mobile sensors to move to multiple coverage holes within the time requirement.展开更多
A new rule to detect intrusion based on IP weight, which is also well implemented in the rule base of author’s NMS, is presented. Compared with traditional ones, intrusion detecting based on IP weight enhanced analys...A new rule to detect intrusion based on IP weight, which is also well implemented in the rule base of author’s NMS, is presented. Compared with traditional ones, intrusion detecting based on IP weight enhanced analysis to packet content. The method also provides a real-time efficient way to analyze traffic on high-speed network and can help to increase valid usage rates of network resources. Practical implementation as a rule in the rule base of our NMS has verified that the rule can detect not only attacks on network, but also other unusual behaviors.展开更多
在无中心飞行器集群网络中,非直通条件节点间不同的中继路径可能导致较大路径损耗落差,为有限资源前提下网络传输能力的提升带来困难。参考5G移动通信中的终端直通(Device to Device,D2D)技术与中继通信中的虚拟多输入多输出(Multiple-I...在无中心飞行器集群网络中,非直通条件节点间不同的中继路径可能导致较大路径损耗落差,为有限资源前提下网络传输能力的提升带来困难。参考5G移动通信中的终端直通(Device to Device,D2D)技术与中继通信中的虚拟多输入多输出(Multiple-Input Multiple-Output,MIMO)技术,提出一套D2D通信与虚拟MIMO技术结合的无中心飞行器集群网络传输方案。重点研究在正交资源模式下,将不同的协作传输协议与空时编码进行组合,在信噪比、误比特率、接入概率等方面对通信性能的影响。仿真结果表明:D2D通信与虚拟MIMO技术结合的传输方案在不增加资源的前提下,对集群网络的通信性能有明显提升,且引入分布式空时编码可进一步优化误比特率性能,但3种传输协议在不同传输质量评价方向的改善有所不同。展开更多
目的 :解决应用服务器出现时间偏差会导致住院患者每日汇总报表数据不一致、护士看不到医生医嘱及患者的次日用药无法领取等隐患问题。方法:通过深入分析和大量模拟实验,提出一种基于网络时间协议(network time protocol,NTP)的时间同...目的 :解决应用服务器出现时间偏差会导致住院患者每日汇总报表数据不一致、护士看不到医生医嘱及患者的次日用药无法领取等隐患问题。方法:通过深入分析和大量模拟实验,提出一种基于网络时间协议(network time protocol,NTP)的时间同步改进技术,即定时更新NTP服务器硬件时间,以防止NTP服务器因故存在的硬件时钟累积误差问题;同时,采用自动校正NTP服务器冷启动后的系统时间,避免线上的客户机与不正确的时间进行同步。结果:在时间同步微调模式下,采用脚本后的改进技术大大缩短了时间同步。观察10 s的偏差同步时间可节省7 h以上,若时间更长(<600 s),则节省时间更多。结论:缩短了在线设备与NTP服务器的同步时间,解决了极端情况下的时间偏差问题。展开更多
介绍了NTP(Network Time Protocol)网络时间协议工作原理,基于网络时间同步服务器构建网络时间同步系统,通过对网络环境下影响同步精度的因素进行深入分析,设计了网络时间同步应用软件,并开展重复性实验,对网络时延和时刻偏差作了详细...介绍了NTP(Network Time Protocol)网络时间协议工作原理,基于网络时间同步服务器构建网络时间同步系统,通过对网络环境下影响同步精度的因素进行深入分析,设计了网络时间同步应用软件,并开展重复性实验,对网络时延和时刻偏差作了详细分析。展开更多
文摘This paper presents a novel real-time routing protocol, called CBRR, with less energy consumption for wireless sensor networks (WSNs). End-to-End real-time requirements are fulfilled with speed or delay constraint at each hop through integrating the contention and neighbor table mechanisms. More precisely, CBRR maintains a neighbor table via the contention mechanism being dependent on wireless broadcast instead of beacons. Comprehensive simulations show that CBRR can not only achieve higher performance in static networks, but also work well for dynamic networks.
文摘The data acquisition stations and the data processing center of the Science and Application Center for Lunar and Deep-space Exploration (SACLuDE) are located at different geographical sites. They respectively have their own local networks and interconnect with each other through access to the core data network. This paper describes the clock drift in the computer and other networked devices building up the infrastructure of the above local networks. The network time variance of the stochastic model is also estimated. The poor precision of network synchronization will bring about potential hazards to the network operation and application running in the networks, which is clarified in the present paper. At the end of the paper, a cost-effective and feasible solution is proposed based on the Global Position System (GPS) and the Network Time Protocol (NTP).
基金TheNationalNaturalScienceFoundationofChina (No .6 9984 0 0 3)
文摘The authors propose a new persistent transmission based real time Ethernet MAC protocol that provides a predictable upper bound for the delivery delay of real time frames. Moreover, it is compatible with the protocol used by the existing Ethernet controllers for conventional datagram traffic and thus standard Ethernet stations can be used in the system without any modification. The paper describes the protocol in detail and analyses the maximum delivery delay for real time traffic and the efficiency of the channel.
基金supported by the National Natural Science Foundation of China under Grant No. 61133016
文摘Coverage holes often appear in wireless sensor networks due to sensor failure or the inheritance of sensor＇s random distribution. In the hybrid model, mobile sensors in the network are acquired to heal coverage holes by their mobifity. When multiple coverage holes appear in the sensor network and each of them has a time requirement （in which the coverage hole has to be healed）, conflicts for the requests of the same mobile sensor may arise. A distributed multiple mobile sensor schedufing protocol （DMS） is proposed in this paper to solve this problem by finding mobile sensors in the time response zone defined by the time requirement of each coverage hole. Simulation results show that DMS can well schedule the mobile sensors to move to multiple coverage holes within the time requirement.
文摘A new rule to detect intrusion based on IP weight, which is also well implemented in the rule base of author’s NMS, is presented. Compared with traditional ones, intrusion detecting based on IP weight enhanced analysis to packet content. The method also provides a real-time efficient way to analyze traffic on high-speed network and can help to increase valid usage rates of network resources. Practical implementation as a rule in the rule base of our NMS has verified that the rule can detect not only attacks on network, but also other unusual behaviors.
文摘在无中心飞行器集群网络中,非直通条件节点间不同的中继路径可能导致较大路径损耗落差,为有限资源前提下网络传输能力的提升带来困难。参考5G移动通信中的终端直通(Device to Device,D2D)技术与中继通信中的虚拟多输入多输出(Multiple-Input Multiple-Output,MIMO)技术,提出一套D2D通信与虚拟MIMO技术结合的无中心飞行器集群网络传输方案。重点研究在正交资源模式下,将不同的协作传输协议与空时编码进行组合,在信噪比、误比特率、接入概率等方面对通信性能的影响。仿真结果表明:D2D通信与虚拟MIMO技术结合的传输方案在不增加资源的前提下,对集群网络的通信性能有明显提升,且引入分布式空时编码可进一步优化误比特率性能,但3种传输协议在不同传输质量评价方向的改善有所不同。
