On the Information Loss of the Max-Log Approximation in BICM Systems
Artikel i vetenskaplig tidskrift, 2016

We present a comprehensive study of the information rate loss of the max-log approximation for M-ary pulse-amplitude modulation (PAM) in a bit-interleaved coded modulation (BICM) system. It is widely assumed that the calculation of L-values using the max-log approximation leads to an information loss. We prove that this assumption is correct for all M-PAM constellations and labelings with the exception of a symmetric 4-PAM constellation labeled with a Gray code. We also show that for max-log L-values, the BICM generalized mutual information (GMI), which is an achievable rate for a standard BICM decoder, is too pessimistic. In particular, it is proved that the so-called harmonized GMI, which can be seen as the sum of bit-level GMIs, is achievable without any modifications to the decoder. We then study how bit-level channel symmetrization and mixing affect the MI and the GMI for max-log L-values. Our results show that these operations, which are often used when analyzing BICM systems, preserve the GMI. However, this is not necessarily the case when the MI is considered. Necessary and sufficient conditions under which these operations preserve the MI are provided.

Författare

Mikhail Ivanov

Signaler och system, Kommunikationssystem, informationsteori och antenner, Kommunikationssystem

Christian Häger

Signaler och system, Kommunikationssystem, informationsteori och antenner, Kommunikationssystem

Fredrik Brännström

Signaler och system, Kommunikationssystem, informationsteori och antenner, Kommunikationssystem

Alexandre Graell i Amat

Signaler och system, Kommunikationssystem, informationsteori och antenner, Kommunikationssystem

Alex Alvarado

University College London (UCL)

Erik Agrell

Signaler och system, Kommunikationssystem, informationsteori och antenner, Kommunikationssystem

IEEE Transactions on Information Theory

0018-9448 (ISSN)

Vol. 62 3011 - 3025 7436797

Styrkeområden

Informations- och kommunikationsteknik

Ämneskategorier

Kommunikationssystem

DOI

10.1109/TIT.2016.2543740