7.12 Echo control characteristics

26.1313GPPRelease 18RequirementsTerminal acoustic characteristics for telephonyTS

Tools: ARFCN - Frequency Conversion for 5G NR/LTE/UMTS/GSM

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 22 and Table 33 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".

NOTE: The limits for specifying the categories in Figure 22 and Table 33 are provisional pending further analysis and validation.

NOTE: The categories in Figure 22 and Table 33 are labelled in a functional order and the subjective impression of the respective categories is for further study.

All percentage values and averaged level differences described in the relevant test of 3GPP TS 26.132 shall be reported.

Figure 22: Classification of echo canceller performance

Table 33: 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