  The construction of optimal non-uniform mappings for discrete input
memoryless channels (DIMCs) is investigated. An efficient algorithm to find
optimal mappings is proposed and the rate by which a target distribution is
approached is investigated. The results are applied to non-uniform mappings for
additive white Gaussian noise (AWGN) channels with finite signal
constellations. The mappings found by the proposed methods outperform those
obtained via a central limit theorem approach as suggested in the literature.
