User's Manual

Date Code 20091009 SEL-3031 Instruction Manual
Performance Monitoring, Testing, and Troubleshooting
Monitoring Radio Performance
5.3
You may need to repeat these steps before the availability reaches the desired level.
Note: There are 16 zones available in the SEL-3031 where a radio link only uses a
maximum of 10 zones. Skipping zones will turn on zones not previously used and may
give worse performance. The default SKIP setting of NONE will make the SEL-3031
SKIP zones 11–16.
If the availability of most of the zones is bad (low) and positioning the antenna did not
help then the radio link has a large amount of interference or there is an obstruction to
the Fresnel zone that is causing reflection issues. The interference can be caused by a
number of items. A path study is critical to determine how good the line-of-sight is and
how high the antennas need to be. If the path study results do not match your actual
results you will need to make sure all of the parameters used to make the path study
were correct. If the results still do not match then there is an unaccounted obstruction
in the path (either buildings or trees) that is causing the decrease in availability. View
Section 2: Installation for more information on properly installing the antenna. If the
availability numbers are less than desired then the problem is within the location,
interference, or multipath radio issues. If the antenna tower is not located high enough
and proper steps are not done to detect noise floors or obstructions to the fresnel zone
then the availability numbers may not reach those used in the path study.
Monitoring MIRRORED BITS Performance
When using one, two, or three ports of the SEL-3031 for MIRRORED BITS
communications it is important to monitor the availability of the channel. The
SEL-3031 provides channel availability information and the M
IRRORED BITS devices
each contain communications data for each MIRRORED BITS channel. This section
describes how these work and how to optimize the M
IRRORED BITS channel to achieve
a high level of availability.
The end of the previous section describes how to measure the availability of the radio
link. All SEL relays that have M
IRRORED BITS give a full channel monitoring report
that will give the unavailability and a report on all of the data drops. The SEL-3031
displays the availability and SEL M
IRRORED BITS devices display the unavailability.
The relationship of the two is represented below.
Availability = 1 – Unavailability
The SEL-3031 will show a lower availability than shown by the SEL relays with
M
IRRORED BITS. The difference lies in how the radio monitors each packet of
MIRRORED BITS. Upon detecting bad packets the SEL-3031 removes the packets
before they reach the relay. The relay will only declare a dropped channel if it receives
bad data or after a period of time expires without seeing a new data packet. This gives
the SEL-3031 a chance to ride through several bad hops, remove corrupted data, keep
the channel up and operating, and minimize the amount of total unavailability as seen
by the M
IRRORED BITS devices.
Before you use an SEL device’s M
IRRORED BITS communications report, make sure
you go through Monitoring and Improving Radio Link Performance to verify the radio
is optimized and the SKIP setting is set to avoid noisy zones.