The novel noncoherent coded modulation (NCM) scheme introduced by Raphaeli (see IEEE Trans. Commun., vol.44, no.2, p.172-83, 1996) is extended for non-constant energy symbols. Theoretical performance analysis, based on deriving the pairwise error distribution over an additive white Gaussian noise (AWGN) channel applying the independent overlapped observations noncoherent maximum likelihood sequence estimation (IO-NMLSE) metric is presented. Tight Gaussian approximation together with upper and lower bounds and a method for numerically evaluate them are presented. The NCM scheme has a performance that approaches that of a coherent detection for increasing complexity. Sub-optimal decoding algorithms introduced by Raphaeli (see IEEE Trans. Commun., vol.44, no.3, p.312-23, 1996), provide good tradeoff between maximizing performance and minimizing system complexity.