A Wireless TSN Scheduling Algorithm Based on Strict Priority with Dynamic Queues

Time-Sensitive Networking (TSN) is an IEEE 802.1 standard set to provide deterministic data transmission over Ethernet-based networks. In TSN, Strict Priority (SP) scheduling is a fundamental technique ensuring high-priority traffic to be transmitted before low-priority traffic. This prioritization strives for low-latency communication for critical applications, such as industrial automation and automotive systems. This scheduling algorithm operates by assigning each frame a priority level of eight priorities and processing frames in descending order of priority, effectively creating a hierarchical transmission model with a constant queue number (8 queues). This paper investigates the performance of standard SP. In addition, it proposes a novel Synchronized Strict Priority with Dynamic Queues (S-SPDQ) scheduling for optimizing the processing delay as a part of the overall system latency, which is especially relevant for Wireless TSN (WTSN). The proposed algorithm was implemented as a bare-metal program on ESP32S2 which is a 32-bit Xtensa LX7 microcontroller. The SS-PDQ scheduling improves the SP model by introducing queue dynamicity to minimize overall latency and implementing time-based synchronization to ensure precise transmission delay estimation, paving the way for future enhancements in time-aware algorithms. Compared with the standard SP, the S-SPDQ introduced an average reduction in memory consumption by 50%, in the dequeuing process time by 49%, and the transmission delay by 12%. For the end-to-end latencies in selected use cases, the average reduction is 17% for 1 -queue, $\mathbf{1 5 \%}$ for $\mathbf{4}$-queues and $\mathbf{1 2 \%}$ for $\mathbf{7}$-queues.