On the Global Optimality of Whittle's index policy for minimizing the age of information

TL;DR

This paper proves that Whittle's index policy is asymptotically optimal for minimizing the age of information in large networks with unreliable channels, using a novel assumption-free mathematical approach.

Contribution

It introduces a new mathematical method to establish the asymptotic optimality of Whittle's index policy without any assumptions, for specific network settings.

Findings

Whittle's index policy is asymptotically optimal in many-users regimes.

Numerical results confirm the theoretical optimality and strong performance.

The approach is assumption-free and mathematically rigorous.

Abstract

This paper examines the average age minimization problem where only a fraction of the network users can transmit simultaneously over unreliable channels. Finding the optimal scheduling scheme, in this case, is known to be challenging. Accordingly, the Whittle's index policy was proposed in the literature as a low-complexity heuristic to the problem. Although simple to implement, characterizing this policy's performance is recognized to be a notoriously tricky task. In the sequel, we provide a new mathematical approach to establish its optimality in the many-users regime for specific network settings. Our novel approach is based on intricate techniques, and unlike previous works in the literature, it is free of any mathematical assumptions. These findings showcase that the Whittle's index policy has analytically provable asymptotic optimality for the AoI minimization problem. Finally, we lay out numerical results that corroborate our theoretical findings and demonstrate the policy's notable performance in the many-users regime.