Installation Instructions

LISA-U2 series - System Integration Manual
UBX-13001118 - R19 Early Production Information System description
Page 94 of 175
1.11.4 Voiceband processing system
The voiceband processing on the LISA-U2 modules is implemented in the DSP core inside the baseband chipset.
The external digital audio devices can be interfaced directly to the DSP digital processing part via the I
2
S digital
interface. With exception of the speech encoder/decoder, audio processing can be controlled by AT commands.
The audio processing is implemented within the different blocks of the voiceband processing system:
 Sample-based Voice-band Processing (single sample processed at 16 kHz for Wide Band AMR codec or
8 kHz for all other speech codecs)
 Frame-based Voice-band Processing (frames of 320 samples for Wide Band AMR codec or 160 samples for
all other speech codecs are processed every 20 ms)
These blocks are connected by buffers (circular buffer and voiceband sample buffer) and sample rate converters
(for 8 / 16 to 47.6 kHz conversion).
The voiceband audio processing implemented in the DSP core of LISA-U2 series modules is summarized in Figure
51.
I2S_RXD
Switch
I2S1_RXD
UBF
2/6
UBF
1/5
Hands-
free
To
Radio TX
Uplink
Digital Gain
I2S1_TXD
Switch
I2S_TXD
Scal_Rec
Digital Gain
Tone
Generator
I2Sx RX
UBF
4/8
UBF
3/7
DBF
3/7
DBF
4/8
DBF
1/5
DBF
2/6
Legend:
UBF= Uplink Biquad Filter
DBF = Downlink Biquad Filter
I2Sx TX
Sidetone
From
Radio RX
Speech level
PCM
Player
Mix_Afe
Figure 51: Audio processing system of LISA-U2 series modules
LISA-U2 modules audio signal processing algorithms are:
 Speech encoding (uplink) and decoding (downlink).The following speech codecs are supported in firmware
on the DSP for speech encoding and decoding:
GERAN GMSK codecs
o GSM HR (GSM Half Rate)
o GSM FR (GSM Full Rate)
o GSM EFR (GSM Enhanced Full Rate)
o HR AMR (GSM Half Rate Adaptive Multi Rate - Narrow Band)
o FR AMR (GSM Full Rate Adaptive Multi Rate - Narrow Band)
o FR AMR-WB (GSM Full Rate Adaptive Multi Rate - Wide Band)