Abstract:

The premise of secure communication is to accurately reconstruct and cancel cooperative interference signals in authorized receivers.However,due to the influence of hardware and propagation environment,and restricted by actual engineering accuracy,a time-frequency synchronization error always exists.Therefore,aiming at the problem of imperfect time-frequency synchronization of the cooperative interference transceiver in physical layer secure communication,the residual interference power with a time-frequency synchronization error is derived under the Gaussian eavesdropping channel model.The influence of the time-frequency synchronization error on the system performance is analyzed theoretically,and the closed expressions for the authorized user interference suppression ratio,demodulation bit error rate and secure communication security capacity are obtained,while the theoretical performance is verified by computer simulation.Simulation results show that the suppression degree of the cooperative interference signal decreases,that the interference suppression ratio and security capacity of authorized users decrease,and that the demodulation bit error rate increases with the increase of time delay or frequency offset.In a certain range,the time-frequency synchronization error will not affect the performance of the three indicators.When the signal-to-noise ratio is 10 dB,it is shown that the normalized delay is less than 0.06,that the normalized frequency offset is less than 10^-5,that the delay and frequency offset have a little impact on the system security communication performance,and that the loss of security capacity is less than 16%.Accordingly,analyzing the influence of the time-frequency synchronization error of cooperative interference can provide guidance and theoretical support for the design of a secure communication system.

Key words: cooperative jamming cancellation, time-frequency synchronization errors, jamming cancellation ratio, bit error rate, secrecy capacity