FP-based Sub-band Precoding Scheme for the MU MIMO-OFDM Systems

Abstract

Full-dimensional (FD) precoding is a cutting-edge technology that can be employed at the base station (BS) to enhance the spectral/energy efficiency or connection reliability of a multi-user (MU), multi-input-multi-output (MIMO), orthogonal frequency-division multiplexing (OFDM) system at the expense of high channel state information (CSI) feedback overheads and precoder design complexity. As the broadband millimeter-wave (mmWave) and terahertz (THz) channels, which will be encountered in future mobile networks, are observed to exhibit sparse scattering characteristics with short delay spread, the OFDM subcarrier spacing is likely to be much smaller than the coherence bandwidth; thus, this facilitates the sub-band (SB) precoding scheme as a viable alternative with greatly reduced complexity. In this paper, a SB precoding scheme aiming to maximize total channel capacity is proposed, where the coefficients are derived from optimization of a multi-ratio fractional programming (FP) problem. To evaluate its efficacy, simulation is conducted, where the total sum-rate will be presented and compared with other FD benchmark methods.