Scheduling to Minimize Age of Synchronization in Wireless Broadcast Networks With Random Updates

In this work, a wireless broadcast network with a base station (BS) sending random time-sensitive information updates to multiple users under bandwidth constraint is considered. To measure the effect of data desynchronization when the updates appear randomly because of external environment, the metric Age of Synchronization (AoS) is adopted in this work. It shows the amount of the time elapsed since freshest information at the receiver becomes desynchronized. The AoS minimization scheduling problem is formulated into a discrete time Markov decision process and the optimal solution is approximated through structural finite state policy iteration. An index based heuristic scheduling policy based on restless multi-arm bandit (RMAB) is provided to further reduce the computational complexity. Simulation results show that the proposed index policy achieves compatible performance with the MDP and is close to the AoS lower bound. Our work indicates that, to obtain a small AoS over the entire network, users with larger transmission success probability and smaller random update probability are more likely to be scheduled at smaller AoS.