Low-Complexity Subarray-Based RF Precoding for Wideband Multiuser Millimeter Wave Systems

This correspondence paper proposes a novel low-complexity radio-frequency (RF) precoding and combining scheme for wideband multiuser millimeter wave hybrid-array systems, targeting at maximizing the system energy efficiency. We first derive a nearly-optimal fully-connected RF precoder, via minimizing the correlation across different users and subcarriers. We then extend the optimization solution to subarray-based architectures by exploiting the unitary matrix feature of subarrays. With the obtained phase values of the precoder, we optimize the power allocation on each subcarrier of the baseband precoder. Simulation results are provided and validate the effectiveness of our proposed hybrid precoding scheme.