LANCOM OAP
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54 Wireless and LANCOM OAP
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310agn Wireless
Chapter 5: Advanced wireless LAN configuration
67
EN
R = 0.5 *
√
(
λ
* d)
The wavelength in the 2.4 GHz band is approx. 0.125 m, in the 5 GHz band
approx. 0.05 m.
Example:
With a separating distance of 4 km between the two antennae, the
radius of Fresnel zone 1 in the 2.4-GHz band is
11 m
, in the 5-GHz band
7 m
.
To ensure that the Fresnel zone 1 remains unobstructed, the height of the
antennas must exceed that of the highest obstruction by this radius. The full
height of the antenna mast (M) should be as depicted:
M = R + 1m + H + E (earth's curvature)
The allowance for the curvature of the earth (E) can be calculated at a distance
(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
.
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 regar-
ding maximum transmission power should not be exceeded.
The calculation of effective power considers everything from the radio module
in the transmitting access point to the radio module in the receiving access
point. In between there are attenuating elements such as the cable, plug con-
nections or simply the air transmitting the signals and amplifying elements
such as the external antennas.
WLAN Router
ANTENNA
ADMINISTRATION
WLAN Router
ANTENNA
PRODUCTION
OBSTRUCTION
Fresnel zone 1
Radius R
Security: 1m
Obstruction height H
Earth's curvature E
