Digital Beamforming with PAPR Reduction: An Approach for Energy Efficient Massive MIMO

In this work, we present a novel strategy aiming at obtaining higher energy efficiency in mm-wave digital massive MIMO systems. The proposed approach consists in a joint optimization of time-domain digital beamforming and Tone-Reservation based Peak-to-average Power Ratio (TR-PAPR) reduction. The main idea is to perform broadband beam-steering by adding progressive time delays to the reduced PAPR signals fed to the antennas. These time delays are implemented in digital baseband through time-domain fractional delay filter banks (TDFDFBs). Simulation results show that the increment in MER due to PAPR reduction is maintained for the progressively delayed signals for beam-steering generated by interpolation at the output of the filter bank. As a result, the required power amplifiers (PAs) can all be biased with a lower input back-off (IBO) operation point, leading to significant energy savings while keeping low levels of in-band distortion.