A reduced-complexity demapping algorithm for BICM-ID systems

Abstract

As a highly efficient decoding and demodulation scheme, bit-interleaved coded modulation (BICM) is widely adopted in modern communication systems. In order to enhance the attainable spectral efficiency, usually high-order modulation schemes are used for BICM systems. When combined with iterative demapping and decoding, BICM-ID is capable of further improving the achievable receiver performance. However, the complexity of the standard max-sum approximation of the maximum a posteriori probability in log-domain (Max-Log-MAP) invoked by the iterative demapper is on the order of 2m or O ( 2m) for a 2m-ary modulation constellation having m bits per symbol, which may become excessive for high-order BICM-ID systems. The existing simplified algorithms employed for noniterative demappers are based on exploiting the constellation’s symmetry, which is no longer retained upon the introduction of the a priori information in BICM-ID systems. Hence in this contribution, a simplified iterative demapping algorithm is proposed for substantially reducing the demapping complexity for binary-reflected Gray-labeled constellation. Our detailed analysis shows that the simplified demapping scheme proposed for BICM-ID reduces the computational complexity to O(m). We demonstrate that this dramatic computational complexity only imposes a modest performance degradation with respect to that of the optimal high-complexity Max-Log-MAP scheme

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ORCID for Lajos Hanzo: orcid.org/0000-0002-2636-5214

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