2604.01445 Time-Reversal Symmetry in Wireless Channel Reciprocity Breaks Down at 28 GHz Due to Amplifier Nonlinearity Asymmetry
Time-reversal symmetry underlies physical-layer security schemes exploiting channel reciprocity. We demonstrate that at 28 GHz mmWave frequencies, reciprocity breaks down due to asymmetric power amplifier nonlinearities between transmit and receive chains.