Improving physical layer security in distributed multiple-input multiple-output dual-function radar-communication systems

A distributed multiple-input multiple-output (MIMO) dual-function radar-communication (D-MIMO DFRC) system is composed of multiple distributed dual-function transmitters, multiple radar receivers and multiple communication receivers, which is capable of performing communication and radar tasks simultaneously. In a DFRC system, the goal is on optimising both the sum -rate in communication receivers and detection/localisation performance in radar receivers. The secrecy rate is maximised in D-MIMO DFRC systems by decreasing the eavesdropper data rate as much as possible with a two-step antenna selection method while maintaining optimal radar performance. In the first step of the proposed method, all transmitter antennas have been classified into groups based on their distance from each other, and each group is called a cluster. Then, a cluster of distributed transmitter antennas is selected based on path fading effects. In the second step of this method, the antenna selection algorithm is performed in the pre-selected cluster based on channel capacity information utilising QR decomposition. The results show that this antenna selection method, along with low computational complexity and high performance, leads to the maximisation of the secrecy rate. In DFRC systems, it is desirable to minimise the total transmit power while satisfying system requirements to provide low probability of interception (LPI). Finally, after antenna selection, a power allocation strategy is also applied on the selected antennas to optimise the total transmit power and to maximise throughput in communication radar receivers simultaneously, and as a result it leads to provide LPI.