Structurally distinct constellation labelings exist within both the Gray code and the set-partitioning paradigm. Different labeling choices within either paradigm can provide different bit error rates, especially at low SNR. This paper demonstrates that symmetric ultracomposite (SU) labeling, an extension of the binary reflected Gray code, provides undominated edge profiles for all standard PSK, PAM and square QAM constellations. (The edge profile lists the minimum distance for each binary symbol error.) The SU structure can accomodate either the Gray code or the set-partitioning paradigm. It is the clear labeling choice for standard PSK, PAM and square QAM constellations. An extension of SU labeling provides quasi-SU (QSU) labelings for all
Richard D. Wesel, Xueting Liu