End-to-End Flow Fairness Over IEEE 802.11-Based Wireless Mesh Networks

Abstract

Economies of scale make IEEE 802.11 an attractive technology for building wireless mesh networks (WMNs). However, the IEEE 802.11 protocol exhibits serious link-layer unfairness when used in multi-hop networks. Existing fairness solutions either do not address this problem, or require proprietary MAC protocol to provide fairness. In this paper, we argue that an ideal transport protocol should be able to achieve fairness even on top of an unfair MAC layer such as 802.11. Towards this end, we propose a co-ordinated <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">congestion</i> <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">control</i> algorithm that performs global bandwidth allocation and provides end-to-end flow-level max-min fairness despite weaknesses in the MAC layer. The proposed algorithm features an advanced topology discovery mechanism that detects the inhibition of wireless communication links, and a general collision domain capacity re-estimation mechanism that effectively addresses such inhibition. Through an ns-2-based simulation study we demonstrate that the proposed algorithm substantially improves the fairness across flows, eliminates starvation problem, and simultaneously maintains a high overall network throughput.