Bluetooth is a way of connecting machines to each other without cables or any other physical medium. It uses radio waves to transfer information. Bluetooth is one of the recent development in wireless technology. Bluetooth is recent standard developed by group of electronic manufacturers that will allow any sort of electronic equipment to make it’s own connections ,without wire , cables , or any direct action from user.
This paper begins with brief introduction of Bluetooth technology and explains terms and definitions related to Bluetooth technology. This paper also includes functions and working of Bluetooth technology, characteristics and advantages e.g. wireless technology how avoids interference from other electronic devices and how it is secured. Finally paper is concluded with some uses and examples of Bluetooth technology and future estimations.INTRODUCTION
Bluetooth is the name given to a new technology using short-range radio links, intended to replace the cable(s) connecting portable and/or fixed electronic devices. It is envisaged that it will allow for the replacement of the many propriety cables that connect one device to another with one universal radio link. Its key features are robustness, low complexity, low power and low cost. Designed to operate in noisy frequency environments, the Bluetooth radio uses a fast acknowledgement and frequency hopping scheme to make the link robust. Bluetooth radio modules operate in the unlicensed ISM band at 2.4GHz, and avoid interference from other signals by hopping to a new frequency after transmitting or receiving a packet. Compared with other systems in the same frequency band, the Bluetooth radio hops faster and uses shorter packets.
THE AIM OF "BLUETOOTH"
The aim has been set quite hight. It is to arrive at a specification for a technology that optimizes the usage model of all mobile computing and communications devices, and providing
- Global usage
- Voice and data handling
- The ability to establish ad-hoc connections
- The ability to withstand interference from other sources in open band
- Very small size, in order to accommodate integration into variety of devices
Functionally, one talks about the three core protocols:
- Logical link control and adaptation protocol (L2CAP)
- Service discovery protocol (SDP)
- RFCOMM protocol.
Like SDP, RFCOMM is layered on top of the L2CAP. As a ‘cable replacement’ protocol, RFCOMM provides transport capabilities for high-level services (e.g. OBEX protocol) that use serial line as the transport mechanism.
The Bluetooth air interface is based on a nominal antenna power of 0 dBm. Spectrum spreading has been added to facilitate optional operation at power levels up to 100 mW worldwide. This is accomplished by frequency hopping; 79 hops displaced by 1 MHz, starting at 2.402 GHz and stopping at 2.480 GHz.
Essentially Bluetooth is the term used to describe the protocol of a short range (10 meter) frequency-hopping radio link between devices. These devices are then termed Bluetooth - enabled. Documentation on Bluetooth is split into two sections, the Bluetooth Specification and Bluetooth Profiles.
The Specification describes how the technology works (i.e the Bluetooth protocol architecture),
The Profiles describe how the technology is used (i.e how different parts of the specification can be used to fulfil a desired function for a Bluetooth device)
The Specification is examined first, then the Profiles.
Specification Table Of Contents:
1) Radio-The Radio layer defines the requirements for a Bluetooth transceiver operating in the 2.4 GHz ISM band.
2) Base band-The Base band layer describes the specification of the Bluetooth Link Controller (LC) which carries out the baseband protocols and other low-level link routines.
3) LMP-The Link Manager Protocol (LMP) is used by the Link Managers (on either side) for link set-up and control.
4) HCI-The Host Controller Interface (HCI) provides a command interface to the Baseband Link Controller and Link Manager, and access to hardware status and control registers.
5) L2CAP-Logical Link Control and Adaptation Protocol (L2CAP) supports higher level protocol multiplexing, packet segmentation and reassembly, and the conveying of quality of service information. 6 RFCOMM .The RFCOMM protocol provides emulation of serial ports over the L2CAP protocol. The protocol is based on the ETSI standard TS 07.10.7 SDP . The Service Discovery Protocol (SDP) provides a means for applications to discover which services are provided by or available through a Bluetooth device. It also allows applications to determine the characteristics of those available services.
HOW DOES BLUETOOTH WORK?
Compared with other systems operating in the same frequency band, the Bluetooth radio typically hops faster and uses shorter packets. This is because short packages and fast hopping limit the impact of microwave ovens and other sources of disturbances. Use of Forward Error Correction (FEC) limits the impact of random noise on long-distance links.
Transmission power levels
The Bluetooth radio is built into a small microchip and operates in a globally available frequency band ensuring communication compatibility worldwide. The Bluetooth specification has two power levels defined;
- a lower power level that covers the shorter personal area within a room, and
- a higher power level that can cover a medium range, such as within a home.
Communication routes
One thing that can be noted from the figure above is that, although Bluetooth works in an ad-hoc fashion (and not server-based) all communication is done visavi the Master unit. There is no direct communication between slave units. Nor is it intended for the Master to route messages between slave units. Rather, if slave units find that they want to talk directly to each other, they would form a new piconet, with one of them acting as Master. This does not mean that they have to leave the previous piconet. More likely, they will be parked in the "old" net unless they decide to quit the "old" net altogether. This is not a big decision for the slave units; reconfiguration in Bluetooth is dynamic and very fast.
Overview of Bluetooth characteristics :
- it Separate spread the Frequency band into hop.
- Upto 8 device can be connected to each other
- Signal can be transmitted through wall's.
- Device need not need to point at each other . therefore signal are omnidirectional
- Both synchronous and asynchronous devices are support
Bluetooth wireless communication offers several important and distinct advantages.:
- Wireless connectivity will be made possible from any location in the world that is covered by a network of Bluetooth Access Points.
- The cost of communication is significantly lower than the cost of other contemporary types of wireless communication.
- There will be substantially lower levels of radiation.
- Avoiding interference from other electronic devices.
Weak transmission of signals :-
One of the way Bluetooth devices avoids interference with other system is by sending out very weak signal of 1 milliwatt. By comparison ,the most powerful cell phones can can transmit a signal of 3 watts.The low power limits the range of Bluetooth device to about 10 meters. Cutting the chances of interference between your computer system and your portable cell phone or television.
Even with the low power ,the walls in your house won’t stop a Bluetooth signal , from controlling several devices in different rooms.
Spread spectrum frequency hopping :-
With many different Bluetooth devices in a room , you might thing they would interfere with one another , but its unlikely that several devices will be on the same frequency at the same time because Bluetooth uses a technique called spread spectrum frequency hopping .
In this technique , a device will use 79 indivisual randomly chosen frequencies within a designated range, changing from one to another on a regular basis.In this case of Bluetooth , the transmitter change frequencies 1,600 times per second , meaning that more devices can make full use of limited size of the radio sprectrum , since every Bluetooth transmitter uses spread sprectrum transmitting automatically ,it’s unlikely that two transmitters will be on same frequency at the same time .The same technique will minimizes the risk that portable phones or baby monitors will disrupt Bluetooth devices since any interference on a particular frequency will last only a tiny fraction of second.
When a Bluetooth capable device come within the range of one another , an electronic conversation will take place to determine whether they have data to share or whether one need to control the other . the user doesn’t have to press a button or to give a command –
The electronic conversation happens automatically . once the conversation occurred , the device whether they are part of system , form a network .Bluetooth system creats a personal area network (PAN) or “piconet” that may fill a room or may encompass no more distance than that between the cell phone on a beltclip and the headset you are wearing . Once a piconet is established , the members randomly hope frequencies in unison so they stay in touch with one another and avoid other piconets that may be appearing in the same room.
APPLICATION EXAMPLES
A Bluetooth – mouse could be used at a further distance from a monitor, and while moving about in the room.
A Bluetooth – keyboard could be used further away from the monitor. This would reduce eye – strain for person for person who are long – sighted. Increasing the distance would also reduce exposure to electromagnetic radiation from the monitor.
A bluetooth – keyboard could also be used to address more than one computer, in a dynamic, switch less manner.
Use e-mail while your portable PC is still in the briefcase! When your portable PC receives an e-mail, you’ll an alert on your mobile phone . You can also browse all incoming e-mails and read those you select in the mobile phone’s display.
BLUETOOTH DEFINITIONSThere are 3 types of connections in Bluetooth, as shown to the right:
a) Single-slave
b) Multi-slave (up to 7 ”slaves” on one master)
c) Scatternet
Piconet:
A collection of devices connected via Bluetooth technology in an ad hoc fashion. A piconet starts with two connected devices, such as a portable PC and a mobile phone. The limit is set at 8 units in a piconet (that´s why the required address-space is limited to 3 bits). All Bluetooth devices are peer units and have identical implementations. However, when establishing a piconet, one unit will act as a master for synchonization purposes, and the other unit(s) will be slave(s) for the duration of the piconet connection.
Scatternet:
Two or more independent and non-synchronized piconets that communicate with each other. A slave as well as a master unit in one piconet can establish this connection by becoming a slave in the other piconet. It will then relay communications between the piconets, if the need arises. Master unit:
The device in a piconet whose clock and hopping sequence are used to synchronize all other devices in the piconet. The master also numbers the communication channels.
All devices in a piconet that are not the master (up to 7 active units for each master).
CONCLUSION:
Since the Bluetooth design is a collaboration effort between communication and computer companies it promises to be a new revolution in communication technology and a new era will witness advent of this technology as one of which takes communication to new heights. The groups working on Bluetooth includes IBM, Toshiba, Motorola, Palm etc.. Because of this the final design , Bluetooth provides flexibility that reaches beyond simply beings replacement of wires.
It is estimated that by the year 2006, 800 million devices will contain Bluetooth chips . As of today, teams of developers are creating the means by which these Bluetooth devices will enable users to communicate, and to work more efficiently, in a fascinating and interconnected world.
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