Listener echo cancellation for modems

Details Listener echo cancellation for modems Listener echo cancellation for modems

1995-11-14

1997-10-21

Zele, Krista M.

Telephonic communications

Subscriber line or transmission line interface

Network interface device

379411, 370286, 370290, 375222, H04B 323

Patent

active

056804512

ABSTRACT:
To improve the signal to noise ratio of the receiver of a receiving modem, the receiving modem is equipped with the ability to cancel the listener echo. Cancellation of the listener echo is achieved by coupling to the listener echo canceller of the receiving modem the phase corrected adaptive equalizer output signal, which is conventionally found in modems. The phase corrected adaptive equalizer output signal contains the in-phase, quadrature (also known as X and Y, or real and imaginary, components of the) received modem signal at the symbol rate. Advantageously, doing so results in an improved SNR for the receiver of the receiving modem, thus allowing higher data rates or reduced error rates without requiring extension of the length of the modem equalizer. When the telephone network does not introduce any frequency offset of the modem signal in the channel, the listener echo canceller may be simplified to reduce its cost.

REFERENCES:
patent: 4613731 (1986-09-01), Godard
patent: 5189664 (1993-02-01), Cheng
patent: 5319636 (1994-06-01), Long et al.
patent: 5406552 (1995-04-01), Long et al.
patent: 5418778 (1995-05-01), Cummiskey et al.
patent: 5577027 (1996-11-01), Cheng
patent: 5625646 (1997-04-01), Goodson et al.
Bellcore Technical Committe Contribution, TR-30.3/95-11 "Listener Echo and Modem Performance" Nov. 13, 1995.

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