Simulation-based Evaluation of DMAMAC - A Dual-Mode Adaptive MAC Protocol for Process Control

Control systems automation is widely used in many industrial domains and have strong requirements on delay, throughput, robustness, and reliability. In the domain of networked control systems, the medium of communication is increasingly involving wireless communication along-side conventional wired communication. Issues ranging from energy efficiency and reliability to low-bandwidth have to be addressed to enable the transition to increased use of wireless communication. In earlier work, we have proposed the Dual-Mode Adaptive MAC (DMAMAC) protocol relying on a combination of Time Division Multiple Access (TDMA) and Carrier Sense Multiple Access (CSMA). The DMAMAC protocol is able to dynamically adapt to the two main states found in process control: the steady state and the transient state. Key requirements to the DMAMAC protocol are energy efficiency, low probability of state-switch failures, and a low state-switch delay. The contribution of this paper is a comprehensive simulation-based evaluation of the original DMAMAC protocol along with the evaluation of a new pure TDMA-based variant of the DMAMAC protocol. Our results show that for processes where the steady state dominates, both variants of the DMAMAC protocol can reduce energy consumption by up to 45% in comparison to the closely related single-mode GinMAC protocol. Among the two variants of DMAMAC, the pure TDMA-based variant has the better energy efficiency and higher reliability. The simulation results also show that the hybrid TDMA-CSMA variant of the DMAMAC protocol has a probability of less than 0.3% for a state-switch failure in a given MAC superframe. The simulation study has impacted the design of the DMAMAC protocol by providing insights that have led to design changes in the originally proposed DMAMAC protocol in order to further reduce the state-switch delay between the steady and the transient state.