Cell-free Massive MIMO Systems under Jamming Attack

This paper evaluates the uplink spectral efficiency (SE) performance of a cell-free massive multiple-input-multiple-output (MIMO) network under the attack of several distributed jammers. The signal-to-interference-plus-noise ratio (SINR) formula for the maximum-ratio-combining (MRC) receiver is initially derived for an arbitrary legitimate user-equipment (UE) by considering the harmful impact of jammers. These jammers target the access points (APs) during both training and data transmissions. Two power control methods are developed to improve the SE performance, a max-min one aiming to ensure uniformly good service for UEs, and a second method aiming to achieve proportional fairness. The proposed system is compared with a single cell co-located massive MIMO system, and with another cell-free massive MIMO system including smart jammers, provided with the legitimate UEs' pilot signals. Simulation results demonstrate the superiority of the proportional fairness power control compared with the max-min fairness and the other scenarios under the threat of jammers. The effect of the number of jammers and their transmission power is further presented and analysed.