Telecommunications – Transmitter and receiver at same station – Radiotelephone equipment detail
Reexamination Certificate
2011-03-15
2011-03-15
Rego, Dominic E (Department: 2618)
Telecommunications
Transmitter and receiver at same station
Radiotelephone equipment detail
C379S406010, C379S406050, C379S406080, C370S286000, C370S289000
Reexamination Certificate
active
07907977
ABSTRACT:
Duplex audio communications over a network use compressed audio data, with linear prediction coefficients (LPCs) and variances by which sample values differ from predictions. A adaptive echo canceller for a transceiver develops finite impulse response filter (FIR) coefficients characterizing an echo path between its local audio output and audio input. The received/decompressed audio data is applied to the FIR coefficients, and the predicted echo is subtracted from the uplink signal. Echo is detected as cross-correlation of the receive signal versus the uplink/send signal over time. In one embodiment, the cross-correlation is determined using a pre-whitened receive signal, obtained by adopting the variance values received over the network by the downlink Codec. Apart from the uplink Codec, no speech analysis filter or process is needed. The technique is apt for GSM, AMR and similar compressed audio communications.
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Agere Systems Inc.
Rego Dominic E
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