Polarized beamforming for near-field wireless jamming attacks mitigation

Wireless communication systems are susceptible to jamming attacks and interference in general from other wireless signals. Beamforming is a technique that provide a scheme to counteract the impact of jamming attacks. However, for the situation when the direction of the desired signal is close in space to that of the jamming signal, the performance of the traditional anti-jamming beamformer that utilizes isotropic antenna array elements is significantly degraded because of the fact that signals are indistinguishable from interference in the space domain. Polarized beamforming has been proposed to solve this problem by filtering the interference from the desired signal in both space and polarization domain. However, existing work only considered far-field radiation region of the signal by assuming that the transmitter and the receiver are far apart while near-field wireless communications have been employed in more and more applications. In this paper, an enhanced countermeasure method for mitigating jamming attacks in the near-field radiation region has been proposed by using the polarized beamforming with a planar array. The analytical expression of the steering vectors is derived for near-field propagation. The steering vector for far-field is shown to be an approximation of that of near-field. The beamformer is designed by using the Linearly Constrained Minimum Variance (LCMV) criterion. Simulation results in terms of beam pattern and Bit Error Rate (BER) show a significant performance improvement of the proposed anti-jamming system even when the desired signals and interferences are propagating from the same direction. Simulation results also show that the proposed approach is more efficient in near-field wireless communications than the existing work that only considered far-field propagation.