Resolving Bufferbloat Problem in 802.11n WLAN by Weakening MAC Loss Recovery for TCP Stream

Masataka Nomoto, Toshihiko Kato, Celimuge Wu, and Satoshi Ohzahata

Keywords

IEEE 802.11n, Multirate support, Dymanic rate switching, Block acknowledgment, Bufferbloat

Abstract

IEEE 802.11n wireless LANs provide high-speed data transfer. If the radio condition degrades, however, the transfer rate will be reduced significantly and there may be some problems in the data transfer. In order to clarify this problem, we have evaluated the TCP performance over IEEE 802.11n LAN by changing the distance between the access point and a terminal. As a result, a severe increase of round trip time has been measured in the case of low data rate. This is a sort of bufferbloat problem, which is being actively studied in recent years. The detailed analysis of this experiment is our first contribution. We have inferred that one of the reasons for this increased delay is the powerful retransmission function of 802.11n. So, we propose, as the second contribution, a method to improve TCP delay performance by reducing this retransmission capability and by generating TCP segment loss intentionally. This paper describes the performance evaluations for our proposal in comparison with CoDel, which is an active queue management approach, and with the native 802.11n.

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