Bluetooth Technology

Bluetooth offer low bandwidth wireless connections to become so simple to use that they can easily integrate into daily life. This provides wireless connection between the Internet and other connecting devices. Bluetooth operates on global radio-frequency standards, which works at frequency 2.4 GHz ISM band and provide license-free operation in the United States and other countries. The support of Bluetooth wireless technology within the Bluetooth Special Interest Group and in the user community is provided by 9 Promoter companies: 3Com, Microsoft, Motorola, IBM, Lucent, Ericsson, Intel, Nokia, and Toshiba.

Bluetooth devices operate in a range of about 10 meters. The communication channel support data means asynchronous and voice means synchronous communications with a bandwidth of 1 Mb/sec.

At fixed intervals, the synchronous voice channels are provided using circuit switching with a slot reservation. A synchronous link is called as synchronous connection-oriented link. By using packet switching the asynchronous data channels utilizing polling access scheme. An asynchronous link is called as an asynchronous connection-less link. A packet containing data-voice synchronous combination is also defined. This provides 64 kb/sec voice and 64 kb/sec data in bi-direction.

How does it work?
Bluetooth technology works with radio signals over short distances. The BlueSpace software formulates it all very easy on a VAIO computer. Bluetooth software is specially designed for CLIÉ and Sony Ericsson mobile phones. BlueSpace is unique Sony software, which allows VAIO computer to connect to other Bluetooth devices.
With BlueSpace software following tasks can be performed:
1)It provides Connection to other Bluetooth devices.
2)It checks the status of the connections and seeing an overview of the Bluetooth services.
3)It launches certain applications automatically when connected to other Bluetooth devices.
4)It connects automatically with communication devices when Bluetooth is started.
5)BlueSpace is delivered as standard only on VAIO computers with extended Bluetooth functionality.
6)Its services include file transfer, remotely capturing pictures, image transfer and so on.

For all Sony Bluetooth enabled devices wireless connection takes place in three steps:
1.It performs a device discovery to search for other Bluetooth-enabled devices within radio range.
2.It selects device and then perform a service discovery to search for available services or applications.
3.It establishes a connection with the device by selecting the required service or application.

Protocol Architecture

Bluetooth is a layered protocol architecture consisting of core protocols, cable replacement, telephony control protocols and adopted protocols.

The core protocols consisting of the following elements:
1) Radio:
It lists details of the air interface including frequency, the use of frequency hopping, modulation scheme and transmit power.

2) Baseband
It deals with connection establishment within a piconet, addressing, packet format, timing and power control.

3) Link manager protocol (LMP)
It setup the link between Bluetooth devices and ongoing link management. This protocol includes security parts such as authentication and encryption plus the control and negotiation of Baseband packet sizes.

4) Logical link control and adaptation protocol (L2CAP)
It maintains upper-layer protocols of the Baseband layer. L2CAP provides connectionless as well as connection-oriented services.

5) Service discovery protocol (SDP)
It gives detail device information, services and the characteristics of the services that can be required to enable the establishment of a connection between two or more Bluetooth devices.

Cable Replacement Protocol
In the Bluetooth specification RFCOMM is the cable replacement protocol. RFCOMM represents a virtual serial port, which makes replacement of cable technologies as transparent as possible. Serial ports communications interfaces are one of the most common types used with computing and communications devices. Hence, RFCOMM provides the replacement of serial port cables with the minimum adjustment of existing devices. RFCOMM provides binary data transportation and emulates EIA-232 control signals over the Bluetooth Baseband layer. EIA-232 (RS-232) is a widely used for serial port interface.

Telephony Control Protocols
Bluetooth also defines a telephony control protocol. TCS BIN (telephony control specification—binary) is a bit-oriented protocol, which specifies call control signaling for the establishment of voice and data calls between Bluetooth devices. It also manages mobility procedures for handling groups of Bluetooth TCS devices.

Adopted Protocols
Adopted protocols are specified in definitions issued by other standards making organizations into the overall Bluetooth architecture. The Bluetooth policy is to invent only necessary protocols and use existing standards whenever possible. Following are the adopted protocols:
a)PPP - The point-to-point protocol is an Internet protocol used for transporting IP datagram over a point-to-point link.
b)TCP/UDP/IP - These are the basic protocols of the TCP/IP protocol suite.
c)OBEX - The object exchange protocol is a session protocol for the exchange of objects developed by the Infrared Data Association (IrDA). OBEX offers functionality similar to that of HTTP. Its model is used for representing objects and operations.
d)WAE/WAP - Bluetooth includes the wireless application environment and wireless application protocol into its architecture.

Usage Models
In Bluetooth profile documents number of usage models are defined. A usage model is a protocol set which implement a particular Bluetooth based application. Each profile specifies the protocols and protocol features supporting to particular usage model. Following are the some usage models:
1)File transfer - The file transfer usage model includes the transfer of directories, files, documents, images and streaming media formats. This usage model also includes the capability to browse certain information on a remote device.
2)Internet Bridge – By using this usage model, a PC is wirelessly connected to a mobile phone to provide dial-up networking and fax capabilities.
3)LAN access - This usage model enables devices to access a LAN on a piconet. Once connected, a device works like as it were directly connected to the LAN.
4)Synchronization - This model provides a synchronization of device-to-device personal information management information such as calendar, phone book, message and note information.
5)Three-in-one phone - Telephone handsets implement this usage model act as a cordless phone connecting to a voice base station as an intercom device for connecting to other telephones and as a cellular phone;
6)Headset - The headset operate as a remote device's audio input and output interface.

Bluetooth Applications
Bluetooth is designed to work in many users environment. Up to eight devices can communicate in a small network is known as a piconet. Ten of these piconets coexist in the same coverage range of the Bluetooth radio signals. In order to provide security, each link is encoded and protected against eavesdropping and interference.

Bluetooth provides support following general application areas using short-range wireless connectivity:
1) Data and voice access points
Bluetooth provides real-time data and transmissions by providing effortless wireless connection of portable and stationary communications devices.

2) Cable replacement
Bluetooth eliminates the need cable requirements for connection of practically any kind of communications device. Connections are maintained even when devices are not within line of sight. The range of each radio signal is approximately 10 m but can be extended to 100 m with an amplifier.

3) Ad hoc networking
A device with a Bluetooth radio signal can establish connection to another Bluetooth radio as soon as it comes into range.

Conclusion
Bluetooth specifications are real and adopted by industry leaders. All the Bluetooth enabled devices communicate with each another and with no compatibility problems in hardware. Bluetooth technology operates best for all independent products such as a phone or a printer.