Deterministic real-time access point concepts for industrial hybrid Ethernet/IEEE 802.11 networks

Technological advances in wireless sensors shed some light on the deployment of Industrial Wireless Sensor and Actuator Networks (IWSAN) for diverse applications in process automation due to their multiple advantages related to the reduction in wiring costs, implementation and maintenance. However, the most critical processes, like closed loop control applications which have shorter than 1 ms time cycle and a Packet Error Rate (PER) in the range of 10(-9), still rely on wired connections. Due to this, new concepts that can compete and coexist without troubles with the correspondent wired solutions are necessary, especially those known as Real-Time Ethernet (RTE). So, this article focuses on analyzing the requirements of a deterministic access point (AP) with real-time characteristics that act as a bridge between wired RTE and wireless communication systems. The analysis will focus mainly on the design of the Medium Access Control (MAC) mechanism because this is largely the main responsible for guaranteeing the robustness and determinism required by industrial time-critical applications. To control the wireless segment of the hybrid network, the AP could implement the previously proposed Enhanced Priority MAC (EP-MAC) that support three traffic categories with different requirements related to latency. We conclude the paper showing some results obtained from numerical simulations. Provided results prove that the requirements of the proposed AP, together with EP-MAC, fulfill the tight timing constraints of industrial time-critical applications.