This letter considers a wireless networked control system (WNCS), where a controller sends packets carrying control information to an actuator through a wireless channel to control a physical process for industrial-control applications. In most of the existing work on WNCSs, the packet length for transmission is fixed. However, from the channel-encoding theory, if a message is encoded into a longer codeword, its reliability is improved at the expense of longer delay. Both delay and reliability have great impact on the control performance. Such a fundamental delay-reliability tradeoff has rarely been considered in WNCSs. In this letter, we propose a novel WNCS, where the controller adaptively changes the packet length for control based on the current status of the physical process. We formulate a decision-making problem and find the optimal variable-length packet-transmission policy for minimizing the long-term average cost of the WNCSs. We derive a necessary and sufficient condition on the existence of the optimal policy in terms of the transmission reliabilities with different packet lengths and the control system parameter.

中文翻译：

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用于工业物联网的可变数据包长度的无线反馈控制

这封信考虑了无线网络控制系统 (WNCS)，其中控制器通过无线信道向执行器发送携带控制信息的数据包，以控制工业控制应用的物理过程。在 WNCS 的大部分现有工作中，传输的数据包长度是固定的。但是，从信道编码理论来看，如果将消息编码成更长的码字，其可靠性的提高是以更长的延迟为代价的。延迟和可靠性都对控制性能有很大影响。在 WNCS 中很少考虑这种基本的延迟-可靠性权衡。在这封信中，我们提出了一种新颖的 WNCS，其中控制器根据物理过程的当前状态自适应地改变数据包长度以进行控制。我们制定了一个决策问题，并找到了最小化 WNCS 的长期平均成本的最佳可变长度数据包传输策略。根据不同数据包长度的传输可靠性和控制系统参数，我们推导出最优策略存在的充分必要条件。