Bluetooth

Bluetooth is a wireless technology standard for exchanging data over short distances in the 2.4 GHz ISM band. It enables personal area networks to connect devices such as headphones, keyboards, mice, and smartphones without cables. Developed by Ericsson in 1994, it was named after Harald Bluetooth, a king who united parts of Scandinavia. It is maintained by the Bluetooth Special Interest Group (Bluetooth SIG).

Bluetooth operates via short-range, low-power radio links using a master/slave architecture that forms piconets. A piconet has one master and up to seven active slaves; multiple piconets can interconnect into a scatternet. The standard uses frequency-hopping spread spectrum in the 2.4 GHz band and supports both classic transmissions and low-energy modes.

Over its history Bluetooth has evolved from basic data rates to high-rate and low-energy variants. Classic Bluetooth offered 1 Mbps and, with Enhanced Data Rate (EDR), up to about 3 Mbps. Since Bluetooth 4.0, Bluetooth Low Energy (LE) has been introduced for low-power operation, enabling tiny sensors and beacons. Bluetooth 5 and later added a higher-speed LE mode (2 Mbps) and longer-range options, expanding use in IoT and smart devices.

Typical applications include wireless audio, hands-free calling, file transfer, and peripheral connectivity. The ecosystem uses a range of profiles such as A2DP for stereo audio, HFP for hands-free telephony, HID for input devices, and the GATT/ATT framework for BLE communications. Bluetooth mesh networking has been introduced to support large-scale device networks in home automation and industrial settings.

Security and privacy features include pairing methods, encryption, and authentication. Early versions faced security concerns, leading to ongoing enhancements in later specifications. The Bluetooth SIG defines interoperability standards and profiles, and devices are generally designed to interoperate across versions when possible, subject to profile and mode compatibility.