Performance improvement of chaos MIMO transmission scheme by LDPC code concatenation using symbol MAP detection and STBC

A chaos multiple-input multiple-output (C-MIMO) transmission scheme is developed, which has both physical layer security and channel coding gain with a coding rate of one, by adopting a principle of chaos communications to a MIMO block transmission system. In our previous study, further improvement of transmission quality is achieved by introducing a log-likelihood ratio (LLR) with turbo-coded transmission. Moreover, the increased coding gain is obtained by convolutional code concatenation with symbol maximum a posteriori (MAP) detection that calculates the true-valued LLR, or with a sequential LLR that is an approximate LLR. However, symbol MAP detection has not been considered in LDPC code concatenation. Therefore, in this paper, we propose a C-MIMO transmission system with LDPC code concatenation using symbol MAP detection, and the effectiveness of this scheme is evaluated through numerical simulation. Furthermore, we propose an application of space-time block coding (STBC) to the C-MIMO scheme, and show the improvement of bit error rate in lower SNR regions when the LDPC coding rate is high.