In-band signaling for data communications over digital wireless telecommunications networks
View Patent ↗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.
1. 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;
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.
2. The system of claim 1 wherein the range of frequencies is substantially within a range of 400 Hertz to 700 Hertz.
3. 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;
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.
4. The system of claim 3 wherein the first frequency is approximately 500 Hertz and the second frequency is approximately 600 Hertz.