Voice activated date rate change in simultaneous voice and data transmission
DCFirst Claim
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1. A method for use in data communications equipment, the method comprising the steps of:
- selecting a signal space as a function of the detection of an analog signal;
selecting symbols from the selected signal space as a function of an applied data signal;
providing a resultant signal, where the resultant signal represents the selected symbols when no analog signal is detected and represents the addition of a respective signal point to each one of the selected symbols when the analog signal is detected; and
transmitting the resultant signal.
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Abstract
A simultaneous voice and data modem performs "voice-activated" data rate changes to improve the transmission quality of the voice signal. In particular, when the simultaneous voice and data modem detects that a local telephone set has gone "off-hook," the simultaneous voice and data modem selects a signal space with a lower symbol density, which, although resulting in fewer bits per symbol, provides for a higher quality voice transmission.
47 Citations
11 Claims
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1. A method for use in data communications equipment, the method comprising the steps of:
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selecting a signal space as a function of the detection of an analog signal; selecting symbols from the selected signal space as a function of an applied data signal; providing a resultant signal, where the resultant signal represents the selected symbols when no analog signal is detected and represents the addition of a respective signal point to each one of the selected symbols when the analog signal is detected; and transmitting the resultant signal. - View Dependent Claims (2, 3)
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4. A method for changing a data rate comprising the steps of:
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selecting a first signal space when no off-hook signal is detected; transmitting a data signal at a first data rate, where the data signal is represented by a stream of data symbols selected from the first signal space, the data symbols having k bits per symbol; selecting a second signal space when an off-hook signal is detected wherein the data symbols have j bits per symbol and j<
k, wherein the data signal is now represented by a stream of data symbols selected from the second signal space;encoding a voice signal to provide a stream of signal points subsequent to the detection of the off-hook signal; and adding the stream of signal points to the stream of data symbols selected from the second signal space to provide a stream of data plus voice signal points; wherein the step of transmitting now transmits the data plus voice signal points.
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5. Modem apparatus comprising:
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means for selecting a signal space as a function of the presence of an analog signal; means for selecting symbols from the selected signal space as a function of an applied data signal; means for adding to each one of the selected symbols a respective signal point that represents the analog signal if the analog signal is present to provide a sequence of resultant signal points; and means for transmitting the resultant sequence of signal points. - View Dependent Claims (6, 7)
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8. Apparatus for use in a simultaneous voice and data modem, the apparatus comprising:
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means for coupling the modem to a data signal source, an analog signal source and a communications channel; means responsive to the detection of an analog signal from the analog signal source for providing a resultant signal, wherein if no analog signal is detected, the resultant signal represents a sequence of data symbols selected from a first signal space, and if the analog signal is detected the resultant signal represents a sequence of signal points, where each signal point has a data symbol component and an analog signal component, where the data symbol component is selected from a second signal space; and means for transmitting the resultant signal to a far-end modem over the communications channel. - View Dependent Claims (9, 10)
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11. Data communication equipment apparatus:
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means responsive to an off-hook signal for selecting a first signal space when an off-hook signal is not present and for selecting a second signal space when the off-hook signal is present, where data symbols of the first signal space have k bits per symbol and data symbols of the second symbol space have j bits per symbol and j<
k;means for encoding a voice signal after the off-hook signal is detected to provide a stream of voice signal points; means for encoding a data signal to provide a stream of data symbols from the selected signal space; means for adding the stream of signal points to the stream of data symbols after the off-hook signal is detected to provide a stream of data plus voice signal points; and means for transmitting the data signal as represented by either the stream of data symbols when the off-hook signal is not present or the stream of data plus voice signal points after the off-hook signal is detected.
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Specification