Optimised labeling maps for bit-interleaved transmission with turbo demodulation

It has been shown that iterative demodulation improves dramatically the performance of bit-interleaved schemes and that the improvement depends substantially on the chosen signal labeling. The effect of signal labeling is approached in this paper through the error rate analysis of maximum likelihood demodulation/decoding on one hand, and the statistical analysis of de-mapped bit metrics at the first demodulation iteration, on the other hand. These two features lead to two different optimisation criteria, which are used to design labelings for some practically important cases.