Content for TS 26.131 Word version: 18.0.0

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5.12 Delay 5.12.0 UE delay definition 5.12.1 Handset UE 5.12.2 Headset UE 5.12.3 Electrical interface UE 5.13 Echo control characteristics 5.13.1 Handset 5.13.2 Headset 5.13.3 Handheld hands-free 5.13.4 Desktop hands-free 5.13.5 Electrical interface 5.14 Clock accuracy 5.15 Jitter buffer management behaviour
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5.12 Delay |R11| p. 29

5.12.0 UE delay definition |R12| p. 29

5.12.0.1 Acoustic interfaces |R17| p. 29

For UMTS circuit-switched operation and MTSI-based speech with LTE, NR or WLAN access, the UE delays in the send and receive directions are defined for acoustic interfaces as:

The UE delay in the send (uplink) direction is the delay between the first acoustic event at the MRP to the last bit of the corresponding speech frame at the UE antenna
The UE delay in the receive (downlink) direction is the delay between the first bit of a speech frame at the UE antenna and the first acoustic event at the DRP corresponding to that speech frame

NOTE:

In order to harmonize UMTS and LTE delay definitions, the reference points for UMTS UE delay have been changed in Rel-12. Prior to Rel-12, the UE reference points for UMTS were implicitly defined by the compensation factors declared by system simulator vendors, i.e. half of the air interface delay was attributed to the UE, and the last acoustic event at DRP was used for the receive measurement instead of the first.

Considering 10ms for half of the transmission time in each direction of a UMTS call, a speech frame size of 20ms, a codec look-ahead of 5ms, and a difference between the first and the last acoustic event of 20 ms, the previous reference points took into account a UE implementation independent delay of 2x10ms + 25 ms + 20 ms = 65 ms. The same UE delay remains in the new definition above, which attributes the full air interface delay to the UE but uses the first acoustic event at the DRP, instead of the last (2x20ms + 25 ms + 0 ms = 65 ms). Hence, the UMTS requirements with these new reference points remain the same.

5.12.0.2 Electrical interfaces |R17| p. 30

The UE delays in the send and receive directions are defined for electrical interfaces as:

The UE delay in the send (uplink) direction is the delay between the first electrical event at the input of the electrical interface (analogue or wired digital connection) or first bit of a speech frame at the UE antenna of the wireless digital interface (wireless digital connection) to the last bit of the corresponding speech frame at the UE antenna
The UE delay in the receive (downlink) direction is the delay between the first bit of a speech frame at the UE antenna and the first electrical event at the output of the electrical interface (analogue or wired digital connection) or first bit of a speech frame at the UE antenna of the wireless digital interface (wireless digital connection) corresponding to that speech frame.

5.12.1 Handset UE p. 30

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 UMTS circuit-switched AMR speech codec operation, the sum of the UE delays in sending and receiving directions (T_S + T_R) shall in any case be ≤ 220ms and should be ≤ 185ms.

For MTSI-based speech-only with LTE, NR or WLAN access in error and jitter free conditions and AMR speech codec operation, the sum of the UE delays in sending and receiving directions (T_S + T_R) should be ≤ 150ms. If this performance objective cannot be met, the sum of the UE delays in sending and receiving directions (T_S + T_R) shall in any case be ≤ 190ms.

For MTSI-based speech-only with LTE, NR or WLAN access in conditions with simulated packet arrival time variations and packet loss and AMR 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 8bis, while meeting the speech quality targets defined.

Table 8bis: UE delay and speech quality requirements for LTE, NR and WLAN access

Test Condition	Delay and Loss Profile (Note 1)	Performance Objectives for Maximum Delay	Requirements for Maximum Delay	Speech Quality Requirements (Note 2)
0	Error and jitter free condition	T_S + T_R ≤ 150ms	T_S + T_R ≤ 190ms	No requirement, reference score MOS-LQO_REF
1	dly_profile_20msDRX_10pct_BLER_e2e	T_S + T_R ≤ 150ms	T_S + T_R ≤ 190ms	MOS-LQO_TEST ≥ MOS-LQO_REF - 0.3
2	dly_profile_40msDRX_10pct_BLER_e2e	T_S + T_R ≤ 190ms	T_S + T_R ≤ 230ms	MOS-LQO_TEST ≥ MOS-LQO_REF - 0.3
NOTE 1: The delay profiles for test condition 1 and 2 are theoretically constructed to simulate a semi-persistent scheduling transmission scheme with DRX enabled and target BLER in sending and receiving directions of 10%, with +/- 3ms of EPC jitter. Delay profiles are injected at the IP layer of the test system. Delay profiles are attached electronically to document TS 26.132. The delay profiles in test condition 1 and 2 are static delay variation conditions and do not expose the UE to packet delay variations in the full range of the packet delay budget as defined for QCI1 in TS 23.203. A third test condition that exposes the UE to non-stationary packet delay variations experienced in live operation and packet delay variations in the full range of the packet delay budget for QCI1, and accompanied delay and speech quality requirements, is for further study. NOTE 2: 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.

5.12.2 Headset UE p. 31

5.12.2.1 Wired headset p. 31

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 UMTS circuit-switched AMR speech codec operation, the sum of the UE delays in sending and receiving directions (T_S + T_R) shall in any case be ≤ 220ms and should be ≤ 185ms.

For MTSI-based speech-only with LTE, NR or WLAN access in conditions with simulated packet arrival time variations and packet loss and AMR 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 8, while meeting the speech quality targets defined.

Table 8ter: UE delay and speech quality requirements for LTE, NR and WLAN access

Test Condition	Delay and Loss Profile (Note 1)	Performance Objectives for Maximum Delay	Requirements for Maximum Delay	Speech Quality Requirements (Note 2)
0	Error and jitter free condition	T_S + T_R ≤ 150ms	T_S + T_R ≤ 190ms	No requirement, reference score MOS-LQO_REF
1	dly_profile_20msDRX_10pct_BLER_e2e	T_S + T_R ≤ 150ms	T_S + T_R ≤ 190ms	MOS-LQO_TEST ≥ MOS-LQO_REF - 0.3
2	dly_profile_40msDRX_10pct_BLER_e2e	T_S + T_R ≤ 190ms	T_S + T_R ≤ 230ms	MOS-LQO_TEST ≥ MOS-LQO_REF - 0.3
NOTE 1: The delay profiles for test condition 1 and 2 are theoretically constructed to simulate a semi-persistent scheduling transmission scheme with DRX enabled and target BLER in sending and receiving directions of 10%, with +/- 3ms of EPC jitter. Delay profiles are injected at the IP layer of the test system. Delay profiles are attached electronically to document TS 26.132. The delay profiles in test condition 1 and 2 are static delay variation conditions and do not expose the UE to packet delay variations in the full range of the packet delay budget as defined for QCI1 in TS 23.203. A third test condition that exposes the UE to non-stationary packet delay variations experienced in live operation and packet delay variations in the full range of the packet delay budget for QCI1, and accompanied delay and speech quality requirements, is for further study. NOTE 2: 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.

5.12.2.2 Wireless headset p. 32

For further study.

5.12.3 Electrical interface UE |R17| p. 32

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.

The delay budget B_D to be considered in the performance requirements and objectives depends on the type of electrical interface UE and is given by Table 8quater1.

Table 8quater1: Delay budget for different types of electrical interface UE

Electrical interface type	B_D [ms]
Analogue	0
Wireless digital	20
Wired digital	20
NOTE: The delay for analogue to digital conversion (and vice versa) in the wired digital connection is considered to be part of the budget allowance for vendor specific implementation in the UE delay requirements.

For UMTS circuit-switched AMR speech codec operation, the sum of the UE delays in sending and receiving directions (T_S + T_R) shall in any case be ≤ 220+B_D ms and should be ≤ 185+B_D ms.

For MTSI-based speech-only with LTE, NR or WLAN access in error and jitter free conditions and AMR speech codec operation, the sum of the UE delays in sending and receiving directions (T_S + T_R) should be ≤ 150+B_D ms. If this performance objective cannot be met, the sum of the UE delays in sending and receiving directions (T_S + T_R) shall in any case be ≤ 190+B_D ms.

For MTSI-based speech-only with LTE, NR or WLAN access in conditions with simulated packet arrival time variations and packet loss and AMR 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 8quater2, while meeting the speech quality targets defined.

Table 8quater2: UE delay and speech quality requirements for LTE, NR and WLAN access

Test Condition	Delay and Loss Profile (Note 1)	Performance Objectives for Maximum Delay	Requirements for Maximum Delay	Speech Quality Requirements (Note 2)
0	Error and jitter free condition	T_S + T_R ≤ 150+B_D ms	T_S + T_R ≤ 190+B_D ms	No requirement, reference score MOS-LQO_REF
1	dly_profile_20msDRX_10pct_BLER_e2e	T_S + T_R ≤ 150+B_D ms	T_S + T_R ≤ 190+B_D ms	MOS-LQO_TEST ≥ MOS-LQO_REF -0.3
2	dly_profile_40msDRX_10pct_BLER_e2e	T_S + T_R ≤ 190+B_D ms	T_S + T_R ≤ 230+B_D ms	MOS-LQO_TEST ≥ MOS-LQO_REF -0.3
NOTE 1: The delay profiles for test condition 1 and 2 are theoretically constructed to simulate a semi-persistent scheduling transmission scheme with DRX enabled and target BLER in sending and receiving directions of 10%, with +/- 3ms of EPC jitter. Delay profiles are injected at the IP layer of the test system. Delay profiles are attached electronically to document TS 26.132. The delay profiles in test condition 1 and 2 are static delay variation conditions and do not expose the UE to packet delay variations in the full range of the packet delay budget as defined for QCI1 in TS 23.203. A third test condition that exposes the UE to non-stationary packet delay variations experienced in live operation and packet delay variations in the full range of the packet delay budget for QCI1, and accompanied delay and speech quality requirements, is for further study. NOTE 2: 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.

5.13 Echo control characteristics |R11| p. 33

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 5.13-1 and Table 8a 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. 5.13-1: Classification of echo canceller performance

Figure 5.13-1: Classification of echo canceller performance
(⇒ copy of original 3GPP image)

Table 8a: 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