SZ-DOC-W5-1.pdf LTU/NTU
Version: 1.5 Operating Manual
33 Revision: 2002-09-10
4.2.3 ISDN PRA Interface
Test
Gen.
G.826
Gen.
Test
CRC4_T CRC6
Test
Gen.
Evaluation
CRC6
CRC4_V3
DSL
Channels A & B
TE
ET
Evaluation
G.826
TX
TX
RX
RX
Gen.
Test
CRC6
CRC6
CRC4/E-Bit
Slave (NTU-PRA) Master (LTU or NTU-E1 transp.)
CRC4/E-Bit
Figure 4-2: PRA G.826 Performance Evaluation
When the PRA interface is working with CRC4 processing or monitoring (options 2 and 4) four
CRC4 check bits are generated per sub-multiframe (SMF) received from the ET and the NT2/TE
and compared with the corresponding CRC4 bits in the following SMF. If they do not match, the
corresponding CRC4 error counter is incremented. At the same time, the E-Bits from the ET and
the NT2/TE are counted and can be used for performance monitoring.
For the PRA interface, calculations according to G.826 are only possible when CRC4 processing
or monitoring is selected.
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