Patent ID: 7992067
Filing Date: 2011-08-02
Classification: H03M,H04L

Abstract:
1. A method for coding a digital data string to represent a sequence of acoustic frequencies to be transmitted as an acoustic signal by a genuine acoustic authentication device, the method comprising: coding each of a plurality of groups of bits of said data string to represent a respective frequency value set of one or more acoustic frequencies to be transmitted acoustically to represent the respective group of bits, wherein each group of bits comprises a plurality of bits and the number of acoustic frequencies in a frequency value set is less than the number of bits in the respective group of bits that the frequency value set represents, thereby providing for the duration of the acoustic sequence that is required to represent the plurality of groups of bits being less than that which is required in the event of representing the plurality of groups of bits with a number of frequency values equal to the number of bits in the plurality of groups of bits of said data string; for each of the plurality of groups of bits of said data string, selecting said respective frequency value set according to a predetermined frequency assignation pattern that is generated such that wherein the known probabilities and any given at least one preceding assigned frequency value set used to select a given subsequently assigned frequency value set are configured to be used to statistically determine the likelihood of any given frequency value set following the any given at least one preceding assigned frequency value set, thereby providing for probabilistic transition coding that is configured for being used for error correction of the acoustic signal.