Bluetooth is one of the most common technologies used for creating an indoor positioning system (IPS). It can work well for both proximity solutions and high-accuracy object detection and tracking. Here, we’ll tell you about Bluetooth positioning methods, the alternatives of the technology, and the challenges you can meet when implementing a Bluetooth-based IPS.
Indoor Positioning with Bluetooth
An IPS is a network of nodes used for positioning and tracking objects in buildings and underground. The nodes can either send signals (transmitting devices) or receive them (receiving devices). Some devices can combine both functions.
Bluetooth indoor positioning uses beacons or tags to track stationary and moving objects respectively. Bluetooth beacons send out data packets with unique identifiers by which a receiver can recognize and differentiate them. Bluetooth Low Energy (BLE) beacons are small-sized devices with extremely low power consumption and extended battery life.
To communicate with receiving devices, beacons need a protocol that can be ready-made, for example, iBeacon, AltBeacon, and Eddystone, and customized. A mobile app or SDK integrated into a receiving device, such as a smartphone, receives beacon signals and converts them into the object’s position data.
The accuracy of the position data depends on the method used by the technology. Bluetooth positioning methods include:
- Received signal strength indication (RSSI)
RSSI measures the intensity of the signals emitted by the transmitters. This method is mostly used for proximity solutions for which meter-level accuracy is well enough.
- Angle of arrival (AoA)/Angle of departure (AoD)
AoA and AoD measure the angles at which the transmitted signals reach the receiving devices. The AoA and AoD methods can provide centimeter-level positioning accuracy.
- Trilateration and triangulation
These methods apply in a network of three or more transmitting devices. Trilateration and triangulation involve mathematical models and often support other methods to increase positioning accuracy.
Bluetooth indoor positioning systems find wide applications in various industries. BLE-based solutions can comprise:
- people and asset tracking;
- wayfinding;
- point of interest (POI) information;
- item finding.
Bluetooth application fields embrace logistics, healthcare, entertainment, travel industry, education, manufacturing, and many other areas. Bluetooth IPS solutions can monitor goods handling, secure assets, track and safeguard employees, share information, find lost items, and navigate visitors in public places.
Alternative Technologies Used for Indoor Positioning
Indoor positioning systems can employ a variety of technologies that differ in their implementation features and cost, positioning methods and accuracy, and other aspects. IPS technologies can comprise:
- Radio signal-based IPS
Such technologies use radio propagation and include NFC, RFID, Wi-Fi (WPS), Bluetooth, Thread, ZigBee, ultra-wideband (UWB), Radio Detection and Ranging (RADAR).
- Sound signal-based IPS
These systems rely on echolocation and the use of ultrasonic signals, the example is Sound Navigation and Ranging (SONAR) system.
- Light signal-based IPS
These IPS technologies use light propagation and involve Light Detection and Ranging (LiDAR), infrared systems, and computer vision systems.
- Inertial navigation-based IPS
These systems, such as inertial measurement units (IMUs), use sensor data to track objects in three-dimensional space.
All IPS technologies have strong and weak points. For example, ultrasound systems can detect objects accurately, but their reliability directly depends on the environment. The surrounding objects can negatively affect the ultrasonic waves. Light signals used by infrared systems also have limited capabilities.
Radio signal-based solutions, such as Bluetooth, Wi-Fi, NFC, and RFID, are more common IPS technologies. For example, RFID is a cost-effective and easy-to-implement solution intended for short-range applications. Wi-Fi is a widespread technology used to create highly scalable networks of devices.
Bluetooth is a very popular choice for indoor positioning systems because of the following advantages:
- wide availability (you can find it in almost all modern chips and smart devices);
- high energy efficiency (BLE provides very low power consumption);
- variety of positioning methods (RSSI, AoA/AoD, trilateration, and triangulation);
- simple implementation (the technology is easy to work with).
Challenges of Implementing Bluetooth Indoor Positioning Technology
Depending on the Bluetooth version, you can implement different positioning methods. Thus, if your Bluetooth version is less than 5.1, you can only use RSSI. If your system supports the latest Bluetooth Specification version, you can use the AoA and AoD methods that relate to the direction-finding techniques.
You can always achieve better accuracy by using additional positioning methods. For example, trilateration supports RSSI, and triangulation is often used together with AoA and AoD for more accurate object detection.
You can also improve the positioning accuracy by increasing the number of beacons installed in the facility. In addition, high beacon density can help you maintain signal integrity in noisy environments.
Before deploying an IPS, it’s important to create a detailed map of the room or building where you’re planning to use it and choose suitable software for this purpose. If you’re interested in indoor positioning systems and BLE-based solutions, you can find a lot more in the 2021 guide to Bluetooth indoor positioning.
Previously published at https://www.integrasources.com/blog/bluetooth-indoor-positioning-systems/