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Content for TS 26.131 Word version: 18.1.0

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6.12 Echo control characteristics 6.12.1 Handset 6.12.2 Headset 6.12.3 Handheld hands-free 6.12.4 Desktop hands-free 6.12.5 Electrical interface 6.13 Clock accuracy 6.14 Jitter buffer management behaviour
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6.12 Echo control characteristics |R11| p. 61

Echo cancellation is commonly deployed in the UE to fulfil the Acoustic echo control requirements. Echo cancellers are complex devices of which the subjective performance is affected by several attributes. The main attribute is its ability to suppress echo. The process of suppressing the echo may introduce impairments to the near-end speech signal, mainly manifested as distortion or clipping of the near-end signal during simultaneous speech from both the far and near-end ("double-talk").

To characterise the echo control performance, the activity (in % of total time) and averaged level difference (in dB) of the duration of any level difference according to Figure 14b and Table 16b2 between the clean near-end signal and the send-signal shall be reported for "double-talk" as well as the far-end single talk periods adjacent to the "double-talk".

All percentage values and averaged level differences described in the relevant test of TS 26.132 shall be reported.

Copy of original 3GPP image for 3GPP TS 26.131, Fig. 14b: Classification of echo canceller performance

Figure 14b: Classification of echo canceller performance
(⇒ copy of original 3GPP image)

Table 16b2: Categories for echo canceller performance classification

Category	Description
A1	Full-duplex and full transparency
A2	Full-duplex with level loss in Tx
B	Very short clipping
C	Short clipping resulting in loss of syllables
D	Clipping resulting in loss of words
E	Very short residual echo
F	Echo bursts
G	Continuous echo

6.12.1 Handset p. 62

Requirements are for further study.

6.12.2 Headset p. 62

Requirements are for further study.

6.12.3 Handheld hands-free p. 62

Requirements are for further study.

6.12.4 Desktop hands-free p. 62

Requirements are for further study.

6.12.5 Electrical interface |R17| p. 62

Requirements are for further study.

6.13 Clock accuracy |R14| p. 63

For MTSI-based speech-only with LTE, NR or WLAN access, the clock skew in send direction between the device under test and the reference client should be less than 50 PPM (in absolute value) in error-free conditions.

Compliance shall be checked by the relevant test described in TS 26.132.

6.14 Jitter buffer management behaviour |R14| p. 63

6.14.0 General |R18| p. 63

The UE delay definition is the same as in clause 6.11.0.

6.14.1 Handset UE |R18| p. 63

It is in general desirable to minimize UE delays to ensure low enough end-to-end delays and hence a good conversational experience, guidance is found in ITU-T Recommendation G.114.

For MTSI-based speech-only with LTE, NR or WLAN access in conditions with simulated packet arrival time variations and packet loss and AMR-WB speech codec operation, the sum of the UE delays in sending and receiving directions (T_S + T_R) shall be less than or equal to the delay requirements in Table 16c1, while meeting the speech quality targets defined.

Table 16c1: UE delay and speech quality requirements for LTE, NR and WLAN access

Profile	Delay and Loss Profile	Performance Objectives for Maximum Delay	Requirements for Maximum Delay	Speech Quality Requirements (see Note)
0	Error free condition with minimal jitter	Same as profile 0 in Table 16a1	Same as profile 0 in Table 16a1	No requirement, reference score MOS-LQO_REF
1	artificial_volte_profile	T_S + T_R ≤ 270ms	T_S + T_R ≤ 310ms	MOS-LQO_TEST ≥ MOS-LQO_REF - [0.4]
NOTE: The purpose of this test is to provide a relative comparison of the objective speech quality between the reference and test conditions. This test is not to be construed as a method to evaluate the absolute objective speech quality of the device.

Compliance shall be checked by the relevant tests described in TS 26.132.

6.14.2 Headset UE |R18| p. 63

6.14.2.1 Wired headset p. 63

It is in general desirable to minimize UE delays to ensure low enough end-to-end delays and hence a good conversational experience, guidance is found in ITU-T Recommendation G.114.

For MTSI-based speech-only with LTE, NR or WLAN access in conditions with simulated packet arrival time variations and packet loss and AMR-WB speech codec operation, the sum of the UE delays in sending and receiving directions (T_S + T_R) shall be less than or equal to the delay requirements in Table 16c2, while meeting the speech quality targets defined.

Table 16c2: UE delay and speech quality requirements for LTE, NR and WLAN access

Profile	Delay and Loss Profile	Performance Objectives for Maximum Delay	Requirements for Maximum Delay	Speech Quality Requirements (see Note)
0	Error free condition with minimal jitter	Same as profile 0 in Table 16a2	Same as profile 0 in Table 16a2	No requirement, reference score MOS-LQO_REF
1	artificial_volte_profile	T_S + T_R ≤ 270ms	T_S + T_R ≤ 310ms	MOS-LQO_TEST ≥ MOS-LQO_REF - [0.4]
NOTE: The purpose of this test is to provide a relative comparison of the objective speech quality between the reference and test conditions. This test is not to be construed as a method to evaluate the absolute objective speech quality of the device.

Compliance shall be checked by the relevant tests described in TS 26.132.

6.14.2.2 Wireless headset p. 64

For further study.

6.14.3 Electrical interface UE |R18| p. 64

It is in general desirable to minimize UE delays to ensure low enough end-to-end delays and hence a good conversational experience, guidance is found in ITU-T Recommendation G.114.

For MTSI-based speech-only with LTE, NR or WLAN access in conditions with simulated packet arrival time variations and packet loss and AMR-WB speech codec operation, the sum of the UE delays in sending and receiving directions (T_S + T_R) shall be less than or equal to the delay requirements in Table 16c3, while meeting the speech quality targets defined. The delay budget BD to be considered in the performance requirements and objectives depends on the type of electrical interface UE and is given by Table 16a3.

Table 16c3: UE delay and speech quality requirements for LTE, NR and WLAN access

Profile	Delay and Loss Profile	Performance Objectives for Maximum Delay	Requirements for Maximum Delay	Speech Quality Requirements (see Note)
0	Error free condition with minimal jitter	Same as profile 0 in Table 16a4	Same as profile 0 in Table 16a4	No requirement, reference score MOS-LQO_REF
1	artificial_volte_profile	T_S + T_R ≤ 270+BD ms	T_S + T_R ≤ 310+BD ms	MOS-LQO_TEST ≥ MOS-LQO_REF - [0.4]
NOTE: The purpose of this test is to provide a relative comparison of the objective speech quality between the reference and test conditions. This test is not to be construed as a method to evaluate the absolute objective speech quality of the device.

Compliance shall be checked by the relevant tests described in TS 26.132.