IN-BAND SIGNALING FOR DATA COMMUNICATIONS OVER DIGITAL WIRELESS TELECOMMUNICATIONS NETWORKS

• US 20080056469A1
• Filed: 10/22/2007
• Published: 03/06/2008
• Est. Priority Date: 05/19/1998
• Status: Active Grant

• Current Assignee: Karma Automotive LLC (Wanxiang Group Corporation)
• Original Assignee: Airbiquity Incorporated
• Inventors: Smith, Phillip, Protor, Rod, Leyendecker, Robert, Eatherly, Wayne, Preston, Dan, Preston, Joseph
• Granted Patent: US 8,068,792 B2
• Time in Patent Office: Days
• US Class Current: 379/93.05
• CPC Class Codes: G01S 2205/002 for traffic control, mobile tracking, guidance, surveillance or anti-collision
• CPC Class Codes: G01S 2205/008 using a mobile telephone network
• CPC Class Codes: G01S 5/0027 of actual mobile position, i.e. position determined on mobile
• CPC Class Codes: G08G 1/127 to a central station ; Indicators in a central station
• CPC Class Codes: G10L 19/00 Speech or audio signals analysis-synthesis techniques for redundancy reduction, e.g. in vocoders; Coding or decoding of speech or audio signals, using source filter models or psychoacoustic analysis in musical instruments G10H
• CPC Class Codes: H04M 11/04 with alarm systems, e.g. fire, police or burglar alarm systems

Abstract

An inband signaling modem communicates digital data over a voice channel of a wireless telecommunications network. An input receives digital data. An encoder converts the digital data into audio tones that synthesize frequency characteristics of human speech. The digital data is also encoded to prevent voice encoding circuitry in the telecommunications network from corrupting the synthesized audio tones representing the digital data. An output then outputs the synthesized audio tones to a voice channel of a digital wireless telecommunications network.

Claims

1. A system for communicating digital data over a voice channel of a digital telecommunications network, comprising:

an input for receiving digital data;

a processor for converting the digital data into audio tones; and

an output for outputting the audio tones to digital transmission circuitry that encodes the audio tones in a same manner used for encoding voice signals and transmits the encoded audio tones over the same voice channel in the digital telecommunications network used for transmitting the voice signals.

2. The system of claim 1 wherein a sound card converts binary “

1”

bits in the digital data to a first tone having a first frequency within a human voice range and the sound card converts binary “

0”

bits in the digital data to a second tone having a second frequency within the human voice range.

3. The system of claim 2 wherein the first and second frequency are both between 400 and 1000 Hertz.

4. The system of claim 1 wherein the input is coupled to a telephone line and the processor digitizes the audio tones on the telephone line.

5. The system of claim 4 including a computer that converts the digitized audio tones back into binary bit values.

6. The system of claim 1 further comprising:

a vocoder component for decoding the encoded audio tones received from the voice channel of the digital telecommunications network into audio tones;

a frequency conversion component for converting the audio tones into at least one data packet including a preamble and the digital data;

a packet disassembling component for extracting the digital data from the at least one data packet; and

a storage component for storing the digital data.

7. A method for communicating data over a voice channel of a telecommunications network, comprising:

assembling bits of data into one or more packets, the one or more packets formatted for transmission over a wireless voice channel of the telecommunications network;

converting each bit in the one or more packets into at least one unique frequency, the at least one unique frequency falling within a human voice frequency band;

encoding the converted bits with a vocoder; and

transmitting the encoded bits over the voice channel of the telecommunications network.

8. The method of claim 7 wherein the step of assembling bits of data into one or more packets includes adding a packet preamble to a data payload, the packet preamble including at least one sacrificial bit and a sync pattern.

9. The method of claim 7 wherein the step of converting each bit in the one or more packets into at least one unique frequency includes modulating a frequency of a carrier wave to a first frequency if the bit is a binary “

0” and

a second frequency if the bit is a binary “

1”

.

10. The method of claim 9 wherein the first frequency and the second frequency fall within the range of 400 Hertz to 1600 Hertz.

11. The method of claim 9 wherein the amplitude of the first frequency and the second frequency are approximately 25 millivolts.

12. The method of claim 7 wherein the encoded bits are transmitted over the voice channel of the telecommunications network at a baud rate of 100 bits per second.

13. The method of claim 7 further comprising:

receiving the encoded bits from the voice channel of the telecommunications network;

decoding the encoded bits into the at least one unique frequency with a vocoder;

converting the at least one unique frequency into one or more packets, the one or more packets including a preamble and the data;

extracting the data from the one or more packets; and

storing the data.

14. A system for receiving a data payload over a voice channel of a telecommunications network, comprising:

a vocoder component for decoding a digital data stream received from the voice channel of the telecommunications network into audio tones, the audio tones representing voice data and the data payload;

a frequency conversion component for converting the audio tones into at least one data packet including a preamble and the data payload;

a packet disassembling component for extracting the data payload from the at least one data packet; and

a storage component for storing the data payload.

15. The system of claim 14 wherein the audio tones include a first frequency representing a binary “

0”

bit and a second frequency representing a binary “

1”

bit.

16. The system of claim 14 wherein the frequency conversion component includes:

a first bandpass filter for attenuating frequencies outside of a range of frequencies, the range of frequencies including audio tones that represent a binary “

0”

bit and a binary “

1”

bit;

a second bandpass filter for attenuating frequencies inside of the range of frequencies;

a SNR component coupled to an output of the first bandpass filter and an output of the second bandpass filter, the SNR component determining a signal-to-noise ratio between the output of the first bandpass filter and the output of the second bandpass filter; and

a comparator coupled to the SNR component, the comparator identifying audio tones representing the data payload when the signal-to-noise ratio exceeds a threshold.

17. The system of claim 16 wherein the range of frequencies is between approximately 400 Hertz and approximately 700 Hertz.

18. The system of claim 14 wherein the frequency conversion component includes:

a sampler for extracting a plurality of samples associated with a single bit from the audio tones;

a first discrete Fourier transform for analyzing frequencies contained in the plurality of samples, the first discrete Fourier transform generating a correlation value when the plurality of samples contain a first frequency representing a binary “

0”

bit;

a second discrete Fourier transform for analyzing frequencies contained in the plurality of samples, the second discrete Fourier transform generating a correlation value when the plurality of samples contain a second frequency representing a binary “

1”

bit; and

a bit selection component for comparing the correlation value generated by the first discrete Fourier transform and the correlation value generated by the second discrete Fourier transform, the bit selection component selecting

a binary “

0”

if the correlation value generated by the first discrete Fourier transform is greater than the correlation value generated by the second discrete Fourier transform and

a binary “

1”

if correlation value generated by the second discrete Fourier transform is greater than the correlation value generated by the first discrete Fourier transform.

19. The system of claim 18 wherein the first frequency is approximately 500 Hertz and the second frequency is approximately 600 Hertz.

20. The system of claim 14 wherein the frequency conversion component synchronizes converting the audio tones by shifting a start time for samples of a first and second audio tones until an optimum synchronization value is detected.