User Manual
MN021-01
Page 26 of 28
24.3. Antennas Positioning
Starting with the parameters determined as defined above, the number of radiating points can
be defined. The calculations needed can be implemented in a tool. The number of carriers is
used to define the TFA/TFAF RF Output Power (P
OUT TFA
in
Figure 18) according to the table in Appendix C. As a rule of thumb, the power values for a
double number of carriers is obtained reducing the Power value of 3dB.
Figure 18 Diagram for Power Calculations
According to line-of-sight conditions, the calculation of the maximum coverage distance is
performed using the Free-space propagation formula. This formula is adapted to propagation in
indoor environments introducing an appropriate propagation index and including margin against
fading.
24.3.1. EIRP calculation:
][_][][][ ][ dBCableRFdBSplitterdBiyDirectivitdBmTFAFOUTdBm
AAGPEIRP −−+=
where;
P
OUT TFAF
= Remote Unit RF connector Output Power;
G
Directivity
= Directivity Gain of the Antenna;
A
Splitter
= Splitter Insertion loss;
A
RF_Cable
= RF Cable Loss.
24.3.2. Max Coverage Distance Calculation:
PL
dBmRxdBWallsdBdBm
Exp
PAMFEIRP
m
mto_Prx_min
DistanceMax
1
10
][
][
)10(
4
_
]min[_][][][
−−−
⋅=
π
λ
wher
e;
MF = Margin against Fading;
A
Walls
= Walls supplementary Attenuation;
P
Rx-min
= Minimum Required Power Level;
Exp
PL
= Path Loss Exponent (propagation index);
λ
= Wavelength.
The results can detailed for different Remote Unit configuration (splitter insertion loss, RF cable
length, additional attenuation e.g. walls).
ü Depending on the number of RF carriers, the antenna type and the RF cables type, the maximum distance that the
system is able to perform is estimated. This calculation is used to plan antenna positioning so that the project
requirement (Minimum Down Link Power Level) is met.
ü Technical Suggestion: The design is an iteration process so it’s advisable to start from the hypothesis that the
Cable Loss and the Antenna Gain compensate each other and consequently the EIRP is equal to the TFA Output
Power. To reach a good coverage, a target is to choose the antenna positioning in order to maximize Line of Sight.
TFA
Fiber
Remote
Unit
TFAF
Fiber
Remote
Unit
TFLF
Fiber
Donor
Unit
P
OUT TFAF
RF Cable
Loss
Antenna
Gain
P
IN TFLF