A New Model for Physical Layer Security in Cellular Networks

Abstract—In this paper, we study physical layer security for the downlink of cellular networks. In a cellular network, the confidential messages transmitted to each mobile user can be eavesdropped by the other users in the same cell and also by the users in the other cells. We model the locations of base stations and mobile users as two independent two-dimensional Poisson point processes. By combining tools from stochastic geometry and random matrix theory, we analyze the secrecy rates achievable with regularized channel inversion (RCI) precoding under Rayleigh fading. Our analysis shows that unlike isolated cells, the secrecy rate in a cellular network does not grow monotonically with the transmit power. Moreover, we find that the network tends to be in secrecy outage if the transmit power grows unbounded. Furthermore, we show that there exists an optimal value for the base station deployment density that maximizes the secrecy rate. Index Terms—Physical layer security, cellular networks, stochastic geometry, linear precoding, random matrix theory. I