Trade-off in LDPC coded MIMO systems with iterative and independent demapping

The combination of low-density parity-check (LDPC) codes and bit-interleaved coded modulation (BICM) scheme, could easily break the bound of the cut-off rate and achieve capacity-approaching performance. To overcome the independent demapping loss in BICM scheme, the iterative demapping counterpart of BICM (BICM-ID) was further proposed. In this paper, we will present a viewpoint that the performance of BICM and BICM-ID system cannot be optimized simultaneously, especially for LDPC coded multiple-input multiple-output (MIMO) systems. Furthermore, we use a Monte Carlo method to estimate the achievable SNR region of the BICM and BICM-ID system with the aid of extrinsic information transfer (EXIT) chart tool. Such joint-bound of the achievable SNR region provides a practical and effective way to evaluate existing schemes, and guides the system design in the future.