Low frequency magnetic fields have a number of properties that make them attractive for positioning and communication in challenging environments (underwater, underground or indoors), where conventional high frequency radio (such as GPS or WiFi) cannot penetrate. Advantages include no multipath and excellent penetration. In addition, the produced field is a vector field which leads to some very interesting modulation techniques, at no bandwidth or energy costs.
This was a world first and led to the development of miniature tracking collars that can position an animal to within 30cm in 3-D, at a rate of one position update per second. Lifetime of the tracking collars are in the order of 9 months from a small lithium cell. This research won the best presentation award at ACM SenSys 2010 and has been featured on the BBC news website. Click for more detail, including an explanation of how the system works. Updated tracking in 3-D here!
In a mining disaster (flood, fire or rockburst), communication networks (wired or wireless) are typically destroyed. If miners are trapped deep underground, they currently have no way of communicating with rescue personnel. We have developed and tested a novel multihop underground network using magneto-inductive links. Tests in caves demonstrate an achievable range of 75m through solid rock.
[wp-publications bib=”citations.bib” search=”magneto-inductive”]