Introduction
Bluetooth is
a wireless
technology standard for exchanging data over short distances (using
short-wavelength UHF
radio waves
in the ISM band
from 2.4 to 2.485 GHz) from fixed and mobile devices, and building personal area networks (PANs). Invented by
telecom vendor Ericsson
in 1994, it was originally conceived as a wireless alternative to RS-232 data
cables. It can connect several devices, overcoming problems of synchronization.
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.
Implementation of Bluetooth
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).[14]
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.
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 scatter
net, 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 scatter nets.
Many USB Bluetooth adapters
or "dongles" are available, some of which also include an IrDA adapter
List
of applications
- 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".[23]
- Wireless streaming of audio to headphones 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.
Mobile Robot Temperature Sensing Application via Bluetooth
Application of Bluetooth wireless technology
has become popular among the collaboration between short range communications
such as computing, mobile phone and automotive markets. A device must be able
to interpret certain Bluetooth profiles in order to use Bluetooth technology. Hence,
a KC-21 Bluetooth module is used as a Bluetooth transceiver between
microcontroller unit and mobile phone. The user can use the mobile phone to
send all the instructions to the mobile robot. When the temperature sensor
detects the temperature, the measurement will be send to the mobile phone
through the microcontroller unit and Bluetooth module. This mobile robot is
applied in places that acquired tedious temperature measurement such as in an
airport and hospital. This mobile robot can also be used by firefighter to have
early detection of the heat temperature for a burning case before the cause of
action is consider.
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