MU-MIMO and CSI Feedback Performance of NR/LTE

The Re1-15 physical layer air-interface specifications for NR (5G) and LTE (4G) has been released by 3GPP in September 2018. This paper aims to study two principal gain mechanisms introduced in NR (compared to LTE) targeting spectral efficiency improvements -(i) high order MU-MIMO with up to 12 layer spatially multiplexed transmission and (ii) higher resolution of CSI feedback with Type II feedback mechanism. In order to perform a fair comparison between LTE and NR, we maintain the same overhead, sub-carrier spacing and antenna configurations among other parameters. Although it is known that NR can provide benefits over LTE in terms of deployment flexibility, spectral efficiency and latency using mechanisms like multiple numerology support, lower control channel and reference signal overhead or lower guard bands we believe that the gain mechanisms (i) and (ii) are fundamental and a quantification of this aspect is attractive to operators and vendors who may consider NR or LTE deployments in sub-6 GHz bands.