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written 5.8 years ago by
teamques10
★ 69k
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modified 2.9 years ago
by
RakeshBhuse
• 3.2k
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Wireless communication uses atmosphere as the communication channel, in this the interference and propagation are largely dictated by the transmission frequency.
Any modulation scheme can be used but to avoid interference, certain regulations and standards need to be followed wrt:
1] Modulation type.
2] BW
3] Power.
The ITU, based in Geneva, agency of UN, looks after the regulations and EM spectrum allocation all over the world.
ITU-T examines technical operations and traffic while ITU:R looks after frequency assignment and efficient spectrum utilization.
The most commonly used frequencies lie from 30Hz to 30GHz.
Different bonds are utilized for different purposes.
Example: 300 MHz - 3 GHz $\rightarrow$ can be used for TV Transmission, Bluetooth, Wi-fi, etc.
| Frequency band | Wave length |
|---|---|
| 30 Hz - 300 Hz (ELF) | $10^4$ to $10^3$ Km |
| 300 Hz - 3 KHz (U F) | $10^3$ to $10^2$ Km |
| 3 kHz - 30 KHz (MF) | 100 to 10 Km |
| 30KHz - 300KHz (HF) | 10Km to 1Km |
| 300 kHz - 3MHz (VHF) | 1Km to 100 m |
| 3 MHz - 30 MHz | 100m to 10m |
| 30 MHz - 300 MHz | 10 m to 1m |
| 300 MHz - 3 GHz | 1m to 10cm |
| 3GHz - 30GHz | $10^{-1m}$ to $10^{2m}$ |
| 30 GHz - 300 GHz | $10^{-2m}$ to $10^{3m}$ |