Telephonic communications – Subscriber line or transmission line interface – Network interface device
Patent
1988-11-10
1990-05-15
Ng, Jin F.
Telephonic communications
Subscriber line or transmission line interface
Network interface device
370 321, H04B 323
Patent
active
049264729
ABSTRACT:
The present invention provides a technique for data detection signal processing for removing echo interference and/or distortion from a received 2B1Q coded signal. According to the preferred technique, the received 2B1Q signal Q, where q=(-3, -1, +1, +3), is shifted one bit to the left to generate a corresponding shifted symbol alphabet S, where S=(-2, 0, +2, +4). The shifted received signals are then processed through a transversal filter. That is, the signal is provided to a delay line which is tapped at intervals corresponding to the symbol width of the received signal. Each tap along the delay line is connected through an amplifier to a summing device that provides an output y(n), where ##EQU1## The tap gains, or coefficients a.sub.j, are set to subtract the effects of interference from symbols that are adjacent in time to the desired symbol. In an adaptive embodiment of the invention, the output y(n) resulting from the convolution between the transmitted symbols s(n) and the gain coefficients a.sub.j. The output of the transmission channel and the filter output y(n) are then processed in accordance with a convergence algorithm to develop an error feedback signal which is used to update the gain coefficients a.sub.j.
REFERENCES:
patent: 4785445 (1988-11-01), Guidoux
"Microprocessor Implementation of High-Speed Data Modems", Van Gerwen et al., IEEE Transactions on Communications, vol. COM-25, No. 2, Feb. 1977, pp. 238-250.
"High-Pass Filter Location in 2BiQ Transceivers", P. F. Adams, American National Standards Institute Telecommunications Committee, Doc No. Tidl. 3/86-193, 8, Oct. 1986, pp. 1-6.
Bitmead, Robert R., "Persistence of Excitation Conditions and the Convergence of Adaptive Schemes", IEEE Transactions on Information Theory, IT-30:2 (3/84), pp. 183-191.
Widrow, Bernard, "Adaptive Filters", Aspects of Network and System Theory, (1970), pp. 563-587.
Batruni Roy G.
Wilson Howard A.
National Semiconductor Corporation
Ng Jin F.
Vaas Randall S.
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