An Outage-Probability-Aware MAC Protocol for UAV-Assisted Networks

Unmanned aerial vehicles (UAVs) are widely used in wireless communication, either base stations (BSs) or relays. In some occasions of UAV-assisted communication, such as low-altitude communication in an urban environment, the channel conditions can be poor due to obstacles. Thus, they will experience an outage and cannot receive the signal transmitted by the UAVs. In this article, we propose an outage-probability-aware medium access control (MAC) protocol (OPM) based on the study of outage probabilities in different UAV-assisted environments. Specifically, we first analyze different outage scenarios in information transmission. Then, the physical layer outage probability with channel conditions and ground users' mobility taken into consideration is discussed, while an outage detection (OT) method is proposed, and different measures are taken according to the detection results. Third, a 3-D Markov chain model is used to investigate per-user behavior for the proposed OPM. Finally, the simulation results on packet discard probability, average transmission delay, and system throughput are analyzed. The results show the effectiveness of the proposed protocol, which leads to a 30%-50% decrease in both the probability of packet discard and average transmission delay, along with an increase in throughput of more than 40%.