Joint Resource Allocation with Weighted Max-Min Fairness for NOMA-Enabled V2X Communications

To achieve more efficient spectrum utilization in the intelligent transportation system, non-orthogonal multiple access-enabled (NOMA-enabled) V2X communications have been emerging as a promising technology. In this paper, the resource allocation problem for NOMA-enabled V2X communications is investigated. For V2I links, in view of the user fairness and the different requirements of cellular users (CUEs), weighted max-min rate fairness for CUEs is applied, where both identical weights and different weights are considered. As for V2V users (VUEs), the minimum signal-to-interference-plus-noise ratio (SINR) requirements are imposed on the problem formulation. To solve the proposed optimization problem, it is decoupled into three stages: 1) power allocation for CUEs; 2) power control and subcarrier (SC) assignment for VUE pairs; 3) SC assignment and user clustering for CUEs. For the three stages, algorithms based on the Perron-Frobenius theorem, the Kuhn-Munkres algorithm, and the matching theory are proposed separately. Finally, an algorithm integrated the three stages is presented to obtain a joint solution. The convergence and the optimality of the proposed algorithms can be verified by theoretical analysis and simulations. Moreover, simulation results also indicate that each cluster of the optimal user clustering scheme is inclined to be occupied by the CUEs with diverse channel gains and the minimum weighted rate of all CUEs, τ, will decrease with the increase of the numbers of V2V links and the minimum SINR requirements of VUE pairs.