Patent ID: 7027497

Claim:
An adaptive equalization method in decoding process for decoding a received signal for a code bit b(n) by iterating adaptive equalization of said received signal for a code bit b(n) a plurality of times, an adaptive equalization in which a second soft decision value λ 2 [b(n)] generated by the soft decision of said code bit b(n) is provided as a priori information, and the equalization of a received signal R(n) of an M-channel through utilization of said a priori information and outputting of a first soft decision value λ 1 [b(n)] are iterated to adaptively equalize said received signal R(n), said method comprising the steps of: in a first round of equalization, (a) calculating an estimated impulse response value H m (n) of said M-channel and tap coefficients G(n) for linear filtering by the first round of adaptive equalization of said received signal R(n) of said M-channel, and outputting said first soft decision value λ 1 [b(n)]; in the second and subsequent rounds of equalization, (b) calculating the likelihood b′(n) of a code bit sequence b(n) from said second soft decision value λ 2 [b(n)] obtained by decoding said code bit b(n) based on said first soft decision value λ 1 [b(n)]; (c) calculating an estimated impulse response value vector H L (n) by approximation with the intersymbol interference component for the code bit b(n) regarded as zero, and calculating the tap coefficients G(n) for said linear filtering from said estimated impulse response value vector H L (n) to update said tap coefficients G(n); (d) linear-filtering said likelihood b′(n) of said code bit sequence b(n) with said estimated impulse response value H L (n) to generate a replica of the received signal R(n); (e) subtracting said replica from said received signal R(n) to generate a difference signal R c (n) without intersymbol interference; (f) linear-filtering said difference signal Rc(n) with said tap coefficients G(n) to generate a signal Z(n); and (g) outputting, as the results of said second and subsequent rounds of adaptive equalization, the first soft decision value λ 1 [b(n)] updated with said signal Z(n) and said estimated impulse response value vector H L (n).