An equal-radius constellation with improved PTMER for optical wireless communications

The signal constellations used in optical communication systems with intensity modulation are different than those in radio frequency communication systems. In this paper, we propose a four-symbol constellation called C4, in which three symbols have the equal radius. We investigate its symbol probability rate (SER), and compare with another popularly used four-symbol constellation. The result shows that the average SER profiles of two constellations are quite close, while C4 has a much smaller peak-to-mean-electrical-energy-ratio (PTMER).