Wireless Mesh Networking Summary

As our class has concluded the section on Wireless Mesh Networks, I will summarize what has been discussed and point out a potential area for research. WMNs has attracted significant attention to research groups, because of 1) the challenging nature of networking using a wireless medium for communication and 2) the advantages offered by ad-hoc networks.

Wireless networking poses only a few significant problems, but these problems adversely affect each layer of the network, and many solutions have been suggested at each layer. First, the fact that nodes must share the medium for communication requires that those communicating take turns in order for traffic to flow. Second, because of the hidden node problem, there is inevitably going to be loss due to interference from those outside carrier sensing range. Third, nodes withhold transmission because of the exposed node problem.

At the link layer, we have discussed techniques such as Lagrangian relaxation to allow nodes to have a fair share of bandwidth within their clique of nodes with which they share the medium. We have looked at how network coding can be used to make up for lost packets, such that the receiver is indifferent to which packets it didn't receive. We have also looked at making use of corrupted (partially correct) packets in some cases.

At higher layers, we have discussed how opportunistic routing can be used as a more reliable source of packet transmission, as routes are often broken with traditional routing on a WMN. At the transport layer, adaptive pacing can be used to allow a sender to be silent while its neighbors relay the message.

In short, the nature of wireless networking requires design adaptations from traditional (wired) networking. Many of the aforementioned techniques address the problems caused by 802.11 MAC unfairness and interference due to the hidden node problem. I'm curious to know whether any work has been done to measure the severity of the loss (lack of potential transmission) due to the exposed node problem. And if this loss is significant, I wonder what could be done to remedy it.