Secure Transmission in Integrated Communication-Radar Systems

When the base station (BS) transmits information to users, there may be suspicious targets nearby eavesdropping. In order to ensure the communication security while detecting the suspicious targets, we study the secure transmission in integrated communication-radar systems (ICRSs), where the BS not only communicates with users but also detects the suspicious targets with orthogonal frequency division multiplexing (OFDM) signals. To improve the secrecy capacity without degrading the detection performance, we add artificial noise (AN) into OFDM signals. We first calculate the Cramér–Rao lower bound (CRLB) of the target parameters to be estimated when OFDM signals are used as the detection signals. Then, we investigate the transmission optimization scheme, which maximizes the secrecy capacity under the CRLB constraints. To solve the optimization problem, an effective algorithm based on the Lagrange duality method is proposed to obtain the optimal power and subcarrier allocation. The simulation results reveal the tradeoff between secrecy capacity and estimation performance, and the advantage of our scheme over existing schemes in terms of the estimation performance.