The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jan. 12, 2010
Filed:
Oct. 08, 2004
David Cheng-song Qi, Westford, MA (US);
Yan Wang, Arlington, MA (US);
Timothy G. Wade, Litchfield, NH (US);
David Cheng-Song Qi, Westford, MA (US);
Yan Wang, Arlington, MA (US);
Timothy G. Wade, Litchfield, NH (US);
Cisco Technology, Inc., San Jose, CA (US);
Abstract
High compression rate codecs in gateways servicing Voice-over-Internet Protocol (VoIP) and Voice Band Data (VBD) calls distort modem/fax Answer Back Tones (e.g., 2100 Hz), which may lead to signal distortion and call hang-ups. To prevent such occurrences, a method or corresponding apparatus forces originating and terminating gateways to stay in a low complexity non-voice compression codec (e.g., ITU G.711) after prenegotiating a high complexity, voice compression codec (e.g., G.729 or G.726) during a short beginning period of a voice call. The low complexity codec avoids distorted answer back tone leakage associated with previous solutions that use a notch filter to block the leakage, thereby significantly improving the success rate of a VBD call by completely eliminating modem answer back tone distortion caused by high complexity codecs that use voice compression and by completely eliminating use of the notch filter.