A Kautz-based Real-Time and Energy-Efficient Wireless Sensor and Actuator Network

Wireless Sensor and Actuator Networks (WSANs) are composed of sensors and actuators to perform distributed sensing and actuating tasks. Most WSAN applications (e.g., fire detection) demand that actuators rapidly respond to events under observation. Therefore, real-time and fault-tolerant transmission is a critical requirement in WSANs to enable sensed data to reach actuators reliably and quickly. Due to limited power resources, energy-efficiency is another crucial requirement. Such requirements become formidably challenging in large-scale WSANs. However, existing WSANs fall short in meeting these requirements. To this end, we first theoretically study the Kautz graph for its applicability in WSANs to meet these requirements. We then propose a Kautz-based Real-time, Fault-tolerant and Energy-efficient WSAN (REFER). REFER has a protocol that embeds Kautz graphs into the physical topology of a WSAN for real-time communication and connects the graphs using Distributed Hash Table (DHT) for high scalability. We also theoretically study routing paths in the Kautz graph, based on which we develop an efficient fault-tolerant routing protocol. It enables a relay node to quickly and efficiently identify the next shortest path from itself to the destination only based on node IDs upon routing failure. REFER is advantageous over previous Kautz graph based works in that it does not need an energy-consuming protocol to find the next shortest path and it can maintain the consistency between the overlay and physical topology. Experimental results demonstrate the superior performance of REFER in comparison with existing systems in terms of real-time communication, energy-efficiency, fault-tolerance and scalability.