Predicting the performance of an iterative MIMO MMSE receiver with vertical encoding

This paper proposes a semi-analytical performance prediction method for an iterative receiver that processes signals arriving through a frequency selective multiple-input multiple-output radio channel. Earlier results provide a distribution of the signal-to-interference-and-noise ratio at the output of a frequency-domain soft-cancellation minimum mean square error equalizer, which is subsequently used to approximate the distribution of the log-likelihood ratios (LLRs) of the demapped bits. Extrinsic information transfer (EXIT) charts establish a bijective relationship between the variance of the LLRs and mutual information. We use an approximate distribution of the equalizer/demapper output´s LLR variance to estimate the probability of an intersection between the decoder and equalizer graphs. The probability provides a good estimate of the frame error rate.