TS 26.115
★
Echo Control
for Speech and Multimedia Services
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2020/06 … p.
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- Rapporteur:
- Mr. Usai, Paolino
Content for TS 26.115 Word version: 16.0.0
0 Introduction Word‑p. 4
1 Scope Word‑p. 5
3 Abbreviations
The present document specifies minimum performance requirements for the transmission planning aspects of 3G speech and multi-media services.
The objective is to reach a quality as close as possible to ITU T standards for PSTN circuits. However, due to technical and economic factors, there cannot be full compliance with the general characteristics of international telephone connections and circuits recommended by the ITU T.
The performance requirements are specified the main body of the text; the test methods and considerations are described in [tbd].
The present document specifies minimum performance requirements for the gateway echo control of 3G speech and multi-media services. The present document is applicable to any narrow band speech telephony or multimedia service.
2 References
The following documents contain provisions which, through reference in this text, constitute provisions of the present document.
- References are either specific (identified by date of publication, edition number, version number, etc.) or non specific.
- For a specific reference, subsequent revisions do not apply.
- For a non-specific reference, the latest version applies. In the case of a reference to a 3GPP document (including a GSM document), a non-specific reference implicitly refers to the latest version of that document in the same Release as the present document.
[1] ITU T Recommendation G.114 (2000): "One-way transmission time".
[2] ITU-T Recommendation G.168 (2000): "Digital network echo cancellers".
[3] ITU-T Recommendation G.131 (1996): "Control of talker echo".
[4] ITU-T Recommendation G.703 (1998): "Physical/electrical characteristics of hierarchical digital interfaces".
[5] ITU-T Recommendation G.711 (1988): "Pulse code modulation (PCM) of voice frequencies".
For the purposes of the present document, the following abbreviations apply:
ADC
4 Interfaces
Analogue to Digital Converter
DAC
Digital to Analogue Converter
DTX
Discontinuous Transmission
EC
Echo Canceller
EEC
Electrical Echo Control
EL
Echo Loss
ERL
Echo Return Loss
ERLE
Echo Return Loss Enhancement
PCM
Pulse Code Modulation
POI
Point of Interconnection (with PSTN)
PSTN
Public Switched Telephone Network
TCL
Terminal Coupling Loss
TX
Transmission
The POI with the public switched telephone network (PSTN) will generally be at the 2 048 kbits/ level at an interface in accordance with ITU T Recommendation G.703 [4]/G.704 or STM1 155Mbit/s. At this point, which is considered to have a relative level of 0 dBr, the analogue signals will be represented by 8 bit A law or μ-law according to ITU T Recommendation G.711 [5]. Analogue measurements may be made at this point using a standard send and receive side, as defined in ITU T Recommendations.
5 Narrow Band Speech Telephony Network Echo Control Word‑p. 6
5.1 GSTN Network Echo Cancellation
$ Change history Word‑p. 7
Narrow band speech calls from the 3G mobile system to the public GSTN are terminated on local switch line cards where two to four wire conversion takes place. The hybrid used to carry out this function is never perfect and echo is generated which degrades the speech call quality for the 3G mobile user. To overcome this situation an echo cancellation device should be used at the gateway from the 3G mobile network to the GSTN. This echo control device shall conform to ITU-T G.168 [2].
