Capacity of Large-scale CSMA Wireless Networks

TL;DR

This paper investigates the capacity of large-scale CSMA wireless networks, demonstrating that with proper design, CSMA can achieve throughput scaling comparable to centralized TDMA in random networks.

Contribution

The study develops new models for CSMA protocols that account for their unique characteristics and shows how to tune parameters for optimal throughput scaling.

Findings

CSMA can achieve (rac{1}{\u221a{n}})\

A CSMA scheme with backbone-peripheral routing attains optimal throughput

Proper parameter tuning maximizes CSMA throughput in large networks

Abstract

In the literature, asymptotic studies of multi-hop wireless network capacity often consider only centralized and deterministic TDMA (time-division multi-access) coordination schemes. There have been fewer studies of the asymptotic capacity of large-scale wireless networks based on CSMA (carrier-sensing multi-access), which schedules transmissions in a distributed and random manner. With the rapid and widespread adoption of CSMA technology, a critical question is that whether CSMA networks can be as scalable as TDMA networks. To answer this question and explore the capacity of CSMA networks, we first formulate the models of CSMA protocols to take into account the unique CSMA characteristics not captured by existing interference models in the literature. These CSMA models determine the feasible states, and consequently the capacity of CSMA networks. We then study the throughput efficiency of CSMA scheduling as compared to TDMA. Finally, we tune the CSMA parameters so as to maximize the throughput to the optimal order. As a result, we show that CSMA can achieve throughput as $\Omega(\frac{1}{\sqrt{n}})$, the same order as optimal centralized TDMA, on uniform random networks. Our CSMA scheme makes use of an efficient backbone-peripheral routing scheme and a careful design of dual carrier-sensing and dual channel scheme. We also address the implementation issues of our CSMA scheme.