Explain the bands in cellular telephony.

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 Solution :-

Cellular telephony uses Analog transmission. Frequency modulation is used for communication between the mobile phone and the cell office. Two frequency bands are allocated for this purpose:

i. Communication that is initiated by the mobile phone.

ii. Communication that is initiated by landline phone.

  • Full duplex operation is possible by separating transmit and receive signals into separate frequency bands.
  • Cellular phone units transmit in the lower band of frequencies, 825 to 845 MHz, and receive in the higher band, 870 to 890 MHz
  • Within these two bands, 666 separate channels (333 channels per band) have been assigned for voice and control. 
  • Each channel requires a full-duplex dialog.
  • For preventing interference, adjacent channels are rarely allocated.
  • Some channels are also required for control purpose.
  • This reduces the number of channels available for the cell.
  • Each channel occupies a bandwidth of 30 kHz.



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