Novel Underground Wireless Technology for Soil and Water Management

Demands on fresh water and energy are ever increasing. A great need exists for small, low cost, low power wireless soil moisture sensors, which can be integrated into an automated watering/irrigation control system for need-based application of water. Current sensors are buried at a desired depth and relay soil information to the surface by means of a physical link such as a cable, antenna, or the protruding embodiment of the probe itself. This physical link to the surface is easily damaged by agricultural equipment and is unsightly and obtrusive, making use of these sensors in athletic fields or home lawns undesirable. The authors are developing a novel method for underground communication in wireless sensor networks using magnetic induction. A wireless, fully-buried soil moisture sensing node will be equipped with a ferromagnetic coil. The soil information, superimposed upon a carrier frequency, excites the coil, establishing a quasi-static electromagnetic field. This field induces a voltage at the surface receiver, similarly equipped with a ferromagnetic coil, from which the data is extracted. Transmission will not be affected by soil type, composition, compaction, or moisture content, unlike existing RF transmission technologies, and will require less power and lower operating frequencies than RF transmission. An underground network of these sensors may be formed. The communication range for magneto-inductive systems is short. Therefore, network data is relayed in a multi-hop fashion until it reaches a desired destination for further processing. This novel technology will enable the large-scale deployment of underground wireless soil sensor networks