Performance of CSMA in Multi-Channel Wireless Networks

TL;DR

This paper evaluates CSMA performance in multi-channel wireless networks, revealing its limitations in infrastructure mode and proposing a flow-aware modification to improve resource utilization and stability.

Contribution

It demonstrates CSMA's optimality in ad-hoc mode, identifies its bias against downlink traffic in infrastructure mode, and introduces a flow-aware CSMA to address this issue.

Findings

CSMA is optimal in ad-hoc mode.

CSMA is biased against downlink traffic in infrastructure mode.

Flow-aware CSMA improves network stability and resource utilization.

Abstract

We analyze the performance of CSMA in multi-channel wireless networks, accounting for the random nature of traffic. Specifically, we assess the ability of CSMA to fully utilize the radio resources and in turn to stabilize the network in a dynamic setting with flow arrivals and departures. We prove that CSMA is optimal in ad-hoc mode but not in infrastructure mode, when all data flows originate from or are destined to some access points, due to the inherent bias of CSMA against downlink traffic. We propose a slight modification of CSMA, that we refer to as flow-aware CSMA, which corrects this bias and makes the algorithm optimal in all cases. The analysis is based on some time-scale separation assumption which is proved valid in the limit of large flow sizes.