Investigation on resource assignment and power control schemes for uplink MU-MIMO in multi-cell environments for LTE/LTE-advanced

Abstract

This paper investigates capacity gains for uplink multi-user (MU)-MIMO in a multi-cell environment with single-carrier frequency division multiple access (SC-FDMA) used in LTE/LTE-Advanced. In the SC-FDMA MU-MIMO uplink, contiguous resource blocks (RBs) must be assigned in the frequency domain to each user in order to retain the SC-FDMA property, and the same bandwidth, i.e., the same set of RBs, needs to be assigned to the users that are simultaneously multiplexed in the spatial domain to utilize the inter-user orthogonality of demodulation reference signals. Furthermore, in a multi-cell environment, cell-edge users in particular cause severe fluctuation in inter-cell interference, which also depends on the number of simultaneously multiplexed users in MU-MIMO operation. To alleviate these problems, this paper proposes efficient resource assignment and transmission power control schemes to improve cell throughput without degrading the cell-edge user throughput. Based on system-level simulations, we show that by using the proposed schemes, the cell throughput performance achieved via uplink MU-MIMO is increased by approximately 20% and 40%, for 1-by-4 and 2-by-8 uplink antenna configurations, respectively, with almost the same cell-edge user throughput as that of the single-user MIMO case.