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9 Single Tests
9.3 Bit error test
The bit error rate test (BERT = Bit Error Rate Test) serves
to check the transmission quality of the access circuit.
As a rule, the network operator will guarantee an average
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error rate of 1 x 10
1 bit error in 10 million transmitted bits. A higher bit error
rate will be especially noticeable in transmitting data.
The application program detects the errors in the data
blocks transmitted and requests that the remote partner
send them again, which reduces the effective throughput of
the ISDN connection.
In the bit error test, the tester establishes an ISDN
connection to a remote tester or places a call to itself, sends
a standardized (quasi-) random number string and
compares the received data with that which was sent. The
individual bit errors are summed and depending on the test
procedure and equipment evaluated in accordance with the
ITU Guideline G.821.
During the test, the ARGUS counts the bit errors and after
the test is done it calculates the bit error rate and other
parameters in accordance with G.821.
Since the bit error test checks both B-channels in both
directions at the same time, both B-channels are required.
As a rule, the quality of the network operator's access
circuits is quite good. Therefore, no bit errors should occur
in a 1-minute test.
However, if an error occurs, the test should be repeated with
a measurement time of 15 minutes to achieve higher
statistical precision. The access circuit is heavily distorted, if
more than 10 bit errors occur within a test period of 15
minutes.
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, in other words in long-term operation
ARGUS 3u plus/3u NT
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