Patent ID: 7103107
Filing Date: 2006-09-05
Classification: H04L

Abstract:
1. A demodulator, comprising: a multiple differential phase detected signal output unit configured to calculate phase differences between a received signal and previously received signals of 1, 2, . . . , N symbols (where N is an integer greater than 2) so as to output 1, 2, . . . , N symbol differential phase detected signals; and a soft decision demodulated data estimating unit configured to estimate a transmitted differential phase sequence according to the 1, 2, . . . , N symbol differential phase detected signals using a trellis diagram representing transitions of differential phase states of transmitted signals and a Viterbi algorithm, and to estimate soft decision demodulated data according to the estimated transmitted differential phase sequence and a survival path metric that transits into each state on the trellis diagram, wherein the soft decision demodulated data are estimated as the product of hard decision data and reliability information, and the reliability information is calculated by subtracting a likelihood for a first survival path metric corresponding to a first survival path that transits into a first state on the trellis diagram from a likelihood for a second survival path metric corresponding to a second survival path that transits into a second state on the trellis diagram, wherein the first state is different from the second state; and wherein, in said soft decision demodulated data estimating unit, a bit corresponding to the differential phase of a first state having a minimum survival path metric on the trellis diagram is the hard decision data, and the first survival path metric corresponds to the first survival path that transits into the first state having a minimum survival path metric, and the second survival path metric corresponds to the second survival path that transits into the second state having a minimum survival path metric.