Age of information in multichannel slotted ALOHA: Should collided users send first?

This paper studies whether allowing collided users to send first can improve the Age of information (AoI) performance of multichannel slotted Aloha (MSA) networks. AoI, a fundamental measure of information freshness, is defined as the elapsed time since the generation of the latest successfully received information. When multiple users send status update packets simultaneously in the same sub-channel, conventional MSA does not deal with packet collision, but notifies all the users to contend again, leading to a high average AoI. This paper points out that dealing with packet collisions first can improve information freshness. Specifically, we propose an AoI-oriented protocol for MSA, called MSA-Collided users sending First (MSA-CF). When a collision occurs in MSA-CF, only the collided users send packets in the next few time slots (referred to as the CF procedure). The CF procedure ends when all collided users are successfully updated or when the maximum CF duration is reached. Simulations show that MSA-CF has a lower average AoI compared with MSA. For the duration of the CF procedure, one time slot is a preferable choice in practical implementations. Copyright © 2023 IEEE.