Bluetooth Low Energy
The Bluetooth SIG identifies a number of markets for low-energy technology, particularly in the smart home, health, sport, and fitness sectors.
[9] Cited advantages include: In 2001, researchers at Nokia determined various scenarios that contemporary wireless technologies did not address.
[11] After further development with partners, in particular Logitech and within the European project MIMOSA,[a] and actively promoted and supported by STMicroelectronics since its early stage,[b] the technology was released to the public in October 2006 with the brand name Wibree.
[15][16] The technology was marketed as Bluetooth Smart and integration into version 4.0 of the Core Specification was completed in early 2010.
Mesh specification enables using Bluetooth Low Energy for many-to-many device communications for home automation, sensor networks and other applications.
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.
Profiles for sporting and fitness accessories include: "Electronic leash" applications are well suited to the long battery life possible for 'always-on' devices.
[27] Relevant application profiles include: Announced in January 2020, LE Audio allows the protocol to carry sound and add features such as one set of headphones connecting to multiple audio sources or multiple headphones connecting to one source[29][30] and also adds support for hearing aids.
[36][37] In December 2020, the Bluetooth SIG released a draft specification for a wearable exposure notification service.
[38] Starting in late 2009, Bluetooth Low Energy integrated circuits were announced by a number of manufacturers.
These ICs commonly use software radio so updates to the specification can be accommodated through a firmware upgrade.
Within a channel, data is transmitted using Gaussian frequency shift modulation, similar to classic Bluetooth's Basic Rate scheme.
Bluetooth Low Energy uses frequency hopping to counteract narrowband interference problems.
For reducing the chance of multiple consecutive collisions, a random delay of up to 10 milliseconds is added to each advertising interval.
While the discovery latencies of BLE can be approximated by models[51] for purely periodic interval-based protocols, the random delay added to each advertising interval and the three-channel discovery can cause deviations from these predictions, or potentially lead to unbounded latencies for certain parametrizations.
The application programming interface offered by a Bluetooth Low Energy aware operating system will typically be based around GATT concepts.
An indication is similar to a notification, except that it requires a response from the client, as confirmation that it has received the message.
[58] With newer chipsets and advances in software, by 2014 both Android and iOS phones had negligible power consumption in real-life Bluetooth Low Energy use.
Bluetooth LE has been traditionally transmitting 1 bit per symbol so that theoretically the data rate doubles as well.
The partitioning of the ISM frequency band has not changed being still 40 channels spaced at a distance of 2 MHz.
This is designed to facilitate firmware updates where the application can switch back to a traditional 1M PHY in case of errors.
[62] The "LE Coded" transmissions have not only changed the error correction scheme but it uses a fundamentally new packet format.
The switch block ("extended preamble") is transmitted on the LE 1M PHY but it only consists of 10 times a binary '00111100' pattern.
[63] The new packet format of Bluetooth 5 allows transmitting from 2 up to 256 bytes as the payload in a single burst.
