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Geofencing: The ultra-low power frontier for the Internet of Things

Free-range for devices

Internet of Lawnmowers How are the next 10 billion devices going to connect to the internet of today, tomorrow? Having all of these gizmos talk to one another over your standard 2.4Ghz Wi-Fi is not going to happen, so how will all those gizmos connect to the wider internet, and how will we keep them all safe, happy and updated?

The internet of things will rely on short and medium range wireless networking protocols. From geofencing your lawnmower or Roomba with infrared beacons to Zigbee, Bluetooth, 60Ghz and even visible light networking. Every iota of spectrum the general public can pry out of the hands of regulators will be used, but how is it all going to work?


Geofencing is a critical set of concepts for the internet of things. It not only provides the basic technologies to stop our "things" from working outside of our secured environments, it also serves as a great start to explain the basic communications technologies.

Like "cloud computing", however, geofencing means different things depending on who you talk to.

The first use of geofencing – constraining a device to a given location – comes in two forms. This covers devices that simply won't work outside of the geofence, for example a corporate e-mail client that only works when on corporate premises. The second use of geofencing is devices that freak out when removed from the geofence. Think of the little radio tags that retail stores use for high value items.

These forms of geofencing see practical uses in my everyday life. For the first, I use little infrared beacons to confine a Roomba to a given room. For the second, my Galaxy Note 2 contains a near field radio and the stylus an RFID tag. If I leave the stylus behind, the phone freaks out and reminds me to find the stylus before I get too far away.

The third use of the term geofence – activate when you detect a widget in range – is almost always about advertising. Think creepy Minority Report-style retail stores but here, now and using Bluetooth.

Geofencing used to use GPS. For large enough geographical areas, and clients that have lots of available power, such as truckers, GPS is still viable. Nowadays, however, geofencing is done with ultra-low power beacons.

Beacons are devices that "squawk" small amounts of data every second or so, either directionally or omnidirectionally. Directional beacons (like an infrared beam) are used to make virtual "walls". Omnidirectional beacons are information-based.

Beacons can come in all sizes. The cellular network, for example, consists of mobiles and cell towers that continually advertise themselves to one another via signalling beacons used to control voice telephone traffic.

Advertising beacons on a cellular network occurs at regular intervals, whether or not there is signalling data to be sent. SMS was developed to be able to send text messages through these beacons when there was no signalling data to send.

It's why text messages on older networks get delivered nearly instantaneously when you're out in the middle of nowhere and take forever when you're in a really crowded location such as a stadium.

Google has a patent that is worth a read. Here's another, not by Google, also worth a read.

Beacons can be thought of as a highly localised GPS. If you know enough about where the beacons are placed and when they are supposed to squawk then you can do some maths and pinpoint position down to the centimetre.

Some applications use beacons that – like GPS – just squawk time (and/or location) in order to make this sort of positioning possible. In this manner beacons can be used in combination with an app to do the same sort of geofencing you'd normally rely on "virtual walls" or GPS for.

If you're interested in playing around with beacon-based geofencing and have an iPhone, iBeacon will be worth looking up. You might want to give the privacy implications a thought, however, as well as consider what happens if your geofence decides to move around by 300m or so of its own volition.

Next time, I’ll look at the individual communications technologies that will be used by Internet of Things devices for the next several years. ®

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