Power, Rate, and Decoding Order Optimization for NOMA-Based Vehicular Communications

This paper considers a two-user non-orthogonal multiple access (NOMA) based infrastructure-to-vehicle (I2V) network, where one user requires reliable safety-critical data transmission and the other pursues high-capacity services. Leveraging only slow fading of channel state information, we aim to maximize the expected sum throughput of the capacity hungry user subject to a constraint on the payload delivery success probability of the reliability sensitive user, by jointly optimizing the transmit powers, target rates, and decoding order. We introduce a dual variable and formulate the optimization as an unconstrained single-objective sequential decision problem. Then, we design a dynamic programming based algorithm to derive the optimal policy that maximizes the Lagrangian. Afterwards, a bisection search based method is proposed to find the optimal dual variable. The proposed strategy is shown by numerical results to be superior to the baseline approaches from the perspectives of expected return, performance region, and objective value.