Joint Tx/Rx MMSE Filtering for Single-Carrier MU-MIMO Uplink

In broadband single-carrier (SC) multi-user multipleinput multiple-output (MU-MIMO) transmissions, inter-symbol interference (ISI) caused by frequency-selectivity of the channel, inter-antenna interference (IAI), and inter-user interference (IUI) degrade the transmission quality. This paper proposes a minimum mean square error based joint transmit and receive linear spatial/frequency filtering (joint Tx/Rx MMSE filtering) for SC-MU-MIMO uplink transmissions assuming that each user equipment (UE) only knows the channel state information (CSI) between itself and the base station (BS) (i.e., CSI sharing among UEs is not considered). By Jointly applying each UE’s Tx filtering and BS’s Rx filtering, single-user (SU) MIMO channel between each UE and the BS is transformed into multiple eigenmodes, and MMSE based Tx power allocation and Rx frequency-domain equalization (FDE) are applied to each eigenmode. As a consequence, IAI and ISI are suppressed significantly. At the same time, IUI is suppressed by BS’s Rx filtering. Furthermore, adaptive rank/modulation control (ARMC) is introduced to utilize the received signal-tointerference plus noise power ratio (SINR) gap among eigenmodes. Computer simulation results confirm the effectiveness of proposed joint Tx/Rx MMSE filtering in SC-MUMIMO uplink transmissions. Keywords—Spatial/frequency filtering; single-carrier; MUMIMO; uplink;