Robust Transmit Processing for BICM-OFDM Systems

In this paper, we introduce robust cyclic space-frequency (CSF) filtering for systems combining bit-interleaved coded modulation (BICM) and orthogonal frequency division multiplexing (OFDM). The proposed robust CSF filtering scheme exploits imperfect channel state information at the transmitter (CSIT) and takes into account the reliability of the CSIT via a Bayesian model. To further improve robustness, we combine CSF filtering with orthogonal space-time block coding in the frequency domain and refer to the resulting scheme as SFC-CSF filtering. We also propose a linear prediction method for improving the quality of the CSIT via post-processing. Based on an upper bound on the worst-case pairwise error probability we formulate an optimization problem for the robust CSF filters which can be solved exactly for certain special cases. For the general case, we obtain an approximate solution by solving a related problem with additional constraints. This approximate solution can be further improved with a gradient algorithm for the original problem. Simulation results confirm the excellent performance of BICM-OFDM with robust CSF and SFC-CSF filtering and the effectiveness of the proposed CSIT post-processing method.