  Low-resolution analog-to-digital converters (ADCs) simplify the design of
millimeter-wave (mmWave) massive multi-user multiple-input multiple-output
(MU-MIMO) basestations, but increase vulnerability to jamming attacks. As a
remedy, we propose HERMIT (short for Hybrid jammER MITigation), a method that
combines a hardware-friendly adaptive analog transform with a corresponding
digital equalizer: The analog transform removes most of the jammer's energy
prior to data conversion; the digital equalizer suppresses jammer residues
while detecting the legitimate transmit data. We provide theoretical results
that establish the optimal analog transform as a function of the user
equipments' and the jammer's channels. Using simulations with mmWave channel
models, we demonstrate the superiority of HERMIT compared both to purely
digital jammer mitigation as well as to a recent hybrid method that mitigates
jammer interference with a nonadaptive analog transform.
