Introduction to iBeacons

iBeacon is Apple's branding of the Bluetooth Low Energy beacon specification (AKA Bluetooth Smart proximity sensing) that is part of the Bluetooth 4.0 standard. In the first of a series of articles on the technology, this introduction explains how beacons work, describes typical uses and gives some pointers for further reading.

What is an iBeacon?

The Bluetooth 4.0 spec defines a number of profiles that describe what particular types of device should be able to do and how they should work. The devices that have come to be known as beacons (or iBeacons) implement the proximity profile that lets other devices detect when they are nearby.

Physically, they are small, inexpensive devices containing a battery, some circuitry and a Bluetooth LE transmitter/receiver. However, any Bluetooth 4.0 compatible device can function as a beacon (for example - laptops, smartphones and so on) as long as it communicates in the correct way.

What Does it Do?

Beacons transmit information about themselves at regular intervals (typically every second or so) - this is known as advertising. There is a trade off between range, frequency of transmission and battery life - as an example, a beacon my transmit every second with a range of 5m or so with a battery life of around 2 years.

The data transmitted is very small, its only purpose being to identify the beacon and its distance:

  • *UUID: * This uniquely identifies a set of beacons and would typically be used to detect that a beacon belonged to a particular company (EG: f7826da6-4fa2-4e98-8024-bc5b71e0893e).
  • *Major number: * A number between 0 and 65535, generally used to identify a particular geographical location.
  • *Minor number: * Also between 0 and 65535, identifies the particular beacon at the location.
  • *TX power: * A calibration value that should be equal to the strength of the device's signal measured 1m away.

On the receiving end, this information is accompanied by an RSSI (Received Signal Strength Indication) value, which can be used along with the TX power value from the beacon to estimate its physical distance.

How Are They Used?

The information transmitted by beacons is fixed, one way and extremely simple - so how do they become useful? Firstly, an application is required that recognises when beacons are in range. The iPhone 4s and later (running iOS 7) and Android devices that support Bluetooth 4.0 running at least Android 4.4 (Kit Kat) can run beacon-aware apps. The device also needs to have Bluetooth turned on.

Beacons provide physical context for an app that knows (or can find out) where beacons have been placed. Specific beacon IDs will correspond to certain locations, but the signal strength of multiple beacons can also be used to provide accurate internal positioning via trilateration.
This becomes powerful when combined with dynamic information via the internet.

For example, a shopping mall could install beacons at known locations. Its app would then be able to locate a user on a map and give directions, however it the app could also request dynamic information about a particular location. This could include current events nearby or targetted marketing such as promotions when someone is near the food court and it's around lunchtime.

More Applications

The next article in the series will describe more sophisticated applications and ways in which iBeacons are being put to use.

Further Reading