Timely Status Update in TDMA: Round-Based or User-Based?

This paper investigates the information freshness of two time division multiple access (TDMA) systems: round-based TDMA and user-based TDMA. The age of information (AoI) metric is used to represent the freshness of information, measured by the time since the generation of the most recently received packet. In a conventional round-based TDMA system, multiple users send their packets in rounds, regardless of whether their packets are successfully received by the receiver, possibly leading to a high average AoI of the system. In contrast, we propose a user-based TDMA system that guarantees successful packet reception for each user through feedback before proceeding to the next user. We evaluate the average AoI and average Peak AoI (PAoI) of both TDMA systems. Our theoretical and simulation results indicate that while both systems exhibit the same average PAoI, the user-based TDMA system has a lower average AoI compared with its round-based counterpart. Our findings provide new insights into the design of TDMA systems with different information freshness requirements.