04757495 is referenced by 277 patents and cites 4 patents.

The present invention relates to an apparatus and method for the simultaneous transmission of analog speech and modulated data, such apparatus and method being optimized for use over impaired and bandwidth restricted analog channels, or digital representations of such channels. In each instance of use, an evaluation is made of the available channel bandwidth, with a frequency division multiplex scheme allocating a voice sub-band, with data transmission allocated to sub-bands above, below, or around, this selected voice sub-band. The speech and data sub-band allocations are made by the multiplexor in response to user input of either a requested speech quality, a requested data rate, or a value indicating the relative user weighting of speech quality and data rate. A multi-carrier multi-mode modulation scheme is employed for data transmission, with this scheme having the ability to fully utilize the remaining bandwidth, and further, being capable of adapting to the impairments most likely present on the fringes of bandwidth restricted analog channels. When the analog channel employed is the standard voice-grade telephone circuit, good speech quality simultaneously with 3000 bps data transmission may be expected. The further ability to automatically switch to full bandwidth data transmission when voice transmission is not being attempted is also provided.

Title
Speech and data multiplexor optimized for use over impaired and bandwidth restricted analog channels
Application Number
6/836438
Publication Number
4757495
Application Date
March 5, 1986
Publication Date
July 12, 1988
Inventor
Frederick L Mueller
Palo Alto
CA, US
Mark B Flowers
Mountain View
CA, US
Dirk Hughes Hartogs
Morgan Hill
CA, US
Payne Freret
Los Altos
CA, US
Dwight W Decker
Cupertino
CA, US
Agent
Donald C Feix
Assignee
Telebit Corporation
CA, US
IPC
H04J 1/14
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