Bluetooth Low Energy
What are Bluetooth Low Energy Beacons?
BLE or Bluetooth Low Energy is a recent advancement in the Bluetooth technology standards which allows for the wireless protocol to be applied to new use cases like indoor positioning and direction finding which were previously not feasible. Primarily due to the energy saving techniques implemented in BLE 4.0 series, there is reduction in power consumption when compared to previous Bluetooth standards.
With the ability to efficiently utilize limited power sources, Bluetooth Low Energy is now used in a number of devices which need to communicate small amounts of data over wireless. It is now possible to have devices with battery life measured in months and years rather than days or weeks, while also making them smaller.
This has led to the development of beacon technology and its application in a number of situations. Beacons are very simple Bluetooth Low Energy messages which are transmitted or heard by compatible devices. This device could be a computer, a phone, a wireless AP, or a tag, to name just a few possible devices.
This message has three basic components:
- Universally Unique Identifier (UUID)
- Major
- Minor
These components of the beacon can be configured with information the operator wants to communicate to other BLE-compatible devices. The data communication from the BLE beacons is transferred by a listening device like a gateway to the Internet cloud. This information is typically encrypted and can be configured, for example, in a RTLS environment for indoor asset tracking they can be:
- Asset Type, sub type, battery % (UUID)
- Temperature (Major)
- Humidity (Minor)
In a retail environment it could be interpreted as:
- Retail Brand (UUID)
- Shop Location (Major)
- Product Category (Minor)
Additionally the RSSI value is also passed from these BLE beacons. Normally these beacons are in the advertising mode. When a compatible listener device hears one of these messages, it interprets and sends the information on RSSI, UUID, Major, and Minor identifiers. The RTLS system can then represent these beacons with the information acquired from them, location being interpreted from the RSSI values.
In the past, before Bluetooth Low Energy (LE) was introduced in 2010, real time locating systems (RTLS) used costly Ultra-Wide Band (UWB) devices or radio frequency id (RFID).
Benefits of BLE over RFID (UWB)
- The availability of much lower cost Bluetooth devices, up to 1/4 the price of UWB.
- A much longer battery life than UWB, 5+ years for some devices.
- A much longer range than RFID, up to 300m vs cm.
- The ease of detecting beacons via apps and single board computers using existing operating system Bluetooth APIs.
- The availability of low cost Bluetooth gateways.
- Being based on standard Bluetooth rather than proprietary UWB protocols, custom devices and specialist skills.
How it Works for RTLS Application
Real-time locating systems (RTLS) are used to automatically identify and track the location of objects or people in real time, usually within a building or other contained area. Beacons are attached to objects or worn by people and fixed gateways or apps receive signals from the beacons to determine their location.
Areas where organisations have used Beacon Zone beacons for RTLS include manufacture, warehousing and the tracking of equipment and people. The latter segment has included people on campus, lone workers and evidence based working (e.g. evidence based policing).
As beacons aren’t directly connected to the Internet/Intranet, this requires the use of an intermediate Bluetooth LE device such as a smartphone, single board computer, Ethernet / Wi-Fi gateway or mesh gateway.
For the Ethernet / Wi-Fi gateway case, gateways are placed at known positions. For a beacon-based RTLS, it’s often easiest to use the gateway and beacon MAC addresses. Detected beacon ids are uploaded by each gateway. When the server sees the gateway has detected a beacon, it’s shown on a map or plan at the gateway position or a zone around this gateway.
Beacons aren’t like GPS in that there’s no advertised or calculated physical location. There are two ways to obtain location. The first uses the received signal strength indicator (RSSI) of the beacon. The second way is using angle of arrival (AoA) and special hardware with multiple receiving antenna.
Once proximity data has been received at the server it’s shown on plans or maps. It’s also possible to create alerts based on the data, forward selected data on to other systems (via HTTP) or consume it within other systems (via REST services).
Bluetooth Direction Finding
Direction Finding was introduced with Bluetooth 5.1 in 2019. It uses Angle of Arrival (AoA) and Angle of Departure (AoD) to determine location to sub-meter accuracy. Facilities can track valuable assets, monitor lone workers, check occupancy levels and automatically locate people or students for safety and evacuation.
AoA uses multiple antennas at the receiver and AoD uses multiple antennas at the sender. AoA is more suitable for asset tracking because the sender can be a simple, inexpensive, beacon and complexity is constrained to the receivers, called locators. AoD is more suitable for where-am-I, navigation type scenarios where the multiple antenna senders are fixed. The popularity of asset tracking has resulted in initial products being based on AoA rather than AoD.
AoA beacons transmit special advertising containing a Constant Tone Extension (CTE) for a long enough time to enable the receiver to switch between all the antennas.
Beacon Implementation Types
There are several types of beacon that can be used in many ways. Here, we show the main ways beacon solutions are implemented. These implementation types aren’t mutually exclusive as some beacons can transmit multiple types of data.
1. iBeacon
This is used for user facing services such as retail marketing and visitor spaces such as museums. It works on iOS and Android and needs your app to be installed by end-users.
2. Eddystone (UID and EID)
This is used for user facing services such as retail marketing and visitor spaces such as museums. It works on iOS and Android but iOS can’t detect Eddy stone when the app is in background.
Registering with the optional Google Nearby service creates API notifications in iOS and Android. The EID variant is used for secure applications as it has changing Ids that can’t be spoofed.
3. Sensing
This is used for IoT proximity and sensing scenarios. Apps or a Bluetooth gateway read sensor data and forward it to a server. The Bluetooth part can also use Bluetooth mesh to relay data across a site or area.
4. Tracking
This is used for tracking items or people with an audio alarm on the phone and/or beacon if the item being tracked goes out of range. It can also be used to detect a beacon button press and cause something to happen, for example take a camera photo, on the phone.
This scenario uses the advertising data to detect beacons and Bluetooth GATT to connect to them.
5. GPIO
This is the reverse of the above scenarios in that we are sending information TO the beacon to operate GPIOs. GPIOs can operate relays as in our beacon relay modules.
Is it worth using Bluetooth Low Energy Beacons?
Bluetooth Low Energy beacons are a simple way to provide indoor location of people and assets in an economical way. Additionally, these beacons can have integrated sensors, acquiring the external data like temperature, humidity, and then transmits these data through the gateway to the cloud, for condition monitoring.