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Title:
METHOD FOR TRANSMISSION OF A DIGITAL MESSAGE FROM A DISPLAY TO A HANDHELD RECEIVER
Document Type and Number:
WIPO Patent Application WO/2009/114608
Kind Code:
A3
Abstract:
The invention relates to a method to efficiently transmit a digital message over a unidirectional optical link, such as the link between a computer screen and a security token equipped with photosensitive elements. It is an object of this invention to provide a source coding scheme that is optimized for transmissions of alphanumerical data containing frequent occurrences of numerals and less frequent occurrences of non-numerical data. This is achieved by using a modified Huffman code for source coding, consisting of a nibble-based prefix-free binary code. The output of the coder is efficiently mapped onto a 6B4T channel code, wherein unused ternary codewords can be used to signal data-link layer events. This efficient signalling of data-link layer events, in turn, allows for a synchronization scheme based on repeated transmissions of a finite-length message, combined with an out-of-band clock signal.

Inventors:
MARIEN, Dirk (Processieweg 8, Ranst, Ranst, BE)
Application Number:
US2009/036796
Publication Date:
March 31, 2016
Filing Date:
March 11, 2009
Export Citation:
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Assignee:
VASCO DATA SECURITY, INC. (1901 South Meyers Road, Suite 210Oakbrook Terrace, IL, 60181, US)
VASCO DATA SECURITY INTERNATIONAL GMBH (World-wide Business Center, Balz-Zimmermannstrasse 7, Glattbrugg, Glattbrugg, CH)
MARIEN, Dirk (Processieweg 8, Ranst, Ranst, BE)
International Classes:
H03M5/16
Foreign References:
US4369443A1983-01-18
US4862167A1989-08-29
US20070018861A12007-01-25
US20080305829A12008-12-11
Attorney, Agent or Firm:
GREEN, Stanley, B. (Connolly Bove Lodge & Hutz LLP, 1875 Eye Street Nw, Suite 110, Washington DC, 20006, US)
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