Low-complexity soft demapper for BICM-ID

Abstract

High-order modulation for high bandwidth efficiency transmission is essential in modern communication system. In BICM-ID, the symbol-to-bit demapper suffers from high-complexity. Complexity of the well-known Log-MAP and Max-Log-MAP demapper increases on the order of $O(m \cdot 2^m)$ to demap one symbol, where m is the number of bits per symbol. As a solution, we propose a low-complexity soft demapping algorithm by using mapping transformation and message-passing algorithm which can be applied to non-gray mapping.