Chapter 2
GSM Call Mode Operation
System parameters
4460 GSM System Option and 4468 EDGE System Option
Version 12.20
107
Softkey for measurement limits
The following softkey eases limit handling:
Power measurement limits
In GSM, there are different power steps that determine the nominal RF output
power for a mobile. While a mobile close to a base station will work on a lower
power level, a mobile on the boundary of a cell will need a higher RF power level
in order to make the base station ‘hear’ it.
BER II
The
B
it
E
rror
R
atio is defined as the ratio of falsely
decoded bits in relation to all bits transmitted. It is calcu-
lated for the three different bit classes separately.
Here you enter the upper limit for the BER on the class II
bits.
RBER Ib
The
R
esidual
B
it
E
rror
R
atio is similar to the BER with the
following exception: all frames the mobile detects an
error in are rejected and not used for the RBER. Thus, only
those frames are included in the RBER that were accepted
by the mobile. The RBER is calculated for bit classes Ib and
II only.
Here you enter the permissible maximum for the RBER on
the class Ib bits.
RBER II
The
R
esidual
B
it
E
rror
R
atio is similar to the BER with the
following exception: all frames the mobile detects an
error in are rejected and not used for the RBER. Thus, only
those frames are included in the RBER that were accepted
by the mobile. The RBER is calculated for bit classes Ib and
II only.
Here you enter the upper limit for the RBER on the class II
bits.
FER
The
F
rame
E
rasure
R
atio is defined as the ratio of the
frames rejected by the mobile in relation to all frames
transmitted.
A frame is marked as ‘erased’ and rejected by the mobile
when its error detector finds an error. To do so, the mobile
will use the checksum provided with the class Ia bits.
FBER
The Fast BER is similar to a BER measurement on the class
II bits. The main difference is, that in Fast BER, all bits are
unprotected. To measure the FBER, a special loop function
is used (the so-called type C loop).
NOTE
A separate screen is available for
power level
limits.
Push this softkey if you want to return to the default limit
values. The present values will be replaced by standard values.