  We consider the Gaussian channel with power constraint P. A gap exists
between the channel capacity and the highest achievable rate of equiprobable
uniformly spaced signal. Several approaches enable to overcome this limitation
such as constellations with non-uniform probability or constellation shaping.
In this letter, we focus on constellation shaping. We give a construction of
amplitude and phase-shift keying (APSK) constellations with equiprobable
signaling that achieve the Gaussian capacity as the number of constellation
points goes to infinity.
