Aethra d2000 lite ユーザーズマニュアル
USER’S MANUAL ISDN TESTER AND ANALYZER D2000
PRO
/D2000Lite/D2000
3.5. BER Test
The most used way to verify the transmission quality of a data connection, is
performing a BER (BIT ERROR RATE) test. In order to perform this test , the device
sends a sequence of pseudorandom bits (PRBS) on line and measures the error bits
ratio (BER) as the number of wrong bits received divided by the total number of bits
received. The final result, is then estimated according to absolute parameters or
weighed according to the standard G.821.
performing a BER (BIT ERROR RATE) test. In order to perform this test , the device
sends a sequence of pseudorandom bits (PRBS) on line and measures the error bits
ratio (BER) as the number of wrong bits received divided by the total number of bits
received. The final result, is then estimated according to absolute parameters or
weighed according to the standard G.821.
The test may be carried out in presence of an ISDN connection with signalling
protocol (e.g. E-DSS1), but also in leased data connection with several linking
technologies (e.g. 2Mb G.703, V.35).
protocol (e.g. E-DSS1), but also in leased data connection with several linking
technologies (e.g. 2Mb G.703, V.35).
Some of the parameters concerning the test have to be configured according to the
type of connection under verification.
type of connection under verification.
The final results instead, can be estimated in the same way a part from the type of
access.
access.
Various types of test may be performed in order to verify the BER on a line, the most
common are:
common are:
• Autocall
• Loop
• End-to-end
• Loop
• End-to-end
The ‘Autocall’ mode expects the use of only one testing device, this carries out a call
toward himself by using ISDN connections with signalling protocol over D channel. In
this way it is possible to check the quality of line up to the local exchange. This is the
typical test to carry out in first installation phase.
toward himself by using ISDN connections with signalling protocol over D channel. In
this way it is possible to check the quality of line up to the local exchange. This is the
typical test to carry out in first installation phase.
The ‘loop’ test allows to check a point-to-point connexion by the use of a testing
equipment and a remote loop. According to the network type, it may be a physical
loop or a device used as terminal (e.g. a second D2000
equipment and a remote loop. According to the network type, it may be a physical
loop or a device used as terminal (e.g. a second D2000
PRO
set as ‘act as loopbox’)
which performs a logical loop. The ‘loop’ test checks the global quality of the line, but
it can’t determines the problematic route (NTÆTE or TEÆNT).
it can’t determines the problematic route (NTÆTE or TEÆNT).
To perform the test in ‘loop’ mode, a remote instrument must be set with an active
loop on the channel. See § 3.8.
loop on the channel. See § 3.8.
CHAPTER 3 - PERFORMING A MANUAL TEST
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