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 wireless technology 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.
Bluetooth dynamically adapts the frequency hopping sequence – using Adaptive Frequency Hopping (AFH) – to avoid channels potentially in use by other technologies. Automatic power control reduces the output power to levels required to keep connections and at the same time not interfere with other 2.4 GHz (including other Bluetooth connections) radios in the neighborhood. Forward Error Correction (FEC) allows receivers to correct limited bit errors introduced in harsh environments. As a result, Bluetooth is particularly suitable for industrial, automotive and medical applications, where the reliability provided by Bluetooth is crucial.
According to ABI Research, Bluetooth‑enabled device shipments will reach more than five billion by 2021. Indeed, Bluetooth has become the standard for wireless connectivity between mobile devices, and is available in all smart phones and tablets. There are hundreds of applications for smartphones and custom hand‑held controllers that are used to manage or monitor another system with embedded Bluetooth, and to share media, files, and information among users.
Bluetooth BR/EDR vs Bluetooth low energy
While the core name is the same, there are fundamental differences between Bluetooth BR/EDR and Bluetooth low energy. Bluetooth BR/EDR is intended for audio connections and streaming applications. Bluetooth low energy technology is ideal for applications using periodic transfer of small amounts of data where ultra low power consumption is the focus. It uses a much faster connection mechanism than Bluetooth BR/EDR enabling the radio to be on only for very short period of time. This is why 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 may connect to a laptop via Bluetooth BR/EDR and to a heart rate sensor via Bluetooth low energy. The heart rate sensor only uses Bluetooth low energy, and is thus an example of a single mode Bluetooth low energy device.
In Bluetooth low energy, devices have peripheral and central roles. Once the connection is established, the devices form a master and slave topology similar to Bluetooth BR/EDR. In the example above, the heart rate sensor acts as a peripheral/slave while the smartphone acts as central/master.
A profile is a specification describing a specific use case and is used to achieve interoperability between devices supporting the same profile. Two Bluetooth BR/EDR enabled devices need to have the same profile implemented in order to connect. 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 configuration data between Bluetooth low energy devices. The GATT profiles describe use cases and the GATT services are characteristics (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 server and client exchange information to establish a dialog and to define the payload transport requirements and their repetition rates or event triggers. It is possible for both functions to reside within the same product: the u blox Bluetooth low energy modules (NINA B1, NINA‑B3, ODIN‑W2) have both GATT server and GATT client roles implemented to provide design flexibility. It is also possible to define custom services. For instance, u blox has defined the u blox Serial Port Service to allow for reliable serial data exchange between Bluetooth low energy devices similar to the Bluetooth EDR/BR SPP.
The latest version of the specification, Bluetooth 5, includes three major enhancements to Bluetooth low energy: increased data rate (2 x the speed), extended range (4 x the distance) and enhanced advertising capability. Two of these features will come with a software upgrade and one (extended range) requires new hardware.
The recently introduced Bluetooth mesh enables many‑to‑many Bluetooth low energy networking solutions. Bluetooth mesh is available as a software update to Bluetooth low energy and can be used with any of the Bluetooth low energy versions 4.0, 4.1, 4.2 and 5.0.
Mesh extends the coverage area significantly, even further than Bluetooth 5, because Bluetooth nodes can forward messages acting as relays in a cooperative network.
Bluetooth 5 and Bluetooth mesh open up completely new applications for Bluetooth. Industrial sensor networks, building automation, street lighting, environmental monitoring, and many other applications will require only a single host node to collect, control and manage the data and the mesh network.
Overview of Bluetooth versions and their features:
|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|
|Bluetooth 4.2||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|
|Bluetooth 5||2 Mbps LE||Extends the data rates supported by Bluetooth low energy up to 2 Mbps, thus doubling the speed|
|LE Long Range||Extends the range supported by Bluetooth low energy devices to four times the range|
|LE Advertising Extension||Support for longer advertisement messages for more feature rich Bluetooth beacons and for future IPv6 based mesh|
|Bluetooth mesh||LE Topography Extension||Mesh networking significantly extends the area covered by a cooperative Bluetooth low energy network|