A security method of physical layer transmission using random antenna arrays in wireless communication

A method of using random antenna arrays (RAA) 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 each mobile terminal. When expected mobile terminals (target users) transmit training symbols. The base station estimates the channel from the symbols. Then the base station randomly selects several antennas for weighted transmission, and the weighting coefficients are obtained by using the method of distributed beamforming according to the estimated channel. Signals from all the selected antennas are finally superimposed at the target user so that the maximum likelihood demodulation can be directly employed. The base station randomly changes antennas to transmit each symbol, which makes the channel of any eavesdropper change fast. Hence the eavesdropper can not demodulate his received signals by blind equalization, and the low probability of interception is achieved. A comparison with the traditional method of using random weighting coefficients shows that the RAA method improves the utilization of power. Simulation results show that the bit error rate of the RAA method is reduced by one order of magnitude at the target user, while the eavesdropper can not demodulate correctly.