Patent ID: 6225925
Filing Date: 2001-05-01
Classification: H03M

Abstract:
A method for decoding coded data into a decoded symbol string populated by more probable symbols (""MPS"") and less probable symbols (""LPS""), the method comprising the steps of:receiving a segment of coded data interpreted as a binary fraction C;defining a coding interval of possible values of C, the interval extending from a variable lower bound A to a constant upper bound 1;for each position in the decoded symbol string:computing a test value Z subdividing the coding interval in sub-intervals in accordance with the relative probabilities that an MPS and an LPS occurs in the position, a first sub-interval extending from the lower bound A to the test value Z, the second sub-interval extending from the test value Z to 1, the computing step comprising:computing a first test value Z1 derived from the lower bound A and from a current estimate P of the probability of the LPS symbol,computing a second test value Z2 derived from the lower bound A and from the current estimate P of the probability of the lps symbol, andsetting the test value Z to the lesser of Z1 and Z2;if C is greater than Z:placing an MPS at the current position in the decoded symbol string, andsetting the lower bound A to the test variable Z for use in decoding of a next position in the symbol string; andif C is less than Z:placing an LPS at the current position in the decoded symbol string, andcomputing a new lower bound A and a new binary fraction C for use in decoding of the next position in the decoded symbol string.