Time-Sensitive IIoT Flows Over Wi-Fi: A Network Calculus Approach

Real time control of connected industry devices such as mobile robots constituting Industrial Internet of Things (IIoT) has made time-sensitive communications over Wi-Fi increasingly important. In order to provide support for time-sensitive services over Wi-Fi, key features of the IEEE 802.11 standard such as restricted Target Wake Time (rTWT) and multi-user Orthogonal Frequency Division Multiple Access (OFDMA) can be exploited. However, even with rTWT and OFDMA, Time-Sensitive Networking (TSN) over Wi-Fi is still a challenge given the unpredictability of wireless channels and the increasing number of Wi-Fi-enabled devices. In this paper, we present a comprehensive network calculus-based analysis of the delay bounds achievable in Wi-Fi networks, leveraging these IEEE 802.11 enhancements alongside synchronized priority queuing via IEEE 802.1Qbv. We propose PONTE, a novel Fully Polynomial Time Approximation Scheme (FPTAS) scheduler that guarantees strict non-violation probabilities (e.g., 99.99%) for inelastic, time-critical traffic over an 802.11 wireless network. Our extensive analysis and simulations in an IIoT scenario demonstrate that PONTE effectively manages dense, mixed traffic flows, achieving TSN objectives with minimal impact on fairness. Our approach is two orders of magnitude faster than the state-of-the-art.