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BLE Positioning Explained


Bluetooth Low Energy (BLE) technology is the most common technology used for providing indoor positioning. BLE beacons are typically mounted throughout an indoor venue on walls or other physical entities. The beacon devices emit wireless signals, which BLE receivers (e.g. smartphones) can receive. Usually, beacons are battery powered and must be replaced approximately every 6-12 months, depending on the beacon quality and configuration parameters.


Current smartphones can support the Bluetooth 4.0 protocol. In the future, when smartphones support the Bluetooth 5.1 protocol, they can take advantage of a new feature for direction finding, which is capable of also measuring the direction of the beacon, which can help improve the positioning accuracy significantly.


BLE signals contain metadata which can be processed and used to determine the user’s location. There are two popular protocols for BLE communication, iBeacon and Eddystone. 



iBeacon Metadata (Received):

  • MAC address (unique ID for each beacon - only available on Android)

  • RSS (received signal strength)

  • Proximity UUID (identifier for a collection of beacons)

  • Major (identify general areas, e.g., floor number)

  • Minor (identify more specific areas, e.g., specific region of the Major’s floor)


Eddystone Metadata (Received):

  • MAC address (unique ID for each beacon - only available on Android)

  • RSS (received signal strength)

  • Eddystone UUID

  • Eddystone URL (a url, if desired)

  • Eddystone TLM (current status of the beacon)


The RSS provides a rough measurement of how far away the device is. Intuitively, a strong RSS would indicate that the user is close to that Wi-Fi router and a weak RSS would indicate that the user is far from the Wi-FI router.


There are several methods in which BLE beacons can be used for positioning:

  • BLE proximity

  • BLE trilateration

  • BLE fingerprinting


BLE proximity identifies a rougher user position based on which BLE is visible at the time. BLE trilateration infers the distances between the user and each visible Wi-Fi router and calculates its position based on those distances. 


BLE fingerprinting does not need to know the locations of the Wi-Fi routers but instead creates a large fingerprint map of the RSS of each beacon at various locations and then in real-time compares the measured RSS to the fingerprint map to determine the users position. Constructing the Wi-Fi fingerprint map can be time-consuming and requires a site-survey.



Pros:

  • Available for both Android and iOS devices

  • BLE has a short range, so accuracy is higher (~5 meters)


Cons:

  • Requires deployment of BLE beacons

  • Requires routine maintenance to replace beacon batteries

  • User must have BLE turned on their device

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