SOFT DECISION METHOD FOR DEMODULATING SQUARE QAM RECEPTION SIGNAL AND SOFT DECISION APPARATUS THEREBY

摘要

PURPOSE: A soft decision method for demodulating a square QAM reception signal and an apparatus thereby are provided to enhance the processing speed by using a linear distance probability vector equation instead of a log likelihood ratio method. CONSTITUTION: A soft decision method for demodulating a square QAM reception signal includes a process for calculating a distance probability vector value as a soft decision value corresponding to a bit position of the hard decision by using a function including a conditional decision operation from an in-phase element value and an orthogonal-phase element value of the received signal. The distance probability vector values corresponding to the first to the nth bits are demodulated by one of received signals alpha and beta. The distance probability vector values corresponding to the n+1th to the 2nth bits are demodulated by the residual received signal.