Telephonic communications – Subscriber line or transmission line interface – Network interface device
Patent
1992-08-07
1994-09-27
Dwyer, James L.
Telephonic communications
Subscriber line or transmission line interface
Network interface device
379411, 370 321, H04M 900
Patent
active
053512910
ABSTRACT:
The echo cancellation method includes starting with an arbitrary set of echo filter coefficients. The coefficients are first sequentially re-estimated using a fast converging method.
These operations are repeated a predefined number of times, and then the coefficients estimation is switched to a low converging but more precise method. In addition, an adaptive threshold is being defined and readjusted and all filter coefficients lower than said threshold are being discarded.
Finally, sampling time boundaries are adaptively defined based on non-discarded filter coefficients with reference to said threshold, and in such a way the final echo cancellation algorithm is adaptive to echo variations (backtracking algorithm).
REFERENCES:
patent: 4577071 (1986-03-01), Johnston et al.
patent: 4677668 (1987-06-01), Ardalan et al.
patent: 4894820 (1990-01-01), Miyamoto et al.
patent: 5062102 (1991-10-01), Taguchi
IEEE Trans. On Circuits & Systems, vol. 38, No. 10, Oct. 1990, pp. 1693-1698.
Electrical Communication, vol. 59, No. 3, 1985, pp. 338-344.
Menez Jean
Rosso Michele
Scotton Paolo
Cockburn Joscelyn G.
Dwyer James L.
International Business Machines - Corporation
Smith C.
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