Age of Information in Two-Hop Multicast Networks

Abstract

We consider the age of information in a two-hop multicast network where there is a single source node sending time-sensitive updates to n{2} end nodes through n middle nodes. In the first hop, the source node sends updates to n middle nodes, and in the second hop each middle node relays the update packets that it receives to n end users that are connected to it. We study the age of information experienced by the end nodes, and in particular, its scaling as a function of n. We show that, using an earliest k transmission scheme, the age of information at the end nodes can be made a constant independent of n. In particular, the source node transmits each update packet to the earliest k-{1} of the n middle nodes, and each middle node that receives the update relays it to the earliest k-{2} out of n end nodes that are connected to it. We determine the optimum k-{1} and k-{2} stopping values for arbitrary shifted exponential link delays. © 2023 Elsevier B.V., All rights reserved.