Improving Physical Layer Security in Vehicles and Pedestrians Networks with Ambient Backscatter Communication

Autonomous driving is considered one of the killer technologies in the intelligent era. The information transmission between autonomous vehicles and pedestrians (V2P) is very important to reduce the number of road accidents. Ambient backscatter communication (AmBC) technology can be used to increase the vehicle (or driver) awareness regarding the presence of pedestrians in a crosswalk to realize short-distance transmission of emergency messages. On the other hand, highly secure transmission in V2P networks is required to assure the broadcasting of emergency messages. However, the artificial noise scheme by an additional noise source to improve the physical layer security (PLS) is not suitable due to the dynamic vehicles. Therefore, in this paper, we propose a source-noise assisted AmBC transmission scheme in the V2P system, in which the noise is created by the ambient radio frequency (RF) source to improve the PLS performance. The closed-form expressions for the outage probability of the legitimate user and the intercept probability of eavesdropper are derived. Finally, the diversity gain performance of the system is studied by analyzing the asymptotic behaviors. The theoretical and simulation results show that the proposed scheme improves the system security performance at the expense of system reliability by utilizing the proposed source-noise aided scheme in the V2P network. Besides, the optimal reflection coefficient is related to the power allocation ratio for the signal of the reader and interference noise. The different reflection coefficient is required for achieving the best system performance under different power allocation ratios. Moreover, the results also show that there are error floors for the outage probability, depending on the reflection coefficient. Furthermore, the performance results show that the intercept probability will significantly decrease when the outage probability is fixed in the proposed scheme.