Bluetooth

Bluetooth 

Wireless Communications

Definition:

 a wireless technology standard for exchanging data over short distances (using short-wavelength radio transmissions in the ISMband from 2400–2480 MHz)

 from fixed and mobile devices, creating personal area networks  (PANs) with high levels of security.  It can  connect several devices, overcoming problems of synchronization.

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 will necessarily begin as master, as initiator of the connection; but may subsequently prefer to be slave).

The Bluetooth Core Specification provides for the connection of two or more piconets to form a  scatternets , 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. 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 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. Older Bluetooth dongles, however, have limited capabilities, offering only the Bluetooth Enumerator and a less-powerful Bluetooth Radio incarnation. Such devices can link computers with Bluetooth with a distance of 100 meters, but they do not offer as many services as modern adapters do.

 Usage:

Bluetooth is a standard wire-replacement communications protocol primarily designed for low power consumption, with a short range (power-class-dependent, but effective ranges vary in practice; see table below) 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.

Applications:

*   Wireless control 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 Bluetooth headset and Intercom.

*  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 Wii and Sony's PlayStation 3, PSP Go and PS Vita, 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.

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Bluetooth Single Cell Systems  intro to Bluetooth Cellular Systems 1st & 2nd Generations  2nd Generation Standards Bluetooth Phases
Communication System Systems Communications Wireless 4G