Matrix Unimodular Precoder Interpolation for MIMO-OFDM Wireless Communication Systems

Unitary precoding is an essential step in multiple-input multiple-output (MIMO) wireless systems. For wideband systems that employ OFDM, precoders are typically fed back for a few subcarriers and interpolated in the frequency domain. This does not scale well for wideband (5G/6G) systems since feedback requirements become prohibitive for large bandwidths. Often, these systems possess dominant line-of-sight components with compact channel representations in the time-domain. In this letter, we propose Unimodular interpolation based filter design to compactly represent precoders as realisable matrix all-pass filters. Simulations confirm the effectiveness of the proposed approach over past approaches in terms of achievable rate.