8.27 Consider the four-phase and eight-phase signal constellations shown in Figure P-8.27. Determine the radii ni and 2 of the circles so that the distance between two adjacent points in the two constellations is d. From this result, determine the additional transmitted energy required in the 8-PSK signal to achieve the same error probability as the four-phase signal at high SNR, where the probability of error is determined by errors in selecting adjacent points. M=4 M-8 Figure P4.27