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TS 26.115
Echo Control
for Speech and Multimedia Services

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Mr. Usai, Paolino

Content for  TS 26.115  Word version:  18.0.0

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0  Introductionp. 4

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].

1  Scopep. 5

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  Referencesp. 5

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.
ITU-T Recommendation G.114 (2000): "One-way transmission time".
ITU-T Recommendation G.168 (2000): "Digital network echo cancellers".
ITU-T Recommendation G.131 (1996): "Control of talker echo".
ITU-T Recommendation G.703 (1998): "Physical/electrical characteristics of hierarchical digital interfaces".
ITU-T Recommendation G.711 (1988): "Pulse code modulation (PCM) of voice frequencies".

3  Abbreviationsp. 5

For the purposes of the present document, the following abbreviations apply:
Analogue to Digital Converter
Digital to Analogue Converter
Discontinuous Transmission
Echo Canceller
Electrical Echo Control
Echo Loss
Echo Return Loss
Echo Return Loss Enhancement
Pulse Code Modulation
Point of Interconnection (with PSTN)
Public Switched Telephone Network
Terminal Coupling Loss

4  Interfacesp. 5

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 Controlp. 6

5.1  GSTN Network Echo Cancellationp. 6

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].

$  Change historyp. 7

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