5.2 Setup of the electrical interfaces of test equipment

26.1323GPPRelease 17Speech and video telephony terminal acoustic test specificationTS

5.2.1 Codec approach and specification

In this approach, a codec is used to convert the digital input/output bit-stream of the system simulator to the equivalent analogue values. With this approach a system simulator simulating the radio link to the terminal under controlled and error-free conditions is required, unless otherwise specified for the respective test. The system simulator has to be equipped with a high-quality codec with characteristics as close as possible to ideal.

Definition of 0 dBr point:

D/A converter – a Digital Test Sequence (DTS) representing the codec equivalent of an analogue sinusoidal signal with an RMS value of 3,14 dB below the maximum full‑load capacity of the codec shall generate 0 dBm across a 600 ohm load;

A/D converter – a 0 dBm signal generated from a 600 ohm source shall give the digital test sequence (DTS) representing the codec equivalent of an analogue sinusoidal signal with an RMS value of 3,14 dB below the maximum full‑load capacity of the codec.

Narrowband telephony testing

For testing of a GSM, 3G, LTE, NR or WLAN terminal supporting narrowband telephony, the system simulator shall use the AMR speech codec as defined in the 3GPP TS 26 series of specifications, at the source coding bit-rate of 12,2 kbit/s.

Wideband telephony testing

For testing of a GSM, 3G, LTE, NR or WLAN terminal supporting wideband telephony, the system simulator shall use the AMR-WB speech codec as defined in 3GPP TS 26 series of specifications, at the source coding bit-rate of 12,65 kbit/s.

Super-wideband telephony testing

For testing of a LTE, NR or WLAN terminal supporting super-wideband telephony, the system simulator shall use the EVS speech codec as defined in 3GPP TS 26 series of specifications at 32 kHz sampling rate, mono, at the source coding bit-rate of 24,4 kbit/s unless specified otherwise for the respective test case. The system simulator should support all operation modes of EVS speech codec, the complete EVS RTP payload format, and all SDP attributes as specified in TS 26.445 Annex A; it should be possible to control all the SDP attributes declared and negotiated by the system simulator.

Fullband telephony testing

For testing of a LTE, NR or WLAN terminal supporting fullband telephony, the system simulator shall use the EVS speech codec as defined in 3GPP TS 26 series of specifications at 48 kHz sampling rate, mono, at the source coding bit-rate of 24,4 kbit/s.

5.2.2 Direct digital processing approach

In this approach, the digital input/output bit-stream of the terminal connected through the radio link to the system simulator is operated upon directly.

Narrowband telephony testing

For testing of a GSM, 3G, LTE, NR or WLAN terminal supporting narrowband telephony, the system simulator shall use the AMR speech codec as defined in the 3GPP TS 26 series of specifications, at the source coding bit-rate of 12,2 kbit/s.

Wideband telephony testing

For testing of a GSM, 3G, LTE, NR or WLAN terminal supporting wideband telephony, the system simulator shall use the AMR-WB speech codec as defined in the 3GPP TS 26 series of specifications, at the source coding bit rate of 12,65 kbit/s.

Super-wideband telephony testing

For testing of a LTE, NR or WLAN terminal supporting super-wideband telephony, the system simulator shall use the EVS speech codec as defined in 3GPP TS 26 series of specifications in super-wideband mode, at 32 kHz sampling rate, mono, at the source coding bit-rate of 24,4 kbit/s. The system simulator should support all operation modes of EVS speech codec, the complete EVS RTP payload format, and all SDP attributes as specified in TS 26.445 Annex A; it should be possible to control all the SDP attributes declared and negotiated by the system simulator.

Fullband telephony testing

For testing of a LTE, NR or WLAN terminal supporting fullband telephony, the system simulator shall use the EVS speech codec as defined in 3GPP TS 26 series of specifications in fullband mode, at 48 kHz sampling rate, mono, at the source coding bit-rate of 24,4 kbit/s.