Patent ID: 8503580
Filing Date: 2013-08-06
Classification: H04L

Abstract:
1. A method of generating soft bit values for received symbols transmitted based on a modulation constellation, comprising: demodulating the received symbols via a sequence of demodulation stages, each demodulation stage producing a symbol decision based on a respective effective constellation, each respective effective constellation used by a non-final one of the demodulation stages including subsets of centroids approximating a region of the modulation constellation, adjacent ones of the subsets having one or more common points so that at least two of the adjacent subsets overlap; determining soft bit values for the symbol decisions based on detection metrics computed during demodulation for points included in each respective effective constellation constructed incrementally over the sequence of demodulation stages, the effective constellation produced by a final demodulation stage being devoid of one or more points included in the modulation constellation, determining an effective bit nearest neighbor for each bit of each symbol decision, each effective bit nearest neighbor corresponding to the point included in the effective constellation produced by the final demodulation stage that is nearest one of the symbol decisions with one of the bits of the symbol decision flipped; wherein determining the soft bit values is based on the effective bit nearest neighbors; and identifying one or more points of the effective constellation used by the final demodulation stage that are closest to a true bit nearest neighbor associated with the modulation constellation, each true bit nearest neighbor corresponding to the point included in the modulation constellation that is nearest one of the points in the modulation constellation with a bit flipped.