One of the most attractive applications of unmanned aerial vehicles (UAVs) is deploying wireless communication systems. We consider a UAV-based low-Altitude platform (LAP) to deploy an aerial hotspot to provide Wi-Fi coverage without infrastructure and severe shadowing by urban or mountainous terrain. To address the performance degradation of carrier sense multiple access with collision avoidance (CSMA/CA) by increasing packet collisions with the number of clients, we exploit nonorthogonal multiple access (NOMA). To the best of authors' knowledge, there are no previous studies on uplink NOMA in CSMA/CA networks. In the considered system, owing to the distributed architecture and small channel difference of stations, conventional NOMA methods in cellular systems are not suitable. In this paper, we propose a power allocation scheme for uplink transmissions using predetermined power levels with a stochastic power selection to reduce the probability of packet collisions. A new medium access control procedure for uplink NOMA with CSMA/CA is also presented. The analytic results demonstrate that the proposed scheme achieves better saturation throughput and average packet delay than conventional CSMA/CA.
Manuscript received January 5, 2020; revised June 7, 2020, August 17, 2020, and October 1, 2020; accepted October 1, 2020. Date of publication October 19, 2020; date of current version June 7, 2021. This work was supported by the Future Combat System Network Technology Research Center Program of Defense Acquisition Program Administration and Agency for Defense Development under Grant UD190033ED. (Corresponding author: Hoki Baek.) Yohan Kwon and Jaesung Lim are with the Graduate School of Computer Engineering, Ajou University, Suwon 16499, South Korea (e-mail: dygks8989@ajou.ac.kr; jaslim@ajou.ac.kr).
