FAQ (Frequently Asked Questions)
1. What is the maximum number of Ethernet devices that can
transmit across the link?
There is no limit to the number of client devices whose Ethernet traffic can be
transported. The WIRELESS DOME supports an unlimited number of MAC addresses
across the link.
2. Does you product have an IP address or MAC address?
The WIRELESS Pair has no MAC address, no IP address and no web interface. It
operates in place of a wire to send Ethernet traffic across the RF link in both directions.
3. What is the recommended antenna polarity?
Videolarm generally recommends horizontal polarization for most applications.
Most jamming noise sources in or near 900Mhz utilize vertical polarization. Our
experience indicates that successful installations often perform better with horizontal
polarization. The WIRELESS DOME will support horizontal and vertical installations
(the wall mount bracket does not currently support horizontal installation but can be
easily modified to enable horizontal polarization).
4. How do I use the Site Survey Mode to fine-tune the radio performance?
Radio noise is always a challenge for wireless systems, particularly those in unlicensed
bands. The WIRELESS Master has a built in site survey mode that allows the installer to
manually select any of the 12 channels and evaluate the link performance by reading
the LED link quality display. This mode sends simulated Ethernet traffic over the radio
link and reports the bit error rate (BER). This can be used to assist in the alignment
of antennas or to determine if there are in band or adjacent band interferers. The link
performance may show reduced link quality on channels 1 or 12 due to adjacent
channel noise. Under normal operation the WIRELESS Master automatically chooses a
channel with Strong link quality and will avoid channels that have poor performance.
5. Does your product include network-based management tools?
The WIRELESS Dome has built-in intelligent frequency agility. Upon receiving RF
interference, this allows the radio link to automatically change to a quieter channel based
on continuously monitoring of its own Bit Error Rate. With the channel selection feedback
loop running, the radio is able to always optimize the link without user intervention.
During installation we encourage testing of the radio link by using site survey mode
(DIP 4 ON). This testing will ensure that the radio has found channel(s) that achieve
a low BER. Once the link is tested, the user can turn off DIP 4 and let the link run
autonomously. The user then can ping a client device on the other side of the link to
ensure the radio is in continual operational.
6. Why is 900 MHz better than 2.4 or 5.8 GHz 802.11 for Non-Line-
of-Sight applications?
The improved propagation characteristics of lower frequency RF energy has been
well documented for years. The 2.4 GHz and 5.8 GHz (802.11)
frequencies
are
excellent baseband carriers for clear line-of-sight conditions, however, they do not
propagate well through solids such as building walls, trees or over large expanses of
water.
The trade-offs are bandwidth vs. distance traveled - 802.11 can support higher
throughput (up to 54Mbps) but cannot travel far or through obstacles. By contrast,
Videolarm 900MHz technology can travel much greater distances through solids or air
for that matter, but can only support a 1.5 Mbps data rate (when the band is divided
into 12 channels - 2 MHz each).
7. What is the Fresnel zone?
The Fresnel Zone is the area around the visual line-of-sight that radio waves
spread out into after they leave the antenna. Typically, 20% Fresnel Zone
blockage introduces little signal loss to the link. Beyond 40% blockage, signal
loss will become significant. This calculation is based on a flat earth. It does
not take the curvature of the earth into consideration. The effect of this is to
budge the earth in the middle of the link. It is recommended for long links to
have a microwave path analysis done that takes this and the topography of
the terrain into account.
Содержание PB24L900
Страница 13: ...8 00 203 2 2 00 50 8 Mounting Template ...
