Modulation switching for DSL signal transmission

US6151335A · kind A · utility

Assignee

• Conexant Systems, LLC · US

Inventors

• Kenneth D. Ko · Clearwater, US
• David O. Anderton · Austin, US
• Ismail I. Eldumiati · Irvine, US
• Steven A. Gronemeyer · Cedar Rapids, US
• Don L. Harmer · Anaheim, US
• P. Michael Henderson · Tustin, US
• Joel D. Peshkin · San Juan Capistrano, US
• Raphael Rahamim · Orange, US
• Frederic M. Stubbe · Irvine, US
• John Walley · Ladera Ranch, US
• Kenneth S. Walley · Rancho Santa Margarita, US
• Yongbing Wan · Irvine, US
• Edward S. Zuranski · Largo, US
• Jamal Haque · Tampa, US
• Anthony A. Tzouris · Clearwater, US
• Shrenik P. Patravali · St. Petersburg, US
• Ganning Yang · San Jose, US

Key dates

• Filing date: Dec 2, 1997
• Grant date: Nov 21, 2000
• Expiry date: Dec 2, 2017

Classification

• Technology area (CPC H): Electricity
• CPC primary: H04M11/062
• WIPO field: Telecommunications
• WIPO sector: Electrical engineering

Abstract

A digital subscriber line (DSL) communication system that utilizes the high frequency band of a standard telephone line does not require the use of a plain old telephone service (POTS) splitter in the resident's home, which provided isolation between the POTS frequency band (0 to 4 kHz) and the DSL frequency band. A digital subscriber line modem utilizes either constant envelope modulation or quadrature amplitude modulation for outputting DSL signals upstream to a central office. When a telephone in the resident's home is detected as being off-hook, then the constant envelope modulation is used by the DSL modem in order to lessen the intermodulation product distortion that results in audible noise heard by a user of the telephone. When the telephone is on-hook, then another type of modulation, such as QAM, is used to maximize the upstream data rate capability in the DSL frequency band, since any noise generated by the QAM is not a problem due to the non-use of the POTS frequency band.