User Guide: Technical Reference SECTION 4 NETWORK MANAGEMENT FOR
ioLink 4
PRELIMINARY
Customer Support (202) 333-7031
4-4
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Full Loopback:
This test mode places the modem into a loopback mode at the spreading chip (in the
baseband processing section). The signal path is then from the user’s device through the line
interface circuitry, the forward error correction circuitry and then the spreading circuitry, back through
each of these and out to the user’s device. This allows the user to determine whether the line
interface, forward error correction and baseband processing sections of the modem are operating
correctly.
4.4 Performance Monitoring
There are several performance statistics for DSX-1 devices that are described in RFC 1406. In addition to
these, the
ioWave
Management Information Base (MIB) provides performance-monitoring variables for
features not included in RFC 1406. The additional features that may be monitored are:
•
Pre-FEC:
This is a measure of the rate of bit errors that are received from the link. In usual
operation, the FEC circuitry corrects most of the bit errors so that the error rate of the data sent to the
user’s equipment is smaller than this rate. As this is a feature of the FEC circuitry, it is not available
for E1 modems.
•
RF Signal Level:
The strength of the power received from the RF unit, as a percentage of that
received for an ideal 1 mile link. If this value is 0%, there is a problem with the signal received from
the RF unit; it is likely non-existent. In normal operation, this value should be greater than 83%.
•
Signal level:
The strength of the power associated with the demodulated signal, as a percentage of
that received for an ideal 1 mile link. This is a measure of whether the signal received from the RF
unit is from the other end of the link or from a noise source. If this value is less than 25%, the signal
being received by the RF unit is not correctly encoded, indicating that the RF unit is receiving a noise
signal. The likely causes are either a problem with the other end of the link or the presence of a
strong interference signal. In normal operation, this value should be between 40% and 70%.
