Improving wireless TCP/IP performance using the median filter algorithm

Masters Thesis


Chan, Auc Fai. 2010. Improving wireless TCP/IP performance using the median filter algorithm. Masters Thesis Master of Engineering (Research). University of Southern Queensland.
Title

Improving wireless TCP/IP performance using the median filter algorithm

TypeMasters Thesis
Authors
AuthorChan, Auc Fai
SupervisorLeis, John
Institution of OriginUniversity of Southern Queensland
Qualification NameMaster of Engineering (Research)
Number of Pages226
Year2010
Abstract

The estimation of Retransmission Timeout (RTO) in Transmission Control Protocol (TCP) affects the throughput of the transmission link. If RTO is just a little larger than Round Trip Time (RTT), retransmissions will occur too often, and this increases congestion in the transmission link. If RTO is much larger than RTT, the response to retransmit when a packet is lost will be too slow, and this will decrease the throughput in the transmission link (Comer
2006a).

Currently, the Jacobson/Karels Algorithm is widely used for the estimation of RTO in TCP implementations. The algorithm uses an Exponential Weighted Moving Average (EWMA) fi�lter
to estimate RTT and then determines the RTO from this. The EWMA �filter is good if the RTT follows a Gaussian distribution. In reality, traffic in the Internet is bursty and tends to follow a heavy-tailed distribution. Using an EWMA approach to estimate heavy-tailed distribution is
inadequate.

The median fi�lter has been recognized as a useful non-linear fi�lter due to its edge preserving
and impulse suppressing characteristics, so it is eff�ective in removing impulsive noise (Nodes & Gallagher Jr. 1982). The median fi�lter has been applied to many areas of signal processing, particularly in image processing to remove positive and negative impulsive noise. Thus, it can
perform well for heavy-tailed distributions.

In this project, the median �filter is applied to estimate the RTT over TCP links, under bursty
traffic conditions. Experiments and simulations are conducted to determine if the median fi�lter performs better than the EWMA fi�lter. In the experiments, consistent RTT and a small RTO are obtained, which are desirable factors for high connection throughput. In the simulations,
the median fi�lter not only delivers higher throughput, but also drops fewer packets during transmission than EMWA filter does. Both the experiments and simulations show that the median �filter outperforms the EWMA �filter under bursty traffic conditions.

KeywordsTCP/IP performance; retransmission median filter
ANZSRC Field of Research 2020460609. Networking and communications
400607. Signal processing
460207. Modelling and simulation
Byline AffiliationsDepartment of Electrical, Electronic and Computer Engineering
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Related outputs

Median filtering simulation of bursty traffic
Chan, Auc Fai and Leis, John. 2010. "Median filtering simulation of bursty traffic." Wysocki, T. and Wysocki, B. (ed.) ICSPCS 2010: 4th International Conference on Signal Processing and Communication Systems. Gold Coast, Australia 13 - 15 Dec 2010 New York, United States. https://doi.org/10.1109/ICSPCS.2010.5709668
Comparison of weighted average and median filters for wireless retransmission timeout estimation
Chan, Auc Fai and Leis, John. 2008. "Comparison of weighted average and median filters for wireless retransmission timeout estimation." Wysocki, Tadeusz A. and Wysocki, Beata J. (ed.) 2nd International Conference on Signal Processing and Communication Systems (ICSPCS 2008). Gold Coast, Australia 15 - 17 Dec 2008 Piscataway, NJ. United States. https://doi.org/10.1109/ICSPCS.2008.4813668