this definition is normalized so that formula_12 for 2-pam or (2×2)-qam. if the average number of nearest neighbors per transmitted bit formula_13 is equal to one, the effective coding gain formula_2 is approximately equal to the nominal coding gain formula_10. however, if formula_16, the effective coding gain formula_2 is less than the nominal coding gain formula_10 by an amount which depends on the steepness of the formula_4 "vs." formula_5 curve at the target formula_4. this curve can be plotted using the union bound estimate (ube)