In Internet of Things systems, Web services enable interoperable machine-to-machine communication over networks. Polling mechanism is a practical way for a Web service-based control system to enable its actuator to respond to its controller under uncertain environments where the actuator does not know exactly when the controller updates its command. Fast response demands a high polling frequency (polling mechanism handles the event in time-driven mode) which may lead to heavy network traffic. Therefore, how to make the optimal tradeoff between the network traffic and delay in a Web service-based control system becomes an interesting problem. This paper formulates the problem of finding the optimal polling frequency control policy of a Web service-based control system as a constrained Markov decision process (CMDP). The policy is such that the actuator responds to the controller within a tolerable delay threshold while minimizing network traffic. An algorithm called CMDPA is proposed to solve the problem. Simulation and field experiments show our policy performance. Note to Practitioners—This paper addresses the interesting problem of making a good tradeoff between network traffic and delay demand in a Web service-based control system setting. It helps to improve the operation efficiency of Internet of Things systems that use the Web service technology to carry out communication between controllers and actuators while keeping delay within a given range. Our simulation and experimental investigations show that the solution developed here outperforms current solutions, such as time-driven or event-driven solutions.

中文翻译：

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基于Web服务的网络流量与延迟平衡控制系统优化


在物联网系统中，Web 服务支持通过网络进行可互操作的机器对机器通信。轮询机制是基于Web服务的控制系统使其执行器能够在执行器不确切知道控制器何时更新其命令的不确定环境下响应控制器的一种实用方法。快速响应需要较高的轮询频率（轮询机制以时间驱动的方式处理事件），这可能会导致网络流量过大。因此，如何在基于Web服务的控制系统中在网络流量和延迟之间做出最佳权衡成为一个有趣的问题。本文将寻找基于 Web 服务的控制系统的最优轮询频率控制策略的问题表述为约束马尔可夫决策过程 (CMDP)。该策略使得执行器在可容忍的延迟阈值内响应控制器，同时最小化网络流量。提出了一种称为 CMDPA 的算法来解决该问题。模拟和现场实验显示了我们的政策绩效。从业者注意事项——本文解决了在基于 Web 服务的控制系统设置中在网络流量和延迟需求之间进行良好权衡的有趣问题。它有助于提高使用Web服务技术在控制器和执行器之间进行通信的物联网系统的运行效率，同时将延迟保持在给定范围内。我们的模拟和实验研究表明，这里开发的解决方案优于当前的解决方案，例如时间驱动或事件驱动的解决方案。