Capacity of iterative detection and decoding of space-time bit-interleaved coded-modulation BPSK codes

We consider MlMO schemes with N_t transmit and N_r receive antennas using BPSK modulation in quasi-static fading. We show that space-time (ST) bit-interleaving coded-modulation (BICM) approaches mapping binary codes to BPSK ST codes show a loss over coded-modulation (CM) MIMO capacity. This is despite the use of an optimal inner detector and is illustrated using capacity CDFs for the CM and ST-BICM cases. The CDFs are translated to plots of outage probabilities as functions of SNR. For capacity-achieving schemes, these indicate that SNR losses of ST-BICM over CM approaches decrease with N_r and increase with N_t. Finally, we amend our method for where the outer binary code is only capacity-approaching - we find this provides accurate predictions of FERs for ST-BICM using an outer turbo code.