PriorityMAC: A Priority-Enhanced MAC Protocol for Critical Traffic in Industrial Wireless Sensor and Actuator Networks

This paper proposes PriorityMAC, a priority-enhanced medium access control protocol, designed for critical traffic in industrial wireless sensor and actuator networks (IWSAN). A notable trend in industrial automation in recent years has been the replacement of wired communication by IWSANs. Exceeding the required delay bound for unpredictable and emergency traffic could lead to system instability, economic and material losses, system failure, and, ultimately, a threat to human safety. Guaranteeing the timely delivery of the IWSAN critical traffic and its prioritization over regular traffic (e.g., noncritical monitoring traffic) is a significant challenge. Therefore, we present the design, implementation, performance analysis, and evaluation of PriorityMAC. A series of novel mechanisms (e.g., high priority indication space) are proposed to enable high-priority traffic to hijack the transmission bandwidth of the low-priority traffic. To the best of our knowledge, this is the first priority-enhanced MAC protocol compatible with industrial standards for IWSAN. PriorityMAC is implemented in TinyOS and evaluated on a testbed of Telosb motes. The experimental results indicate that PriorityMAC efficiently handles different traffic categories with different latency requirements, thereby achieving a significant improvement in the delivery latency compared with the current industrial standards.