Saturday, July 12, 2008

Learn Bluetooth in ONE Minute?

Dad ! What is Bluetooth?

Dad, Where Bluetooth technology is used?

"A cordless Mouse communicates with its PC using Bluetooth.

Cordless Keyboard to PC communication is through bluetooth.

Cordless Headset to the Mobile Phone is through Bluetooth.

PenDrive to PC can be Bluetooth."

Dad, What are all the important points I should remember, if the exam question is "Write a short note on Bluetooth"?

Dad : 1) Bluetooth is the name of a King who lived in Denmark.

2) It uses Radio Frequency of 2.4GHz ISM band

3) It uses Gaussian FSK Modulation technique ( in Version.1)

4) It uses Fast Frequncy-Hopping Spread Spectrum (Fast FHSS).

5) The speed of version.1 is 1 Mbps. Version 2 has 3 Mbps speed.

6) Effective distance is 10 meters.

7) Data is transmitted in packets during time slots which are of fixed duration.

8) Security :FHSS allows only the synchronized receivers to receive the data.

In addition, it uses 128 bit encryption of data.

9) Using Bluetooth,you can connect a computer to a Printer,Fax,Headset,Mobile phone,Camera,Mouse,etc.

10. It is Personal Area Network(PAN).

11) IEEE standard is 802.15

Johny : What is Frequency Hopping?

Dad : Hopping means Jumping. Let us see an example. Radio Mirchi FM is trasmitting at 98.3MHz. Just imagine, For every five seconds, if its frequency is changing between 98.3 and 99.3 MHz, then how will you listen to the songs. You have to change or hop between these frequencies every five seconds. In case of Bluetooth, the information is transmitted in different frequencies by such method. The receiver is synchronized for the same pattern.

Johny: How many times it will HOP in a second?

Dad: 1600 times per second. The hoppings per second is very high. Hence Bluetooth is NOT a NORMAL frequency Hopping; but a FAST Frequency Hoping Technique.

Johny: In the Mirchi example, it was jumping between two frequencies. In case of Bluetooth, how many frequencies are used?

79 frequencies. So, the message transmitted is SPREAD across a wide range of frequencies. That is why it is called as SPREAD spectrum.

Johny: OK OK OK. Now I understand, why they are calling this transmission as FFHSS (Fast Frequency Hopping Spread Spectrum)

But Dad, What is the Advantage of these frequency jumpings?

Dad: Only the receiver knowing the 'pseudo random pattern of frequency change' will receive the data. So it is a kind of security.

Johny : What is ISM band?

Dad : ISM band means Industrial,Scientific and Medical Frequency Band. You need not get license from the Government for using these frequencies. 2450 and 5800 MHz are commonly used ISM Band frequencies.

Johny: What is PAN?

Dad: PAN stands for Personal Area Network. A PAN can be either a PICONET or SCATTERNET. A piconet will be having only one Master and upto 7 slaves. If there are more than 7 slaves, the rest of slaves must be PARKED. To activate a parked slave, a currently active slave should be parked.

Johny: I dont Understand Parking. Can you explain with an example?

Dad: Suppose, you go to a Hotel. There are only 7 seats. All seats are occupied. The watchman asks to WAIT IN THE WAITING ROOM till some seat becomes vacant. This WAITING is called as parking. So you are PARKED now.

This watchman is so clever. He watches these 7 people continuously. If he found anyone is simply sitting idle, he shifts him to the waiting room and gives you that seat..

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