Debating the limits of wireless mesh nets

By John Cox, NetworkWorld.com, 07/22/04

A highly technical argument is unfolding online about the bandwidth limits of wireless mesh networks. Or of some wireless mesh networks.

The opening salvo is by Francis daCosta, founder and CTO of Mesh Dynamics www.meshdynamics.com. He argues that wireless mesh nodes that use a single radio to communicate with other nodes inevitably clobber network performance. You can read his basic summary, posted June 29, here.

Not surprisingly, the Mesh Dynamics products use a two-radio architecture and so, daCosta says, are exempt from this.

The thread includes a lengthy counter-post by Narasimha Chari, chief architect at rival mesh vendor Tropos Networks.

Chari and others (see below) make several arguments against daCosta: that there is some fall-off in performance but it's not as bad as he says; or that there are other ways to mitigate it; or that daCosta is confusing bandwidth constraints with network size (or "scale").

Chari cites several academic papers, with their links, to support his argument. But Jim Thompson, formerly CTO at Wayport and most recently holder of several posts at Vivato, says at least two of them require an organizational membership, and offers a page with links to summaries of these and other papers.

Thompson offers his own assessment of daCosta's claims here.

Thompson argues that this claim isn't new, but that some elements of it are false or misleading and have been addressed by researchers. Further, Thompson says that if you're willing to scrap the 802.11 MAC and replace it with another, you can build nets that actually increase capacity the more nodes you add to it.

Yet another response is from Sascha Meinrath, project coordinator for the Champaign-Urbana Community Wireless Network (CUWiN www.cuwireless.net/contacts.html), a neighborhood wireless communications network.

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Comments

Despite much debate, there is agreement that performance does degrade in single radio systems.

There is some quibbling about whether its 1/n vs. ½**n. - which depends on whether you have a string of pearls configuration or a more realistic dense/dynamic mesh configuration.

The point that seems to have been lost in the noise is that our multiple radio approach does NOT suffer from this degradation. Hence the interest from both the commercial and military sectors in our technology.

Please review this link to understand why our approach is different and why it does not suffer from the same degradation as other mesh approaches:

http://www.meshdynamics.com/Publications/MDStructuredMesh.pdf

Francis daCosta
Founder and CTO
www.meshdynamics.com

Posted by: Francis daCosta on August 2, 2004 07:00 PM

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