On the Cross-Layer Impact of TCP ACK Thinning on IEEE 802.11 Wireless MAC Dynamics

Hyogon KIM  Heejo LEE  Sangmin SHIN  

IEICE TRANSACTIONS on Communications   Vol.E90-B   No.2   pp.412-416
Publication Date: 2007/02/01
Online ISSN: 1745-1345
DOI: 10.1093/ietcom/e90-b.2.412
Print ISSN: 0916-8516
Type of Manuscript: LETTER
Category: Wireless Communication Technologies
IEEE 802.11,  TCP ACK filtering,  ACK thinning,  cross-layer interaction,  

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ACK thinning refers to the technique to discard or reduce TCP acknowledgements (ACKs) for the purpose of diverting scarce bandwidth to TCP data traffic. It has been shown that under some circumstances the technique is effective to boost the TCP throughput on wireless links, in particular the IEEE 802.11 wireless LAN (WLAN). In this letter, however, we show that ACK thinning backfires under congestion due to its cross-layer impact on the 802.11 MAC dynamics. With the ACK filtering example, we demonstrate the phenomenon and analyze the cause. Based on the analysis, we show how the IEEE 802.11 contention window size control solves the problem.