In this paper, we propose a new BICM design which considers hierarchical (nonequally spaced) constellations, a bit-level multiplexer, and multiple interleavers. It is shown that this new scheme outperform previous BICM designs because it exploits the temporal structure of the coded sequence. An analytical bound on the bit error rate (BER) of the proposed BICM scheme in terms of the constellation parameters and the multiplexing is developed for Nakagami-m fading channels. This bound is used to design a BICM transceiver with improved BER performance. Numerical results show that the gains compared to conventional BICM designs depend on the fading parameter and reach 2 dB for a target BER of 10-7 and m=5.