Link Budget Dimensioning
link budget dimensioning involves the coverage target parameters , signal propagation model ,and technical assumption.
in UMTS, the link budget situation gets more complex and iterative tool is needed to perform and estimate the expected cell radius. this is due to the fact that in CDMA , the cell radius depends on the traffic .
A link budget is conventionally performed for one mobile located at the edge of cell and there for transmitting at maximal.
first step we calculate the cable loss which containing feeder , jumper , cabinet and TMA losses which is constant for each uplink and downlink.
total line loss= jumper loss +TMA loss+ cabinet loss +number of connectors *0.5 + feeder loss.
1-process analysis
1.1 MAPL calculation:
+first step we calculate the cable loss which containing feeder , jumper , cabinet
and TMA losses which is constant for each uplink and downlink.
total line loss= jumper loss +TMA loss+ cabinet loss +number of connectors *0.5 + feeder loss.
+then find EIRP (effective isotropic radiated power
EIRP(DL)=Transmitted power-total line loss +antenna gain
EIRP(UL)= 21dB (CS) OR 23dB (PC)
which antenna gain depends on type of the antenna as discussed before also TX power is practically set to be 43dBm. and for UE it is equal to 23dB.
+then find processing gain
Processing gain=10 log (SF)
+then find SIR : this parameter depends on the value of Eb/N0 and type of area and services .
SIR (DL)=Eb/N0 -Processing gain
+choose values for noise figure =7 dB for DL and 2.3dB for UL
+RX sensitivity:
RX sensitivity =noise density +noise figure + 10 log (service rate ) + SIR
+Losses:
Ʃ Losses=total line loss +penetration loss + body loss
+margins :
Ʃ margins=Interference margins+ shadowing margins +1.9
+Gains :
Ʃ Gain=Antenna gain + TMA (UL only )+hand over gain (UL only ) +2
+MAPL :
we calculate the MAPL for both Uplink and Down link and choose the minimum value.
MAPL= TX power+Ʃ Gain+ Ʃ margins - Ʃ losses - RX sensitivity
