As to the GSM1800 system:：
PL(dB) =32.45+20lg(1800)+20lgd(km)= 97.5+20lgd(km)
D 1m 10m 20m 25m 30m 35m 40m
Ls 37 57 63 65 67 68 69
For In-building signal, GrenTech experienced Formula is as follow:
L=LD+10LgD (m) + FAF
Here, the FAF means the loss led by the internal obstruction; the experienced value is as follow
FAF 900MHz 1800MHz
Wood Board 5～6Db 6～8dB
Glass 7～8dB 8～10dB
Brick Wall 10～12dB 14～16dB
Concrete Wall 15-20dB 20-25dB
Elevators 30-40dB 35-40dB
Supposed
The output power of the antennas for GSM1800 P0=10dBm
The gain of omni antenna G0=3dBi, the FAF of the wall is about 20dB,
L (20m) =63+10lgD (m) +FAF
=63+13+20=96
So the RSSI=P0+G0-L=10+3-96=-83 (dBm)