26.1313GPPRelease 17RequirementsTerminal acoustic characteristics for telephonyTS
The stability loss presented to the PSTN by the 3G, LTE, NR or WLAN network at the POI should meet the principles of the requirements in clauses 2 and 3 of ITU-T Recommendation G.122 . These requirements will be met if the attenuation between the digital input and digital output at the POI is ≥ 6 dB at all frequencies in the range 100 Hz to 8 kHz under the worst case acoustic conditions at the UE (any acoustic echo control should be enabled). For the normal case of digital connection between the Air Interface and the POI, the stability requirement can be applied at the Air Interface.
The worst case acoustic conditions will be as follows (with volume control set to maximum for each following condition):
Handset UE: the handset lying on, and the transducers facing, a hard surface with the ear-piece uncapped;
Headset UE: for further study;
Hands-free UE: no requirement other than echo loss.
NOTE: The test procedure must take into account the switching effects of echo control and discontinuous transmission (DTX) if applicable.