  Orthogonal frequency-division multiplexing (OFDM) time-domain signals exhibit
high peak-to-average (power) ratio (PAR), which requires linear radio-frequency
chains to avoid an increase in error-vector magnitude (EVM) and out-of-band
(OOB) emissions. In this paper, we propose a novel joint PAR reduction and
precoding algorithm that relaxes these linearity requirements in massive
multiuser (MU) multiple-input multiple-output (MIMO) wireless systems.
Concretely, we develop a novel alternating projections method, which limits the
PAR and transmit power increase while simultaneously suppressing MU
interference. We provide a theoretical foundation of our algorithm and provide
simulation results for a massive MU-MIMO-OFDM scenario. Our results demonstrate
significant PAR reduction while limiting the transmit power, without causing
EVM or OOB emissions.
