7.7 Acoustic echo control

26.1323GPPRelease 18Speech and video telephony terminal acoustic test specificationTS

7.7.1 General

The echo loss (EL) presented by the GSM, 3G, LTE or NR networks at the POI should be at least 46 dB during single talk. This value takes into account the fact that UE is likely to be used in a wide range of noise environments.

The calculation of weighted terminal coupling loss (TCLw) is based on the attenuation from reference point input to reference point output versus frequency bands. The following common measurement steps are applicable for all types of UE described below:

a) The attenuation from reference point input to reference point output shall be measured using the compressed real speech signal described in clause 7.3.3 of ITU-T P.501 [33]. The test signal level shall be ‑10 dBm0.

b) The first 17,0 s of the test signal (6 sentences) are discarded from the analysis to allow for convergence of the acoustic echo canceller. The analysis is performed over the remaining length of the test sequence (last 6 sentences).

c) The analysis shall be conducted in 1/3-octave band intervals between 300 to 3400 Hz as given by the R.10 series of preferred numbers in ISO 3 [54]. For the calculation, the averaged measured echo level at each frequency band is referred to the averaged test signal level measured in each frequency band.

d) The TCLw is calculated according to ITU-T Recommendation G.122 [8], annex B, clause B.4 (trapezoidal rule).

7.7.2 Acoustic echo control in a hands-free UE

The hands-free UE is set up according to clause 5.

The TCLw is measured and calculated according to clause 7.7.1.

7.7.3 Acoustic echo control in a handset UE

The handset UE is set up according to clause 5. The ambient noise level shall be ≤ ‑64 dBPa(A).

The TCLw is measured and calculated according to clause 7.7.1.

7.7.4 Acoustic echo control in a headset UE

The headset UE is set up according to clause 5. The ambient noise level shall be ≤ ‑64 dBPa(A).

The TCLw is calculated according to clause 7.7.1.

7.7.5 Acoustic echo control in an electrical interface UE

The electrical interface UE is setup according to clause 5.1.6. In order to simulate an acoustic echo, the electrical reference interface shall introduce an echo loss of 30 dB.

The TCLw is measured and calculated according to clause 7.7.1.