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Investigation of TCP Behaviour over Wireless Channels

Research Student: Ritesh Taank, M.Sc., B.Sc.

Supervisor: Dr. X Peng

The aim of the research is to investigate the feasibility of developing an optimised version of the Transmission Control Protocol (TCP), which governs today's major communications networks, from the wired backbones to the heterogeneous networks.

Wireless Networks have gained much popularity in recent years, and this trend is set to grow. Interoperability issues surrounding the linking of heterogeneous networks (i.e. both wired and wireless) are attracting attention from researchers around the globe. Due to emerging wireless applications and the advent of high-speed wireless IP communications carried by the Internet, there is an urgent call for calibration and enhancements to TCP (which works alongside IP) for improved performance.

Conventional implementations of TCP have, over the years, been fine tuned to the characteristics observed in traditional wired networks. Unfortunately, wireless environments and, in particular, Multi-hop Ad-hoc Networks (MANETs) behave very differently, enough for it to make it difficult for the standard implementations of TCP to make incorrect assumptions about the state of the network. The main problem is that packet losses in traditional wired networks are usually as a result of congestion somewhere in the network path, a situation which conventional TCP can resolve efficiently in terms of throughput and link utilisation.

In wireless networks, however, such environments are prone to packet losses due to high bit error rates (BER), unstable channel characteristics, and host mobility induced disconnections. TCP interprets these packet losses as an indication of congestion and inappropriately invokes congestion control mechanisms (i.e. retransmissions and increasing delays), leading to unnecessary degradation of network performance.

To rectify the associated problems, there have been several attempts at creating enhanced TCP implementations that work better in wireless environments; however, each solution is targeted towards specific network orientations/applications only. Therefore, a more general and universal solution is required.

Publications

 

R. Taank, and X.-H. Peng, Investigation of the effects of feedback channel losses for wireless TCP experiments, in Proc. IEEE Int. Symp. On Personal, Indoor and Mobile Radio Communications (PIMRC), Sept. 2007.

 

R. Taank, and X.-H. Peng, An experimental testbed for evaluating end-to-end TCP performance over wired-to-wireless paths, in Proc. IEEE 5th Consumer Communications and Networking Conference (CCNC), Jan. 2008.

 

R. Taank, and X.-H. Peng, Impact of indoor 802.11g WLAN error characteristics on TCP retransmission: A cross-layer approach, in Proc. IEEE 4th International Conference on Wireless Communications, Networking and Mobile Computing (WiCOM), Oct. 2008.

 

R. Taank, and X.-H. Peng, An experimental evaluation of sender-side TCP enhancements for wired-to-wireless paths: A real-world home WLAN case study, IEEE 23rd International Conference on Information Networking and Applications (AINA), May 2009.