Relay deployment and network optimization for NOMA-enabled double-layer airborne access vehicular ad hoc networks

In this paper, we design a nonorthogonal multiple access (NOMA)-enabled double-layer airborne access vehicular ad hoc networks (VANETs) architecture with a tethered high-altitude platform (HAP), multiple miniaturized unmanned aerial vehicles (UAVs) and vehicles, based on which the relay deployment and network optimization problems are investigated. Specifically, based on our designed architecture, we first propose a UAV relay deployment scheme by using the particle swarm optimization algorithm to maximize network coverage ratio. Then, to guarantee the performance of network edge vehicles, we introduce the NOMA technique into the double-layer airborne access VANETs. Moreover, the network optimization problem is formulated as a joint UAV height optimization, channel allocation, and security assurance problem, such that the total achievable data rate is maximized. Challenged by the coupled relationship between the optimization variables, we decouple the optimization problem as two subproblems and devise an efficient iterative algorithm to optimally allocate according to the golden section method and the matching theory. Finally, simulation results demonstrate that the proposed NOMA-enabled double-layer airborne access VANETs architecture can achieve significant performance superiority in terms of the total achievable data rate.