Towards a Collision-Free WLAN: Dynamic Parameter Adjustment in CSMA/E2CA

TL;DR

This paper introduces CSMA/E2CA, an enhanced MAC protocol for WLANs that quickly achieves collision-free operation through dynamic parameter adjustment, improving performance especially in high-error scenarios.

Contribution

It proposes CSMA/E2CA with a novel deterministic backoff after two successful transmissions and a method for dynamic contention parameter adjustment.

Findings

CSMA/E2CA converges faster to collision-free state.

Higher throughput in high-error wireless environments.

Effective dynamic parameter adjustment improves performance.

Abstract

Carrier Sense Multiple Access with Enhanced Collision Avoidance (CSMA/ECA) is a distributed MAC protocol that allows collision-free access to the medium in WLAN. The only difference between CSMA/ECA and the well-known CSMA/CA is that the former uses a deterministic backoff after successful transmissions. Collision-free operation is reached after a transient state during which some collisions may occur. This article shows that the duration of the transient state can be shortened by appropriately setting the contention parameters. Standard absorbing Markov Chain theory can be used to describe the behaviour of the system in the transient state and to predict the expected number of slots to reach the collision-free operation. The article also introduces CSMA/E2CA, in which a deterministic backoff is used two consecutive times after a successful transmission. CSMA/E2CA converges quicker to collision-free operation and delivers higher performance than CSMA/CA in harsh wireless scenarios with high frame error rates. To achieve collision-free operations when the number of contenders is large, it may be necessary to dynamically adjust the contention parameter. The last part of the article suggests an approach for such parameter adjustment which is validated by simulation results.