Physical layer security of MIMO frequency selective channels by beamforming and noise generation

This paper addresses physical layer security in MIMO communications over frequency selective wireless channels in the presence of passive eavesdroppers, i.e. the associated channels are unknown to the legitimate transmitter. Signalling is based on orthogonal frequency division multiplexing (OFDM). Spatial beamforming is performed to improve the quality of the legitimate link. With the aim of confusing the eavesdroppers, a fraction of the available power is allocated to transmit artificial noise. Frequency diversity is shown to significantly improve secrecy. A probabilistic analysis of secrecy is presented.