US Patent 7120207 Transmission method and radio receiver

The invention relates to a method and a receiver for obtaining a soft decision in detection of a TFM signal. In the method, the phase of a signal sample is reversed rotated twice in the way that the real part of the sample indicates the phase of the sample and that the rotation is opposite to the phase belonging to the old state of a trellis diagram. Transition metrics are completed with the aid of the real part of the signal sample. Then path metrics are computed, the path with larger metrics is selected as a survivor and the survivor with the largest metric is selected as the best survivor. The sign of the demodulated bit is determined and the weight of the demodulated bit is calculated.