Controlling Packet Drops to Improve Freshness of information

TL;DR

This paper investigates optimal packet dropping strategies in real-time information update systems to minimize age of information metrics, considering single and multiple source scenarios over wireless channels.

Contribution

It derives optimal static drop policies for minimizing average age of information in systems without buffer storage, including competitive multi-source environments.

Findings

Static policies like dropping old or new packets are often optimal.

Optimal policies depend on system scenarios and can be stationary Markov policies.

Non-cooperative game solutions nearly optimize the overall system age metrics.

Abstract

Many systems require frequent and regular updates of a certain information. These updates have to be transferred regularly from the source to the destination. We consider scenarios in which an old packet becomes completely obsolete, in the presence of a new packet. In this context, if a new packet arrives at the source while it is transferring a packet, one needs to decide the packet to be dropped. New packet has recent information, but might require more time to transfer. Thus it is not clear as to which packet to be dis- carded, and this is the main focus of the paper. Recently introduced performance metrics, called average age of information (AAoI) and peak age of information (PAoI) of the information available at the destination, are the relevant performance measures. These type of systems do not require storage buffers, of size more than one, at the source queue. We consider single source / multiple sources regularly updating information to a single destination possibly over wireless channels to derive optimal drop policies that optimize the AAoI. We showed that the state independent (static) policies like dropping always the old packets or dropping always the new packets is optimal in many scenarios, among an appropriate set of stationary Markov policies. We consider relevant games when multiple sources compete. In many scenarios, the non-cooperative solution almost minimizes the social objective, the sum of AAoIs of all the sources.