Value of Information in Networked Control Systems Subject to Delay

In this paper, we study the trade-off between the transmission cost and the control performance of a networked control system subject to network-induced delay. Within the linear–quadratic–Gaussian (LQG) framework, the joint design of control policy and networking strategy is decomposed into separate optimization problems. Based on the trade-off analysis, a delay-dependent Value-of-Information (VoI) metric which quanties the value of transmitting a data packet is introduced. The VoI enables the decision-makers embedded in subsystems to design the triggering policy. The proposed scalable VoI inherits the task criticality of the existing VoI metric. Additionally, the sensitivity to the system parameters such as information freshness and network delays is directly derivable. The VoI-based scheduling policy is shown to outperform the periodical triggering policy and the Age-of-Information (AoI) based policy for network control systems under transmission delay. The effectiveness of the constructed VoI with arbitrary network delay is validated through numerical simulations.