Two-stage space-time receiver structure for multiuser hybrid mmW massive MIMO systems

This paper considers a hybrid two-stage space-time receiver structure for uplink millimeter wave (mmW) based systems, where the user terminals (UTs) and the base station (BS) are equipped with a large antenna array and the number of radio frequency (RF) chains is lower than the number of antennas. In the first stage the analog transmit and receive beam-formers/precoders are computed for each UT - BS pair considering multi-user interference free links, to maximize the desired signal power for each UT. In the second one, an iterative block space-time equalizer is designed to explicitly remove the multi-user interference. The designed space-time equalizer is optimized by using as a metric the mean square error (MSE) between the transmitted data vector and its estimate after the digital equalizer. Our performance results havye shown that the proposed iterative space-time equalizer outperforms the linear MMSE based receivers for hybrid mmW massive MIMO architectures.