Voice activated date rate change in simultaneous voice and data transmission

• US 5,475,691 A
• Filed: 11/15/1993
• Issued: 12/12/1995
• Est. Priority Date: 11/15/1993
• Status: Expired due to Term

• Current Assignee: Delaware Radio Technologies LLC
• Original Assignee: AT&T Corporation (AT&T, Inc.)
• Inventors: Chapman, Joseph Q., Holmquist, Kurt E.
• Primary Examiner(s): Safourek, Benedict V.
• Application Number:
  US08/151,677
• Time in Patent Office: 757 Days
• Field of Search: 370/20, 370/69.1, 370/76, 370/84, 370/85.7, 370/95.1, 370/110.1, 370/110.4, 370/111, 370/125, 379/97, 379/98, 375/5, 375/39, 375/216, 375/261, 375/264, 455/54.2, 455/58.1, 455/58.2, 455/82
• US Class Current: 370/527
• CPC Class Codes: H04L 1/0003 by switching between different modulation schemes
• CPC Class Codes: H04L 1/0017 where the mode-switching is based on Quality of Service requirement
• CPC Class Codes: H04L 1/0025 Transmission of mode-switching indication
• CPC Class Codes: H04L 1/0039 other detection of signalling, e.g. detection of TFCI explicit signalling H04L1/0046, H04L27/0012 and H04L25/0262 take precedence
• CPC Class Codes: H04L 27/3477 by using the outer points of the constellation or of the constituent two-dimensional constellations
• CPC Class Codes: H04M 11/06 Simultaneous speech and data transmission, e.g. telegraphic transmission over the same conductors
• CPC Class Codes: H04M 11/062 using different frequency bands for speech and other data
• CPC Class Codes: Y02D 30/50 in wire-line communication networks, e.g. low power modes or reduced link rate

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.

Claims

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.

2. The method of claim 1 wherein the analog signal is a voice signal.

3. The method of claim 2 wherein the detection of the voice signal is provided by an off-hook signal.

4. A method for changing a data rate comprising the steps of:

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.

5. Modem apparatus comprising:

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.

6. The apparatus of claim 5 wherein the analog signal is a voice signal.

7. The apparatus of claim 6 wherein the means for selecting a signal space operates in response to detecting an off-hook signal, which represents the presence of the voice signal.

8. Apparatus for use in a simultaneous voice and data modem, the apparatus comprising:

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.

9. The apparatus of claim 8 wherein the analog signal is a voice signal.

10. The apparatus of claim 9 wherein the analog signal source is a telephone and further including a means of detecting the presence of the analog signal by the off-hook status of the telephone.

11. Data communication equipment apparatus:

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.