A Physical Layer Secure Wireless Communication Method Using Random Antenna Switching

A method of using random antenna switching (RAS) is proposed to guarantee the information security during the physical layer transmission. The method uses multiple antennas at the base station and a single antenna at the mobile terminal. The expected mobile terminal (target user) first transmits a training symbol which is used by the base station to estimate the channel. The base station then randomly selects several antennas to transmit each symbol. The weighting coefficients are obtained according to the estimated channel, which is similar to the distributed beamforming except that the magnitudes are random in this paper. Signals from all the selected antennas are finally superimposed in phase at the target user so that the maximum likelihood demodulation can be directly implemented. The RAS makes the channel for an eavesdropper change fast and randomly to prevent the eavesdropper from demodulating the signals. Simulation results show that the target user's bit error rate of RAS is lower with less transmission power than the traditional method of using random weighting coefficients, while the eavesdropper cannot correctly demodulate and hence the low probability of interception is achieved.