1) Start with the name. Bluetooth got its name from a Danish king! A king called Harald Blåtand (which is Bluetooth when anglicised-converted to English) who united Denmark and a part of Norway into a single kingdom. Bluetooth technology can now be thought as to unite two electronic devices.
Some really cool myths-
- The king wore a blue crown.
- The founders wrote notes with blue ink.
- It sends out waves of “blue” frequency.
2) Bluetooth uses the ISM(industrial, scientific and medical) band which are reserved for scientific and medical purposes-and are not supposed to be used for communication. In this band, it occupies the frequency range 2402-2480 MHz. Wi-Fi also uses the ISM band.
3) Bluetooth can connect up to 8 devices at a time without any interference. This is possible because Bluetooth makes use of FHSS-which stands for Frequency Hopping Spread Spectrum.
In this method of transmitting radio signals, the carrier is switched rapidly amongst multiple frequency channels.
So there’s hardly a chance that two devices will be transmitting signals at the same frequency. Even if they do-they do it only for a very short instant as the frequency is continuously hopping/changing values. Also, The device sending the information(master) switches between the receivers(slave devices) using a kind of Round Robin scheme.
4) Now comes the reason for Bluetooth’s short range. The usual Bluetooth devices work in about 10 m or 32 feet. It’s short range comes from the fact that it sends out signals of low Power(about 1 mW-goes to a limit of 3 mW). And the reason for using low power signals is to avoid interference with other signals using the ISM band.
5) Bluetooth uses a combination of modulation processes. By far, the most favorable modulation for Bluetooth transmission is Frequency Shift Keying(FSK). FSK identifies a positive deviation from the center frequency representing a binary one and a negative deviation from the center frequency representing a zero. The image below illustrates the method.
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