Bit-interleaved coded modulation in the wideband regime

This paper studies the wideband regime of bit-interleaved coded modulation (BICM) in Gaussian channels. Simple formulas for the minimum energy per bit and the wideband slope, both for coded modulation and for bit-interleaved coded modulation, are given. The wideband slope can be decomposed into the product of two terms, respectively due to the fading characteristics and the modulation and binary labeling rule. BICM is found to be suboptimal in the sense that its minimum energy per bit can be larger than the corresponding value for coded modulation schemes. The minimum energy per bit using standard Gray mapping on M-PAM, or M-2-QAM is given by a simple formula, and shown to approach -0.34 dB as M increases.