Experiments of multi-channel 802.11 wireless mesh networks with TCP proxies

IEEE 802.11 wireless access technology is a possible candidate for constructing wireless mesh networks. However, multi-hop 802.11 wireless networks suffer heavy co-channel interference. In this paper, the 802.11-based networks are extended to operate using multi-radio multi-channel designs to inhibit the interference effects. Using a partially overlapped channel scenario and an orthogonal channel scenario, it has been confirmed that the introduction of multiple channels is capable of improving network performance. Despite these gains, TCP performance degrades exponentially with hop counts; therefore, wireless mesh networks may further be improved by adding an n-hop proxy service. In terms of hop counts, these proxies break long connections into relatively shorter connections with tighter transport layer control. A trade-off between the number of proxies and the length of proxies has become evident through testbed evaluation. With respect to this trade-off, the queuing delays at proxies and the amount of collisions over the lossy wireless links signify the need for a suitable protocol to control the efficient usage of multiple channels and proxies.