simply BLUETOOTH

I think all of us the readers of this blog are already famliar with bluetooth technology. We must have used it in various electronics equipments like cell-phones, laptops, cameras, bluetooth headset, Wireless sets and also in some wireless keyboards and mouses too. We all know that bluetooth is very useful mean of data communication for short range and is very useful in portable devices. Then what actually is this Bluetooth? How does it transfers data then?? Lets have a look…

Bluetooth is a proprietary open wireless technology standard for interchanging data over short range of distance from fixed and mobile devices, creating Personal Area Network (PAN) with high level of security. It was originally created in 1994 by Telecom Vendor “Ericsson” as an alternate to RS-232 device.(RS-232 is the traditional name for a series of standards for serial binary single-ended data and control signals connecting between a DTE (Data Terminal Equipment) and a DCE (Data Circuit terminating Equipment)) But since 1998, it is managed by Bluetooth Special Interest Group (SIG). SIG has more than 15,000 member companies in the areas of telecommunication, computing, networking, and consumer electronics.Bluetooth is designed in such a way that it can be used by general public. Design-wise, the three main goals for Bluetooth were: small size, minimal power consumption, and low price. The technology was designed to be simple, and the target was to have it become a de facto standard in wireless connectivity. Bluetooth is available in several version according to its speed of Data transfer.

Bluetooth V 1.0

1. Bluetooth v 1.0 and v 1.1 : This were early versions wit lots of bugs in it. Thus this is no more available.
2. Bluetooth v 1.2 : This transfers data at the rate of 1 Mbps (theoretically) and 712 Kbps practically. This is back compatible with v 1.1 and also has improved resistance to Radio frequency Interference.
3. Bluetooth v 2.0 : The main achievement is the introduction of an Enhanced Data Rate (EDR) in this version. This made the transfer rate rise up to 3 Mbps.
4. Bluetooth v 2.1 : This version is a little improved version of v 2.0 and too had EDR, and is also fully backward compatible with v 1.2. It also introduced Extended inquiry response (EIR), which provides more information during the inquiry procedure to allow better filtering of devices before connection. but the speed is fairly similar as of v 2.0.
5. Bluetooth v 3.0 : Bluetooth 3.0 supports theoretical data transfer speeds of up to 24 Mbps as it is introduced as HS(High Speed) version.
6. Bluetooth v 4.0 : The Bluetooth SIG completed the Bluetooth Core Specification version 4.0, which includes Classic Bluetooth, Bluetooth high speed and Bluetooth low energy protocols. Bluetooth high speed is based on Wi-Fi, and Classic Bluetooth consists of legacy Bluetooth protocols. This version has been adopted as of June 30, 2010.

Block Diagram:

Figure 1: Block Diagram of Bluetooth system

Bluetooth Radio: Its main function is to transmit and receive data.

Link Controller: It sends and receives data, identifies the sending device, performs authentication etc

Link Manager: It manages the activity of link controller.

Bluetooth communicates via low power radio waves on a frequency of 2.4GHz to 2.48GHz. The range of Bluetooth depends on the power class of of the radio used. Mailnly, there are three class of bluetooth radio.

• Class 1: Range upto 100 metres
  
• Class 2: Range upto 10 metres
• Class 3: Range upto 1 metre

Most of the devices found around us in mobile equipments uses class 2 bluetooth radio. 

How does it works then?? 

Bluetooth is packet based protocol with master slave structure.  When a device comes within the range of another, the device automatically converses and form a network. The PAN(Personal Area Network) of bluetooth is known as Piconet. The connection initiating device is considered as master and another as slave. A master can communicate with 7 other devices at a time. Once piconet is established, the members hop(transmission of packets of data in different frequencies) in unison and each other are synchronized with each other. Normally in most of the countries hopping is possible in 79 different frequency channels. Since one device can participate in several piconets i.e. being a slave in one and master in another, interlacing of pattern occurs. This is known as Scatternet. A scatternet supports upto 10 diffferent piconets to be connected at time. 

 Figure 2: Bluetooth piconet and scatternet scenarios:

                                      a) Point-to-point connection between two devices.
                                      b) Point-to-multipoint connection between a master and three slaves.
                                      c) Scatternet that consists of three piconets.

How Bluetooth connection occurs??

Bluetooth connection strictly follows a series of steps to ensure high security in data transmission.

• Initially, the device stays in passive state i.e. being connected with network but  without any activity.
• The master sends an enquiry request to all the devices. the devices respond with their address.
• The master chooses a device and synchronises with access point in clock and frequency.
• A link is estalished and master enters the access point using Service Discovery Protocol.(SDP).
• Master device creates channel with that access point.
• Sometimes for security, pairing is performed in order to restrict accessto authorised uses only by using an encrypted key called Personal Identification Number(PIN). 

Applications:

 Based upon usage model for bluetooth technology to facilitate its applications, several profiles are created so hat communication takes place smoothly. some such profiles are Headset Profile(HSP), Human Interface Device Profile(HID), File Transfer Profile(FTP), Audio/Video Remote Control Profile(AVRCP) etc. Some other applications are:

• Data communication between Cell phones 
• Data communication between PC to PC 
• Wireless Controls
• Short range Networking  

Advantages :

• Simple and secure connection
• no effect of noise
• highly secure for privacy concerns
• reliable
• easy to set up in small size products
• economical
• minimal power consuming

This was all that I could share with you. Hope you understood this technology. For futher more about it you may comment or may personally mail me. I'm always there to help you.So lets start exploring more about it and to the Engineering friends who are planning to use bluetooth in your project work, I wish you all the best for your success.

References:

http://en.wikipedia.org/wiki/Bluetooth

http://www.forums.nokia.com/