Securing Uplink Transmissions in Cellular Network via User-Specific Reconfigurable Intelligent Surfaces

This letter makes an attempt to design a user-specific reconfigurable intelligent surface (US-RIS) aided secure uplink communication scheme. In the considered scenario, the mobile terminal (MT) equipped with a US-RIS needs to transmit confidential information to the base station (BS) under the threat from the eavesdropper, while the uplink resource is reused by a device-to-device (D2D) pair to further improve the spectral efficiency. The formulated nonconvex optimization problem is to jointly design the transmit phase shifter matrixes of the US-RIS and the power control of the D2D communication for maximizing the secrecy rate as well as the data rate of the D2D communication. We then alternately optimize the phase shifter matrixes and D2D transmit power by using successive convex approximation and difference between two concave functions programming, respectively. Simulation results validate the effectiveness of our designed scheme.