Bandpass spectral shaping of data signals

Details Bandpass spectral shaping of data signals Bandpass spectral shaping of data signals

1997-03-03

1999-09-14

Chin, Stephen

Pulse or digital communications

Pulse code modulation

375222, 370507, 341144, 341145, H04B 1404

Patent

active

059533749

ABSTRACT:
A process for transmitting data selects sample values that represent data symbols and then converts the sample values to voltage levels in a transmitted PAM signal. A receiver samples the PAM signal and identifies the data symbols from the sampled voltage levels. At least some of the data symbols have multiple alternative representations; and for a data symbol having multiple alternatives, a sample value is selected to reduce low and high frequency components in the PAM signal. Accordingly, the PAM signal carries less information at low and high frequencies and is less disturbed by transformers, low pass filters, and local loop impairment in the transmission channel. The process for selecting sample values determines a weighted average of the lowest and highest frequency components. The weighting of the average can be selected according to a measured frequency response of the channel during initialization.

REFERENCES:
patent: 4403331 (1983-09-01), Halpern et al.
patent: 4903292 (1990-02-01), Dillon
patent: 5394437 (1995-02-01), Ayanoglu et al.
patent: 5455839 (1995-10-01), Eyuboglu
patent: 5546395 (1996-08-01), Sharma et al.
patent: 5687194 (1997-11-01), Paneth et al.
Telecommunications Industry Association TR-30 Committee Contribution, "DC Suppresser for 56 K Modems," pp. 1-2 (Oct. 16-17, 1996).
Telecommunications Industry Association TR30.1 Group Contribution, "A Spectral Shaping Technique for PCM Modems," pp. 1-4 (Nov. 13-15, 1996).

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