Joint Transceiver Optimization for CJ-Aided Security Communication Systems With Frequency Mismatch

Cooperative jamming (CJ) can reduce the receiving performance of eavesdroppers and will be reconstructed and canceled at the licensed receiver to ensure reliable communication. However, due to hardware impairments and the limited accuracy of frequency synchronization algorithms, a frequency offset exists between the CJ transmitter and licensed receiver, yielding imperfect jamming cancellation at the licensed receiver. In this letter, assume channel state information of eavesdropper (CSIE) is perfect, a joint transceiver optimization algorithm for CJ cancellation with frequency mismatch is proposed. To maximize the system's achievable secrecy rate with frequency mismatch, we first derive the closed-form expression of the system's achievable secrecy rate; then, the security performance of the system is optimized from two aspects: power allocation at the transmitter and jamming cancellation factor optimization at the receiver. Moreover, the feasibility of the proposed optimization scheme under imperfect CSIE is analyzed. Simulations show that the proposed transceiver method significantly improves the system security performance compared with the traditional one.