Bluetooth Low Energy (Bluetooth LE, colloquially BLE, formerly marketed as Bluetooth Smart) is a wireless personal area network technology designed and marketed by the Bluetooth Special Interest Group (Bluetooth SIG) aimed at novel applications in the healthcare, fitness, beacon, security, and home entertainment industries. Compared to Bluetooth Classic, Bluetooth Low Energy is intended to provide considerably reduced power consumption and cost while maintaining a similar communication range.
BLE and Bluetooth Classic use different sets of radio frequencies, and BLE is, therefore, independent of classic Bluetooth, and has no direct compatibility. However, Bluetooth Basic Rate/Enhanced Data Rate (BR/EDR) and BLE can coexist. The original specification was developed by Nokia in 2006 under the name Wibree, which was integrated into Bluetooth 4.0 in December 2009 as Bluetooth Low Energy.
Mobile operating systems including iOS, Android, Windows Phone and BlackBerry, as well as desktop computer operating systems including macOS, Linux, Windows 11, Windows 10 and Windows 8, natively support Bluetooth Low Energy.
Compatibility Bluetooth Low Energy is distinct from the previous (often called "classic") Bluetooth Basic Rate/Enhanced Data Rate (BR/EDR) protocol, but the two protocols can both be supported by one device: the Bluetooth 4.0 specification permits devices to implement either or both of the LE and BR/EDR systems.
Bluetooth Low Energy uses the same 2.4 GHz radio frequencies as classic Bluetooth, which allows dual-mode devices to share a single radio antenna, but uses a simpler modulation system.
Branding
In 2011, the Bluetooth SIG announced the Bluetooth Smart logo so as to clarify compatibility between the new low-energy devices and other Bluetooth devices.
Bluetooth Smart Ready indicates a dual-mode device compatible with both classic and low-energy peripherals. Bluetooth Smart indicates a low-energy–only device which requires either a Smart Ready or another Bluetooth Smart device in order to function.
With the May 2016 Bluetooth SIG branding information, the Bluetooth SIG began phasing out the Bluetooth Smart and Bluetooth Smart Ready logos and word marks and reverted to using the Bluetooth logo and word mark along with a new blue color.
Target market The Bluetooth SIG identifies a number of markets for low-energy technology, particularly in the smart home, health, sport, and fitness sectors. Cited advantages include: low power requirements, operating for "months or years" on a button cell. small size and low cost. compatibility with a large installed base of mobile phones, tablets, and computers.
History
In 2001, researchers at Nokia determined various scenarios that contemporary wireless technologies did not address. The company began developing a wireless technology adapted from the Bluetooth standard which would provide lower power usage and cost while minimizing its differences from Bluetooth technology. The results were published in 2004 using the name Bluetooth Low End Extension.
After further development with partners, in particular Logitech and within the European project MIMOSA, and actively promoted and supported by STMicroelectronics since its early stage, the technology was released to the public in October 2006 with the brand name Wibree. After negotiations with Bluetooth SIG members, an agreement was reached in June 2007 to include Wibree in a future Bluetooth specification as a Bluetooth ultra-low-power technology.
The technology was marketed as Bluetooth Smart and integration into version 4.0 of the Core Specification was completed in early 2010. The first smartphone to implement the 4.0 specification was the iPhone 4S, released in October 2011. A number of other manufacturers released Bluetooth Low Energy Ready devices in 2012.
The Bluetooth SIG officially unveiled Bluetooth 5 on 16 June 2016 during a media event in London. One change on the marketing side was that the point number was dropped, so it is now just called Bluetooth 5 (and not Bluetooth 5.0 or 5.0 LE like for Bluetooth 4.0). This decision was made to "simplify marketing, and communicate user benefits more effectively". On the technical side, Bluetooth 5 will quadruple the range by using increased transmit power or coded physical layer, double the speed by using optional half of the symbol time compared to Bluetooth 4.x, and provide an eight-fold increase in data broadcasting capacity by increasing the advertising data length of low-energy Bluetooth transmissions compared to Bluetooth 4.x, which could be important for IoT applications where nodes are connected throughout a whole house. An "advertising packet" in Bluetooth parlance is the information that is exchanged between two devices before pairing, i.e. when they are not connected. For example, advertising packets allow a device to display to the user the name of another Bluetooth device before pairing with it. Bluetooth 5 increased the data length of this advertising packet. The length of this packet in Bluetooth 4.x was 31 bytes (for broadcast topology).
The Bluetooth SIG officially released Mesh Profile and Mesh Model specifications on 18 July 2017. Mesh specification enables using Bluetooth Low Energy for many-to-many device communications for home automation, sensor networks, and other applications, where sensors, robots, smartphones, and other equipment need to be coordinated.
Applications
Borrowing from the original Bluetooth specification, the Bluetooth SIG defines several profiles – specifications for how a device works in a particular application – for low-energy devices. Manufacturers are expected to implement the appropriate specifications for their device in order to ensure compatibility. A device may contain implementations of multiple profiles.
The majority of current Low Energy application profiles are based on the Generic Attribute Profile (GATT), a general specification for sending and receiving short pieces of data, known as attributes, over a low-energy link. The Bluetooth mesh profile is an exception to this rule, being based on the General Access Profile (GAP).
Mesh profiles Bluetooth mesh profiles use Bluetooth Low Energy to communicate with other Bluetooth Low Energy devices in the network. Each device can pass the information forward to other Bluetooth Low Energy devices, creating a "mesh" effect – for example, switching off an entire building of lights from a single smartphone.
MESH (Mesh Profile) – for base mesh networking. MMDL (Mesh models) – for application layer definitions. The term "model" is used in mesh specifications instead of "profile" to avoid ambiguities.
Health care profiles There are many profiles for Bluetooth Low Energy devices in healthcare applications. The Continua Health Alliance consortium promotes these in cooperation with the Bluetooth SIG:
BLP (Blood Pressure Profile) – for blood pressure measurement HTP (Health Thermometer Profile) – for medical temperature-measurement devices GLP (Glucose Profile) – for blood glucose monitors CGMP (Continuous Glucose Monitor Profile)
Sports and fitness profiles Profiles for sporting and fitness accessories include: BCS (Body Composition Service) CSCP (Cycling Speed and Cadence Profile) – for sensors attached to a bicycle or exercise bike to measure cadence and wheel speed CPP (Cycling Power Profile) HRP (Heart Rate Profile) – for devices which measure heart rate LNP (Location and Navigation Profile) RSCP (Running Speed and Cadence Profile) WSP (Weight Scale Profile)
Generic sensors ESP (Environmental Sensing Profile) UDS (User Data Service)
HID connectivity HOGP (HID over GATT Profile) allowing Bluetooth LE-enabled wireless mice, keyboards and other devices offering long-lasting battery life.
Proximity sensing
"Electronic leash" applications are suited to the long battery life possible for "always-on" devices. Manufacturers of iBeacon devices implement the appropriate specifications for their device to make use of proximity-sensing capabilities supported by Apple's iOS devices.
Relevant application profiles include: FMP (the "find me" profile) – allows one device to issue an alert on a second misplaced device. PXP (the proximity profile) – allows a proximity monitor to detect whether a proximity reporter is within a close range. Physical proximity can be estimated using the radio receiver's RSSI value, although this does not have absolute calibration of distances. Typically, an alarm may be sounded when the distance between the devices exceeds a set threshold.
An example of proximity sensing usage is WebAuthn Hybrid Transport with cloud-assisted Bluetooth Low Energy (caBLE), allowing roaming authenticators such as smartphones to authenticate with WebAuthn credential (known as passkey). Bluetooth Low Energy is used as a proximity check between roaming authenticators and clients (such as personal computers).
Alerts and time profiles The phone alert status profile and alert notification profile allow a client device to receive notifications such as incoming call alerts from another device. The time profile allows current time and time zone information on a client device to be set from a server device, such as between a wristwatch and a mobile phone's network time.
Battery
The Battery Service exposes the Battery State and Battery Level of a single battery or set of batteries in a device.
Audio Announced in January 2020, LE Audio is built on top of Bluetooth 5.2 / 5.3. It allows the Bluetooth LE protocol to carry audio, with lower battery consumption compared to regular Bluetooth Audio; features like one set of headphones connecting to multiple audio sources or multiple headphones connecting to one source (known as Auracast); and support for hearing aids. It introduces LC3 as its default codec. The standard has a lower minimum latency claim of 20–30 ms vs. Bluetooth Classic audio's 100–200 ms.
Specifications on the implementation of Basic Audio Profile and Coordinated Set Identification was released in 2021, and the Common Audio Profile and Service in March 2022. On 12 July 2022, the Bluetooth SIG announced the completion of Bluetooth LE Audio.
Auracast
Auracast implements public audio broadcasting services, allowing multiple receivers to connect to a single audio transmitter without going through Bluetooth device pairing first. It is a trademark owned by the Bluetooth SIG.
+Auracast: Required device roles by device type Transmitter Receiver Assistant Source Sink Assistant Initiator Acceptor Commander Sender Receiver Hearing aid
Auracast is based on the following Bluetooth LE profiles and services:
Basic Audio Profile (BAP) 1.0.1 Public Broadcast Profile (PBP) 1.0 Common Audio Profile (CAP) 1.0 Telephony and Media Audio Profile (TMAP) 1.0 Hearing Access Profile (HAP) 1.0 Broadcast Audio Scan Service 1.0 Published Audio Capabilities Service 1.0.1
Auracast transmitters use wireless advertisements to broadcast information about available streams – such as transmitter name, type of audio, program title, and language – which can be displayed on the receiver and in the apps on smartphones and smartwatches, or processed by the receiver to automatically connect to preferred sources.
Bluetooth LE–enabled smartphones function as an assistant to control Auracast receivers like headphones and earbuds. Broadcast Audio URI, marketed as "Scan to Listen", provides information required to connect to the specific audio stream, encoded with a QR code or transmitted using NFC. This allows users to directly select a specific audio stream in applications such as audio guides in a museum, simultaneous translations in multiple languages, silent TV screens in a bar or community center, public events or music performances at conference halls / sports venues / houses of worship, station and service announcements in public transport, and flight announcements in airports.