This paper is concerned with the finite-time control problem for a class of networked control systems(NCSs) with short time-varying delays and sampling jitter.Considering a state feedback controller,the closed-loop NC...This paper is concerned with the finite-time control problem for a class of networked control systems(NCSs) with short time-varying delays and sampling jitter.Considering a state feedback controller,the closed-loop NCS is described as a discrete-time linear system model,and the uncertain parts reflect the effect of the the network-induced delays and short sampling jitter of the system dynamics.Then a robust approach is proposed to solve the finite-time stability and stabilization problems for the considered NCS.An illustrative example is provided to demonstrate the effectiveness of the proposed theoretical results.展开更多
A dynamic network Qo S control mechanism was proposed based on traffic prediction. It first predicts network traffic flow and then dynamically distributes network resources, which makes full use of network flow self-s...A dynamic network Qo S control mechanism was proposed based on traffic prediction. It first predicts network traffic flow and then dynamically distributes network resources, which makes full use of network flow self-similarity and chaos. So it can meet changing network needs very well. The simulation results show that the dynamic Qo S control mechanism based on prediction has better network performance than that based on measurement.展开更多
This paper evaluates the performance of Internet Protocol Security (IPSec) based Multiprotocol Label Switching (MPLS) virtual private network (VPN) in a small to medium sized organization. The demand for security in d...This paper evaluates the performance of Internet Protocol Security (IPSec) based Multiprotocol Label Switching (MPLS) virtual private network (VPN) in a small to medium sized organization. The demand for security in data networks has been increasing owing to the high cyber attacks and potential risks associated with networks spread over distant geographical locations. The MPLS networks ride on the public network backbone that is porous and highly susceptible to attacks and so the need for reliable security mechanisms to be part of the deployment plan. The evaluation criteria concentrated on Voice over Internet Protocol (VoIP) and Video conferencing with keen interest in jitter, end to end delivery and general data flow. This study used both structured questionnaire and observation methods. The structured questionnaire was administered to a group of 70 VPN users in a company. This provided the study with precise responses. The observation method was used in data simulations using OPNET Version 14.5 Simulation software. The results show that the IPSec features increase the size of data packets by approximately 9.98% translating into approximately 90.02% effectiveness. The tests showed that the performance metrics are all well within the recommended standards. The IPSec Based MPLS Virtual private network is more stable and secure than one without IPSec.展开更多
为降低现有列车网络控制系统(train control and management system,TCMS)端到端时延、抖动不确定性对列车控制功能时间确定性的影响,提高列车控制功能迭代效率,基于下一代列车网络控制系统(next generation TCMS,NG-TCMS),提出通信与...为降低现有列车网络控制系统(train control and management system,TCMS)端到端时延、抖动不确定性对列车控制功能时间确定性的影响,提高列车控制功能迭代效率,基于下一代列车网络控制系统(next generation TCMS,NG-TCMS),提出通信与计算资源联合调度模型,将端到端确定性从网络层延伸至列车控制功能。首先,结合NG-TCMS中时间敏感网络提供的全局统一时间基准,将列车控制功能拆分为具有依赖关系的状态采集、逻辑计算、数据转发、命令执行任务,并通过有向无环图进行形式化。以最小化执行时间为调度目标,分别通过一阶逻辑约束转化为可满足性模理论(satisfiability modulo theories,SMT)问题进行最优求解,以及抽象为整数线性规划(integer linear programming,ILP)问题进行最优求解。同时,提出基于任务松弛度和抖动继承值的快速求解方法,将一次性求解所有任务的大规模调度转化为迭代求解单任务或双任务的小规模调度,以解决控制功能数量陡增导致调度问题复杂度激增,SMT方法和ILP方法难以快速求解的问题。最后,参考CR450动车组列车控制功能设计算例,以30 min为求解时间上限,分析SMT方法、ILP方法、快速求解方法在求解时间与所得调度方案资源利用率方面的性能差异。结果表明,快速求解方法能在20 min内完成1000个含零抖动和抖动约束的控制功能调度,高效调度系统资源,满足NG-TCMS快速迭代需求。研究结果可为基于NG-TCMS构建具有端到端时间确定性的列车网络控制功能及任务调度方法提供参考。展开更多
基金supported by National Natural Science Foundation of China(Nos.61290322,61273222,61322303 and 61473248)Doctoral Fund of Ministry of Education of China(No.20121333110008)+1 种基金Hebei Province Hundred Excellent Innovation Talents Support ProgramHebei Province Applied Basis Research Project(No.13961806D)
文摘This paper is concerned with the finite-time control problem for a class of networked control systems(NCSs) with short time-varying delays and sampling jitter.Considering a state feedback controller,the closed-loop NCS is described as a discrete-time linear system model,and the uncertain parts reflect the effect of the the network-induced delays and short sampling jitter of the system dynamics.Then a robust approach is proposed to solve the finite-time stability and stabilization problems for the considered NCS.An illustrative example is provided to demonstrate the effectiveness of the proposed theoretical results.
基金Funded by the National Natural Science Foundation of China(No.41301084)the Scientific Research Project of Hunan Province Education Department,China(No.13C713)the Natural Science Foundation of Hunan Province,China(No.13JJ6075)
文摘A dynamic network Qo S control mechanism was proposed based on traffic prediction. It first predicts network traffic flow and then dynamically distributes network resources, which makes full use of network flow self-similarity and chaos. So it can meet changing network needs very well. The simulation results show that the dynamic Qo S control mechanism based on prediction has better network performance than that based on measurement.
文摘This paper evaluates the performance of Internet Protocol Security (IPSec) based Multiprotocol Label Switching (MPLS) virtual private network (VPN) in a small to medium sized organization. The demand for security in data networks has been increasing owing to the high cyber attacks and potential risks associated with networks spread over distant geographical locations. The MPLS networks ride on the public network backbone that is porous and highly susceptible to attacks and so the need for reliable security mechanisms to be part of the deployment plan. The evaluation criteria concentrated on Voice over Internet Protocol (VoIP) and Video conferencing with keen interest in jitter, end to end delivery and general data flow. This study used both structured questionnaire and observation methods. The structured questionnaire was administered to a group of 70 VPN users in a company. This provided the study with precise responses. The observation method was used in data simulations using OPNET Version 14.5 Simulation software. The results show that the IPSec features increase the size of data packets by approximately 9.98% translating into approximately 90.02% effectiveness. The tests showed that the performance metrics are all well within the recommended standards. The IPSec Based MPLS Virtual private network is more stable and secure than one without IPSec.
文摘为降低现有列车网络控制系统(train control and management system,TCMS)端到端时延、抖动不确定性对列车控制功能时间确定性的影响,提高列车控制功能迭代效率,基于下一代列车网络控制系统(next generation TCMS,NG-TCMS),提出通信与计算资源联合调度模型,将端到端确定性从网络层延伸至列车控制功能。首先,结合NG-TCMS中时间敏感网络提供的全局统一时间基准,将列车控制功能拆分为具有依赖关系的状态采集、逻辑计算、数据转发、命令执行任务,并通过有向无环图进行形式化。以最小化执行时间为调度目标,分别通过一阶逻辑约束转化为可满足性模理论(satisfiability modulo theories,SMT)问题进行最优求解,以及抽象为整数线性规划(integer linear programming,ILP)问题进行最优求解。同时,提出基于任务松弛度和抖动继承值的快速求解方法,将一次性求解所有任务的大规模调度转化为迭代求解单任务或双任务的小规模调度,以解决控制功能数量陡增导致调度问题复杂度激增,SMT方法和ILP方法难以快速求解的问题。最后,参考CR450动车组列车控制功能设计算例,以30 min为求解时间上限,分析SMT方法、ILP方法、快速求解方法在求解时间与所得调度方案资源利用率方面的性能差异。结果表明,快速求解方法能在20 min内完成1000个含零抖动和抖动约束的控制功能调度,高效调度系统资源,满足NG-TCMS快速迭代需求。研究结果可为基于NG-TCMS构建具有端到端时间确定性的列车网络控制功能及任务调度方法提供参考。
