Constellation™ November 2003
3-6 Installation and Commissioning
UBER is a measurement that shows BER (Bit Error Rate) before FEC (Forward
Error Correction) takes place. UBER readings can vary over a wide range, in a
normally operating radio, from zero to as high as 5 E10-4 for some modem
options. Different modems use different error correcting schemes and as a
result, the "normal" UBER range can vary. Even with these high UBER
readings the radio will meet or exceed its 10 E-12 error floor performance. The
UBER is time-averaged and a reading may reflect a constant error rate or a
burst of errors from path activity or radio switching that has been averaged
over time.
The causes of UBER may be Path activity, Transmitter IMD (Inter-Modulation
Distortion), LO (Local Oscillator) phase noise, or any combination of these.
Turning down the transmitter output power to improve the UBER is not
necessary or recommended as the radio is designed to operate at the higher
transmit power and with FEC. UBER readings can vary from radio to radio due
to variations in the previously mentioned parameters; this does not indicate a
faulty component but is a normal variation.
The following UBER readings may indicate a problem if they are in excess of:
• 1 E-3 for 4DS-3,
• 1 E -4 for 28T and 16 T high power
• 4E-7 for 8, 16T, 28T and 155 standard power.
If dribbling errors are occurring and UBER readings are greater than those
mentioned above, the monitoring of UBER can be a useful troubleshooting
tool. If the UBER is reset and the rate remains lower for a period of time and
then jumps to a high value, it is an indication of an error burst which could be
related to path activity. If the UBER value is constant and high, it may indicate
a transmitter that has its output power set too high, or a defective module. In
this case, the effect of corrective action can be indicated quickly by observing
the UBER reading rather than waiting for hours or days to verify that the
dribbling errors have been eliminated.
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