  Reconfigurable Intelligent Surfaces (RIS) are passive or semi-passive
heterogeneous metasurfaces and consist of many tunable elements. RIS is gaining
momentum as a promising new technology to enable transforming the propagation
environment into controllable parameters. In this paper, we investigate the
co-design of per-subcarrier power allocation matrices and multielement RIS
phase shifts in downlink wideband MIMO transmission using 28 GHz frequency
bands. Our contributions in improving RIS-aided links include (1) enhanced
system modeling with pathloss and blockage modeling, and uniform rectangular
array (URA) design, (2) design of gradient ascent co-design algorithm, and (3)
asymptotic (Big O) complexity analysis of proposed algorithm and runtime
complexity evaluation.
