Precoded Multirank Transmission with Linear Receivers for LTE-A Uplink

The 3rd generation partnership project (3GPP) defined the requirements for the upcoming long term evolution advanced (LTE-A) systems, aiming at peak spectral efficiencies of 30 bit/s/Hz in the downlink and 15 bits/s/Hz in the uplink. These ambitious targets can be accomplished only by using advanced multiple input multiple output (MIMO) antenna techniques. In this paper, we evaluate closed loop precoded multirank transmission for single carrier frequency division multiplexing (SC-FDM) as selected uplink modulation scheme by using the precoding codebook defined for LTE downlink. Its performance is compared with orthogonal frequency division multiplexing (OFDM). Results show that OFDM outperforms SC-FDM for medium-high ranks, but the gap can be reduced by adding further diversity branches. While narrowband precoding shows considerable gain over open loop transmission for all ranks, wideband precoding works with a very small feedback overhead but results to be a valid option mainly for low-rank transmission, where the low peak-to-average power ratio (PAPR) of SC-FDM signals is also preserved.