Design and Analysis of Hierarchically Modulated BICM-ID Receivers With Low Inter-Layer Interferences

In this article, we present a novel methodology to optimize Hierarchically Modulated Bit-Interleaved Coded Modulation with Iterative Decoding (HM-BICM-ID). This methodology allows designing a receiver which supports several configurations. Each configuration is able to decode the same transmitted signal over the air with different fidelity. This concept permits using radios with varying processing capabilities, e.g. handheld radios, vehicular based radios etc. However, earlier simulation results have shown that HM-BICM-ID loses, if compared to non-hierarchical schemes, in Bit Error Rate (BER) performance due to Inter-Layer Interferences and design restrictions. Our proposed iterative tunable procedure optimizes hierarchical modulation schemes considering two criteria, the Harmonic Mean of the minimum squared Euclidean Distance and the bit error probability. The optimization is done by moving critical constellation points towards the optimal direction. A novel modulation scheme has been found and simulation results show an improved asymptotic BER performance in a wide range of channel conditions for an exemplary two-layered HM-BICM-ID. Finally, we present an analysis of HM-BICM-ID in context of Extrinsic Information Transfer Charts.