Telephonic communications – Subscriber line or transmission line interface – Network interface device
Patent
1993-04-08
1995-08-29
Dwyer, James L.
Telephonic communications
Subscriber line or transmission line interface
Network interface device
379411, 379406, 370 321, H04B 320
Patent
active
054467870
ABSTRACT:
A method for avoiding self-oscillation in a four-wire loop in conjunction with echo cancellation is effected with the aid of an adaptive filter (15). Self-oscillation is avoided for both long and short connections and also when signalling with narrow-band signals, by restricting the permitted range of the coefficients of the adaptive filter in a manner such that the absolute value of the filter transfer function will be sufficiently small so that amplification in the four-wire loop is less than one. This is achieved by limiting the absolute value of the filter transfer function (1Hcal), to a value which is smaller than a determined function of the echo transfer function (H.sub.fa) in the far-end of the loop and the echo transfer function (H.sub.ne) in the near-end of the loop.
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William A. Sethares et al., Bursting in Adaptive Hybrids, IEEE Transactions on Communications, vol. 37, No. 8, pp. 791-799, Aug. 1989.
Abraham Krieger and Elias Masry, Constrained Adaptive Filtering Algorithms: Asymptotic Convergence Properties for Dependent Data, IEEE Transactions on Information Theory, vol. 35, No. 6, pp. 1166-1176, Nov. 1989.
J. W. Cook and R. Smith, An integrated Circuit for Analogue Line Interfaces With Adaptive Transmission and Extra Facilities, Br Telecom Technol. J., vol. 5, No. 1, pp. 32-42, Jan. 1987.
Dwyer James L.
Shehata Magdy W.
Telefonaktiebolaget LM Ericsson
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