MIXED VOICE AND SPREAD SPECTRUM DATA SIGNALING WITH ENHANCED CONCEALMENT OF DATA
First Claim
1. A method of preparing an analog audio signal and a digital bit stream for transmission via an analog communication channel, the method comprising:
- generating a chip sequence;
combining the digital bit stream and the chip sequence, to form a spread spectrum sequence;
modulating the spread spectrum sequence onto the audio signal, to form a modulated signal; and
suppressing one or more noise-like artifacts of the modulated signal.
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Abstract
Systems, methods, and devices for mixed voice and spread spectrum data signaling with enhanced concealment of data are disclosed. Audible artifacts may be reduced or suppressed in order to improve the audible quality of the sound. The distortion to the audio may be kept just below perceptibility, yet the data contained within the modulated signal is recoverable on the receiving side. The recovery of the data is robust to the impairments imposed by the communication channel. The disclosed systems, methods, and devices may be implemented in audio conferencing or video conferencing. Various embodiments of the present disclosure provide a data and voice mixer, which includes an improved spread spectrum data hiding transmitter. The transmitter may comprise a spreading encoder, a Phase Shift Keying (PSK) modulator, and a notch filter. A pseudo random switching pattern may be applied to a plurality of chip sequence generators in order to reduce or suppress an undesirable audible artifact. The transmitter may further comprise a phase randomizer operable to rotate the phase of the output of the spreading encoder by a pseudo random increment of approximately 45 degrees.
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Citations
28 Claims
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1. A method of preparing an analog audio signal and a digital bit stream for transmission via an analog communication channel, the method comprising:
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generating a chip sequence;
combining the digital bit stream and the chip sequence, to form a spread spectrum sequence;
modulating the spread spectrum sequence onto the audio signal, to form a modulated signal; and
suppressing one or more noise-like artifacts of the modulated signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. An audio conferencing endpoint, comprising:
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at least one microphone;
an audio and data mixer communicably coupled to the at least one microphone, the audio and data mixer comprising;
a first chip sequence generator operable to generate a first chip sequence;
a spreading encoder operable to combine a digital bit stream and the first chip sequence, to form a spread spectrum sequence;
a phase randomizer operable to rotate a phase of the spread spectrum sequence by a pseudo-random increment every chip; and
a modulator operable to modulate the rotated spread spectrum sequence onto an analog audio signal received from the at least one microphone, to form a modulated signal;
at least one speaker; and
an audio and data separator communicably coupled to the at least one speaker, the audio and data separator comprising;
a demodulator operable to demodulate a received signal, to produce a demodulated signal;
a phase de-randomizer operable to de-randomize the demodulated signal, by multiplying the demodulated signal by a complex conjugate of a pseudo random phase pattern, to produce a phase envelope sequence;
a second chip sequence generator, operable to generate a second chip sequence; and
a spreading decoder operable to multiply the phase envelope sequence by the second chip sequence, to reconstruct a received bit stream. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21, 22)
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23. An audio conferencing system, comprising:
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a plurality of geographically remote endpoints; and
a conference bridge communicably coupled to each of the plurality of endpoints via at least one communication channel;
wherein at least one of the plurality of endpoints comprises;
at least one microphone; and
an audio and data mixer communicably coupled to the at least one microphone, the audio and data mixer comprising;
a first chip sequence generator operable to generate a first chip sequence;
a spreading encoder operable to combine a digital bit stream and the first chip sequence, to form a spread spectrum sequence;
a phase randomizer operable to rotate a phase of the spread spectrum sequence by a pseudo-random increment every chip; and
a modulator operable to modulate the rotated spread spectrum sequence onto an analog audio signal received from the at least one microphone, to form a modulated signal; and
wherein at least another one of the plurality of endpoints comprises;
at least one speaker; and
an audio and data separator communicably coupled to the at least one speaker, the audio and data separator comprising;
a demodulator operable to demodulate a received signal, to produce a demodulated signal;
a phase de-randomizer operable to de-randomize the demodulated signal, by multiplying the demodulated signal by a complex conjugate of a pseudo random phase pattern, to produce a phase envelope sequence;
a second chip sequence generator, operable to generate a second chip sequence; and
a spreading decoder operable to multiply the phase envelope sequence by the second chip sequence, to reconstruct a received bit stream. - View Dependent Claims (24, 25, 26, 27, 28)
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Specification