3. System designIn this section, we

3. System design
In this section, we first make the system’s overview and then describe its design in more details.
Fig. 1 shows typical composition of a WSN for hazardous gases detection. Wireless sensor nodes monitor environmental conditions and in the case of dangerous gas detection notify a WSN operator sending an alert message over the WSN/network. In parallel, a sensor node can perform actuation action, e.g. close a gas valve, to block possible gas emission. Actuation of gas valve can be executed faster than sending an alert message to the operator and waiting for his decision. As specified in Section 1, most of the state-of-the-art works investigate sensor node-operator chain [2,12]. In this work, we focus on sensor node-actuator chain and present the design of energy-aware wireless sensor node and wireless actuator in this section.