Wireless LAN – WLAN
112
3.8
Establishing outdoor wireless networks
BAT54-Rail/F..
Release
7.54
06/08
3.8 Establishing outdoor wireless
networks
BAT access points in combination with appropriate external antennae are
ideally suited to establishing point-to-point wireless connections to other ac-
cess points.
There are two main questions to be answered when setting up the wireless
connection:
D How should the antennae be positioned to ensure a problem-free connec-
tion?
D What performance characteristics do the antennae need to ensure suffi-
cient data rates within legal limitations?
3.8.1 Geometrical layout of the transmission path
Antennae do not emit their signals linearly, but within an angle that depends
on the model in question. The spherical expansion of the signal waves is
characterized by constructive and destructive interference between these
waves at certain distances perpendicular to the line of sight between trans-
mitter and receiver. The areas where the waves amplify or cancel them-
selves out are known as Fresnel zones.
WLAN Router
ANTENNA
ADMINISTRATION
ACCESS POINT
ANTENNA
PRODUCTION
SA-5L SA-5L
Free-space loss
Amplification with antenna
gain
Output power of the ra-
dio module
Loss through ca-
ble, plugs and light-
ning protection
Amplification with antenna
gain
Input signal at the ra-
dio module
Loss through cable,
plugs and lightning
protection
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