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AuroraPresto—User Guide
DSL Physical Layer BERT
A
The ADSL physical layer BERT is a BERT which is
automatically performed by the Alcatel ADSL ATU-R and
ATU-C hardware during a normal transmission. BERT data
is injected into the unused part of the ADSL line bandwidth
and is carried in dummy cells. The user has no control over
the BERT pattern choice, this is defined by the Alcatel
hardware. The BERT line speed can be controlled indirectly
by changing the speed of the data transmission.
When a cell header error is found in a test cell, the current
second is counted as an errored second, the whole cell is
discarded and the payload is not used for the BERT again.
The BERT counts and accumulates payload bit errors
during valid seconds and not during errored seconds. This
is a disadvantage of the Background BERT but, it is
available at all times during Link and Network Level Tests.
You can use the ADSL physical layer BERT alone, or with
the ADSL ATM BERT.
After the ADSL layer has been activated, the ADSL physical
layer BERT runs continuously, checking the integrity of
received frames.
ADSL ATM BERT
AuroraPresto
containing the BERT pattern. Each ATM cell has a 5 byte
header and 48 bytes of payload. The BERT pattern is
inserted into the payload in blocks of 48 x 8 bits in the
transmit direction. In the receive direction the ATM cell
payload is extracted and checked for bit errors by
AuroraPresto
4-58
generates ATM cells with data payloads
.
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