DT Etherlink IV
User Manual
- 35 -
Figure 3.20 G.826 performance evaluation
On the E1 side, four CRC4 check bits are generated per sub-multiframe (SMF) and compared with
the corresponding bits of the next SMF. If they do not match, the CRC4 error counter is
incremented.
On the SHDSL side, six CRC6 check bits are generated per SHDSL frame. CRC6 errors are used
by the software to count the block errors of the SHDSL channel and to evaluate its error
performance according to ITU-T Rec. G.826.
For the E1 interface, calculations according to G.826 are only possible in the framed mode
according to G.704 with the CRC4 option enabled. In the framed mode with the CRC4 option
disabled, only FAS errors are detected.
The estimation of a bit error rate is not within the scope of G.826 calculations.
3.2.5 BERT Test
We suggest BERT testing in the following way: Switch on Loop2 on the remote unit (slave) and
setup the BERT on the master unit.
Figure 3.21. BERT setup Example
Configuration Example:
CO_BERT>CONF
--------------------------------------------------------------------------------
Current BERT configuration:
--------------------------------------------------------------------------------
Interface : E1-1, Internal (to SHDSL1)
Pattern : 2E7
TX Slots : [00-15] PG PG PG PG PG PG PG PG PG PG PG PG PG PG PG PG
: [16-31] PG PG PG PG PG PG PG PG PG PG PG PG PG PG PG PG
RX Slots : [00-15] BT BT BT BT BT BT BT BT BT BT BT BT BT BT BT BT
: [16-31] BT BT BT BT BT BT BT BT BT BT BT BT BT BT BT BT
--------------------------------------------------------------------------------
CO_BERT>
Generator
Receiver
Generator
Receiver
Generator
Receiver
CRC6
CRC4
CRC4
CRC4
C
R
C
6
F
E
B
E
G.826
Counters
Receiver
Generator
Receiver
Generator
Receiver
Generator
CRC6
CRC4
CRC4
CRC4
C
R
C
6
F
E
B
E
G.826
Counters
SHDSL
SLAVE
MASTER
E1
E1
E1
E1
TX
RX
TX
RX
TX
RX
TX
RX
Master
Regenerator
Slave
E1 Interface
1
LOOP 2 1:R
BERT activated
Loop2 activated
