Adaptive Multiuser Access for UAV-Assisted IoT Monitoring Networks Under Bursty Traffic

We propose a new adaptive transmission scheme for a massive Internet of Things (IoT) monitoring network where IoT devices generate time-critical and event-triggered bursty traffic and are aided by an unmanned aerial vehicle (UAV) aggregating and relaying IoT data to a base station. In this network, the IoT devices generate smooth traffic until an event of interest occurs, where more IoT devices wake up and the overall IoT network is flooded with a dynamic burst of traffic. We note that existing transmission schemes and access mechanisms, designed based on overall average traffic rates, overuse network resources of time and energy when traffic is smooth, but suffer from packet collisions when traffic is bursty. To address this, our proposed scheme employs multiuser shared access (MUSA) based grant-free non-orthogonal multiple access and uses short packet communication for ultra low latency IoT-to-UAV transmission. Specifically, to accommodate bursty traffic, we design an analytical framework and maximize the transmission success probability by optimizing the number of transmission time slots, subject to stringent reliability and latency constraints. We compare the performance of the proposed scheme with a state-of-the-art transmit power diversity scheme using a fixed number of time slots, which shows that the proposed scheme achieves superior reliability and stability at moderate to high average traffic rates.