Adaptive Power Allocation for D2D Assisted Cooperative Relaying System with NOMA

This paper considers the power allocation problem for a device-to-device (D2D) assisted cooperative relaying system with non-orthogonal multiple access (NOMA). Under the constraint of satisfying each user’s minimum rate requirement, we formulate the optimization problem to maximize the sum rate. Specifically, by satisfying one user’s minimum rate requirement, the data rate of the other user is maximized. Then with the Karush-Kuhn-Tucker (KKT) conditions, we obtain two closed-form solutions of power allocation factor. Simulation results substantiate that compared with the traditional framework with orthogonal multiple access (OMA), D2D assisted cooperative relaying system is capable of improving the data rate effectively. Furthermore, by adaptively adjusting the power allocation factor, the proposed power allocation algorithm achieves the maximum sum rate under the two-user model.