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Bluetooth

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  • Difficulty Level : Medium
  • Last Updated : 09 Jun, 2022
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It is a Wireless Personal Area Network (WPAN) technology and is used for exchanging data over smaller distances. This technology was invented by Ericson in 1994. It operates in the unlicensed, industrial, scientific and medical (ISM) band from 2.4 GHz to 2.485 GHz. Maximum devices that can be connected at the same time are 7. Bluetooth ranges up to 10 meters. It provides data rates up to 1 Mbps or 3 Mbps depending upon the version. The spreading technique that it uses is FHSS (Frequency-hopping spread spectrum). A Bluetooth network is called a piconet and a collection of interconnected piconets is called scatternet

Bluetooth Architecture: 

The architecture of Bluetooth defines two types of networks:

1. Piconet
2. Scatternet

Piconet:

Piconet is a type of Bluetooth network that contains one primary node called the master node and seven active secondary nodes called slave nodes. Thus, we can say that there is a total of 8 active nodes which are present at a distance of 10 meters. The communication between the primary and secondary nodes can be one-to-one or one-to-many. Possible communication is only between the master and slave; Slave-slave communication is not possible. It also has 255 parked nodes, these are secondary nodes and cannot take participation in communication unless it gets converted to the active state.

Scatternet:

It is formed by using various piconets. A slave that is present in one piconet can act as master or we can say primary in another piconet. This kind of node can receive a message from a master in one piconet and deliver the message to its slave in the other piconet where it is acting as a slave. This type of node is referred to as a bridge node. A station cannot be mastered in two piconets.

Bluetooth protocol stack: 

  1. Radio (RF) layer: It performs modulation/demodulation of the data into RF signals. It defines the physical characteristics of Bluetooth transceivers. It defines two types of physical links: connection-less and connection-oriented. 
     
  2. Baseband Link layer: The baseband is the digital engine of a Bluetooth system and is equivalent to the MAC sublayer in LANs.  It performs the connection establishment within a piconet. 
     
  3. Link Manager protocol layer: It performs the management of the already established links which includes authentication and encryption processes. It is responsible for creating the links, monitoring their health, and terminating them gracefully upon command or failure.
     
  4. Logical Link Control and Adaption Protocol layer: It is also known as the heart of the Bluetooth protocol stack. It allows the communication between upper and lower layers of the Bluetooth protocol stack. It packages the data packets received from upper layers into the form expected by lower layers. It also performs segmentation and multiplexing. 
     
  5. SDP layer: It is short for Service Discovery Protocol. It allows discovering the services available on another Bluetooth-enabled device. 
     
  6. RF comm layer: It is short for Radio Frontend Component. It provides a serial interface with WAP and OBEX. It also provides emulation of serial ports over the logical link control and adaption protocol(L2CAP). The protocol is based on the ETSI standard TS 07.10.
     
  7. OBEX: It is short for Object Exchange. It is a communication protocol to exchange objects between 2 devices. 
     
  8. WAP: It is short for Wireless Access Protocol. It is used for internet access. 
     
  9. TCS: It is short for Telephony Control Protocol. It provides telephony service. The basic function of this layer is call control (setup & release) and group management for gateway serving multiple devices.
     
  10. Application layer: It enables the user to interact with the application.

Advantage: 

  • Low cost.
  • Easy to use.
  • It can also penetrate through walls.
  • It creates an Adhoc connection immediately without any wires.
  • It is used for voice and data transfer.

Disadvantages:  

  • It can be hacked and hence, less secure.
  • It has a slow data transfer rate: of 3 Mbps.
  • It has a small range: 10 meters.

Applications:

  • Used in laptops, and in wireless PCs.
  • In printers.
  • In wireless headsets.
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