Method for transmission of a digital message from a display to a handheld receiver
US7990292B2 · kind B2 · utility
Assignee
Inventor
Key dates
| Filing date | Apr 28, 2008 |
| Grant date | Aug 2, 2011 |
| Priority date | — |
| Expiry date | Apr 19, 2030 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06F21/606
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
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.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.