Acoustic Echo Cancellation for TrFO (AEC for TrFO)

Acoustic echo cancellation (AEC) is implemented in transcoder free operation (TrFO) calls to enhance voice quality when the Internet Protocol (IP) is used on the A interface. For details about the AEC and other voice enhancement technologies.

Acoustic echo arises because of the coupling between the loudspeaker and the earpiece of a telephone handset. Talkers on the far end hear acoustic echo when part of the far-end signal reproduced by the near-end loudspeaker is transferred through the earphone back to the far end.

AEC modules are generally embedded in mobile phones to cancel acoustic echo. Some mobile phones, however, have no AEC modules or poor-quality AEC modules. Transcoder (TC) resources for EC are therefore deployed on the base station controller (BSC) or media gateway (MGW). TC resources are deployed on the BSC when TDM transport is used on the A interface. TC resources are deployed on the MGW when IP transport is used on the A interface.

Supported network node: HUAWEI UMG8900, V200R009C02 and later

Software requirement: This feature is available only when the license is obtained.

Implementation:

The UMG8900 removes echo from the voice signals by modifying the code parameters.

1. The UMG8900 decodes part of the received code streams and obtains the desired code parameters.
2. The UMG8900 modifies the decoded codebook gain parameters obtained.
3. The UMG8900 encodes the modified code parameters and combines them with the other encoded parameters for framing, packetization, and transfer.
4. At the reception end, the UMG8900 decodes the received code stream; the decoded voice signals are free from echo.