Bluetooth is managed by the Bluetooth Special Interest Group (SIG), which has more than 25,000 member companies in the areas of telecommunication, computing, networking, and consumer electronics.] The IEEE standardized Bluetooth as IEEE 802.15.1, but no longer maintains the standard. The Bluetooth SIG oversees development of the specification, manages the qualification program, and protects the trademarks A manufacturer must make a device meet Bluetooth SIG standards to market it as a Bluetooth device A network of patents apply to the technology, which are licensed to individual qualifying devices.
*Name and logo
The name "Bluetooth" is an Anglicised version of the Scandinavian Blåtand/Blåtann, (Old Norse blátǫnn) the epithet of the tenth-century king Harald Bluetooth who united dissonant Danish tribes into a single kingdom and, according to legend, introduced Christianity as well. The idea of this name was proposed in 1997 by Jim Kardach who developed a system that would allow 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 Vikings and King Harald Bluetooth. The implication is that Bluetooth does the same with communications protocols, uniting them into one universal standard.[11][12][13]
The Bluetooth logo is a bind rune merging the Younger Futhark runes Runic letter ior.svg (Hagall) (ᚼ) and Runic letter berkanan.svg (Bjarkan) (ᛒ), Harald's initials.
Implementation
Bluetooth operates at frequencies between 2400 and 2483.5 MHz (including guard bands of 2 MHz at the bottom end and 3.5 MHz at the top). This is in the globally unlicensed (but not unregulated) Industrial, Scientific and Medical (ISM) 2.4 GHz 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 1 MHz. Bluetooth 4.0 uses 2 MHz spacing, which accommodates 40 channels. The first channel starts at 2402 MHz and continues up to 2480 MHz in 1 MHz steps. It usually performs 1600 hops per second, with Adaptive Frequency-Hopping (AFH) enabled.
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 data rate of 1 Mbit/s is possible. The term Enhanced Data Rate (EDR) is used to describe π/4-DPSK and 8DPSK schemes, each giving 2 and 3 Mbit/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 structure. 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 312.5 µs intervals. Two clock ticks make up a slot of 625 µs, and two slots make up a slot pair of 1250 µs. 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.
Communication and connection
A master Bluetooth device can communicate with a maximum of seven devices in a piconet (an ad-hoc computer network using Bluetooth technology), though not all devices reach this maximum. The devices can switch roles, by agreement, and the slave can become the master (for example, a headset initiating a connection to a phone necessarily begins as master—as initiator of the connection—but may subsequently operate as slave).
The Bluetooth Core Specification provides for the connection of two or more piconets to form a scatternet, in which certain devices simultaneously play the master role in one piconet and the slave role in another.
At any given time, data can be transferred between the master and one other device (except for the little-used broadcast mode.[citation needed]) The master chooses which slave device to address; typically, it switches rapidly from one device to another in a round-robin fashion. Since it is the master that chooses which slave to address, whereas a slave is (in theory) supposed to listen in each receive slot, being a master is a lighter burden than being a slave. Being a master of seven slaves is possible; being a slave of more than one master is difficult.[citation needed] The specification is vague as to required behavior in scatternets.
Many USB Bluetooth adapters or "dongles" are available, some of which also include an IrDA adapter.[citation needed]
Uses
th is a standard wire-replacement communications protocol primarily designed for low-power consumption, with a short range based on low-cost transceiver microchips in each device. Because the devices use a radio (broadcast) communications system, they do not have to be in visual line of sight of each other, however a quasi optical wireless path must be viable. Range is power-class-dependent, but effective ranges vary in practice; see the table on the right.
Officially Class 3 radios have a range of up to 1 metre (3 ft), Class 2, most commonly found in mobile devices, 10 metres (33 ft), and Class 1, primarily for industrial use cases,100 metres (300 ft)] Bluetooth Marketing qualifies that Class 1 range is in most cases 20–30 metres (66–98 ft), and Class 2 range 5–10 metres (16–33 ft).
Version
Data rate
Max. application throughput
1.2
1 Mbit/s
>80 kbit/s
2.0 + EDR
3 Mbit/s
>80 kbit/s
3.0 + HS
24 Mbit/s
See Version 3.0 + HS
4.0
24 Mbit/s
See Version 4.0 LE
The effective range varies due to propagation conditions, material coverage, production sample variations, antenna configurations and battery conditions. Most Bluetooth applications are for indoor conditions, where attenuation of walls and signal fading due to signal reflections make the range far lower than specified line-of-sight ranges of the Bluetooth products. Most Bluetooth applications are battery powered Class 2 devices, with little difference in range whether the other end of the link is a Class 1 or Class 2 device as the lower powered device tends to set the range limit. In some cases the effective range of the data link can be extended when a Class 2 device is connecting to a Class 1 transceiver with both higher sensitivity and transmission power than a typical Class 2 deviceMostly however the Class 1 devices have a similar sensitivity to Class 2 devices. Connecting two Class 1 devices with both high sensitivity and high power can allow ranges far in excess of the typical 100m, depending on the throughput required by the application. Some such devices allow open field ranges of up to 1 km and beyond between two similar devices without exceeding legal emission limits.
The Bluetooth Core Specification mandates a range of not less than 10 metres (33 ft), but there is no upper limit on actual range. Manufacturers' implementations can be tuned to provide the range needed for each case.
*Bluetooth profiles
To use Bluetooth wireless technology, a device must be able to interpret certain Bluetooth profiles, which are definitions of possible applications and specify general behaviours that Bluetooth-enabled devices use to communicate with other Bluetooth devices. These profiles include settings to parametrize and to control the communication from start. Adherence to profiles saves the time for transmitting the parameters anew before the bi-directional link becomes effective. There are a wide range of Bluetooth profiles that describe many different types of applications or use cases for devices.
*List of applications
A typical Bluetooth mobile phone headset.
Wireless control of and communication between a mobile phone and a handsfree headset. This was one of the earliest applications to become popular.
Wireless control of and communication between a mobile phone and a Bluetooth compatible car stereo system.
Wireless control of and communication with tablets and speakers such as iOS and Android devices.
Wireless Bluetooth headset and Intercom. Idiomatically, a headset is sometimes called "a Bluetooth".
Wireless streaming of audio to headphones with] or without[] communication capabilities.
Wireless networking between PCs in a confined space and where little bandwidth is required
Wireless communication with PC input and output devices, the most common being the mouse, keyboard and printer.
Transfer of files, contact details, calendar appointments, and reminders between devices with OBEX.
Replacement of previous wired RS-232 serial communications in test equipment, GPS receivers, medical equipment, bar code scanners, and traffic control devices.
For controls where infrared was often used.
For low bandwidth applications where higher USB bandwidth is not required and cable-free connection desired.
Sending small advertisements from Bluetooth-enabled advertising hoardings to other, discoverable, Bluetooth devices.
Wireless bridge between two Industrial Ethernet (e.g., PROFINET) networks.
Three seventh and eighth generation game consoles, Nintendo's Wiiand Sony's PlayStation 3, use Bluetooth for their respective wireless controllers.
Dial-up internet access on personal computers or PDAs using a data-capable mobile phone as a wireless modem.
Short range transmission of health sensor data from medical devices to mobile phone, set-top box or dedicated telehealth devices.
Allowing a DECT phone to ring and answer calls on behalf of a nearby mobile phone.
Real-time location systems (RTLS), are used to track and identify the location of objects in real-time using “Nodes” or “tags” attached to, or embedded in the objects tracked, and “Readers” that receive and process the wireless signals from these tags to determine their locations.
Personal security application on mobile phones for prevention of theft or loss of items. The protected item has a Bluetooth marker (e.g., a tag) that is in constant communication with the phone. If the connection is broken (the marker is out of range of the phone) then an alarm is raised. This can also be used as a man overboard alarm. A product using this technology has been available since 2009.
Calgary, Alberta, Canada's Roads Traffic division uses data collected from travelers
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