On the Value of Retransmissions for Age of Information in Random Access Networks without Feedback

TL;DR

This paper investigates how retransmissions affect the age of information in a slotted ALOHA network without feedback, showing that retransmissions can reduce AoI at low generation rates despite throughput costs.

Contribution

It introduces a model considering non-fresh packet generation and analyzes the impact of retransmissions on AoI without feedback, revealing conditions where retransmissions are beneficial.

Findings

Retransmissions can lower AoI at low generation rates.

Sending stale packets can be advantageous for AoI.

Retransmissions may reduce throughput despite improving AoI.

Abstract

We focus on a slotted ALOHA system without feedback, in which nodes transmit time-stamped updates to a common gateway. Departing from the classical generate-at-will model, we assume that each transmitter may not always have fresh information to deliver, and tackle the fundamental question of whether sending stale packets can be beneficial from an age-of-information (AoI) standpoint. Leaning on a signal-flow-graph analysis of Markov processes the study reveals that, when packets can be lost due to channel impairments, retransmissions can indeed lower AoI for low generation rates of new information, although at a cost in terms of throughput.