Moxa ANT-WSB-ANM-05 Manuel D’Utilisation
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Understanding Industrial WLAN – IEEE 802.11
Setting Up Point-to-Point Connections
This sector introduces the basic principles involved in designing point-to-point links and provides tips on
aligning the antennas.
aligning the antennas.
The following basic questions must be answered when designing long range wireless links:
• What antennas are required for the desired application?
• How must the antennas be positioned to ensure a problem-free connection?
• What performance characteristics do the antennas need to ensure sufficient data throughput within the
legal limits?
MOXA Antenna Calculator
You can use the Moxa Antenna Calculator to calculate the
output power of the access points as well as the achievable
distances and data rates. The program can be used from our
website at
output power of the access points as well as the achievable
distances and data rates. The program can be used from our
website at
www.moxa.com/Event/IW/2009/Industrial_Wireless_
Typology/index.htm
After selecting your components (access points, antennas,
cable, etc.) the calculator works out the data rates, ranges,
and the antenna gain settings that have to be entered into the
access point.
cable, etc.) the calculator works out the data rates, ranges,
and the antenna gain settings that have to be entered into the
access point.
Positioning the Antennas
Antennas do not broadcast their signals linearly, but within an angle that depends on the model in question.
The spherical expansion of the signal waves results in amplification of or interference to the effective power
output at certain intervals of the connection between the transmitter and receiver.
The spherical expansion of the signal waves results in amplification of or interference to the effective power
output at certain intervals of the connection between the transmitter and receiver.
The Fresnel Zone must remain free from obstruction in order to ensure that the maximum level of output
from the transmitting antenna reaches the receiving antenna. Any obstructing element protruding into this
zone will significantly impair the effective signal power. The object not only screens off a portion of the
Fresnel Zone, but the resulting reflections also lead to a significant reduction in signal reception.
from the transmitting antenna reaches the receiving antenna. Any obstructing element protruding into this
zone will significantly impair the effective signal power. The object not only screens off a portion of the
Fresnel Zone, but the resulting reflections also lead to a significant reduction in signal reception.
The concept of RF LOS is based on a parabolic free space zone called the Fresnel Zone that will ensure a
more stable link if at least 60% of the vertical radius is kept obstacle free. The figure below shows how to
estimate the Fresnel Zone of a wireless link where
more stable link if at least 60% of the vertical radius is kept obstacle free. The figure below shows how to
estimate the Fresnel Zone of a wireless link where
r (meter) is the vertical radius of the oval, d (km) is the
distance between the transceivers, and
f (GHz) is the radio frequency.