Information Freshness in Multi-Hop Wireless Networks

TL;DR

This paper develops and analyzes policies for minimizing information age in multihop wireless networks, introducing new methods that are practical, adaptable, and capable of handling complex network scenarios.

Contribution

It introduces three classes of policies—stationary randomized, age difference, and age debt—that optimize age of information in multihop wireless networks with various constraints.

Findings

Closed-form expressions for average AoI with stationary policies

Heuristic age difference policies improve local age management

Age debt policies handle complex cost functions and routing scenarios

Abstract

We consider the problem of minimizing age of information in multihop wireless networks and propose three classes of policies to solve the problem - stationary randomized, age difference, and age debt. For the unicast setting with fixed routes between each source-destination pair, we first develop a procedure to find age optimal Stationary Randomized policies. These policies are easy to implement and allow us to derive closed-form expression for average AoI. Next, for the same unicast setting, we develop a class of heuristic policies, called Age Difference, based on the idea that if neighboring nodes try to reduce their age differential then all nodes will have fresher updates. This approach is useful in practice since it relies only on the local age differential between nodes to make scheduling decisions. Finally, we propose the class of policies called Age Debt, which can handle 1) non-linear AoI cost functions; 2) unicast, multicast and broadcast flows; and 3) no fixed routes specified per flow beforehand. Here, we convert AoI optimization problems into equivalent network stability problems and use Lyapunov drift to find scheduling and routing schemes that stabilize the network. We also provide numerical results comparing our proposed classes of policies with the best known scheduling and routing schemes available in the literature for a wide variety of network settings.