Age of Information for Slotted ALOHA with Synchronization Frames at Multiple Access Points

The traditional large-scale and low-power Internet of Things systems cannot meet the requirement of freshness of information. In this paper, a frame-slotted Aloha (FSA) based synchronization strategy is proposed to update information for multi-node access, which makes the information at the receiver side as fresh as possible. Firstly, a multi-point access model of the system from the perspective of FSA is studied, and the corresponding data flow and framework analysis are presented. Secondly, the age of information (AoI) analysis of FSA is conducted, and the expression of the average AoI and the optimal frame size under frame synchronization are derived. Finally, numerical simulation results show that the proposed strategy achieves the lower AoI in FSA based multi-node wireless sensor networks.