Improved design of bit mapping based on EXIT-chart analysis for DVB-T2 system

摘要

In this paper, we focus on the design of bit mapping scheme to improve the error-control performance for the second generation digital video broadcasting-terrestrial (DVB-T2) standard. Generally in the case of low-density parity-check (LDPC)-coded modulation system, the nonuniform bit reliabilities inherent to the high-order modulation and irregular LDPC code imply the mismatch between the decoder and the demodulator. Hence, the bit mapping is plugged between the two modules to match the unequal error protections (UEPs) of different coded bits to different modulation levels. This scheme gives a remarkable performance improvement with no added complexity in the bit-interleaved coded modulation (BICM) system. By performing the curve-fitting on the extrinsic information transfer (EXIT) chart, we propose a DEMUX design methodology to improve the bit mapping scheme. Design examples are given for the DVB-T2 system under the AWGN channel as well as the Rayleigh channel. Simulation results indicate that the proposed DEMUX schemes can even surpass the performance of the DEMUX operation specified in the DVB-T2 standard1.