Bluetooth is a wireless technology standard for exchanging data over short distances (shortwave UHF radio waves in the 2.4 to 2.485 GHz ISM band) from fixed and mobile devices and creating networks. personnel (PAN). Invented by Dutch electrical engineer Jaap Haartsen, working for telecom provider Ericsson in 1994, it was originally designed as a wireless alternative to RS-232 data cables. Bluetooth is managed by the Bluetooth Special Interest Group (SIG), which has more than 30,000 member companies in the telecommunications, IT, networking and consumer electronics fields. The IEEE has standardized Bluetooth as IEEE 802.15.1, but no longer maintains the standard. Bluetooth SIG oversees the development of the specification, manages the qualification program and protects the brands. A manufacturer must meet the Bluetooth SIG standards to market it as a Bluetooth device. A patent network applies to the technology, which is licensed to individual qualified devices.

The development of short-link radio technology, later named Bluetooth, was launched in 1989 by Nils Rydbeck, CTO at Ericsson Mobile in Lund, Sweden and by Johan Ullman. The goal was to develop wireless headsets, according to two inventions by Johan Ullman, and. Nils Rydbeck instructed Tord Wingren to specify and Jaap Haartsen and Sven Mattisson to develop. Both worked for Ericsson in Lund. The specification is based on frequency hopping spread spectrum technology.

The name “Bluetooth” is an anglicized version of the Scandinavian Blåtand / Blåtann (Old Norse blátǫnn), the epithet of King Harald Bluetooth of the 10th century that united dissonant Danish tribes into one kingdom. The implication is that Bluetooth unites the communication protocols. The idea for this name was proposed in 1997 by Intel’s Jim Kardach who developed a system that allows mobile phones to communicate with computers. At the time of this proposal, he was reading Frans G. Bengtsson’s historical novel, The Long Ships, about the Vikings and King Harald Bluetooth.

The Bluetooth logo is a link rune fusing the Younger Futhark (Hagall) (ᚼ) and (Bjarkan) (ᛒ) runes, the initials of Harald.

Bluetooth operates at frequencies between 2402 and 2480MHz, or 2400 and 2483.5MHz including guard bands 2MHz wide at the bottom end and 3.5MHz wide at the top. This is in the globally unlicensed (but not unregulated) industrial, scientific and medical (ISM) 2.4GHz short-range radio frequency band. Bluetooth uses a radio technology called frequency-hopping spread spectrum. Bluetooth divides transmitted data into packets, and transmits each packet on one of 79 designated Bluetooth channels. Each channel has a bandwidth of 1MHz. It usually performs 800hops per second, with Adaptive Frequency-Hopping (AFH) enabled. Bluetooth Low Energy uses 2MHz spacing, which accommodates 40 channels. Originally, Gaussian frequency-shift keying (GFSK) modulation was the only modulation scheme available. Since the introduction of Bluetooth 2.0+EDR, π/4-DQPSK (differential quadrature phase shift keying) and 8DPSK modulation may also be used between compatible devices. Devices functioning with GFSK are said to be operating in basic rate (BR) mode where an instantaneous bit rate of 1Mbit/s is possible. The term Enhanced Data Rate (EDR) is used to describe π/4-DPSK and 8DPSK schemes, each giving 2 and 3Mbit/s respectively. The combination of these (BR and EDR) modes in Bluetooth radio technology is classified as a “BR/EDR radio”. Bluetooth is a packet-based protocol with a master/slave architecture. One master may communicate with up to seven slaves in a piconet. All devices share the master’s clock. Packet exchange is based on the basic clock, defined by the master, which ticks at 312.5µs intervals. Two clock ticks make up a slot of 625µs, and two slots make up a slot pair of 1250µs. In the simple case of single-slot packets the master transmits in even slots and receives in odd slots. The slave, conversely, receives in even slots and transmits in odd slots. Packets may be 1, 3 or 5 slots long, but in all cases the master’s transmission begins in even slots and the slave’s in odd slots. The above is valid for “classic” BT. Bluetooth Low Energy, introduced in the 4.0 specification, uses the same spectrum but somewhat differently; see Bluetooth Low Energy#Radio interface.

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