Installation guide

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

Evaluation

G.826

Gen.

Test

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.