Low Complexity Soft Input Decoding in an Iterative Linear Receiver for Overloaded MIMO

Satoshi DENNO  Tsubasa INOUE  Yuta KAWAGUCHI  Takuya FUJIWARA  Yafei HOU  

IEICE TRANSACTIONS on Communications   Vol.E103-B   No.5   pp.600-608
Publication Date: 2020/05/01
Online ISSN: 1745-1345
DOI: 10.1587/transcom.2019EBP3159
Type of Manuscript: PAPER
Category: Wireless Communication Technologies
MIMO,  overloaded,  linear detection,  iterative decoding,  soft-input-soft-output (SISO),  

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This paper proposes a low complexity soft input decoding in an iterative linear receiver for overloaded MIMO. The proposed soft input decoding applies two types of lattice reduction-aided linear filters to estimate log-likelihood ratio (LLR) in order to reduce the computational complexity. A lattice reduction-aided linear with whitening filter is introduced for the LLR estimation in the proposed decoding. The equivalent noise caused by the linear filter is mitigated with the decoder output stream and the LLR is re-estimated after the equivalent noise mitigation. Furthermore, LLR clipping is introduced in the proposed decoding to avoid the performance degradation due to the incorrect LLRs. The performance of the proposed decoding is evaluated by computer simulation. The proposed decoding achieves about 2dB better BER performance than soft decoding with the exhaustive search algorithm, so called the MLD, at the BER of 10-4, even though the complexity of the proposed decoding is 1/10 as small as that of soft decoding with the exhaustive search.