A QAM CONSTELLATION WHICH IS ROBUST IN THE PRESENCE OF PHASE NOISE; ENCODER AND DECODER FOR THIS CONSTELLATION

摘要

A circularly symmetric QAM constellation reduces phase noise. Points of the constellation are situated on concentric circles. The constellation may be encoded and decoded either coherently or noncoherently. A differential encoder for the constellation does not operate by straight subtraction. A differential decoder for the constellation can use an estimated metric to recover the original signal.