On the Security of Full-Duplex Relay-Assisted Underwater Acoustic Network With NOMA

Wireless underwater acoustic (UWA) networks serve several civilian and military applications. The multiple reflections and dispersion, along with the long propagation delay limit the sum rate of UWA networks. Earlier works discussed adding full-duplex (FD), relay assistance, and non-orthogonal multiple access (NOMA) to enhance the system sum rate. Another challenge in UWA networks is the power limitation of devices. Hence, power optimization is crucial to maximize the energy efficiency. Furthermore, securing the UWA network against eavesdropping is essential to guarantee the confidentiality of communication. This work optimizes the power to maximize the secrecy sum rate (SSR) of a FD relay-assisted NOMA (FD-R-NOMA) underwater acoustic network subjected to an eavesdropper (Eve) attack. The network is studied in two states: when the network has or not the channel information (CI) of the threat. FD-R-NOMA UWA network shows to be more resilient to eavesdropping with higher secrecy energy efficiency when compared to the conventional half-duplex orthogonal multiple access network. Also, the results reveal that knowing the CI of the Eve improves the SSR of the network. Besides, the results show the effect of factors like the location of Eve, interference cancellation efficiency, noise in the environment, and sensor distributions in the system.