Radio-On-Demand Sensor and Actuator Networks (ROD-SAN): System Design and Field Trial

Wireless sensor and actuator networks (WSANs) are required to achieve both energy-efficiency and low-latency in order to prolong the network lifetime while being able to quickly respond to intermittently-transmitted control commands. These two requirements are in general in a relationship of trade-off when each node operates with well-known duty-cycling modes: nodes need to make their radio interfaces (IFs) frequently active in order to promptly detect the communication requests from the other nodes. One approach to break this inherent trade-off, which has been actively studied in recent literature, is the introduction of wake-up receiver that is installed into each node and used only for detecting the communication requests. The radio IF in each node is woken up only when needed through a wake-up message received by the wake-up receiver. While the effectiveness of this type of on-demand WSANs has been shown in several studies by theoretical analysis and computer simulations, its implementation and large-scale experimental investigations are missing. Therefore, in this paper, we first design and implement radio-on-demand sensor and actuator networks (ROD-SAN) including all protocols to realize on-demand WSANs, from the lowest layer of wake-up signaling to the application layer offering the functionalities of information monitoring and networked control. Then, we show experimental results obtained through our field trial in which 20 nodes are deployed in an outdoor area with the scale of 450m X 200m. The numerical results provide us with practical insights on the effectiveness as well as limitations of on-demand WSANs.