Abstract
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 (V2U) 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.
Highlights
N ON-ORTHOGONAL multiple access (NOMA) is a promising technology to improve spectrum efficiency by allowing users to share the time/frequency resources [1]
For the power control issues, we propose a sequence-based power allocation (SPA) strategy, where the vehicles set the power according to their positions in the platoon
The main contributions of this paper are summarized as follows: 1) We investigate the vehicle safety message transmission problem and propose an SPA strategy to simplify the procedure of power allocation with a low signaling overhead; 2) We theoretically analyze the effect of the platoon dynamics, including vehicle joining and vehicle leaving, on the signal-to-interferenceplus-noise ratio (SINR) of the vehicles, which can be beneficial to proposing power adjustment mechanism; 3) We employ a power-reserved mechanism for newly joining vehicles in the platoon, by which the newly joining vehicles can transmit messages to the unmanned aerial vehicle (UAV) on a power level that does not affect the transmission of other vehicles; 4) We develop a power-moving mechanism to ensure the SINR when the platoon declines the distance headway gap caused by vehicles leaving
Summary
N ON-ORTHOGONAL multiple access (NOMA) is a promising technology to improve spectrum efficiency by allowing users to share the time/frequency resources [1]. The main contributions of this paper are summarized as follows: 1) We investigate the vehicle safety message transmission problem and propose an SPA strategy to simplify the procedure of power allocation with a low signaling overhead; 2) We theoretically analyze the effect of the platoon dynamics, including vehicle joining and vehicle leaving, on the SINR of the vehicles, which can be beneficial to proposing power adjustment mechanism; 3) We employ a power-reserved mechanism for newly joining vehicles in the platoon, by which the newly joining vehicles can transmit messages to the UAV on a power level that does not affect the transmission of other vehicles; 4) We develop a power-moving mechanism to ensure the SINR when the platoon declines the distance headway gap caused by vehicles leaving.
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