Troubleshooting
QB.11-R Installation and Management
Link Problems
159
–
Remote Partners
indicates how many SUs are connected (in case of a BSU) or whether a Base is connected (in
case of a Subscriber).
–
Base Announces
should increase continuously.
–
Registration Requests
and
Authentication Requests
should be divisible by 3. WORP is designed in a way that
each registration sequence starts with 3 identical requests. It is not a problem if, once in a while, one of those
requests is missing. Missing requests frequently is to be avoided.
•
Monitor / Per Station (Information per connected remote partner):
Check that the received signal level (RSL) is
the same on both sides; this should be the case if output power is the same. Two different RSLs indicate a broken
transmitter or receiver. A significant difference between Local Noise and Remote Noise could indicate a source of
interference near the site with the highest noise. Normally, noise is about –80 dBm at 36 Mbps. This number can vary
from situation to situation, of course, also in a healthy environment.
•
Monitor / Link Test (Information used by Administrators for on-the-spot checking):
Check the received signal
level (RSL) and noise level. Compare the RSL with the values from path analysis. If the figures differ significantly
from the values recorded at the Per Station window, check for environment conditions that change over time.
Analyzing the Spectrum
The ultimate way to discover whether there is a source of interference is to use a spectrum analyzer. Usually, the antenna
is connected to the analyzer when measuring. By turning the antenna 360 degrees, one can check from which direction
the interference is coming. The analyzer will also display the frequencies and the level of signal is detected.
Proxim recommends performing the test at various locations to find the most ideal location for the equipment.
Avoiding Interference
When a source of interference is identified and when the level and frequencies are known, the next step is to avoid the
interference. Some of the following actions can be tried:
• Changing the channel to a frequency away from the interference is the first step in avoiding interference. The installer
can select a
DFS Preferred Channel
.
• Each antenna has a polarization; try to change to a polarization different from the interferer.
• A small beam antenna looks only in one particular direction. Because of the higher gain of such an antenna, lowering
the output power or adding extra attenuation might be required to stay legal. This solution cannot help when the
source of interference is right behind the remote site.
• Lowering the antennas can help avoid seeing interference from far away.
Move the antennas to a different location on the premises. This causes the devices to look from a different angle, causing
a different pattern in the reception of the signals. Use obstructions such as buildings, when possible, to shield from the
interference.
Conclusion
A spectrum analyzer can be a great help to identify whether interference might be causing link problems on Tsunami
QuickBridge.11 systems.
Before checking for interference, the link should be verified by testing in an isolated environment, to make sure that
hardware works and your configurations are correct. The path analysis, cabling and antennas should be checked as well.
Statistics in the web interface under Monitor tell if there is a link, if the link is healthy, and a continuous test can be done
using the Link Test.
