Achieving Fair Throughput among TCP Flows in Multi-Hop Wireless Mesh Networks

Ting-Chao HOU  Chih-Wei HSU  

IEICE TRANSACTIONS on Communications   Vol.E93-B   No.4   pp.916-927
Publication Date: 2010/04/01
Online ISSN: 1745-1345
DOI: 10.1587/transcom.E93.B.916
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Network
TCP,  delayed ACK,  fairness,  802.11 DCF,  

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Previous research shows that the IEEE 802.11 DCF channel contention mechanism is not capable of providing throughput fairness among nodes in different locations of the wireless mesh network. The node nearest the gateway will always strive for the chance to transmit data, causing fewer transmission opportunities for the nodes farther from the gateway, resulting in starvation. Prior studies modify the DCF mechanism to address the fairness problem. This paper focuses on the fairness study when TCP flows are carried over wireless mesh networks. By not modifying lower layer protocols, the current work identifies TCP parameters that impact throughput fairness and proposes adjusting those parameters to reduce frame collisions and improve throughput fairness. With the aid of mathematical formulation and ns2 simulations, this study finds that frame transmission from each node can be effectively controlled by properly controlling the delayed ACK timer and using a suitable advertised window. The proposed method reduces frame collisions and greatly improves TCP throughput fairness.