  Spatial coupling is utilized to improve the performance of iterative channel
estimation, multiuser detection, and decoding for multiple-input multiple-input
(MIMO) bit-interleaved coded modulation (BICM). Coupling is applied to both
coding and BICM---the encoder uses a protograph-based spatially-coupled
low-density parity-check (SC LDPC) code. Spatially and temporally coupled (STC)
BICM is proposed to enable iterative channel estimation via coupling. Linear
minimum mean-squared error (LMMSE) estimation is applied for both channel
estimation and detection to reduce the complexity. Tractable density evolution
(DE) equations are derived to analyze the convergence property of iterative
receivers in the large-system limit, via a tool developed in statistical
physics---replica method. The DE analysis implies that the STC BICM can improve
the performance of iterative channel estimation especially for higher-order
modulation. Numerical simulations show that the STC BICM can provide a
significant gain of the performance at high signal-to-noise ratios for 64
quadrature amplitude modulation (QAM), as well as an improvement in the
decoding threshold, compared to conventional BICM.
