Minimizing Age of Information in Slotted ALOHA With Short-Packet Communications

Age of information (AoI) has emerged as a novel metric for quantifying the freshness of information at the receiver side. This metric has found numerous applications in real-time monitoring and control systems where stale information may lead to critical errors. Slotted ALOHA (SA) is becoming popular for AoI-sensitive applications in such systems due to its distributed operation with reduced coordination costs. In practice, packets in SA networks are typically short and characterized by finite blocklength, which significantly affects AoI performance. In this paper, we address the problem of minimizing AoI in short-packet SA networks where multiple devices transmit their time-stamped status packets to a common access point. We aim to determine the average AoI and the average peak AoI (PAoI) as key performance metrics and to optimize both the transmission probability of a device in the SA protocol and the blocklength of a packet in short-packet communications. We also investigate how the minimum average AoI and the minimum average PAoI behave as the number of devices increases. Through numerical studies, we validate our theoretical findings.