The objective of this book is to examine the main aspects of a particularly simple coded modulation scheme known as bit-interleaved coded modulation (BICM). BICM is based on bit-level operations, which allows for a straightforward combination of a binary encoder with a nonbinary modulation. Simplicity and flexibility are the reasons for the omnipresence of BICM in current communication systems and also what motivated us to look into BICM-based transceivers.

This work is intended for readers with a background in communication theory who are interested in theoretical aspects of BICM transmission. Various issues we have addressed in this work are motivated by questions we received from the audience during talks and lectures we have given over the years. We have tried to make the content tutorial in style hoping that the numerous examples we have included clarify and illustrate well the main results. The objective was to make the text accessible to graduate students and researchers working on coded modulation and BICM-related issues. To clearly delimitate the main results, we have separated the text—as much as possible—into definitions, lemmas, theorems, and corollaries.

From the beginning of this project, our objective was threefold. First, we wanted to clearly define all the building blocks in BICM transceivers. This is mostly done in Chapters 1–3, which contain definitions and some simple examples. When writing the text, we discovered that many of the “conventional” assumptions made in BICM, while often justified, were not necessarily as obvious as they seemed. We thus introduced elements of analysis to help explain these assumptions, often taken for granted.

The second objective is to present tools that allow us to analyze BICM receivers. This is the core of Chapters 4 and 6, which provide complementary views on the performance limits of BICM receivers, the former from an information-theoretic perspective and the latter from a communication-theoretic point of view. For completeness, in parallel with the analysis of BICM, we also present the analysis of the optimal (maximum-likelihood) decoder. Chapter 5 focuses on the probabilistic characterization of the so-called L-values (log-likelihood ratios), as these signals are the most distinguishable signature of BICM receivers. Chapters 4–6 can be read independently of each other.

The third objective was to indicate how the apparently simple BICM transceivers can be designed and optimized. This is done in Chapters 7–9, where we define and analyze the effects of mismatched L-values as well as focus on the design of the interleaver and code.

We opted in this book for a reference-free text, but to acknowledge the inspiration and contributions of many researchers, we have included at the end of each chapter a section with bibliographic notes. Owing to the large number of publications available in this area, we might have missed some previous works. We sincerely apologize if this is the case.