On the Latency, Rate, and Reliability Tradeoff in Wireless Networked Control Systems for IIoT

Abstract

Wireless networked control systems (WNCSs) provide a key enabling technique for Industry Internet of Things (IIoT). However, in the literature of WNCSs, most of the research focuses on the control perspective, and has considered oversimplified models of wireless communications which do not capture the key parameters of a practical wireless communication system, such as latency, data rate and reliability. In this paper, we focus on a WNCS, where a controller transmits quantized and encoded control codewords to a remote actuator through a wireless channel, and adopt a detailed model of the wireless communication system, which jointly considers the interrelated communication parameters. We derive the stability region of the WNCS. If and only if the tuple of the communication parameters lies in the region, the average cost function, i.e., a performance metric of the WNCS, is bounded. We further obtain a necessary and sufficient condition under which the stability region is nbounded, where n is the control codeword blocklength. We also analyze the average cost function of the WNCS. Such analysis is non-trivial because the finite-bit control-signal quantizer introduces a non-linear and discontinuous quantization function which makes the performance analysis very difficult. We derive tight upper and lower bounds on the average cost function in terms of latency, data rate and reliability. Our analytical results provide important insights into the design of the optimal parameters to minimize the average cost within the stability region. Index Terms-Industrial Internet of Things, sensor-actuator network, wireless networked control, mission-critical communications, performance analysis.

Adaptive Stochastic ADMM for Decentralized Reinforcement Learning in Edge Industrial IoT

“…The Industrial Internet of Things (IIoT), as a subset of IoT, interconnects a multitude of industrial devices, actuators, and people at work. The fourth industrial revolution aims to tackle a set of new technological challenges in industrial control, automation and intelligence [1]. Currently, many of the data from the IIoT networks are processed and stored off-site in remote areas (i.e., cloud).…”

“…Variable 𝜽 is shared across all agents. Decentralized RL tasks with parametrized approximation also fit in the same form as (1) only with the local loss as the expectation of individual cumulative costs.…”

“…Aiming at a communication efficient, scalable and adaptive decentralized RL scheme for edge-computing-empowered IIoT networks, we investigate the stochastic ADMM based RL solvers. In the following, we will firstly study the adaptive stochastic ADMM for solving (1) and then apply the results to decentralized RL. The main contributions of this paper can be summarized as follows:…”

Age of Loop for Wireless Networked Control Systems Optimization

“…In recent work on WNCS, authors have been increasingly exploring the inter-relation between the control and communication schemes. In [2] and [3], for example, the authors demonstrate how the latency and reliability trade-off directly impacts the system level stability, proposing a codesign of both control and communication entities. Specifically in [2], authors have demonstrated a counter-intuitive conclusion that the plant can still be stabilized with an arbitrarily large delay under certain channel conditions.…”

“…In [2] and [3], for example, the authors demonstrate how the latency and reliability trade-off directly impacts the system level stability, proposing a codesign of both control and communication entities. Specifically in [2], authors have demonstrated a counter-intuitive conclusion that the plant can still be stabilized with an arbitrarily large delay under certain channel conditions. Another interesting finding was presented in [4], where authors elucidate an example how one can optimize long-term system performance by assuming more risks with less reliable transmissions in exchange for lower latency.…”