Design and Optimization of BICM-ID Systems


Vision

      Bit-Interleaved Coded Modulation with Iterative Detection/Decoding (BICM-ID) has been recognized as being a bandwidth efficient coded modulation and transmission scheme, of which transmitter is comprised of a concatenation of encoder and bit-to-symbol mapper separated by a bit interleaver. Iterative detection-and-decoding takes place at the receiver, where extrinsic log likelihood ratio (LLR) obtained as the result of the maximum a posteriori probability (MAP) algorithm for demapping/decoding is forwarded to the decoder/demapper via de-interleaver/interleaver, and used as the a priori LLR for decoding/demapping, according to the standard turbo principle.

      Performances of BICM-ID have to be evaluated by the convergence and asymptotic properties, which are represented by the threshold signal-to-noise power ratio (SNR) and bit error rate (BER) floor, respectively. In principle, since BICM-ID is a serially concatenated system, analyzing its performances can rely on the area property of the extrinsic information transfer (EXIT) chart. Therefore, the transmission link design based on BICM-ID falls into the issue of matching between the demapper and decoder EXIT curves. The major goal of this project is to achieve better matching between the two curves for minimizing the gap while still keeping the tunnel open, aiming, without requiring heavy detection/decoding complexity, at achieving lower threshold SNR and BER floor.