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US 6,636,560 B1Granted
Increased bit rate of telephony modems using controlled intersymbol interface
AssigneeTexas Instruments Incorporated
InventorAlan Gatherer
Life of this patent
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Abstract
The operation of a line card in the local exchange of a point-to-point switched telephone network is modified to increase the data rate of voiceband modem transmission by increasing the sampling rate and providing controlled intersymbol interference using partial response techniques.
Claims3
A method of transmitting data using voiceband frequencies over point-to-point switched telephone networks, comprising:
- transmitting data symbols in digital form to a line card of a local exchange switch;
- performing digital-to-analog conversion from the digital data to data in analog form in the line card;
- sending the analog data from the line card to an end user modem;
- wherein the data symbols are sent from the line card to the end user modem at a rate above the Nyquist limit and are received at the end user modem with controlled intersymbol interference;
- and
- wherein for each symbol Ak transmitted, the symbol Ak−1+1.2732Ak+Ak+1 is received by the end user modem.
3 more elements
A method of transmitting data using voiceband frequencies over point-to-point switched telephone networks, comprising:
- transmitting data symbols in digital form to a line card of a local exchange switch;
- performing digital-to-analog conversion from the digital data to data in analog form in the line card;
- sending the analog data from the line card to an end user modem;
- wherein the data symbols are sent from the line card to the end user modem at a rate above the Nyquist limit and are received at the end user modem with controlled intersymbol interference;
- and
- wherein the controlled intersymbol interference is the sum of two shifted sinc pulses.
3 more elements
Dependencies are inferred from the claim text.