Pulse or digital communications – Systems using alternating or pulsating current – Plural channels for transmission of a single pulse train
Patent
1994-09-12
1996-01-02
Chin, Stephen
Pulse or digital communications
Systems using alternating or pulsating current
Plural channels for transmission of a single pulse train
375265, 371 43, 341 4, H04L 512, H04L 2302
Patent
active
054815673
ABSTRACT:
The present invention discloses an improvement over existing techniques for transmitting data over voice-band telephone channels by automatically adapting the amount of warping or compression that is applied to a sequence of signal points. A sequence of warped signal points, each of which is related to a respective signal point of a predetermined base constellation according to a warp function, is received in a decoder via a transmission channel having a non-linear component. After each of the received signal points is unwarped using substantially an inverse of the warp function, the average dispersions of the received inner and outer signal points about corresponding sequences of expected signal points are calculated. The difference between the average dispersion of the inner and outer points is then computed and used to update the amount of warping or compression in order to further minimize the effects of the channel non-linearity. The desired amount of warping is communicated to the transmitting encoder.
REFERENCES:
patent: 5115453 (1992-05-01), Calderbank et al.
patent: 5265127 (1993-11-01), Betts et al.
patent: 5343500 (1994-08-01), Betts et al.
Kalet et al, "QAM Transmission Through a Companding Channel-Signal Constellations and Detections", IEEE Trans. on Communications, vol. 42 No. 2/3/4 Feb./Mar./Apr. 1994 pp. 417-429.
Betts, W., "Nonlinear Encoding by Surface Projection," International Conference on Data Transmission, Conference Publication No. 356, Savoy Place, London, England, Sep. 23-25, 1992, 6 pages.
Betts William L.
Zuranski Edward S.
AT&T Corp.
Chin Stephen
Webster Bryan E.
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