Control Efficient Power Allocation of Uplink NOMA in UAV-Aided Vehicular Platooning

Power allocation in non-orthogonal multiple access (NOMA) systems is essential to avoid multi-user detection failure. However, controlling the uplink transmission power brings extra signaling overhead, especially in dynamic environments. In this paper, we investigate the uplink transmission power allocation problem in an unmanned aerial vehicle (UAV)-aided platooning NOMA system, where the UAV acts as a relay to assist inter-vehicle communications. Platoon vehicles are admitted to the same vehicle-to-UAV channel via our proposed sequence-based power allocation (SPA) strategy. Instead of achieving the optimal energy efficiency, our goal is to design a simple yet effective power control scheme. Specially, in SPA strategy, vehicles determine their transmission power according to their positions in the platoon. Considering platoon dynamics due to vehicle mobility, a power-reserved mechanism is further incorporated in the proposed strategy to pre-allocate power resources for newly joined vehicles. In addition, a power-moving mechanism is further employed to guarantee the uplink signal-to-interference-plus-noise ratio (SINR) of vehicles by changing vehicle transmission power into higher levels during vehicle leaving a platoon. As the system only needs to update vehicle positions for the SPA strategy, only a small amount of signaling is required in our power allocation strategy. Extensive simulation results are provided to demonstrate that the proposed SPA strategy ensures the required SINR of platoon communication in different dynamic scenarios.