Interference-Aware AAV-TBS Coordinated NOMA: Joint User Scheduling, Power Allocation and Trajectory Design

Abstract

We propose an autonomous aerial vehicle (AAV)-terrestrial base station (TBS) coordinated non-orthogonal multiple access (NOMA) scheme where AAV as an air BS coordinates with TBS to serve the users at cell edge via coordinated multi-point, and investigate its resource allocation problem for interference management and system performance enhancement. With the proposed scheme, the interference links between TBS and AAV-served users are enabled to carry useful information, therefore, an enhanced degree of freedom is achieved, leading to a much higher sum-rate over the non-coordinated AAV-assisted NOMA systems where the interference of AAV-served users from TBS is extensively suppressed. Moreover, joint optimization of user scheduling, power allocation and AAV three-dimensional (3D) trajectory design is conducted to maximize the sum-rate of edge users while maintaining a high quality of service at cell-center users, with the consideration of imperfect channel estimation: a) A user scheduling principle dedicated for AAV-TBS coordinated NOMA systems is presented, based on which a two-step user scheduling and power allocation (USPA) algorithm is proposed, with the derivation of optimal power allocation solution; b) A joint USPA algorithm is proposed with closed-form results; c) Considering the line of sight (LoS) and non-LoS factors in the air to ground channel, the 3D trajectory of AAV is designed based on successive convex approximation. It achieves an enhanced system performance, while requiring a lower complexity than the former two-step algorithm.