Bluetooth

Bluetooth is universal for short-range wireless voice and data communication. 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. 

What is Bluetooth?

Bluetooth simply follows the principle of transmitting and receiving data using radio waves. It can be paired with the other device which has also Bluetooth but it should be within the estimated communication range to connect. When two devices start to share data, they form a network called piconet which can further accommodate more than five devices.

Points to remember for Bluetooth:

• Bluetooth Transmission capacity 720 kbps.
• Bluetooth is Wireless.
• Bluetooth is a Low-cost short-distance radio communications standard.
• Bluetooth is robust and flexible.
• Bluetooth is cable replacement technology that can be used to connect almost any device to any other device.
• The basic architecture unit of Bluetooth is a piconet.

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 master. 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 specifies the details of the air interface, including frequency, the use of frequency hopping and transmit power. 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, addressing, packet format, timing and power control. 
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 (L2CAP) 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. Service Discovery Protocol (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 a cabal replacement protocol. 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 the gateway serving multiple devices.
   
10. Application layer: It enables the user to interact with the application.

Types of Bluetooth

Various types of Bluetooth are available in the market nowadays. Let us look at them.

• In-Car Headset: One can make calls from the car speaker system without the use of mobile phones.
• Stereo Headset: To listen to music in car or in music players at home.
• Webcam: One can link the camera with the help of Bluetooth with their laptop or phone.
• Bluetooth-equipped Printer: The printer can be used when connected via Bluetooth with mobile phone or laptop.
• Bluetooth Global Positioning System (GPS): To use GPS in cars, one can connect their phone with car system via Bluetooth to fetch the directions of the address.

Advantage: 

• It is a low-cost and easy-to-use device.
• It can also penetrate through walls.
• It creates an Ad-hoc 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.
• Bluetooth communication does not support routing.
• The issues of handoffs have not been addressed.

Applications:

• It can be used in laptops, and in wireless PCs, printers.
• It can be used in wireless headsets, wireless PANs, and LANs.
• It can connect a digital camera wirelessly to a mobile phone.
• It can transfer data in terms of videos, songs, photographs, or files from one cell phone to another cell phone or computer.
• It is used in the sectors of Medical health care, sports and fitness, Military. 

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