We address a special kind of Internet of Things (IoT) systems that are also real-time. We call them real-time IoT (RT-IoT) systems. An RT-IoT system needs to meet timing constraints of system delay, clock synchronizat...We address a special kind of Internet of Things (IoT) systems that are also real-time. We call them real-time IoT (RT-IoT) systems. An RT-IoT system needs to meet timing constraints of system delay, clock synchronization, deadline, and so on. The timing constraints turn to be more stringent as we get closer to the physical things. Based on the reference architecture of IoT (ISO/IEC 30141), the RT-IoT conceptual model is established. The idea of edge subsystem is introduced. The sensing & con-trolling domain is the basis of the edge subsystem, and the edge subsystem usually must meet the hard real-time constraints. The model includes four perspectives, the time view, computation view, communication view, and control view. Each view looks, from a different angle, at how the time parameters impact an RT-IoT system.展开更多
容错是硬实时系统的关键能力,容错调度算法可以在有错误发生的情况下满足任务的实时性需求.在主副版本机制的容错调度算法中,主版本出错后留给副版本运行的时间窗口小,副版本容易错失截止期.针对副版本需要快速响应的问题,提出副版本不...容错是硬实时系统的关键能力,容错调度算法可以在有错误发生的情况下满足任务的实时性需求.在主副版本机制的容错调度算法中,主版本出错后留给副版本运行的时间窗口小,副版本容易错失截止期.针对副版本需要快速响应的问题,提出副版本不可抢占的全局容错调度算法FTGS-NPB(fault-tolerant global scheduling with non-preemptive backups),赋予副版本全局最高优先级,使副版本在主版本出错后可以立刻获得处理器资源,并且在运行过程中不会被其他任务抢占.这样,副版本可以在最短时间内响应.分别基于截止期分析和响应时间分析建立了FTGS-NPB的可调度性测试,并分析了两种可调度性测试分别适用于不同的优先级分配算法.仿真实验结果表明,FTGS-NPB可以有效地减少实现容错的代价.展开更多
基金Project supported by the MITT Intelligent Manufacturing Project of Chinathe Study of Interconnection Standard and Experimental Verification in the Intelligent Manufacturing Plant for Naval Architecture and Marine Engineeringthe Science and Technology Program of Jiangxi Province,China(No.20161BBE50062)
文摘We address a special kind of Internet of Things (IoT) systems that are also real-time. We call them real-time IoT (RT-IoT) systems. An RT-IoT system needs to meet timing constraints of system delay, clock synchronization, deadline, and so on. The timing constraints turn to be more stringent as we get closer to the physical things. Based on the reference architecture of IoT (ISO/IEC 30141), the RT-IoT conceptual model is established. The idea of edge subsystem is introduced. The sensing & con-trolling domain is the basis of the edge subsystem, and the edge subsystem usually must meet the hard real-time constraints. The model includes four perspectives, the time view, computation view, communication view, and control view. Each view looks, from a different angle, at how the time parameters impact an RT-IoT system.
文摘固定优先级任务可调度性判定是实时系统调度理论研究的核心问题之一.目前已有的各种判定方法可归结为两大类:多项式时间调度判定和确切性判定.多项式时间调度判定通常采用调度充分条件来进行,为此,许多理想条件下基于RM(rate monotonic)调度算法的CPU利用率最小上界被提了出来.确切性判定利用RM调度的充要条件,保证任何任务集均可被判定,并且判定结果是确切的.但是由于时间复杂度较差,确切性判定方法难以实现在线分析.提出了一种改进的RM可调度性判定方法(improved schedulability test algorithm,简称ISTA).首先介绍了任务调度空间这一概念,并提出了二叉树表示,然后进一步提出了相关的剪枝理论.在此基础上,研究了任务之间可调度性的相关性及其对判定任务集可调度性的影响,提出并证明了相关的定理.最后基于提出的定理,给出了一种改进的伪多项式时间可调度性判定算法,并与已有的判定方法进行了比较.仿真结果表明,该算法平均性能作为任务集内任务个数的函数具有显著提高.
文摘容错是硬实时系统的关键能力,容错调度算法可以在有错误发生的情况下满足任务的实时性需求.在主副版本机制的容错调度算法中,主版本出错后留给副版本运行的时间窗口小,副版本容易错失截止期.针对副版本需要快速响应的问题,提出副版本不可抢占的全局容错调度算法FTGS-NPB(fault-tolerant global scheduling with non-preemptive backups),赋予副版本全局最高优先级,使副版本在主版本出错后可以立刻获得处理器资源,并且在运行过程中不会被其他任务抢占.这样,副版本可以在最短时间内响应.分别基于截止期分析和响应时间分析建立了FTGS-NPB的可调度性测试,并分析了两种可调度性测试分别适用于不同的优先级分配算法.仿真实验结果表明,FTGS-NPB可以有效地减少实现容错的代价.
