User's Manual

SARA-G3 and SARA-U2 series - System Integration Manual
UBX-13000995 - R18 Advance Information System description
Page 70 of 206
Switch
I2S_RXD
UBF
2/6
UBF
1/5
Hands-
free
To
Radio TX
Uplink
Digital Gain
I2S_TXD
Switch
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 33: SARA-U2 modules audio processing system block diagram
SARA-U2 modules audio signal processing algorithms are:
x 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)
UTRAN codecs:
o UMTS AMR2 (UMTS Adaptive Multi Rate version 2 – Narrow Band)
o UMTS AMR-WB (UMTS Adaptive Multi Rate – Wide Band)
x Mandatory sub-functions:
o Discontinuous transmission, DTX (GSM 46.031, 46.041, 46.081 and 46.093 standards)
o Voice activity detection, VAD (GSM 46.032, 46.042, 46.082 and 46.094 standards)
o Background noise calculation (GSM 46.012, 46.022, 46.062 and 46.092 standards)
x Function configurable via specific AT commands (see the u-blox AT Commands Manual [3])
o Signal routing: +USPM command
o Analog amplification, digital amplification: +USGC, +CLVL, +CRSL, +CMUT command
o Digital filtering: +UUBF, +UDBF commands
o Hands-free algorithms (echo cancellation, Noise suppression, Automatic Gain control) +UHFP command
o Sidetone generation (feedback of uplink speech signal to downlink path): +USTN command
o Playing/mixing of alert tones:
Service tones: Tone generator with 3 sinus tones +UPAR command
User generated tones: Tone generator with a single sinus tone +UTGN command
PCM audio files (for prompting): The storage format of PCM audio files is 8 kHz sample rate, signed 16
bits, little endian, mono