  Multi-antenna (MIMO) processing is a promising solution to the problem of
jammer mitigation. Existing methods mitigate the jammer based on an estimate of
its subspace (or receive statistics) acquired through a dedicated training
phase. This strategy has two main drawbacks: (i) it reduces the communication
rate since no data can be transmitted during the training phase and (ii) it can
be evaded by smart or multi-antenna jammers that are quiet during the training
phase or that dynamically change their subspace through time-varying
beamforming. To address these drawbacks, we propose joint jammer mitigation and
data detection (JMD), a novel paradigm for MIMO jammer mitigation. The core
idea is to estimate and remove the jammer interference subspace jointly with
detecting the transmit data over multiple time slots. Doing so removes the need
for a dedicated rate-reducing training period while enabling the mitigation of
smart and dynamic multi-antenna jammers. We instantiate our paradigm with
SANDMAN, a simple and practical algorithm for multi-user MIMO uplink JMD.
Extensive simulations demonstrate the efficacy of JMD, and of SANDMAN in
particular, for jammer mitigation.
