CALCULATION TECHNIQUE FOR SUM-PRODUCT DECODING METHOD (BELIEF PROPAGATION METHOD) BASED ON SCALING OF INPUT LOG-LIKELIHOOD RATIO BY NOISE VARIANCE

摘要

PROBLEM TO BE SOLVED: To achieve a decoding technique (approximate decoding technique) of achieving stable operation even if noise variance is low at the implementation with a fixed fractional part arithmetic operation having a finite dynamic range.;SOLUTION: A computer executes calculation using a sum-product decoding method (belief propagation method) with respect to (LDPC or turbo) codes. For calculating an update equation of a log extrinsic value ratio from an input, a (separated) correction term is prepared obtained by variable transformation (scale transformation) of the update equation so that the update equation is represented by a sum (combination) of a plurality of terms by transformation of the equation and a communication channel noise variance is a term separated from other terms constituting a sum of a plurality of terms as a term to be a factor (scale factor) by which a log is multiplied. With an estimated communication channel noise variance as an input, the (separated) correction term is approximated by a simple function so as to cause the computer to make calculation (iteration) on the basis of a fixed fractional part on bit strings of finite length.;COPYRIGHT: (C)2011,JPO&INPIT