Physical Layer Security in D2D Communication System Underlying Cellular Networks

Due to the openness of the physical layer, the physical layer security has been widely discussed. It is considered as an effective way to improve the secrecy rate that we add artificial noise to D2D communications underlaying cellular networks. Compared to previous studies, in this paper we not only think of the situation where artificial noise is added to the original communication signal between the base station and the cellular user, but also consider the design of the intended information signal and artificial noise signal between corresponding D2D pair. In order to improve system secret rate under limited resources, we propose an idea of the power distribution coefficient for two legitimate communication links(one link between BS and CU and the other link between a D2D pair). Then we build convex optimization model and adopt a mixed penalty function algorithm to obtain optimal value of power distribution coefficient. On this basis, a joint optimization allocation scheme for transmit power between BS and DU-T is proposed, which satisfies the best security mechanism of physical layer in D2D communication underlying cellular networks. Simulation results show that as taking the optimal solution, system secret rate is clearly improved.