Low-complexity MIMO-BICM receivers with imperfect channel state information: Capacity-based performance comparison

This paper provides a performance comparison of soft MMSE and max-log demodulators for multiple-input multiple-output (MIMO) bit-interleaved coded modulation (BICM) systems with imperfect channel state information. We use the capacity of the equivalent modulation channel as a code-independent performance metric. Our results show that the conventional approach of mismatched demodulation is noticeably inferior to optimal demodulators that are derived by conditioning on the channel estimate right from the beginning. Numerical simulations further demonstrate the importance of appropriate pilot power allocation.