UBC Theses and Dissertations

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UBC Theses and Dissertations

An approach to shaping away wireless interference in 802.11 traffic at different transmission rates Wong, Jimmy Chak Ming


IEEE 802.11 wireless networks are widely deployed and used nowadays, especially in enterprise and university settings. The widespread usage means increased airspace congestion when many users connect at the same time, which slows down the wireless network performance. Two infamous problematic scenarios are the hidden terminal and the exposed terminal, where a victim node will suffer decreased throughput because of interference from other nodes which are unfairly using up the available airspace. This wireless unfairness occurs due to the design of the 802.11 protocol and the vast number of clients connected. The thesis presents a VOIDShaper Engine, which captures the network traffic at a central upstream router through which all wireless access points connect, and uses a previously developed VOID tool to analyze the traffic and generate a network interference map. With this map, VOIDShaper can find the interference between pairs of TCP Flows, and apply corrective traffic shaping rules on the interfering TCP flows directly at the router. All experiments were run in the Emulab testbed; we see that with traffic control, bandwidth fairness is achieved by using the HTB and SFQ queuing strategies at the router. The goals of this work are 1) to use VOIDShaper to detect and shape wireless traffic at the same 802.11 transmission rates due to interference, 2) to analyze how VOIDShaper responds to wireless interference when the nodes are transmitting at different wireless data rates, 3) to devise an algorithm and shaping policy for traffic which is sent at symmetric or different 802.11 transmission rates.

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