System overview
The block diagram of the WGSN for the monitoring of combustible
gas concentration is presented in Fig. 1. The system consists
of a number of sensor and relay nodes, a network coordinator, and
possibly one or more wireless actuators.
The sensor node monitors the combustible gas concentration in
the environment. It is set up for several ranges of gas concentration,
as we discuss below. Wireless communication between the sensor
node and the network coordinator is implemented via the relay
node.
The network coordinator is responsible for creating and controlling
the network, indicating the current situation and alerting the
external and emergency services. Alerting the emergency services
may be implemented through the GSM cellular network by sending
an SMS or with the TCP/IP protocol over Ethernet or GSM/GPRS.
Apart from alerting of the potential emergency, the coordinator is
able to carry out preventive actions by seating the valve controlling
the gas delivery and deactivating electrical devices. These emergency
preventive measures are the responsibility of the wireless
actuators, which are part of the network and communicate with
the coordinator over the wireless link.