Capacity-Approaching Signal Constellations for the Additive Exponential Noise Channel
The authors present a new family of signal constellations, called log constellations that can be used to design near-capacity coded modulation schemes over Additive Exponential Noise (AEN) channels. Log constellations are designed by geometrically approximating the input distribution that maximizes the AEN channel capacity. The mutual information achievable over AEN channels with both Coded Modulation (CM) and Bit-Interleaved Coded Modulation (BICM) approaches is evaluated for various signal sets via computer simulations. The Additive Exponential Noise (AEN) channel constitutes the natural discrete-time model for the continuous-time Gaussian channel when the transmitted signal is affected by a fast-varying phase noise.