Outage Analysis of Ground-Aerial NOMA with Distinct Instantaneous Channel Gain Ranking

Future wireless networks envision to provide seamless connectivity to a multitude of devices including unmanned aerial vehicles (UAVs). This paper investigates a unique case where we aim to serve ground users and a UAV, with distinct channel characteristics and access environments in three-dimensional (3D) space, based on non-orthogonal multiple access (NOMA). Unlike traditional distance-based ranking or channel-gain-based ranking, we apply NOMA in uplink and downlink transmissions by evaluating instantaneous channel gain and distance-dependant path-loss together. The communication links of ground and aerial users have different fading environments and path losses which make it crucial to analyse instantaneous channel gain before applying NOMA. To this end, we derive new mathematical expressions of outage probabilities in downlink and uplink transmissions based on instantaneous distinct signal power (IDSP) for each user, verified by simulations. Next, we investigate the impact of different system parameters, e.g. data rate, path loss exponent, channel fading characteristics and UAV height, on outage behaviour. The results confirm that ground-aerial NOMA can be successfully employed in future wireless networks to provide cellular connectivity with improved spectral efficiency to a broader range of devices with individual data rate requirements.