Echo canceller

Details Echo canceller Echo canceller

1996-11-13

1998-08-25

Matar, Ahmad F.

Telephonic communications

Subscriber line or transmission line interface

Network interface device

379406, 379411, 36472419, H04M 900

Patent

active

057990786

ABSTRACT:
Digital filters are used to simulate the transmission function of a real system by means of echo cancellers, where a high-speed digital signal processor with a large memory is needed to compute and update the filter coefficients. To reduce the cost of the echo canceller, an autocorrelation, i.e. the correlation of a block of a defined number of sampling values of the transmitted signal with received echoes derived from this transmitted signal, is used by the invention to determine the time periods at which an echo arrives, and at which an update of the filter coefficients then takes place. In this way the number of filter coefficients to be computed and the cost of their computation are significantly reduced, so that echo cancellers for telephone terminals can be produced in a cost-effective manner.

REFERENCES:
patent: 4570036 (1986-02-01), Virdee
patent: 4977591 (1990-12-01), Chen et al.
patent: 5062102 (1991-10-01), Taguchi
patent: 5351291 (1994-09-01), Menez et al.
patent: 5390250 (1995-02-01), Janse et al.
patent: 5423976 (1995-06-01), Glanville et al.
patent: 5636323 (1997-06-01), Umemoto et al.
patent: 5638439 (1997-06-01), Kawada et al.
patent: 5687229 (1997-11-01), Sih
patent: 5737410 (1998-04-01), Vahatalo
Patent Abstracts of Japan, vol. 15, No. 417 (E-1125), 23 Oct. 1991 & JP 03 173229 A (Nec Corp.), 26 Jul. 1991.
"Processing Methods to Improve Voice Communication Via Intercom Stations" by R. Wehmann et al, from the Telecommunications Engineer, 48th year, Oct. 1994, pp. 27-28.
"Combination of Noise Reduction and Echo Combination During Intercommunications", by T. Hugh et al, Communications Electronics, Berlin 43 (1993), pp. 274-280.

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