Chapter 2
GSM Call Mode Operation
GSM tests
58
4460 GSM System Option and 4468 EDGE System Option
Version 12.20
Mode
On this selection field, you may select between BER, Fast BER
and RBER measurements.
BER
The BER (=
B
it
E
rror
R
ate) is defined as the
ratio of the bits that the mobile receives incor-
rectly to all bits transmitted. The BER is calcu-
lated for all three bit classes independently.
As you know, bits of the Ia class are highly pro-
tected against transmission errors by the so-
called channel encoding process. This compli-
cated procedure is used, because any loss of
class Ia bits will have a great effect on speech
quality.
Class II bits are not protected at all and there is
no channel encoding on either side. They are
just sent as ‘plain vanilla’ data from the 4400
to the mobile and back. This is the reason why
people concentrate on the BER of class II bits
when a quick and simple test of the mobile’s
receiver is needed: The test data is sent back
and forth without any coding and error correc-
tion. This allows to solely test the mobile’s
receiver rather than a combination of the
mobile’s receiver, decoder and encoder (see also
section
“Basic test menu”
for details).
Note:
A more detailed description of the voice
coding procedure can be found in section
“Voice coding”
.
