Circular array directional modulation over fluctuating two-ray fading channel

To achieve the physical layer security communication towards any desired direction in 3D space, a directional modulation transmitter model based on uniform circular array is proposed. Zero-forcing beamforming and null space projection are used for useful signals and artificial noise (AN) transmission. Closed-form expressions of lower bound for average secrecy capacity(ASC) and upper bound for secrecy outage possibility(SOP) under fluctuating two-ray (FTR) fading channel are derived. Curves of system security performance against signal-to-noise ratio (SNR) are contrasted. Computer simulations show that the proposed directional modulation achieves undistorted modulated signal in desired direction for circular array with 64 elements and SNR with 10 dB, as well as that the error vector magnitudes(EVM) are up to 100% and BERs are higher than 40% in most undesired directions. Our method can realize secure transmission in 3D space without encryption and its security performance can be improved by larger SNR under FTR fading channel.