Xpm Bit Error Ratio Test - Nortel DMS-100 Series Maintenance Manual

Link testing
BERP testing can be performed on the DS-1 links connecting the host
controller to the Star Hub. To perform the BERP test on a DS-1 link, it is
necessary to have a loopback at some point on the transmission path. The
DS-1 loopback is at the peripheral side (P-side) of the host LTC. All 24
channels on the DS-link are looped back. When a DS-1 loopback is used, the
DS-1 link being tested must be removed from service.

XPM bit error ratio test

The host LTC+, LGC+, or RCC2 performs the XPM bit error ratio test
(XBERT) for the Star Hub. The XBERT is a diagnostic test that does the
following:
• detects and measures pulse code modulation (PCM) bit errors that occur in
XPM and Star Remote System cards
• commissions DS-1 links and trunks that are physically looped back at the
remote end without the use of a remote node
The XBERT detects bit errors in the transmission of high-speed data in the
cards of the host XPM and cards in the Star Remote System. All XBERT
testing requires the NT6X99AA IBERT line card provisioned in a Star Hub or
Star Module line drawer.
Test conditions
For accurate fault detection, the XBERT tests are run on an active in-service
XPM unit. They can also be run on an out-of-service unit. At least one unit
of the Star Hub must be in service.
Note: The XBERT should not be used as a tool for providing accurate bit
error ratio assessments. The XBERT does not use the International
Telegraph and Telephone Consultative Committee (CCITT) standard test
patterns in its test procedure. Instead, it uses XPM tone PCM to provide the
64-kbps test bit stream.
Test types
XBERT runs two tests, with the use of the INITIATE (I) command, which
specifically involve the STAR. The test names and their corresponding cards
are shown in the following table.
Table 7-14 XBERT tests
Test name
XBERTBIC
XBERTDCC
Star Remote System manual maintenance 7-21
Related cards
NT6X44, NT6X50, NTMX76, NT6X54, NT6X73
Not applicable
DMS-100 Family NA100 Star Remote System XPM15 and up