  We design a jamming-resistant receiver scheme to enhance the robustness of a
massive MIMO uplink system against jamming. We assume that a jammer attacks the
system both in the pilot and data transmission phases. The key feature of the
proposed scheme is that, in the pilot phase, we estimate not only the
legitimate channel, but also the jamming channel by exploiting a purposely
unused pilot sequence. The jamming channel estimate is used to constructed
linear receive filters that reject the impact of the jamming signal. The
performance of the proposed scheme is analytically evaluated using asymptotic
properties of massive MIMO. The optimal regularized zero-forcing receiver and
the optimal power allocation are also studied. Numerical results are provided
to verify our analysis and show that the proposed scheme greatly improves the
achievable rates, as compared to conventional receivers. Interestingly, the
proposed scheme works particularly well under strong jamming attacks, since the
improved estimate of the jamming channel outweighs the extra jamming power.
