A Low Complexity Iterative Receiver for Coded MIMO-OFDM Systems

A novel low-complexity iterative receiver for coded multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems is proposed in this paper. The soft-in soft-out (SISO) detector is simply a parallel interference cancellation (PIC) -maximum ratio combining (MRC) operation. Usually, the probability density function (PDF) of PIC-MRC detector output is approximated as Gaussian, whose variance is calculated with soft information fed back from the channel decoder. With this approximation, the log likelihood ratios (LLRs) of transmitted bits are under-estimated. Thus the LLRs are multiplied by a constant factor to achieve a performance gain. The constant factor is optimized according to the extrinsic information transfer (EXIT) chart of the channel decoder. Simulation results show that the proposed iterative receiver can significantly improve the system performance and converge to the matched filter bound (MFB) with low computational complexity at high signal-to-noise ratios (SNRs).