# Minimizing The Age of Information in a CSMA Environment

## TL;DR

This paper derives a closed-form expression for the average age of information in a CSMA network, formulates an optimization to minimize it by tuning back-off times, and demonstrates the scheme's performance and limitations.

## Contribution

It introduces a stochastic hybrid systems approach to analyze and optimize the age of information in CSMA networks, providing a convex optimization framework for back-off time calibration.

## Key findings

- Optimized CSMA reduces average age compared to standard scheme.
- The optimization problem is convex and efficiently solvable.
- Standard CSMA can be outperformed by other distributed schemes in some cases.

## Abstract

In this paper, we investigate a network of N interfering links contending for the channel to send their data by employing the well-known Carrier Sense Multiple Access (CSMA) scheme. By leveraging the notion of stochastic hybrid systems, we find a closed form of the total average age of the network in this setting. Armed with this expression, we formulate the optimization problem of minimizing the total average age of the network by calibrating the back-off time of each link. By analyzing its structure, the optimization problem is then converted to an equivalent convex problem that can be solved efficiently to find the optimal back-off time of each link. Insights on the interaction between the links is provided and numerical implementations of our optimized CSMA scheme in an IEEE 802.11 environment is presented to highlight its performance. We also show that, although optimized, the standard CSMA scheme still lacks behind other distributed schemes in terms of average age in some special cases. These results suggest the necessity to find new distributed schemes to further minimize the average age of any general network.