7.8 Distortion

26.1313GPPRelease 17RequirementsTerminal acoustic characteristics for telephonyTS

7.8.1 Sending distortion (excluding electrical interface UE)

The sending part shall meet the following distortion requirements:

NOTE 1: Digital signal processing other than the transcoder itself is included in this requirement (e.g., echo cancelling).

Distortion shall be measured between the MRP and the SS audio output (output of the reference speech decoder of the SS). The ratio of signal‑to‑total distortion power measured with the proper noise weighting (see table 4 of ITU‑T Recommendation G.223) shall be above the limits given in table 31.

NOTE 2: Frequencies from 315 Hz to 816 Hz do not apply to the hands-free UE case, but only to handset and headset UE.

Table 31: Limits for signal‑to‑total distortion ratio

Frequency (Hz)

Sending level

(dBPa at the MRP)

Sending Ratio (dB)

315

-4,7

28

408

-4,7

32

510

-4,7

32

816

-4,7

32

1 020

5

30

0

35

-4.7

35

-10

33

-15

30

-20

27

Limits for intermediate levels are found by drawing straight lines between the breaking points in table 31 on a linear (dB signal level) ‑ linear (dB ratio) scale.

Compliance of the sending distortion shall be checked by the test described in TS 26.132.

NOTE 3: It should be ensured that the test signal is treated by speech processing algorithms as a speech-like signal, and not a noise-like signal. Test signals with a time-stationary envelope may be treated by certain algorithms, e.g., noise suppression algorithms defined in 3GPP TS 06.77 R99 [16], as a noise-like signal. If speech processing algorithms, including but not limited to noise suppression algorithms, are shown to treat the test signal as a noise-like signal, even where an activation signal has been utilized, then the test should be repeated with said speech processing algorithms disabled. The results of both sets of tests and the state of the processing algorithms should be documented in the test report.

7.8.2 Receiving (excluding electrical interface UE)

The receiving part between the SS audio input (input of the reference speech encoder of the SS) and the applicable acoustic measurement point (DRP with diffuse-field correction for handset and headset modes; free field correction for hands-free modes) shall meet the requirements in this sub-clause at the nominal setting of the volume control (except where another volume setting is specified):

The ratio of signal‑to‑total distortion power measured with the proper noise weighting (see table 4 of ITU-T Recommendation G.223) shall be above the limits given in table 32 when the sound pressure at the applicable acoustic measurement point is < 10 dBPa. For a sound pressure ≥ 10 dBPa at the applicable acoustic measurement point there is no distortion requirement.

NOTE 1: Frequencies from 315 Hz to 816 Hz do not apply to the hands-free UE case, only to handset and headset UE.

Table 32: Limits for signal-to-total distortion ratio

Frequency (Hz)

Receiving level

at the digital interface (dBm0)

Receiving ratio

at nominal volume setting (dB)

Receiving ratio

at maximum volume setting (dB)

315

-16

20

408

-16

28

510

-16

28

816

-16

28

1 020

0

25,5

tbd

-3

31,5

tbd

-10

33,5

tbd

-16

33,5

tbd

-20

33

tbd

-30

30,5

tbd

-40

22,5 (*)

tbd

-45

17,5 (*)

tbd

NOTE: (*)For levels -40 and -45 dBm0 a lower signal-to-total distortion ratio may not be possible, and hence would not be regarded as a failing result. However, the obtained results would be reported.

Limits for intermediate levels are found by drawing straight lines between the breaking points in the table on a linear (dB signal level) ‑ linear (dB ratio) scale.

Compliance of the receiving distortion shall be checked by the appropriate method in TS 26.132.

NOTE 2: It should be ensured that the test signal is treated by speech processing algorithms as a speech-like signal, and not a noise-like signal. Test signals with a time-stationary envelope may be treated by certain algorithms, e.g., noise suppression algorithms defined in 3GPP TS 06.77 R99 [16], as a noise-like signal.

7.8.3 Sending distortion (electrical interface UE)

The sending part shall meet the following distortion requirements:

NOTE 1: Digital signal processing other than the transcoder itself is included in this requirement (e.g., echo cancelling).

Distortion shall be measured between the MRP and the SS audio output (output of the reference speech decoder of the SS). The ratio of signal‑to‑total distortion power measured with the proper noise weighting (see table 4 of ITU‑T Recommendation G.223) shall be above the limits given in table 32a1 for electrical interface UE with analogue connection and table 32a2 for electrical interface UE with digital connection.

Table 32a1: Limits for signal‑to‑total distortion ratio for analogue connection

Frequency (Hz)

Sending level

(dBV at at the output of the electrical reference interface)

Sending Ratio (dB)

315

-60

28

408

-60

32

510

-60

32

816

-60

32

1 020

-50

30

-55

35

-60

35

-65

33

-70

30

-75

27

Table 32a2: Limits for signal‑to‑total distortion ratio for digital connection

Frequency (Hz)

Sending level

(dBm0 at at the output of the electrical reference interface)

Sending Ratio (dB)

315

-16

28

408

-16

32

510

-16

32

816

-16

32

1 020

-6

30

-11

35

-16

35

-21

33

-26

30

-31

27

Limits for intermediate levels are found by drawing straight lines between the breaking points in tables 32a1 and 32a2 on a linear (dB signal level) ‑ linear (dB ratio) scale.

Compliance of the sending distortion shall be checked by the test described in TS 26.132.

NOTE 2: It should be ensured that the test signal is treated by speech processing algorithms as a speech-like signal, and not a noise-like signal. Test signals with a time-stationary envelope may be treated by certain algorithms, e.g., noise suppression algorithms defined in 3GPP TS 06.77 R99 [16], as a noise-like signal. If speech processing algorithms, including but not limited to noise suppression algorithms, are shown to treat the test signal as a noise-like signal, even where an activation signal has been utilized, then the test should be repeated with said speech processing algorithms disabled. The results of both sets of tests and the state of the processing algorithms should be documented in the test report.

7.8.4 Receiving distortion (electrical interface UE)

The receiving part between the SS audio input (input of the reference speech encoder of the SS) and applicable electric measurement point (input to the electrical reference interface) shall meet the requirements in this clause at the nominal setting of the volume control (except where another volume setting is specified):

The ratio of signal to total distortion power measured with the proper noise weighting (see table 4 of ITU-T Recommendation G.223) shall be above the limits given in table 32b.

NOTE 1: Frequencies from 315 Hz to 816 Hz do not apply to the hands-free UE case, only to handset and headset UE.

Table 32b: Limits for signal‑to‑total distortion ratio

Frequency (Hz)

Receiving level

at the digital interface (dBm0)

Receiving ratio

at nominal volume setting (dB)

Receiving ratio

at maximum volume setting (dB)

315

-16

20

408

-16

28

510

-16

28

816

-16

28

1 020

0

25,5

tbd

-3

31,2

tbd

-10

33,5

tbd

-16

33,5

tbd

-20

33

tbd

-30

30,5

tbd

-40

22,5 (*)

tbd

-45

17,5 (*)

tbd

NOTE: (*)For levels -40 and -45 dBm0 a lower signal-to-total distortion ratio may not be possible, and hence would not be regarded as a failing result. However, the obtained results would be reported.

Limits for intermediate levels are found by drawing straight lines between the breaking points in table 32b on a linear (dB signal level) ‑ linear (dB ratio) scale.

Compliance of the receiving distortion shall be checked by the appropriate method in TS 26.132.

NOTE 2: It should be ensured that the test signal is treated by speech processing algorithms as a speech-like signal, and not a noise-like signal. Test signals with a time-stationary envelope may be treated by certain algorithms, e.g., noise suppression algorithms defined in 3GPP TS 06.77 R99 [16], as a noise-like signal.