Multiplex communications – Wide area network – Packet switching
Patent
1980-04-09
1982-01-26
Ng, Jin F.
Multiplex communications
Wide area network
Packet switching
370 23, 375 1, H04J 302
Patent
active
043131972
ABSTRACT:
It is known to multiplex speech signals and nonspeech signals over a common communication path. One arrangement uses a portion of the frequency spectrum of the path for speech signals with the remainder for nonspeech signals. Another inserts data signals during gaps in the speech signals. Still another treats a speech signal as a carrier signal and modulates the speech signal with data signals. Unfortunately, users of such known arrangements experience excessive distortion or perceive others as encroaching on the path. These and other problems are mitigated by my improved signal processor (100, 200) for the spread spectrum (de)multiplexing of speech signals and nonspeech signals. In an illustrative embodiment, at a transmitter, a block (110) of speech signals may be converted (140) from a time domain to a frequency domain by a Fourier transformation. A Fourier component may be pseudo-randomly selected (130) from a subset of such components. Responsive to the selected component, a prediction (160) of the component may be substituted therefor, the prediction being thereafter modified (170), e.g., by its amplitude being incremented or decremented to reflect the multiplexing of a logic 1 or a logic 0 nonspeech signal. The modified prediction may be converted (150) back to the time domain for transmission to a receiver. At the receiver, a parallel demultiplexing (200) occurs for extracting (270) speech signals and nonspeech signals from the multiplexed signals.
REFERENCES:
patent: 1895461 (1933-01-01), Heising
patent: 3304372 (1967-02-01), Filipowsky
patent: 3311704 (1967-03-01), Filipowsky
patent: 3406344 (1968-10-01), Hopper
patent: 3492429 (1970-01-01), Schroeder
patent: 3984626 (1976-10-01), Mounts
patent: 4221934 (1980-09-01), Schiff
"A Guided Tour of the Fast Fourier Transform", by G. D. Bergland, IEEE Spectrum, vol. 6, No. 7, Jul. 1969, pp. 41-52.
Spread Spectrum Systems, Chapter I, by R. C. Dixon, New York: John Wiley & Sons, 1976, pp. xi-xv, 1-12.
Bell Telephone Laboratories Incorporated
Chin Tommy P.
Ng Jin F.
Roddy Richard J.
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