Bluetooth is a wireless technology that allows devices such as computers, phones, and other electronics to connect and exchange information within short ranges of up to 10-100 meters. It uses radio transmissions in the ISM band between 2400-2483.5 MHz to form ad-hoc networks between devices. Bluetooth devices can operate at different power classes and data rates to support both voice calls and asynchronous data transfer between connected devices like transferring contacts between a phone and laptop. The Bluetooth Special Interest Group develops specifications to ensure interoperability between devices from different manufacturers.

1. BLUETOOTH:
It is an typical cabin or a home or even a car is equipped with a number of electronic gadgets such
as desktop,laptop,modem,mobile phone,etc. this devices form a Personal Aera Network(PAN).A number
of technologies have been proposed for PANs. NOteable among them are bluetooth,IrDA(Infrared Data
Association) and IEEE 802.11 .
When we bring two devices, say laptop and a mobile phone , close to each other,these two can
automatically form a network and exchange data (Eg. we can transfer the address book from the mobile
phone to the laptop).In Networks, formed spontaneously by coming closer two or more devices, are
termed as ad-hoc networks. In ad-hoc network, the topology and the number of nodes at any time are
not fixed the topology may change dynamically with time,and the number of nodes in the network may
also change with time.
FEATURES:
It is a low cost technology –its cost will soon be as low as a cable connection. Since most of the
bluetooth-enabled devices have to operate through a battery, the power consumption is also
very low.
It is based on radio transmission in the ISM band. It is not controlled by any government
authority and hence no special approval is required to use bluetooth radio systems.
It has to short ranges. The range of bluetooth device is typically 10 meters, though with higher
power , the range can be increased to 100 meters .
It is based on open standards formulated by a consortium of industries and a large number of
equipment vendors are commited to this technology.
Bluetooth special Intrest Group (SIG) founded in february 1998 by Ericsson, Intel,Ibm,Toshiba and Nokia
released version 1.0 of Bluetooth specification in july 1999. Version 1.1 of Bluetooth specifications was
released in February 2001.
Most of electroinc devices can be Bluetooth-enabled . These include a PC,Laptop,Digital camera,mobile
phone,pager,MP3 player, headset,printer,LCD projector,domestic appliances such as TV, music players
etc. A piece of software is run on the device. A Bluetooth –enabled device communicates with another
Bluetooth-enabled device over the radio medium to exchange information or transfer data.
SPECIFICATIONS:
Frequency of operation :
Bluetooth devices operate in the ISM band in the frequency range 2400-2483.5 Mhz. This band consist
of 79 channels each of 1 Mhz bandwidth, with a lower guard band of 2 Mhz and upper guard of 3.5 Mhz.

2. Modulation:
Gaussian Frequncy shift keying (GFSK) is used as the modulation technique. Binary 1 is
represented by a positive frequency deviation and 0 by negative frequency deviation.
Operating range :
Three classes of devices are defined
Class 1 devices transmit maximum of 100 mw. The range of such devices is 100 meter.
Class 2 devices transmit 10 mw. The range is 50 meters.
Class 3 devices transmit 1 mw.The range is 10 meters.
Most of the commerically available devices have a transmitting power of 1 milliwatt and hence
a range of 10 meters.
Services supported:
Both voice and data services are supported by Bluetooth devices. For voic3e communication,
Synchronous connection oriented (SCO) links are used which support circuit switching
operation. For data communication, Asynchronous connection less (ACL) links are used which
are packet switching.
Data rates:
Bluetooth can support three voices channel and one asynchronous data cahannel.
Voice communication -64kbps data rate is used in both directions.
Asynchronous channel – are of two types symmetric(433.9kbps) and asymmentric
channel(723.2kbps in one direction and 57.6 kbps in other direction)
Network topology:
In a PAN, a set of devices form a small network called piconet. In a piconet, there will be one
master and one or more slaves. All the slaves tune to the master. The master decides the hop
frequency sequence and all the slaves tune to these ferquencies to establish communication
linksAny devices (desktop,mobile phone etc.)can be a master or slave.In addition to these
active slaves, a picnet can contain many slaves that are in parked mode.These parked devices
are synchronized with the master, but they are not active on the channel. The communication
between the master and the slave uses Time Division Duplex (TDD).

3. Communication between Master and Slave:
The master and slave communicate in the form of packets.Each packet is transmitted in time
slot.Each time slot is of 625 microseconds duration.Master starts the transmisson in even slots
by sending a packet addressed to a slave and the slave sends the packets in odd numbered
slotA packet generally occupies one time slot, but can extend up to five slots.
Bluetooth Addressing:
Each Bluetooth module (the radio teansceiver) is given a 48-bit address containing three fields
LAP(Lower Address Part) with 24 bits.
UAP(Upper Address Part)with 8 bits.
Non-significant Address Part with 16bits.
This address is assigned by manufacturer of the Bluetooth module and consists of company ID
and company assigend number.This address is unique to every Bluetooth device. In Bluetooth
specifications,this address is referred to as BD_ADDR.
Each active member in apiconet will have a 3-bit address. In addition to the maximum of 7
active mambers, many more devices can be in “parked” mode. The parked members also need
to have address so that the master can make them active for exchange of packets.Parked
member address is either the BD_ADDR of 48bits or an 8-bit parked member address denoted
by PM_ADDR.
Bluetooth profiles:
To ensure interoperability between devices manufactured by different vendors,Blurtooth SIG
released the Bluetooth profiles which define the precise characteristics and protocols
supported by these devices.The buletooth profiles are defined for headset, cordless phone, fax
machine, LAN access point, serial communication, dail-up networking, file
transfer,synchronization of data between two devices,etc.
Conclusion:
Bluetooth is a fast spreading wireless technology7 of data transferwith variable speeds from
741kbps to 4mbps. It is largely implemented in moblies it suceeded infrared technology and will
be superspeed by redtooth. Bluetooth doesnot have line of sight propogation for file transfer
and therefore only communicating device should only be in range of bluetooth not necessarily
in the line of sight.