Security Capacity by Nonlinear Transmission in MIMO Systems for Physical Layer Security

To enhance the information security in multiple input multiple output (MIMO) wireless communication systems, nonlinear transmission is studied in this paper by pushing the power amplifier (PA) at the transmitter to operate in the nonlinear region, even near to the saturate point. Linearization reception technique is then adopted at the legal user’s receiver to remove the distortion caused by the nonlinear PA, so that the distortion-free signal can be drawn, and correct demodulation and decoding could be achieved. While for the eavesdroppers, the information required to complete the nonlinear reception could hardly be obtained, since the critical training sequence is designed to be invisible to the eavesdropping users, so the security transmission between the legitimate users can be obtained. Then, the security capacity by nonlinear transmission is analyzed in the MIMO–OFDM systems, where the signal to distortion plus noise ratio is derived, and the upper approximation is also presented. Numerical simulations are carried out to verify the effectiveness of the proposed scheme with practical reception algorithm, and it is shown that obvious security capacity can be acquired with both memory and memoryless PAs.