Design and Analysis of Bit-Interleaved Coded Modulation With Pseudorandom Sequence

In this paper, we design and analyze an improved bit-interleaved coded modulation (CM) scheme with a pseudorandom sequence (BICM-P). For the proposed scheme, the pseudorandom sequence is introduced into a systematic encoder at the transmitter and serves as side information at the receiver. With this design, the receiver can enjoy the benefit of increased Hamming distance when applying this side information at the receiver. In particular, we present a new constellation mapping principle to take advantage of the side information in the modulator, which leads to different signal constellations for the information bits and the parity-check bits. We then analytically derive the constellation-constrained capacity for BICM-P and quantify its gain as a nonlinear function associated with the two constellations. For the practical use of BICM-P, this paper indicates that the side information makes the regular low-density parity-check (LDPC) code irregular. Accordingly, the density evolution analysis tool is developed to design and optimize the regular LDPC code for BICM-P. The performance of LDPC-coded BICM-P on additive white Gaussian noise (AWGN) channels and fast Rayleigh fading channels is analyzed using extensive simulations. We observe that, at high code rates (≥1/2), LDPC-coded BICM-P has a substantial gain (0.1117-0.6558 dB) compared with LDPC-coded BICM on the AWGN channel. The performance gains will become more significant (0.7541-2.3481 dB) on the fast Rayleigh fading channel.