The challenge for telecom industry in the acoustic and network echo canceller
Keywords:Acoustics, Adaptive filtering, Echo suppression, Mobile phones, Noise abatement, Quality of service, Speech, Initial convergence, Linear adaptive filter, Network echo canceller, Speech quality, Telecom industry
AbstractThe telecom industry is designing echo cancellation chip to give the best speech quality under server environment and with minimum cost with Zarlink Semiconductor TruePlex technology. The major function blocks of TruePlex include, the Linear adaptive filter, which emulates the linear echo path to cancel the majority of echo in the received path. Non-linear echo canceller is another part that cancels some non-linear components in the echo so that the residual can be further reduced. Noise reduction is more important in the mobile phone where noise power is much stronger than speech. Output Limiter emulates DAC clipping so that the adaptive filter still see a linear echo path even the speaker clips. Anti-Howling controls the loop stability during initial convergence or when echo path changes. All these function blocks make the chip to fully cancel the echo without affecting the incoming speech quality under server condition such as lower than -2OSNR and enhanced echo return of 10dB.
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