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:
Oct. 04, 1994
Filed:
Apr. 27, 1993
Gottfried Ungerbock, Langnau am Albis, CH;
International Business Machines, Armonk, NY (US);
Abstract
The start-up time for typical current generation modems for full-duplex data transmission over the Public Switched Telephone Network (PSTN) as specified in CCITT Recommendations V.32 and V.32bis is about 4 to 8 seconds. This invention reduces that start-up time to about 0.5 to 1 second by applying interleaved and overlapping sending and receiving operations of two connected modems, the calling modem and the answering modem. Both modems send and receive simultaneously in a predetermined sequence at different frequency ranges, channel probing tones (e.g. for evaluating the channel bandwidth), repetitive identification messages (e.g. for determining reference times, identifying modulation rates and center frequencies), repetitive response messages (e.g. for transmitting the determined bandwidths and reference times to the other modem and determining round-trip delays), and training sequences (e.g. for determining echoes, frequency shifts, and receiver settings). The modems then transmit data in a full-duplex mode at the modulation rate and center frequency appropriate for the channel and at an initial bit rate. The maximum achievable bit rate may be achieved later during the full-duplex transmission through rate negotiations.