Multi-Channel Wireless Mesh Networks With TCP Proxies

Wireless mesh networks based on 802.11 technology could potentially be an inexpensive means of constructing large-scale wireless infrastructure networks. Wireless mesh networks attempt to capitalize on multiple hop communication to achieve transmissions over relatively larger distances. One fundamental concern is that multi-hop wireless networks may suffer heavily from co-channel interference. If multiple channels from the 802.11 spectrum are employed across adjacent links of communication, the interference effects can be mitigated. In practice, either overlapping channels or independent orthogonal channels can be assigned to the different links with varying effects. Topology control can be used to help manage these channels to limit the interference effects while providing for the necessary capacity and scalability requirements. By means of analyses and testbed experiments, I have validated that the introduction of multiple channels can improve overall system performance. With respect to the end-users, end-to-end performance over multiple wireless hops should be the primary concern. Under UDP-based communication sessions, network congestion is not the main contributor to transport layer performance degradation. Upon further investigation, TCP performance degrades exponentially with hop count, because it incorrectly interprets lost packets as a sigh of network congestion. Since TCP performance weakens for connections with more wireless hops, I further evaluate if network performance can be improved by adding an n-hop TCP proxy service. These proxies have the effect of breaking long connections into shorter connections with tighter transport layer control. A trade-off between the number of proxies and the hop count between proxies becomes evident through testbed evaluation. Analyzing various mesh characteristics and the relationships between MAC and transport layers can help establish a suitable protocol for future work.