Patent ID: 8660199

Claim:
A method of demodulating a quadrature amplitude modulation (QAM) signal, the method comprising: determining a reception point corresponding to a symbol in the QAM signal that is received, the symbol being mapped to one reference point of a plurality of reference points in a rotated constellation, the plurality of reference points being represented by an in-phase (I) coordinate and a quadrature-phase (Q) coordinate; selecting a plurality of candidate points corresponding to a portion of the plurality of reference points based on distances between the reception point and the respective reference points; and demapping the reception point by calculating a plurality of log-likelihood ratios based on the plurality of candidate points, the plurality of log-likelihood ratios corresponding to bits of data represented by the reception point, wherein the selecting the plurality of candidate points comprises: determining a channel response of a communication channel through which the QAM signal is received; and selecting the plurality of candidate points based on the channel response, a plurality of one-dimensional distances, and a plurality of two-dimensional distances between the reception point and the respective reference points.