in the "power-limited regime" (where the nominal spectral efficiency formula_1 [b/2d or b/s/hz], "i.e." the domain of binary signaling), the effective coding gain formula_2 of a signal set formula_3 at a given target error probability per bit formula_4 is defined as the difference in db between the formula_5 required to achieve the target formula_4 with formula_3 and the formula_5 required to achieve the target formula_4 with 2-pam or (2×2)-qam ("i.e." no coding). the nominal coding gain formula_10 is defined as