The present document is one of the parts of the specification of the Digital Enhanced Cordless Telecommunications (DECT) Common Interface (CI).
This part of the DECT CI specifies the speech and audio coding and transmission requirements.
In order to ensure satisfactory interworking of different portable and fixed units, it is necessary to specify the transmission performance of the analog information over the digital link. This requires not only use of a common speech algorithm, but also standardization of frequency responses, reference speech levels (or loudness) at the air interface and various other parameters.
The present document applies to DECT equipment which includes all the necessary functions to provide real-time two-way speech conversation and stereo audio transmission. Several speech services are defined in the present document, including conventional 3,1 kHz telephony, wideband 7 kHz voice transmission, super-wideband 14 kHz and fullband 20 kHz service. DECT Fixed part providing such services may be connected to the public circuit switched (PSTN/ISDN) network, to private networks or to the Voice over Internet Protocol (VoIP) network.
Tethered fixed point local loop applications are not required to comply with the requirements of the present document.
For the DECT systems which connect to the Public Switched Telephone Network (PSTN) via an analog interface, the additional requirements, which are implemented in the FP, have as much as possible been aligned with ETSI TBR 038.
A summary of the control and the use of the DECT echo control functions, to guide on need for options to manufacturers and installers, is found in annex A.
Information concerning test methods can be found in ETSI EN 300 176-1 and ETSI EN 300 176-2 (previously covered by ETSI TBR 010). The test methods take into account that DECT is a digital system.
The present document includes New Generation DECT, a further development of the DECT standard introducing wideband speech, improved data services, new slot types and other technical enhancements.
In addition, the present document includes DECT Evolution, providing SWB and FB speech and audio capabilities and a new speech coding algorithm for NB and WB allowing to increase the audio quality of the NB and WB speech service and improve bandwidth efficiency.
The latest update for DECT Evolution includes the support of ultra-band, high resolution, low-latency speech and audio coding, and additional PP types supported with LC3plus coding. An application profile using these new PP types can be found in ETSI TS 103 706.