METHODS FOR IN-BAND SIGNALING THROUGH ENHANCED VARIABLE-RATE CODECS

• US 20100067565A1
• Filed: 10/15/2008
• Published: 03/18/2010
• Est. Priority Date: 09/15/2008
• Status: Active Grant

• Current Assignee: Karma Automotive LLC (Wanxiang Group Corporation)
• Original Assignee: Airbiquity Incorporated
• Inventors: Birmingham, Kifay, Zhao, Lee, Quimby, David, Hirano, Michael
• Granted Patent: US 7,983,310 B2
• Time in Patent Office: Days
• US Class Current: 375/219
• CPC Class Codes: H04L 25/0384 Design of pulse shapes pulse shape for impulse radio H04B1/7172
• CPC Class Codes: H04L 27/10 Frequency-modulated carrier systems, i.e. using frequency-shift keying H04L27/32 takes precedence
• CPC Class Codes: H04M 11/066 Telephone sets adapted for data transmision

Abstract

Improvements are disclosed for in-band signaling, i.e., transmission of data in a voice channel of a digital wireless network during a voice call session. A family of narrow-band signaling methods is disclosed to successfully pass data-carrying signals through the low-bit rate modes of the EVRC-B vocoder commonly used in CDMA wireless channels. Some embodiments generate a tapered signaling waveform in tandem with another waveform using FSK-modulation. These features can be used in cell phones or other wireless communication devices, including automotive applications.

Claims

1. An in-band signaling modem for use in a digital wireless telecommunications device to send data over a voice channel of a digital wireless telecommunications network, the in-band signaling modem comprising:

software stored in a memory in the wireless telecommunications device, the software executable in a processor in the wireless telecommunications device;

the software configured to control the processor to generate a predetermined first signaling waveform for transmission over the voice channel, the first signaling waveform having a frequency within a range of approximately 400-3400 Hz; and

wherein the first signaling waveform is tapered at the beginning of the waveform, such that it gradually increases in amplitude from substantially zero amplitude to a predetermined peak amplitude, for reducing distortion of the signaling waveform by a vocoder in the voice channel.

2. An in-band signaling modem according to claim 1 wherein the first signaling waveform is tapered at the end of the waveform, such that it gradually decreases in amplitude from the peak amplitude to substantially zero amplitude;

and

the first signaling waveform has a duration within a range of approximately 1-3 seconds.

3. An in-band signaling modem according to claim 2 wherein the digital wireless telecommunications device comprises a cell phone.

4. An in-band signaling modem according to claim 2 wherein the telecommunications device is integrated into a motor vehicle and arranged for automatic operation to send data in an emergency over a voice channel of the digital wireless telecommunications network.

5. An in-band signaling modem according to claim 2 wherein the first signaling waveform has a duration of approximately three seconds and has a frequency greater than approximately 2 kHz.

6. An in-band signaling modem according to claim 2 wherein the first signaling waveform is generated prior to transmission and stored in a memory in the communications device.

7. An in-band signaling modem according to claim 2 wherein the first signaling waveform comprises approximately a 3 second, 2225 Hz tone for backward compatibility with legacy detectors.

8. An in-band signaling modem according to claim 2 wherein the software is further configured to control the processor to generate a combination signaling waveform for transmission over the voice channel, the combination signaling waveform comprising the first signaling waveform and a second signaling waveform, the second signaling waveform characterized by FSK (phase shift keying) modulation of two audio frequencies;

and the first and second signaling waveforms transmitted in tandem.

9. An in-band signaling modem according to claim 8 wherein the first signaling waveform is generated by applying a selected one of the Hamming, Parzen, Gaussian, Bartlett, and Kaiser window functions.

10. A computer program stored in a machine-readable storage medium for execution in a digital processor in a digital wireless telecommunications device to send data over a voice channel of a digital wireless telecommunications network, the program configured to transmit a predetermined signaling waveform having at least one tapered end for transmission prior to sending data in the voice channel.

11. A computer program product storing executable code for use in a digital wireless telecommunications device to send data over a voice channel of a digital wireless telecommunications network wherein the code is executable on processor in the cell phone

and wherein the code is configured to generate a combination signaling waveform for transmission prior to transmitting data over the voice channel, the combination signaling waveform selected to reduce distortion in a vocoder;

and further

wherein the combination signaling waveform includes at least two different bursts in tandem, each burst having a duration of at least approximately 1.0 second, and at least one of the bursts comprising a substantially sinusoidal waveform having a frequency greater than approximately 2 kHz and tapered at the beginning of the waveform from substantially zero amplitude to a predetermined peak amplitude.

12. The computer program product of claim 11, wherein the code is configured to generate the combination signaling waveform having a total duration of at least approximately three seconds.

13. The computer program product of claim 12, wherein the second burst waveform is characterized by FSK (phase shift keying) modulation of two audio frequencies, and the second burst either precedes or follows the first burst.

14. The computer program product of claim 11, wherein the first burst comprises approximately a three-second, 2225 Hz tone.

15. A method for adapting an audio frequency waveform to traverse a vocoder in a voice channel of a digital wireless telecommunication system with reduced distortion, the method comprising:

generating a first audio frequency waveform;

extending the duration of the first waveform to a selected duration within a range of approximately 1-3 seconds; and

applying a windowing function to the first waveform so as to taper the leading and trailing ends of the first waveform, for reducing distortion in certain low rate vocoders that may be encountered when transmitting the first waveform in the voice channel of a digital wireless telecommunication system.

16. The method of claim 15 and further comprising:

generating a second waveform for transmission in tandem with the first waveform;

wherein the second waveform is characterized by FSK (phase shift keying) modulation of two audio frequencies.

17. The method of claim 16 wherein the windowing function is selected from the group consisting of the Hamming, Parzen, Gaussian, Bartlett, and Kaiser window functions.

18. A method for communicating digital data over a voice channel of a digital wireless telecommunications network comprising:

receiving digital input data;

encoding the input data into audio frequency tones for transmission via the voice channel;

generating a signaling waveform;

first transmitting the signaling waveform over the voice channel to prepare a transmission side vocoder;

and then transmitting the audio frequency tones that encode the input data over the voice channel.

19. The method of claim 18 wherein the signaling waveform comprises at least two different bursts in tandem, each burst having a duration of at least approximately 1.0 second, and at least one of the bursts comprising an audio frequency waveform that is tapered at the beginning of the waveform, such that it gradually increases in amplitude from substantially zero amplitude to a predetermined peak amplitude, for reducing distortion of the signaling waveform by a vocoder in the voice channel.

20. The method of claim 19 wherein the first burst is tapered and a second burst waveform is characterized by FSK (phase shift keying) modulation of two audio frequencies.