Patent ID: 7120207
Filing Date: 2006-10-10
Classification: H04L

Abstract:
1. A method for obtaining a soft decision in detection of a TFM signal, comprising: sampling a received signal, reverse rotating the phase of a signal sample in the way that the real part of a complex signal indicates the phase of the sample to produce phase changes of possible transitions, reverse rotating the phase changes of possible transitions determined by the modulation method used so that the rotation is opposite to the phase belonging to the old state of a trellis diagram, computing transition metrics for the state transitions in a trellis diagram with the aid of the real part of the signal sample and computing path metrics for each survivor path, selecting the path with larger metrics as a survivor from paths entering a state node, and the phase of that survivor is set as the phase state of the new correlative state in question, selecting the survivor with the largest metric as the best survivor, determining the sign of the demodulated bit with the aid of the last bit of the previous state of the best survivor and calculating the weight of the demodulated bit as the difference of the path metrics of the best survivor and a selected path joining it.