Improving Age of Information for Frame Slotted ALOHA Under Multiple-Packet Reception

Frame slotted ALOHA (FSA) has been thede factomultiple-access protocol for many energy-efficient Internet of Things applications. To improve the age of information (AoI) that measures the freshness of the status update, we devote this paper to designing an age-threshold FSA protocol that adaptively limits the contention in each frame to users with age gains as high as possible, by focusing on a multiple-packet reception (MPR) physical layer model of practical importance for the first time. For an ideal scenario where the coordinator always knows the exact age gain of each user, we propose a low-complexity algorithm to approximate the optimal age gain threshold and frame length for maximizing the expected slot-average AoI reduction within the upcoming frame, which provides a design clue for other scenarios. With this clue, for a practical scenario where the coordinator has to estimate the age gains based on its feasible observations, we design a Bayesian method to update individual distributions of the local ages of all the users based on both the channel statuses and the AoI of each user, and propose an algorithm to approximate optimal access parameters based on these distributions. We also evaluate the computational complexity of the proposed practical scheme and discuss how to generalize it to consider random channel errors. Numerical experiments show that our proposed practical scheme outperforms state-of-the-art schemes for a wide range of MPR configurations.