EXIT-chart aided design of row-permutation assisted twin-interleaver BICM-ID

Twin-interleaver bit-interleaved LDPC coded modulation (BICM) has been widely adopted and studied in the context of digital terrestrial transmission (DTT) systems. Extrinsic-information transfer (EXIT) charts have been used as an analysis tool to evaluate the iterative decoding performance and to design a twin-interleaver BICM system. Since BICM using iterative decoding (BICM-ID) exhibits capacity-approaching decoding performance, developing the conventional twin-interleaver BICM DTT system to a BICM-ID system has also been attempted. When considering the twin-interleaver BICM-ID systems, there are a couple of aspects that should be taken into account. We will demonstrate that anti-Gray mapping should be adopted for improving the iterative decoding performance instead of the classic Gray symbol mapping. However, the previous literature related to designing the associated row-permutation interleaver (RPI) was mainly focused on BICM systems relying on Gray mapping. Hence, we will design the RPI of the twin-interleaver BICM-ID DTT systems using an anti-Gray mapping. Explicitly, we use: 1) the EXIT-chart analysis that accurately visualizes the overall iterative decoding and demapping performance of the twin-interleaver BICM-ID DTT systems using anti-Gray mapping and 2) a preprocessing stage for eliminating duplicate RPI candidates by using a parameter that roughly predicts the EXIT-chart analysis result before the EXIT-chart analysis is involved. By the elimination of the duplicates, over 99% of the initial candidates of the RPIs can be removed from the original {M} ! candidates, where {M} stands for the number of modulated bits in a symbol. Given this drastically reduced number of candidates, the proposed design method finds novel RPIs, having superior bit-error ratio performances over the conventional RPIs in the context of the DVB-T2 standard.</p