West Australian WiFi mesh sniffs out bushfires
Edith Cowan University team re-write MAC protocol to build meshed sensors
A team of researchers from Edith Cowan University's (ECU’s) Centre for Communications Engineering Research (CCER) has built sensors which can sniff out a forest fire, then use WiFi to tell the world.
Professor Daryoush Habibi, Dr Iftekhar Ahmad and Mr Amro Qandour wrote their own mesh networking software to pull off the feat. The trio also devised and built the sensors.
The project’s raison d'être, says Professor Habibi, is the limitations of current remote sensors.
“Older models have a line of sight range of 150 metres, or only 20 to 25 metres without line of sight. That’s not enough to monitor a large area.” It’s certainly not enough to make wireless sensors feasible in West Australia’s extensive forests. Older designs also rely on satellite communications, an option which makes for large devices as batteries and solar panel sizes must both be substantial to power a transmitter capable of sending signals into orbit.
The ECU team’s new sensors run 802.11n WiFi. Each unit is around 10cm x 10cm x 5cm, including battery. Solar panels need only be 10cm x 10 cm and a simple mount can attach the devices to trees. Professor Habibi says his team’s tests have shown ranges of 25kms or more are possible for single nodes. That performance, combined with sensors that can detect many gases that are telltale signs of fire, mean the devices will warn of fire before smoke is sighted.
Software for the networks was developed by the ECU team, which wrote its own media access control (MAC) protocol.
“We wanted greater control over power consumption and polling times than is possible with another MAC protocol,” Professor Habibi says. “For example, we wanted polling intervals to be variable depending on the season. In winter the chance of fire is not that great so polling every one to four hours is adequate. In summer you want to poll a lot more often. Also in summer you solar cell will provide more power.”
The mesh network is also self-healing. Each node seeks out its brethren to find a working member of the network, prioritising routes to ensure word of fire reaches the outside world.
When that happens, it does so courtesy of the I2C bus used to connect sensors to each node. The Bus also connects a GSM module which is used in sensors closest to civilisation, or in locations known to have coverage from mobile phone networks.
The ECU team has, to date, tested the system only in the city of Perth. Professor Habibi argues the urban environment is actually a tougher proving ground than the forests, thanks to extensive electromagnetic interference and the presence of many tall buildings. He and the team are now in discussions with the Fire & Emergency Services Authority of Western Australia and electricity network operator Western Power about a more substantial trial. ®