Investigation into long-range wireless sensor networks

Abstract

Advances in technology have allowed for the development of wireless sensor networks consisting of small autonomous sensor nodes that communicate with one another via wireless technology. Most designs of wireless sensor networks concentrate on miniaturisation where sensor nodes can only communicate over a short distance and must be closely positioned to monitor an area. In contrast, this thesis presents a long-range wireless sensor network where nodes are separated by large distances, giving the advantage of being able to monitor a large geographic area.

The long-range communications capability allows the sensor network to monitor environmental conditions over a large area. This technology has practical agricultural applications such as monitoring the level of water in cattle feeding troughs or monitoring soil moisture to ensure that irrigation is conducted efficiently. The sensor network can also be deployed on the Great Barrier Reef to constantly monitor the water quality.

The design of the long-range wireless sensor network emerged from a long-range radio propagation model developed particularly for this application. This model was used to develop the specification for the radio transceiver hardware which was later developed and integrated with a commonly-used node called the Mote. A CSMA/CA (carrier-sense, multiple access with collision avoidance) MAC (Medium Access Control) protocol and a routing protocol were then selected for use on a four-node prototype network which was deployed across Townsville for field-testing.

The results of field-testing showed that a long-range ad-hoc network was formed and the maximum operational wireless link was 13.2 km long. This project shows that it is possible to use a wireless sensor network over a long-distance. Future work in this field should include further optimisation of the MAC and routing protocols.