Improved embedded parameter estimation for bit-interleaved coded modulation with iterative decoding

Code-aided parameter estimation is considered for bit-interleaved coded modulation with iterative decoding (BICM-ID). The computational overhead caused by the estimation is minimized by embedding the parameter estimation into the iterative decoding. It is apparent that the performance of the estimation depends on the availability of accurate symbol a posteriori probabilities (SAPPs). Since the decoder computes bit a posteriori probabilities (BAPPs), the SAPPs are traditionally computed through a straightforward bit-to-symbol probability conversion. For advanced mappings which are optimized for BICM-ID, however, the latter method does not result in reliable SAPPs. Therefore, a new method is proposed and simulation results verify that the resulting iterative estimator-detector yields a close to perfectly synchronized performance.