Trango Broadband Wireless Access5830™ User Manual
User Manual Rev 1
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seasonal density and moisture content of the plants, and other factors such as
wind may change the losses, care must be used when planning a link through
this type of environment.
FCC OET Bulletin 70 gives a generalized equation for foliage loss which is
presented here
as a guideline only. It is imperative to verify that the system
has sufficient fade margin for proper operation by conducting a field test
when non-LOS links are involved.
Loss = 0.2 F
0.3
x
R
0.6
Where:
F= Frequency in MHz
R= Depth of foliage transversed in meters
Example:
For 5.8 GHz and 10 meters of foliage depth (to estimate a typical distance of
aiming through several trees towards a tower):
Loss = 0.2 x 5800
0.3
x 10
0.6
= 10.7 dB
A fade margin of 12 dB in this case appears to be sufficient, but it is prudent to
add more fading margin (on the order of 10 dB) to account for other signal
losses and verify the RSSI/throughput performance at the customer premises.
This effectively reduces the range obtainable.
6.5.2.4.
Signal Loss due to Rain
At 5.8 GHz, attenuation due to rain is roughly .25 dB/km for a rain rate of 100
mm/hr and .60 dB/km for a rain rate of 150 mm/hr per FCC OET bulletin 70.
For a 10 mile link the total loss would be :
For a 100mm/hr rain event, Loss = 0.25 dB/km X 1 km/0.6mile x 10 miles =
4.16 dB
For a 150mm/hr rain event, Loss = 0.60 dB/km X 1 km/0.6mile x 10 miles =
10.0 dB
6.6.
Availability
Availability of the link represents the percentage of the time that the link is
working at or below a given bit error rate (BER). The table below shows the
