  Vehicle-to-vehicle (V2V) communication appeals to increasing research
interest as a result of its applications to provide safety information as well
as infotainment services. The increasing demand of transmit rates and various
requirements of quality of services (QoS) in vehicular communication scenarios
call for the integration of V2V communication systems and potential techniques
in the future wireless communications, such as full duplex (FD) and
non-orthogonal multiple access (NOMA) which enhance spectral efficiency and
provide massive connectivity. However, the large amount of data transmission
and user connectivity give rise to the concern of security issues and personal
privacy. In order to analyze the security performance of V2V communications, we
introduce a cooperative NOMA V2V system model with an FD relay. This paper
focuses on the security performance of the FD-NOMA based V2V system on the
physical layer perspective. We first derive several analytical results of the
ergodic secrecy capacity. Then, we propose a secrecy sum rate optimization
scheme utilizing the instantaneous channel state information (CSI), which is
formulated as a non-convex optimization problem. Based on the differential
structure of the non-convex constraints, the original problem is approximated
and solved by a series of convex optimization problems. Simulation results
validate the analytical results and the effectiveness of the secrecy sum rate
optimization algorithm.
