Timely Status Updates in Slotted ALOHA Networks With Energy Harvesting

TL;DR

This paper analyzes the age of information in energy-harvesting slotted ALOHA networks, proposing optimized transmission strategies and analyzing their impact on AoI and throughput.

Contribution

It introduces an analytical framework for AoI in energy-harvesting ALOHA networks, including optimized transmission policies and approximate AoI and AVP calculations.

Findings

Optimized policies outperform baseline strategies in AoI and throughput.

Decoding multiple packets with successive interference cancellation improves performance.

Adaptive transmission based on battery level and timing enhances network efficiency.

Abstract

We investigate the age of information (AoI) in a scenario where energy-harvesting devices send status updates to a gateway following the slotted ALOHA protocol and receive no feedback. We let the devices adjust the transmission probabilities based on their current battery level. Using a Markovian analysis, we derive analytically the average AoI. We further provide an approximate analysis for accurate and easy-to-compute approximations of both the average AoI and the age-violation probability (AVP), i.e., the probability that the AoI exceeds a given threshold. We also analyze the average throughput. Via numerical results, we investigate two baseline strategies: transmit a new update whenever possible to exploit every opportunity to reduce the AoI, and transmit only when sufficient energy is available to increase the chance of successful decoding. The two strategies are beneficial for low and high update-generation rates, respectively. We show that an optimized policy that balances the two strategies outperforms them significantly in terms of both AoI metrics and throughput. Finally, we show the benefit of decoding multiple packets in a slot using successive interference cancellation and adapting the transmission probability based on both the current battery level and the time elapsed since the last transmission.