Equalizer for ISDN-U interface

Details Equalizer for ISDN-U interface Equalizer for ISDN-U interface

1989-06-19

1991-02-19

Ng, Jin F.

Multiplex communications

Wide area network

Packet switching

375 12, 375 14, H04J 300

Patent

active

049950312

ABSTRACT:
A receiver for a digital data transmission system comprises a sampling device for sampling digital data signals received from a subscriber loop. A precursor equalizer connected to the output of the sampling device equalizes, in effect filters, the sampled digital data signal. A timing recovery circuit connected to the output of the precursor equalizer controls the sampling device in dependence upon the filtered digital data signal. The precursor equalizer has a difference equation such that the equalized digital data signal has at least one zero-crossing occurring substantially one baud before the main cursor of each pulse. For twisted wire pair subscriber loops, the precursor equalizer may have a different equation: ##EQU1## which produces a single precursor zero-crossing. Alternatively, the precursor equalizer may have a difference equation: ##EQU2## which produces two precursor zero crossings, y(n) being the input to the filter, w(n) its output, h.sub.0 the main cursor height before equalization and h.sub.-1 the precursor height before equalization. The latter precursor equalizer may be modified by multiplying each of the coefficients (h.sub.-1 /h.sub.0).sup.2 and h.sub.-1 /h.sub.0 by a factor ##EQU3## for more precise determination of the zero crossings. A (1-Z.sup.-1) filter may be provided ahead of the precursor equalizer.

REFERENCES:
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patent: 4800573 (1989-01-01), Cupo
patent: 4815103 (1989-03-01), Cupo et al.
IEEE Transactions on Communications, "A Maximum-Likelihood Sequence Estimator with Decision-Feedback Equalization", by Won U. Lee and F. S. Hill, Jr., vol. COM-25, No. 9, Sep. 1977, pp. 971-979.
A Transmission System for ISDN Loops, by Ephraim Arnon et al, IEEE, 1986, pp. 192-200.
Digital Subscriber Loop Transmission Using Echo Canceller and Balancing Networks, by Misao Fukuda et al, IEEE, 1985, pp. 1181-1185.
IEEE Transactions on Communications, "Line Equalizer for a Digital Subscriber Loop Employing Switched Capacitor Technology", by Toshiro Suzuki et al, vol. COM-30, No. 9, Sep. 1982, pp. 2074-2082.
An ISDN 2B+D Basic Access Transmission System, by Roy B. Blake et al, AT&T Bell Laboratories, Whippany, N.J.
"A New Transmission System for ISDN Access at 144 kB/s", by Michael Vry, ISSLS 1984.
British Telecom Technology Journal, "A Long Reach Digital Subscriber Loop Transceiver", by P. F. Adams et al, vol. 5, No. 1, Jan. 1987, pp. 25-31.

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