Rohde & Schwarz CMU-K20, Operating Manual

Page: 55 / 646

CMU-K20/-K21/-K22/-K23/-K24 Signalling Mode
1115.6088.12 2.21 E-10
Additional Information... Alternative Settings
and Measurements
... on Step 1
"
MS Receiver Reports
GSM mobile phones continuously measure the signal
strength and quality of several nearby base stations. The
measured values for the active base station (serving cell
BTS) are regularly sent to the CMU in the so-called meas-
urement reports.
The received signal input level (RX Level) is expressed in
terms of dimensionless power levels ranging from 0 to 63.
These levels depend linearly on the absolute signal levels
measured in dBm. A high power level implies a high received
signal input level.
The received signal quality (RX Quality) is expressed in
terms of dimensionless quality levels (actually “error levels”)
ranging from 0 to 7. The quality levels depend linearly on the
logarithm of the bit error rate. A high quality level implies a
high bit error rate and thus a poor received signal quality.
'
chapter 4, p. 4.135 ff.
The exact definition of RX Level
and RX Quality is given in section
Panel MS Rcv. Reports – Re-
ceived Results of the Mobile
Phone.
The dependence of RX Level and
RX Quality on the CMU’s output
level can be quickly checked by
varying the
TCH Level in the used
timeslot.
Different TCH levels can be set in
the used timeslot and in the un-
used timeslots. This is useful for
some tests specified by GSM.
... on Step 2
#
P/PCL Measurement
The P/PCL measurement forms the second application in the
measurement group Power . In this application, the average
burst power of the mobile can be measured over the whole
range of power control levels and for up to three different
channels at once. The PCLs and channels to be measured
can be selected; the total measurement time is below 3 s.
'
chapter 4, p. 4.97 ff.
The different „applications“
Power/t Norm. GMSK, P/PCL etc.
split up the measurement group
Power in several related sub-
groups.
For a general discussion of
measurement control and appli-
cations see chapters 3 and 5.
$
PCL/Channel and Trigger
The PCL set for the mobile station and the traffic channel
number can be checked and modified, if required, in the
Power menu. This is in contrast to the Non Signalling mode
where no settings concerning the device under test can be
made.
Finally the two modes differ in the trigger modes available: In
the
Non Signalling mode an external trigger signal may be
used whereas in the Signalling mode the measurements
must be triggered by the input signal (Free Run , RF Power,
IF Power mode) or by the CMU's signalling unit (Signalling
trigger).
'
chapter 4, p. 4.97 ff.
The frame trigger signal (Signal-
ling trigger mode) is also fed to
pin 2 of the AUX 3 connector
where it can be tapped off to syn-
chronize external devices to the
CMU's TDMA timing.
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