High speed data modem using multilevel encoding

Details High speed data modem using multilevel encoding High speed data modem using multilevel encoding

1983-09-26

1987-02-24

Fleming, Michael R.

Excavating

375 39, H04L 512, G06F 1110

Patent

active

046463054

ABSTRACT:
A 14.4 kilobit/second modem uses an encoding scheme in which groups of five bits are encoded as one of thirty-two (2.sup.5) possible code groups. This is done by using quadrature amplitude modulation and a 6 by 6 space-state constellation which allows a maximum of thirty-six different points to be encoded. Since only thirty-two points are needed the four outer corner points of the constellation are not used. In order to achieve the desired 14.4 KBPS data rate the baud clock must run at 2880 Hz. However, this bandwidth is very close to the maximum bandwidth available on voice-grade telephone lines. Accordingly, data encoding and data recovery techniques must be used which maximize the probabilities of correctly receiving the encoded data signals. These techniques include (1) data scrambling/descrambling; (2) assigning groups of five bits to constellation points, including performing rotational and Gray encoding; (3) a baud clock recovery scheme at the receiver which is performed prior to partial response encoding; and (4) a start-up technique using a three-level partial response ideal reference sequence during initial training at the receiver. In addition, the invention uses passband equalization, class I partial response encoding accomplished by the passband equalizer, and independent inphase and quadrature Viterbi decoders at the receiver.

REFERENCES:
patent: 3388330 (1968-06-01), Kretzmer
patent: 3887768 (1975-06-01), Forney et al.
patent: 4123710 (1978-10-01), Stuart et al.
patent: 4271527 (1981-06-01), Armstrong
patent: 4327439 (1982-04-01), Gockler
patent: 4346473 (1982-08-01), Davis
patent: 4464767 (1984-08-01), Bremer
patent: 4466109 (1984-08-01), Sari
patent: 4483012 (1984-11-01), Wei
patent: 4484338 (1984-11-01), Clark et al.
A. J. Viterbi & J. K. Omura, Principles of Digital Communication and Coding, McGraw-Hill, 1979, pp. 295-298.
S. Qureshi, "An Adaptive Decision-Feedback Receiver Using Maximum-Likelihood Sequence Estimation," Proceedings of the 1973 ICC, pp. 14-10 to 14-16.
S. Qureshi and E. E. Newhall, "An Adaptive Receiver for Data Transmission Over Time-Dispersive Channels," IEEE Transactions on Information Theory, vol. IT-19, No. 4, Jul. 1973, pp. 448-457.
D. D. Falconer & F. R. Magee, Jr., "Adaptive Channel Memory Truncation for Maximum Likelihood Sequence Estimation," Bell System Technical Journal, vol. 52, No. 9, Nov. 1973, pp. 1541-1562.
J. G. Smith, "Odd-Bit Quadrature Amplitude-Shift Keying," IEEE Transactions on Communications, Mar. 1975, pp. 385-389.
F. R. Magee, Jr., "A Comparison of Compromise Viterbi Algorithm and Standard Equalization Techniques Over Band-Limited Channels," IEEE Transactions on Communications, vol. COM-23, No. 3, Mar. 1975, pp. 361-367.
A. Lender, "The Duobinary Technique for High Speed Data Transmission," IEEE General Winter Meeting, 1963, Conf. Paper CP63-283.
A. Lender, "Correlative Level Encoding for Binary Data Transmission," IEEE Spectrum, Feb. 1966.
E. Kretzmer, "Generalization of a Technique for Binary Data Communication," IEEE Transactions on Communication Technology.
A. S. Acampora, "Analysis of Maximum Likelihood Sequence Estimation Performance for Quadrature Amplitude Modulation," The Bell System Technical Journal, vol. 60, No. 6, Jul.-Aug. 1981, pp. 865-885.
E. E. Arshadnia & S. A. Tretter, "Performance of a QAM Communication System Using a 32 Point Signal Constellation with Partial Response Encoding and Viterbi Decoding".
IBM Europe, "Proposal for a 14,400 Bit Per Second Modem for Use on 4 Wire Telephone Circuits," CCITT, Feb. 1983.
P. Treynor, "Modem Uses Microprocessor to Achieve 9600 bps on Voice Channel," , Tele. Eng. and Manag., Apr. 1, 1980.
D. N. Godard, "Passband Timing Recovery in an All Digital Modem Receiver," IEEE Transactions on Communications, vol. 26, No. 5, May 1976.

Affiliated with

Also associated with

Rating

High speed data modem using multilevel encoding does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with High speed data modem using multilevel encoding, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and High speed data modem using multilevel encoding will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-114208