UMTS Sensitivity

by Kamal Vij

Quite often when someone has worked with 2G for a while, his mind starts relating all radio issues to RxLev (dBm) of the BCCH Channel.

In 3G, BCCH is purely used to carry the Cell Specific System Information in he form of SIBs. The RF signal strength is measured using CPICH power.

For calculating the Sensitivity, we will stick to the basic formula :

Rx Sensitivity = Thermal Noise + NF (of Receiver) + SNR required 






  • Thermal Noise = Botlzman’s Costant (Joules/kelvin) * Temp (Kelvin) * BW (Hz)
  • Where  Botlzman’s Costant  = 1.38E-23 J/K
  • where Temp is temperature of the environment  (in Kelvin)
  • Frequency part is different in GSM and UMTS.  In GSM everything  happens in 200 KHz, whereas in 3G Noise is measured over the efffective BW of 3.84 MHz. 





Thermal Noise  in 2G :  -120 dBm 





Thermal Noise  in 3G :  -108 dBm