3GPP43.050Release 16Transmission planning aspects of the speech service in the GSM Public Land Mobile Network (PLMN) systemTS
Because of the improved signal‑to‑noise ratio, both the headset MS and the handset MS are likely to give better transmission quality when DTX is enabled than that of handsfree MS.
Annex B (normative):
Test setups for terminal acoustics shall be as specified in  3GPP TS 26.132.
When DAI is used for testing of single mode GSM MS, the measurement signals shall be as specified in the relevant test-cases in  3GPP TS 51.010.
Annex C (normative):
Transmission requirements testing
Unless otherwise stated, testing shall be performed according to  3GPP TS 26.132.