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US 4,495,620 AGranted
Transmitting data on the phase of speech
AssigneeAT&T Bell Laboratories
InventorsRaymond Steele, Wai C. Wong, Costas S. Xydeas
Life of this patent
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AssigneeAT&T Bell Laboratories
InventorsRaymond Steele, Wai C. Wong, Costas S. Xydeas
Estimating the term…
The present invention relates to a means for achieving simultaneous transmission of data and speech with only a minimal expansion of the bandwidth of the speech signal. A Fourier transform (14) is performed on the speech signal and a predetermined number of phase components are replaced with data (d(n)) in an appropriate form. The number of phase components replaced with data is determined by approximately classifying the speech (16) as either "silence", no data inserted; "unvoiced" speech, M phase components convey data; and "voiced" speech, J phase components convey data; where J is less than M, and M is not greater than the number of phase components in the message band of the speech signal. An inverse Fourier transform (22) is subsequently performed on the combined data and speech signal. The combined message signal (G(t)) will comprise approximately the same bandwidth as the original speech signal, by virtue of the frequency domain insertion of the data into the speech. At the receiver the signal is inspected and a classifier (38) determines if data is embedded in the received signal. If data is deemed embedded, a Fourier transformation is performed, the data carrying phase components are inspected, and the data signal regenerated in an appropriate form. The phase components used for the conveyance of data are replaced by random phase components, and the inverse Fourier transformation performed. Median filtering is employed to mitigate the effects of end-of-block distortion and yield the recovered speech signal.
In a simultaneous transmission system for data and analog speech:
A transmitter responsive to both an analog speech signal (s(t)) and a data stream (d(n)) for simultaneously transmitting the analog speech signal and the data stream as a combined message signal (g(t)) wherein the transmitter comprises
A receiver capable of recovering both an analog speech signal (s(t)) and a binary data stream (d(n)) from a combined message signal (g(t)) representative of a combination of the analog speech signal and the binary data stream wherein the receiver comprises
Dependencies are inferred from the claim text.