Frozen-Sequence Constrained High-Order Polar-Coded Modulation

Polar coded modulation (PCM) is one of the most promising approaches towards high spectral efficiency. It is able to provide excellent performance comparing to the conventional turbo coded modulation schemes. In this paper, we consider the design of the PCM schemes with high modulation order, e.g., 256QAM or 1024QAM etc. Different with the legacy PCM of low modulation order, the coded bits in high-order PCM with all-zero frozen-sequence will demonstrate obvious correlations which lead to catastrophic performance loss. In order to evaluate this loss, we introduce a quantitative metric, named the bit conditional mutual information (BCMI), to analyze the correlation. Then a new PCM scheme based on the constrained frozen-sequence is proposed to eliminate the correlations among the coded bits. Theoretical analysis and simulation results show that the proposed scheme can ensure the performance of PCM and significantly outperform that of the turbo coded modulation schemes.