Age of Gossip with the Push-Pull Protocol

TL;DR

This paper analyzes the age of information in wireless networks using push, pull, and push-pull gossip protocols, revealing that push-pull achieves constant age, outperforming push and pull protocols.

Contribution

It introduces a stochastic hybrid systems framework to analyze age of information for all three protocols, demonstrating the superior performance of push-pull in maintaining fresh data.

Findings

Push-pull protocol achieves constant age of information.

Push protocol only achieves logarithmic age.

Numerical simulations confirm theoretical results.

Abstract

We consider a wireless network where a source generates packets and forwards them to a network containing $n$ nodes. The nodes in the network use the asynchronous push, pull or push-pull gossip communication protocols to maintain the most recent updates from the source. We use the version age of information metric to quantify the freshness of information in the network. Prior to this work, only the push gossiping protocol has been studied for age of information analysis. In this paper, we use the stochastic hybrid systems (SHS) framework to obtain recursive equations for the expected version age of sets of nodes in the time limit. We then show that the pull and push-pull protocols can achieve constant version age, while it is already known that the push protocol can only achieve logarithmic version age. We then show that the push-pull protocol performs better than the push and the pull protocol. Finally, we carry out numerical simulations to evaluate these results.