Coded modulation communication system

Details Coded modulation communication system Coded modulation communication system

1989-05-26

1991-02-12

Safourek, Benedict V.

Pulse or digital communications

Repeaters

Testing

371 43, 341 95, 341100, H04L 512, H04L 2302

Patent

active

049930460

ABSTRACT:
In Trellis coded modulation system in which an input digital signal in parallel form is encoded by a convolutional encoder which adds an additional bit to the input digital signal for error correction purpose, and a mapping circuit designated amplitude and phase for each symbol for QAM signal, the number of parallel bits at output of said convolutional encoder is the same as the number of parallel bits of an input digital signal. An input digital signal is first rate converted so that m+n bits in every T period is converted to m bits in every T' period, where T'=(m/(m+n)).T. The convolutional encoder adds n number of bits so that the total number of parallel bits is m+n, which is applied to the mapping circuit. In a receive side, a received signal having m+n bits in every T' period is decoded through an error correction decoder which provides m bits in every T' period, then, the decoded signal is rate converted to m+n bits in every T period. So, the number of parallel bits does not increase in spite of convolutional encoding, but a transmission rate is a little increased. The coding gain in the present invention is improved since the number of levels of the QAM signal is not increased although the bandwidth of the signal is a little increased because of the higher clock rate.

REFERENCES:
patent: 4077021 (1978-03-01), Csajka et al.
patent: 4520490 (1985-05-01), Wei
patent: 4534040 (1985-07-01), Thapar
patent: 4586182 (1986-04-01), Gallager
patent: 4713817 (1987-12-01), Wei
patent: 4748626 (1988-05-01), Wang
"Trellis-Coded Modulation with Redundant Signal Sets Part I: Introduction", Ungerboeck, IEEE Communications Magazine, Feb. 1987, vol. 25, No. 2, pp. 5-11.
"Trellis-Coded Modulation with Redundant Signal Sets Part II: State of the Art", Ungerboeck, IEEE Communications Magazine, Feb. 1987, vol. 25, No. 2, pp. 12-21.
"Channel Coding with Multilevel/Phase Signals", Ungerboeck, IEEE Transactions on Information Theory, vol. IT-28, No. 1, Jan. 1982, pp. 55-67.

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