Nonbinary LDPC-Coded Spatial Multiplexing for Rate-2 MIMO of DVB-NGH System

To improve the performance on high spatial correlation channels, the enhanced spatial multiplexing (eSM) precoding scheme with the binary low density parity check (LDPC) codes is employed for the rate-2 MIMO transmission in the DVB-NGH standard. However, it just brings very limited performance gain about 0.2–0.4 dB compared with the plain spatial multiplexing scheme in high correlation channels, while it has not any gain in low correlation channels. In this paper, a nonbinary (NB) LDPC coded modulation (CM) eSM scheme is proposed. The binary DVB-NGH LDPC codes are replaced by regular quasi-cyclic NB LDPC codes, and each NB-LDPC coded symbol is directly mapped to two modulation symbols on two transmit antennas. To investigate the performance gain, average mutual information performances of bit-interleaved-coded-modulation (BICM) and CM MIMO systems are analyzed in flat Rayleigh fading channels, which are corresponding to the binary and NB coding scheme, respectively. The information-theoretic analysis turns out that the proposed NB-LDPC CM-MIMO scheme is much superior to the current binary-LDPC BICM-eSM scheme. Simulation results also verify that the proposed scheme has significant up to 3dB performance gain compared with the BICM-eSM scheme under different modulation orders, power imbalances, and channel correlations. Therefore, the proposed scheme is much more reliable and robust, and thus very suitable for the future broadcasting applications.