Multiplex communications – Pathfinding or routing – Combined circuit switching and packet switching
Reexamination Certificate
2000-06-22
2002-12-10
Marcelo, Melvin (Department: 2663)
Multiplex communications
Pathfinding or routing
Combined circuit switching and packet switching
C370S493000, C370S522000
Reexamination Certificate
active
06493338
ABSTRACT:
TECHNICAL FIELD
This invention is related to wireless telecommunications and more specifically to a system that transmits digital data over the audio channel of a digital wireless network “in-band.”
BACKGROUND OF THE INVENTION
A cellular telephone allows a user to talk to another user without being tethered to a “land line.” The cell phone includes circuitry that samples the audio signals from the user's voice. These voice signals are converted into a digital form using an A-D converter. The digitized voice signals are encoded by a voice coder (vocoder) and then modulated onto a carrier frequency that transmits the voice signals over a cell network. The voice signals are sent over the wireless cellular network either to another phone in the wireless cell network or to another phone in a land-line phone network.
Different coders/decoders (codecs), modulators, vocoders, Automatic Gain Controllers (AGC), Analog to Digital converters (A/D), noise reduction circuits, and Digital to Analog converters (D/A) are used in the cellular and landline phone networks. These telephone components can implement different coding schemes for encoding and decoding the voice signals.
These telecommunication components are designed to efficiently transmit voice signals over wireless and landline voice communication channels. For example, a digital vocoder uses predictive coding techniques to represent the voice signals. These predictive coders filter out noise (non-voice signals) while compressing and estimating the frequency components of the voice signals before being transmitted over the voice channel.
A problem arises when voice communication equipment, such as the vocoder, are used for transmitting digital data. The vocoders may interpret signals representing digital data as a non-voice signal. The vocoder might completely filter out or corrupt those digital data signals. Therefore, digital data can not be reliably transmitted over the same digital audio channel used for transmitting voice signals.
It is sometimes necessary for a user to transmit both audio signals and digital data to another location at the same time. For example, when a cellular telephone user calls “911” for emergency assistance, the user may need to send digital location data to a call center while at the same time verbally explaining the emergency conditions to a human operator. It would be desirable to transmit this digital data through a cell phone without having to use a separate analog wireless modem.
Accordingly, a need exists for transmitting digital data over a voice channel of a digital wireless communications network.
SUMMARY OF THE INVENTION
An inband signaling modem communicates digital data over a voice channel in a digital 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.
The foregoing and other features and advantages of the invention will become more readily apparent from the following detailed description of preferred embodiments of the invention, which proceeds with reference to the accompanying drawings.
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Eatherly Wayne
Leyendecker Robert
Preston Dan A.
Preston Joseph D.
Proctor Rod L.
Airbiquity Inc.
Marcelo Melvin
Mehra Inder Pal
Stoel Rives LLP
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