Age of Information for Preemptive/Non-Preemptive Transmissions in Large-Scale IoT Networks

In the Internet of Things (IoT) era, data freshness is critical for real-time monitoring and control applications. Data freshness is quantified via the Age of Information (AoI), which tracks the age of the most recent received packet at the destination. This paper utilizes a spatiotemporal mathematical model to characterize the AoI of a target IoT link that exists within a large-scale IoT network. The large-scale IoT network is modeled by a heterogeneous Poisson field (HPF) of interferers. Then, the AoI of the target link, with a single packet storage capability, is characterized via an absorbing Markov chain that accounts for the interwoven effects of packet size, transmission rate, and interfering IoT devices. In particular, the proposed model investigates the impact of packet segmentation in order to operate at a reliable rate in the presence of IoT interference. To this end, the AoI of preemptive and non-preemptive transmission schemes are studied and compared. Comparing the AoIs of the preemptive and non-preemptive transmission schemes, the results show that no scheme always outperforms the other. In contrast, the number of segments and preemption scheme should be determined based on the packet size, arrival rate, and interference congestion level to minimize the AoI.