A Joint Optimization Scheme for Artificial Noise and Transmit Filter for Half and Full Duplex Wireless Cyber Physical Systems

While half and full duplex wireless enabled cyber physical systems (CPSs) are gaining more importance and research attention, maintaining the security of CPS systems remains a vital challenge. The broadcast nature of wireless channels makes it possible for unauthorized receivers, called eavesdroppers, to capture the information signal. Wireless physical layer security techniques aim to harden the secrecy characteristics of wireless systems, decreasing the signal quality of a prospective eavesdropper. This paper considers a joint optimization of artificial noise (AN) signal and transmit filter for the information signals in order to achieve a target secrecy level. As eavesdropping attacks are very critical threats in CPS networks, and the need for high secrecy techniques remains valid. The proposed framework includes a scenario with two multi-antenna legitimate parties and a multi-antenna eavesdropper node (or multiple cooperating eavesdroppers). The transmit filter and AN signal are jointly optimized by the transmitters, where receiver nodes can make use of optimal transmit filters. The problem is derived for the cases where the legitimate CPS nodes perform full duplex and half duplex transmissions. The impact of channel estimation errors and self interference are also discussed.