Bluetooth is a wireless protocol for exchanging data over short distances from fixed and mobile devices, creating personal area networks.
There are two important parameters of Bluetooth devices – class and supported profiles.
“Class” signifies the distance at which a Bluetooth connection is possible. Most mobile devices are Class 2, which means they have a range of up to 10 m. Class 1 devices are rare and have a range of up to 100 feet.
A “profile” is a type of Bluetooth connection. The most common are the Headset (HSP) and Handsfree (HFP) profiles that enable the device to connect to a wireless headset or handsfree.
Some other profiles are OBEX (OBject EXchange) which allows transfer of files, contacts and events; A2DP, which adds support for streaming of stereo sound and AVRC, which allows remote control of playback.
A2DP (Advanced Audio Distribution Profile)
A2DP is used for streaming stereo music wirelessly to headphones or speakers over Bluetooth.
Unlike other Bluetooth profiles (Headset and Handsfree), A2DP is one-way only and streams a stereo signal.
aptX
The aptX audio codec is a proprietary audio codec compression algorithm, which allows the real-time streaming of high quality stereo audio over a Bluetooth A2DP connection between a source device and the accessory device.
aptX technology must be incorporated in both the source and the accessory device for it to have any effect. Full backwards compatibility however allows audio streaming even when one of the devices is not aptX compatible, though in this case, the connection won’t benefit from the technology.
EDR (Enhanced Data Rate)
An optional part of the Bluetooth specification that provides a faster data rate (speed) and possibly improved battery life. Not all Bluetooth devices support EDR and will depend on the Bluetooth version and supported profiles. Both devices need to support EDR, in which case EDR is used automatically.
Bluetooth Low Energy (Bluetooth LE or BLE for short)
Bluetooth LE Audio is developed to enhance performance in power consumption, latency, and bandwidth. LE Audio and Classic Audio standards will continue to coexist and have features that will be supported by both. LE Audio will have a wider set of features, lower power consumption, and better perceived audio quality.
LE Audio is the next generation of Bluetooth Audio, making audio streaming over Bluetooth Low Energy possible. It enables new use cases and significantly reduces power consumption compared to Classic (BR/EDR) Audio.