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:
Jun. 30, 1992
Filed:
Jun. 13, 1988
C Chiu Chan, Cedar Grove, NJ (US);
Marvin A Epstein, Monsey, NY (US);
Paul A Gilmour, Bloomfield, NJ (US);
ITT Corporation, New York, NY (US);
Abstract
An improved modem system for HF data transmission over a varying communication channel transmits data in packets formatted into successive frames, each having two identical training sequences following a sequence of data. Each training sequence has a time length longer than the expected time length of the multipath dispersion in the communication channel, in order to isolate one training sequence in each frame from multipath interference from the preceding data sequence. The 'clean' training sequence allows the receiving modem system to derive very accurate channel estimates for each frame by autocorrelation to the known symbol sequence stored at the receiver. By interpolating across the channel estimates for the current and previous frames, the modem system can track the communication channel by interpolated estimates for any part or any point in time of the data sequence. An improved data recovery algorithm divides the received data sequence in each frame into a series of data blocks, each of which is processed through a respective decision loop using the interpolated channel estimates corresponding to the time position of the data block in the data sequence. The interpolated channel estimate for each data block is used to set the tap values for the filter functions of the corresponding decision loop.