Bluetooth is a short range wireless technology that operates in the unlicensed Industrial, Scientific and Medical (ISM) 2.4 GHz radio frequency band.
Robust connectivity in a globally deployed ecosystem
Bluetooth is currently available in two variants: BR/EDR (basic rate/enhanced data rate) for audio and streaming applications and Bluetooth low energy (BLE) for intermittent transmission of data in battery operated sensor devices.
The latest revision of the Bluetooth Specification, Bluetooth 5, increases the range and speed of Bluetooth low energy. With mesh networking, Bluetooth low energy nodes can form large scale networks with extended reach.
Bluetooth dynamically adapts the frequency hopping sequence (Adaptive Frequency Hopping / AFH) to avoid channels potentially in use by other technologies. As a result, Bluetooth is particularly suitable for industrial, automotive and medical applications, where the reliability provided by Bluetooth is key.
According to ABI Research, Bluetooth enabled device shipments will reach more than five billion by 2021. Indeed, Bluetooth has become a standard for wireless connectivity between mobile devices with an unmatched ecosystem, available in all smart phones and tablets, which is important for connecting hand‑held generic devices with other installed Bluetooth enabled devices.
Bluetooth BR/EDR vs Bluetooth low energy
While the core name is the same, there are fundamental differences between Bluetooth low energy (previously known as Bluetooth Smart) and Bluetooth BR/EDR (previously known as Classic Bluetooth).
Bluetooth low energy technology is ideal for applications using periodic transfer of small amounts of data where low cost and ultra‑low power consumption is the focus. It is particularly useful for sensors in Internet of Things (IoT) applications.
Dual‑mode Bluetooth devices support both Bluetooth low energy and Bluetooth BR/EDR. This is, for instance, the case with a smartphone; it connects to a laptop via Bluetooth BR/EDR and to a heart rate sensor via Bluetooth low energy. The heart rate sensor is an example of a single‑mode Bluetooth low energy device.
In Bluetooth low energy, one speaks of peripheral and central roles for a device. Once the connection is established, the devices form a master and slave topology similar to Bluetooth BR/EDR. To use the above mentioned example, the heart rate sensor acts as a peripheral/slave while the smartphone acts as central/master.
For two Bluetooth BR/EDR enabled devices to connect they need to have the same profile implemented. For instance, Personal Area Networking (PAN) allows two or more devices to form an ad‑hoc network and the Serial Port Profile (SPP) replaces a serial communication interface.
In Bluetooth low energy, the Generic Attribute (GATT) profiles define a hierarchical data structure used to exchange data between Bluetooth low energy devices. The GATT profiles describe use cases and the GATT services are characteristics collections (data, descriptions, possible actions, etc.) that define the capabilities of a Bluetooth low energy device.
GATT defines clients (“devices that want data”) and the servers (“devices that have data”). The GATT server stores data transported over the Attribute Protocol (ATT) and accepts requests, commands and confirmations from the GATT client. The GATT server sends responses and GATT server event triggered messages to the GATT client. As an example, the u‑blox NINA‑B1 Bluetooth low energy module has both GATT server and GATT client roles implemented.
It is also possible to define custom services. For instance, u‑blox has defined the u‑blox Serial Port Service to allow for serial data exchange between Bluetooth low energy devices similar to the Bluetooth EDR/BR SPP.
|BR/EDR Secure Connections||Provides 128‑bit AES encryption strength|
|Dual Mode Topology||Enables a device to act as a Bluetooth dual‑mode hub and Bluetooth low energy peripheral at the same time|
|L2CAP Dedicated Channels||Enables IPv6 over Bluetooth low energy|
|Internet protocol support profile (IPSP)||A Bluetooth low energy sensor can access the Internet through a gateway device|
|LE Privacy 1.2||Keeps Bluetooth low energy devices from being tracked|
|LE Secure Connections||Provides 128‑bit AES encryption strength for Bluetooth low energy|
|LE Data Length Extension||Increases data throughput up to 2.5x|
|2 Mbps LE||Extends the data rates supported by Bluetooth low energy up to 2 Mbps|
|LE Long Range||Extends the range supported by Bluetooth low energy devices to more than double the range|
|LE Advertising Extension||Support for longer advertisement messages which prepares for future IPv6 based mesh|