Joint Channel Assignment and Power Allocation for NOMA-based D2D Communications with Imperfect CSI

Abstract

In this paper, we propose a channel assignment and power allocation sheme for non-orthogonal multiple access (NOMA) device-to-device (D2D) communications. Our optimization goal is to maximize the sum rate of the D2D system, and considering the fairness factor simultaneously. Importantly, we innovatively consider the impact of imperfect channel state information (CSI) in our system, which makes our proposed algorithm more realistic and effective. We split the problem into two sub-problems: 1) one-to-one matching for the cellular user and D2D transmitter and finding the appropriate receivers for the D2D transmitter to form the D2D group; 2) power allocation for each D2D group. For the channel assignment, we derive a closed form expression of the scheduled data rate of D2D link with considering imperfect CSI by using mathematical approximation methods. And we transform the power allocation subproblem from a non-convex problem to convex one and use the Lagrangian multiplier method to get the optimal power allocation coefficients, considering the sensitivity of the successive interference cancellation (SIC) receiver. Moreover, the theoretical analysis and simulation results are presented to evaluate our proposed scheme for the NOMA-based D2D communications.