Rohde & Schwarz CMU-K20, Operating Manual

Page: 282 / 646

Adaptive Multi-Rate (AMR) Speech Codec
CMU-K20/K21/K22/K23/K24
1115.6088.12 4.204 E-12
To prepare an
AMR test…
4. Press
Connect. Control
to open the
Connection Control
menu and access the
Connection
tab.
5. If necessary, disconnect the MS under test and ensure that the CMU is in the
Signal Off, Signal On,
or
Synchronized
signaling states.
6. Press the
Network
hotkey to open the
Network
tab. If necessary, press the
hotkey again to access the softkey-oriented version of the tab.
7. Press
Traffic Mode
and select the AMR codec supported by your mobile phone
(AMR Full Rate
or
AMR Half Rate).
To test downlink
codec
adaptation…
8. Press
AMR Rate Set
to select up to four codec modes and adjust the upper
and lower decision thresholds.
9. Return to the
Connection
tab and set up a call to or from the MS.
The CMU enters the
Call Established
signalling state.
10. Press
TCH Level
and vary the used TS level.
The
Codec Mode DL
requested by the MS must be in accordance to the AMR Rate
Set settings.
To test uplink
codec
adaptation…
11. Press
Codec Mode UL
and select one of the UL codec modes 1 to 4 for the MS
under test.
The
Codec Mode UL
used by the MS must be equal to the selected mode.
To test the
speech quality…
The speech quality of an AMR codec is tested in terms of bit error rate or audio
tests:
•
The bit error rate is measured in the
Receiver Quality
menu; see section
Receiver Quality Measurements
on p. 4.118 ff.
BER
and
BER Average
tests can
be made without restriction. Note that the AMR Full Rate codec does not
provide any Class II bits and that both AMR codecs always operate in circuit-
switched mode (no BLER results).
•
Audio tests can be performed with option R&S CMU-B41,
Audio Generator and
Analyzer.
All
Audio
menus and remote-control commands are described in the
R&S CMU 200/300 operating manual.
Fig. 4-91 Connection Control – Network parameters (AMR)
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