Patent ID: 7676734

Claim:
A decoding apparatus for decoding a low density parity check coded message using a message passing algorithm configured for propagating messages between a plurality of check nodes and a plurality of variable nodes, the check and variable nodes corresponding to the low density parity check code, comprising: parts for setting a first message as a log likelihood ratio having, as a base, a real number “a” which is a power of 2; a check node processing calculating unit for receiving the first message and a variable node processed message delivered from a variable node to a check node to calculate a check node processed message delivered from the check node to the variable node; a variable node processing calculating unit for receiving the check node processed message calculated by the check node processing calculating unit to calculate the variable node processed message; wherein the check node processing calculating unit includes a first converting circuit for converting an absolute value x of the first message into a value of the power of 2 to output the value, and a second converting circuit for subdividing an input y into a plurality of domains having boundary values prescribed with powers of 2, wherein the boundary values of the plurality of domains are correctly expressed by a finite number of bits when in binary form, the input value y being a sum of values converted by the first converting circuit from absolute values x of the first message from a totality of the variable nodes less one variable node, the second converting circuit converting all the numbers in the domain into integers; a termination processing unit for stopping message passing between the variable node processing calculating unit and the check node processing calculating unit if at least one of the conditions of 1) a prescribed number of iterations are reached; and 2) a result of hard decision calculating meets a parity check equaling 0, is met; and a decoder for calculating a low density parity check decoded message from the variable node processed message using hard decision decoding.