ABOUT PAL

3GPP Speech Quality Test Service

 
PAL is a dedicated audio test lab and provides speech quality test service that conformed to 3GPP requirements.
 
Our differentiations between others are:
 
a. Customizing your test
 

PAL provides not only regular 3GPP, GCP, PTCRB tests but also some customizing test specifications. Customers may need to conduct testing follow some special requirements of some main operator specifications – like AT&T, Vodafone, and CMCC. PAL has capability to provide these kinds of customizing test service.

 
b. On-site debugging support
 

PAL provides not only sample delivering test but also on-site debugging/witness test service. On-site testing is allowed during the test period. Customers will have chances to have comprehensive understanding of the test and then try to solve their issues sooner.

 
c. Complete Test Environment
 

PAL has both anechoic chamber and ETSI room (conforms to ETSI EG 202 396-1 guide). We can evaluate your device performance in two different test environments and compare the deviations.

 

 
Anechoic chamber
 
ETSI Room
 
d.  Complete Test Equipement
 
1) Support both narrowband and wideband codecs.
2) Support all 2G and 3G bands.
3) PAL has fixtures to support all product categories – Handset, Headset, and Handsfree.
4) PAL has both HATS (Head and Torso simulator) and standalone artificial mouth and measurement microphone.
5) Support handset with width up to 200mm – 10 inch phablet is fitted.
 
 
e. Experienced engineers
 

All tests will be conducted by our acoustic engineers instead of test operators. Customers have chances to get some recommendations and explanations during the test for free.

 
 
The below is the general introduction of 3GPP speech quality test requirements:
 
Ensure the quality of the phone call, 3GPP specification requirements demand to measure audio test items, in order to achieve quality control, to bring consumers a good experience, mobile voice test specification is in TS 26.132, test standards specification is in TS 26.131, the following is the phone audio test items. Generally the test mode can be divided handset mode, headset mode, and hands-free mode.
 

Handset Mode
1.         Overall loss\loudness ratings.
2.         Idle channel noise.
3.         Sensitivity\Frequency characteristics.
4.         Sidetone Masking Rating-STMR.
5.         Acoustic echo loss.
6.         Distortion.
7.         Sending Performance in the presence of ambient noise.
Headset Mode
1.         Overall loss\loudness ratings.
2.         Idle channel noise.
3.         Sensitivity\Frequency characteristics.
4.         Sidetone Masking Rating-STMR.
5.         Acoustic echo loss.
6.         Distortion.
Hands-free Mode
1.         Overall loss\loudness ratings.
2.         Idle channel noise.
3.         Sensitivity\Frequency characteristics.
4.         Acoustic echo loss.
5.         Distortion.

 
 
l Test Requirement
 
 
I. Overall loss\loudness ratings:
 

Mainly in the test sending\receiving path loudness rating, the sound of loudness affect the sound quality during the call.

 

a.         Sending loudness rating(SLR)
 

The purpose of the test item is to evaluate the microphone transmitted loudness , the loudness affect sound quality during the call.

 

b.         Receiving loudness rating(RLR)

 

The test project is to confirm the speaker volume to ensure that users have the appropriate volume to use.

 
II. Idle channel noise:
 
This test is used to evaluate the phone itself receiving \ sending noise.
 

a.         Sending

 

This test is used to assess the phone's sending path noise. The maximum noise level produced by the apparatus at the output of the system simulator under silent conditions in the sending direction shall not exceed -64dBm0(A) .

 

b.         Receiving

 

This test is used to assess the phone's receiving path noise.

The maximum noise level at handset and headset user equipment when no signal is transmitted to the input of the system simulator at the maximum volume the measured noise shall be under -54dBPa.

 
III. Sensitivity\Frequency characteristics:
 
a.         SFR 
 

The ratio of artificial mouth input sound pressure transmission microphone to voice codecs (codec) of output voltage. 

 

b.         RFR

 

The ratio of the amount of the artificial ear obtained by the sound pressure and the input voltage of the codec.

 
IV. Sidetone Masking Rating-STMR:
 
The ratio of the input signal output signal from the ear reference point to the artificial mouth reference point, users accustomed to during the call can hear their own voice, and if there is not enough side tone, the user will have a hollow feeling, this test only in handheld mode and headset mode. The talker sidetone masking rating shall be at least 15dB and should be less than 23dB for the nominal setting of the volume control.
 
V. Acoustic echo loss:
 
Mainly used to assess the echo suppression, echo loss norms TCLw at least greater than 46dB. Echo loss is the attenuation of the input speech and the speech coder of the encoder output.
 
VI. Distortion(Sending,Receiving):
 
Mainly to test sending \ receiving distortion of processing sound signals.
 
a.         Sending:
 

The sending part shall be measured between MRP and system simulator audio.

 

b.         Receiving:
 

The sending part shall be measured between DRP and system simulator audio.

 

 
VII. Sending Performance in the presence of ambient noise:
 
For sending path, in handset mode, the user equipment shall reduce the ambient noise picked up by microphone without significantly degrading the quality of the speech signal.
This test item mainly measure and analyse at different background noise environment, showing the transmitting end sound quality, sound quality is divided three MOS test.
 
a.         N-MOS: Transmission quality of the background noise.
b.         S-MOS: Transmission quality of the speech.
c.         G-MOS: Overall transmission quality.