Hybrid analog/digital precoding can potentially achieve high spectral efficiencies while requiring less cost and power consumption than fully-digital solutions. This makes it an attractive candidate architecture for millimeter wave systems, which requires deploying large antenna arrays at both the transmitter and receiver to guarantee sufficient received signal power. Most of prior work though on hybrid precoding focuses on narrow-band channels and assumes a fully-connected hybrid architecture. MmWave systems, though, are expected to employ wideband with frequency selectivity.
Hybrid precoding, a combination of analog and digital precoding, is an attempt to reach a compromise between complexity and performance. By exploiting more than one radio frequency chain, hybrid precoding enables a millimeter wave (mmWave) system to take advantage of both spatial multiplexing and beamforming gain. A major challenge with hybrid precoding is its configuration in wideband systems because the analog beamforming weights should be the same across the entire band.