Optimal resource allocation for OFDM wiretap channel with cooperative jammer

We consider single-user OFDM wiretap channel with an external cooperative jammer (CJ), where the CJ helps the destination to interfere the eavesdropper. The achievable secrecy rate is derived. The source power and CJ power are optimized over all sub-carriers to maximize the sum secrecy rate under a total system power constraint. The simulation results indicate that the secrecy rate with optimal resource allocation is higher than that of the network without a CJ. It indicates that the network with an external CJ using optimal resource allocation improves the security performance greatly.