Patent Document ID: 5566191
Application ID: 08057813
Patent Flag: 1

Claim One:
1. In conducting maximum likelihood decoding on a received code train on a receiving side, said received code train corresponding to a transmission code train obtained by coding an information train by using convolutional codes on a transmission side, a soft decision maximum likelihood decoding method for providing each received code with a likelihood metric of a candidate code thereof in the form of a soft decision likelihood metric represented by a multi-valued level, said soft decision maximum likelihood decoding method comprising the steps of: deriving an instantaneous received amplitude of the received codes every predetermined period; making a calculation on each instantaneous received amplitude on the basis of a predetermined function and outputting a result of the calculation as a weighting coefficient; making corrections by multiplying a plurality of soft decision likelihood metric values derived from received codes by said weighting coefficient; and conducting maximum likelihood decoding by using corrected soft decision likelihood metric values derived at said step of making corrections; wherein the predetermined function defines a relationship between said weighting coefficient and said instantaneous received amplitude that is a monotonically increasing function of an amplitude which has been normalized by a maximum received amplitude and which opens upwards, and that is a quadratic function of an amplitude which has been normalized by a maximum received amplitude.