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BLUETOOTH

By

 PALLABI   SARKAR

  Electronics & Communication Engineering Department
  Asansol Engineering College
  Kanyapur, Sen Raleigh Road, Asansol 713304, Burdwan, India

 

INTRODUCTION
Unifying telecom and computing industries is the basic reason behind the concept of the Bluetooth. Wireless connections between devices like mobile phones, desktop or notebook computers thatís without any cable are made possible with the concept of Bluetooth. Devices which carry Bluetooth enabled chips, can transfer data at a pace of 720 Kbps within 50 meters(150 feet) of range or even beyond through walls, clothing and even luggage bags or thin sheets as such.
BLUETOOTH PROTOCOL
The Bluetooth radio system which is built into a small microchip  operates in a frequency band available globally. This ensures worldwide interoperability. A collection and combination of several protocols is what constitutes a Bluetooth protocol. Most of the Bluetooth devicesrequire:
        The Bluetooth Core protocols and
        The Bluetooth radio protocols  
BLUETOOTH PROTOCOL STACK
Bluetooth protocol stack is a combination of multiple application specific stacks. Several applications run over many vertical layers from this stack. The Bluetooth protocol stack is partitioned into layers according to their functions. These are described as follows:
Base band: The physical RF link between Bluetooth units forming a piconet is enabled by the Baseband and the Link Control layer. The transmission with different Bluetooth devices is synchronized using inquiry and paging procedures. This layer enables this action.
Link Manager Protocol (LMP): LMP indulges itself in message exchange when two Bluetooth devices come within each othersís radio range. Each device possess a link manager which then discovers each other and the LMP does itís task. These messages can perform several security functions like encryption, authentication etc. LMP also performs several other functions like:
        The LMP controls the power modes
        Duty cycles of Bluetooth devices are controlled
        The connection state is also controlled by LMP
Logical Link Control and Adaptation Protocol (L2CAP): The segmentation of large packets and the reassembly of the corresponding fragmented packets is done in this layer. Multiplexing of Bluetooth packets from different applications also takes place in this layer.
Service Discovery Protocol (SDP): A Bluetooth device is enabled to join a piconet using SDP. This protocol helps a device inquire about the services available in a piconet and methodologies of accessing them.
Cable Replacement Protocol: This protocol helps in Radio Frequency Communication (RFCOMM) which is a serial line communication protocol.The ďcablereplacementĒ protocol emulates RS-232 control and data signals over Bluetooth baseband protocol.
Telephony Control Specification Binary: This is a bit- oriented protocol. It helps in defining the call control signaling protocol which is used for:
     set up of speech between Bluetooth devices
     data calls between Bluetooth devices.
AT-Commands: This  protocol defines commands by means of which mobile phones can be used and controlled for fax and data transfer.
TCP/IP: This protocol is mainly used for communication through Internet. TCP/IP finds use in printers and mobile handsets also.
PPP: Point to point connections is mainly accomplished by PPP which is over RFCOMM. 
Obex Protocol: This is a session protocol mainly established to exchange objects.  
Content Formats: The format of electronic business card and personal calendar entries developed by the Versit consortium is defined by the specifications of vCard and vCalendar.