Wireless LAN – WLAN
BAT54-Rail/F..
Release
7.54
06/08
3.7
IEEE 802.11i for point-to-point connections
111
M = R + 1m + H + E (earth's curvature)
The allowance for the curvature of the earth (E) can be calculated at a dis-
tance (d) as E = d² * 0.0147 – i.e. at a distance of 8 km this is almost 1m
Example: With a distance of 8 km between the antennae, the result in the
2.4-GHz band is a mast height above the level of the highest obstruction of
approx. 13 m, in the 5-GHz band 9 m.
U Antenna power
The power of the antennas must be high enough to ensure acceptable data
transfer rates. On the other hand, the country-specific legal regulations re-
garding maximum transmission power should not be exceeded.
The calculation of effective power considers everything from the radio mod-
ule in the transmitting access point to the radio module in the receiving ac-
cess point. In between there are attenuating elements such as the cable, plug
connections or simply the air transmitting the signals and amplifying ele-
ments such as the external antennas.
WLAN Router
ANTENNA
ADMINISTRATION
WLAN Router
ANTENNA
PRODUCTION
OBSTRUCTION
Fresnel zone 1
Radius R
Safety: 1m
Obstruction height H
Earth's curvature E
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