Hybrid Linear and Nonlinear Uplink Cooperative Interference Cancellation for Cellular-Connected UAV

Aerial-ground interference has been deemed as the main challenge to realize the cellular-connected unmanned aerial vehicle (UAV) communications. Due to the strong line-of-sight (LoS)-dominant aerial-ground channels, UAVs could cause/suffer severe interference to/from a large number of co-channel base stations (BSs) in their uplink/downlink communications. In this paper, we propose a new cooperative interference cancellation (CIC) scheme with hybrid linear and nonlinear processing for the UAV's uplink communication to mitigate its strong interference to co-channel BSs, by leveraging the local cooperation between each co-channel BS and its adjacent BSs. In particular, the helping BSs quantize and forward their received signal from the UAV to the co-channel BS, which can combine these quantized signals with its own received signal to decode its served terrestrial user's message via either linear or nonlinear interference cancellation, which achieves the best rate performance of the UAV and terrestrial users under different conditions. To exploit their complementary benefits, we aim to select an optimal subset of co-channel BSs to perform the linear/nonlinear interference cancellation and optimize the UAV's transmit power over its assigned resource blocks (RBs) to maximize the weighted sum rate of the UAV and all co-channel BSs. As this problem is non-convex and difficult to be optimally solved, we propose an alternating optimization (AO) algorithm to obtain a high-quality suboptimal solution. Numerical results show that our proposed CIC scheme achieves better performance than other baseline CIC schemes.