On the Efficacy of Antenna Selection at the Massive Antenna Jammer

We investigate the efficacy of antenna selection (AS) at ajammer with a massive number of antennas in deteriorating the sum downlink (DL) spectral efficiency (SE) of a legitimate massive MIMO system. To this end, we analyze the DL sum SE of a massive MIMO system when the legitimate base station (BS) uses zero-forcing (ZF) precoding while the jammer employs either maximum ratio (MR) or ZF precoding and uses all its antennas to transmit jamming signal on the DL. We also evaluate the extent of degradation in the sum SE when the jammer selects a fraction of the antennas based on the strength of the estimated channels and uses them to precode. We prove that a massive antenna jammer that employs MR precoding instead of ZF precoding and uses only half of its strongest antennas to precode can achieve nearly 90% of the degradation achieved by a full-antenna jammer.