System Level Performance Evaluation of MU-MIMO Precoder Schemes in Advanced Wireless Networks

In 5G and advanced wireless networks, multi-user multiple-input multiple-output (MU-MIMO) precoding allows multiple users to communicate simultaneously over the same orthogonal frequency division multiplexing (OFDM) time-frequency resources, thereby increasing the system throughput and improving the user experience. This paper develops and assesses the performance of the inverse discrete Fourier transform (IDFT) based downlink (DL) MU-MIMO precoding techniques at base station (BS) through $3^{\text {rd }}$ generation partnership project (3GPP) defined 5G outdoor channel models using system level simulator (SLS). Further, exploiting the channel reciprocity in case of time division duplex (TDD) deployments, the precoder design discussed in this paper relies on 5G sounding reference signal (SRS) based uplink (UL) channel estimates. Owing to lower complexity of wideband precoder weight computation, this paper presents the performance of wideband IDFT DL precoder and compares it with the maximum theoretical throughput of the network. Moreover, the impact of IDFT precoding techniques on DL key performance indicators (KPI) such as system throughput, precoded DL data signal to interference plus noise ratio (SINR), DL scheduled MU-MIMO effective modulation and coding (MCS) are analyzed through SLS. Lastly, the paper compares the proposed SRS based IDFT precoder selection scheme with the existing 3GPP based MU-MIMO precoding schemes relying on channel state information-reference signal (CSI-RS) Type-II codebook.