Semidefinite Relaxation of a Joint Beamforming and Power Control for Downlink V2X Communications

Device-to-Device (D2D) enables direct communication among Vehicle-to-Everything (V2X) applications. Due to the high mobility in a vehicular environment, it is necessary to take into account the fast channel variations when defining resource allocation schemes in V2X networks. Furthermore, an efficient power control for V2X communications is needed to meet the large and growing number of vehicular devices and the growing demand for data traffic. In addition and for several types of networks, the use of transmission beamformer selection to reduce the power is a challenge. In this paper, we consider the power control problem in V2X networks. In addition, a joint beamforming and power control (BFPC) method for downlink V2X communication is proposed. It aims to reduce the total transmit power in the system while guaranteeing Quality of Service (QoS) for both, Vehicle User Equipments (VUEs) and Cellular User Equipments (CUEs). The problem is formulated as a non-convex optimization that we propose to solve it by using SemiDefinite Relaxation (SDR). The simulation results show the effectiveness of our BFPC proposed method compared to fixed power control method.