Extended Mappings for Bit-Interleaved Coded Modulation

The performance of bit-interleaved coded modulation with iterative decoding (BICM-ID) depends strongly on the applied mapping. We analyse the use of extended mapping schemes with more than one label per signal point: assuming a fix signal constellation and a constant number of information bits per symbol, the increase in label length results in an ambiguous mapping scheme but also provides additional parity bits which allow the use of a stronger channel code. We derive the optimum MAP detector and give some optimized mapping schemes for 16-QAM. Simulation results include an EXIT-chart analysis and show the considerable reduction of the asymptotic bit error probability. As a consequence of the more powerful mapping, we can obtain a very low bit error floor with extremely simple channel codes