  Wireless communication systems that rely on orthogonal frequency-division
multiplexing (OFDM) suffer from a high peak-to-average (power) ratio (PAR),
which necessitates power-inefficient radio-frequency (RF) chains to avoid an
increase in error-vector magnitude (EVM) and out-of-band (OOB) emissions. The
situation is further aggravated in massive multiuser (MU) multiple-input
multiple-output (MIMO) systems that would require hundreds of linear RF chains.
In this paper, we present a novel approach to joint precoding and PAR reduction
that builds upon a novel $\ell^p\!-\!\ell^q$-norm formulation, which is able to
find minimum PAR solutions while suppressing MU interference. We provide a
theoretical underpinning of our approach and provide simulation results for a
massive MU-MIMO-OFDM system that demonstrate significant reductions in PAR at
low complexity, without causing an increase in EVM or OOB emissions.
