Bit-Interleaved Coded Modulation: Fundamentals, Analysis and Design

Chapter 9BICM Receivers for Trellis Codes

In this chapter we study a trellis encoder and a bit-interleaved coded modulation (BICM) receiver, i.e., the coded modulation (CM) encoder is a serial concatenation of a convolutional encoder (CENC) and a memoryless mapper, and the bitwise interleaver is not present. This in fact corresponds to the model in Fig. 2.4, where the maximum likelihood (ML) decoder is replaced by a BICM decoder. The study of this somehow unusual combination is motivated by numerical results that show that for the additive white Gaussian noise (AWGN) channel and convolutional encoders (CENCs), removing the interleaver in a BICM transceiver results in improved performance.

This chapter is organized as follows. In Section 9.1 we introduce the idea of BICM with “trivial interleavers” (i.e., no interleaving) and in Section 9.2 we study the optimal selection of CENCs for this configuration. Motivated by the results in Section 9.2, we study binary labelings for trellis encoders in Section 9.3.

9.1 BICM with Trivial Interleavers

The design philosophies behind trellis-coded modulation (TCM) and BICM for the AWGN channel are quite different. On one hand, TCM is constructed coupling together a CENC and a constellation using a set-partitioning (SP) labeling. On the other hand, BICM is typically a concatenation of a binary encoder, a bit-level interleaver, and a mapper with constellation labeled by the binary reflected Gray code (BRGC). The BRGC is often used in BICM because ...