Parameterized EXIT function for demapper and symbol mapping design

We propose an approach using the parameterization of extrinsic information transfer (EXIT) functions for symbol mapping design in bit-interleaved coded modulation (BICM-ID). The EXIT function of demapper is parameterized by a weighed sum of binomial functions. The set of binomial functions is then transformed to an orthonormal basis. Based on the parametric approach, the flatness criterion, aiming at achieving a faster convergence rate in term of number of iterations, can be formulated and symbol mappings can be found by a searching method. Simulation results confirm that good performances can be achieved in terms of convergence rate for fast fading channels when a good (near capacity-achieving) code is employed.