Specifications

AirPrime UMTS / LTE MC/SL-Series Extended AT Command Reference
148 Proprietary and Confidential 2130616
!AVRXPCMIIRFLTR
Supporting chipsets (voice-
enabled devices only):
• MDM6200 (min f/w rev:
P1_0_0_4)
• MSM6290 (min f/w rev:
K2_0_7_51ap)
• QSC6270: (min f/w rev: S2.0)
Note: For MDM8200A, see
!AVRXPCMIIRFLTR on page 170.
Set/report the Rx PCM IIR filter parameters
The modem has a multi-stage PCM (Pulse Code Modulation) IIR (Infinite Impulse
Response) filter. Use this command to set parameters for each stage of the specified
profile.
(Enabling this filter disables the PCM FIR (Finite Impulse Response) filter—see
!AVRXPCMFLTR on page 146.)
Note: This command is only useful when embedding the modem in a handset.
Mobile phones, PDAs or other handheld transmitters and receivers that incorporate
a GSM module are required to comply with the GSM 11.10 3GPP TS51.010 or 3GPP
TS26.132 standard, or with national standards or government regulations. To
conform to the relevant standard you may need to tune certain audio characteristics.
This command lets you tune the receive PCM filter to alter audio characteristics.
Settings are stored in non-volatile memory and persist across power cycles.
To enable the PCM IIR filter (and override the PCM FIR filter):
1. Set the number of stages > 0.
To disable the PCM IIR filter:
1. Set the number of states = 0.
To tune the receive or transmit audio characteristics, follow a procedure similar to the
following:
1. Disable the PCM IIR and FIR filters.
2. Use test equipment to obtain the initial Tx/Rx frequency response (uncor-
rected).
3. Make sure your filter design tool is configured to generate filter coefficients in
signed Q30 format.
4. Identify frequency bands that must be corrected (boosted or attenuated) to
bring the overall response within the bounds specified in the test case, consid-
ering the following points:
• Fit the conformance mask (3GPP specification).
• Minimize overall gain introduced by the PCM filter.
• Modify the filter if necessary to improve quality (higher frequencies are more
legible; lower frequencies will sound muffled).
5. Use !AVRXPCMIIRFLTR with an appropriate number of stages for the speech
codec being used:
• Wideband codecs (e.g. AMR-WB)—Five stages required
• Narrowband codecs (e.g. AMR-NB)—Fewer stages required (for example, 3)
6. Repeat steps 4–5 until the specifications are met.
Device-specific details:
• All chipsets/firmware revisions:
• The change takes effect immediately for the specified profile.
(Continued on next page)
Table 7-5: Voice command details (Continued)
Command Description