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Wireless Mesh Networks
Roland Piquepaille writes "Robert Poor is CTO of Ember Corporation. He contends that point-to-point or point-to-multipoint networks typical of industrial wireless communications systems have limited scalability and reliability. 'In contrast, wireless mesh networks are multihop systems in which devices assist each other in transmitting packets through the network, especially in adverse conditions. You can drop these ad-hoc networks into place with minimal preparation, and they provide a reliable, flexible system that can be extended to thousands of devices.' The article is pretty technical and contains several illustrations and a case study about the deployment of a wireless mesh network in a water treatment plant. Check this column for Poor's conclusions or read this Sensors article if you have more time."
The only way to make something like this work is to have a solid L3 encryption system between the remote and the head end - intermediate stations will certainly get snooped.
IPsec is the way to go, but its still something of a hassle on IPv4. I've seen a lot of noise about mesh networks - this isn't really going to take off until IPv6 gets moving under its own power - perhaps another five years.
I am very easy to get along with, but I don't have time to waste being nice to people who are being stupid. -Theo
Well, I'll buy it as working for a small business but you would find it very difficult to have a big network as all of the network chatter takes up an increasing amount of spectrum. This is the same problem P2P networks have (a similar arch) and they can only solve it by having a network that cannot see all nodes. This is not a good idea for a wider net for obvious reasons.
"To any truly impartial person, it would be obvious that I am right."
You can find a couple of demonstrations of how mesh networks can actually work and be implemented in cities and companies on MeshNetworks' homepage. Very cool how the p2p works....
In their WBT article "The Unwired soldier," authors Allen H. Kupetz and K. Terrell Brown introduce their concept of the 'Wal-Mart Soldier' and explain how "every soldier's communication device will be an individual network element with a unique IP address. All the network devices on the battlefield - including those embedded in tanks or other vehicles - will instantly form, heal, and update the network as users come and go. That is, they will associate in an ad hoc manner."
"But unlike cell-based solutions," the authors write, "network coverage and service levels will improve when soldier density increases. Network resources are also better utilized because networks are self-balancing as well. The soldier's subscriber device can hop to distant network access points, away from points of congestion, shifting network capacity to where the demand is."
Here's the really wild part, though: "Finally, this technology will function as a PAN (personal area network), a LAN (local area network), and a WAN (wide area network), simultaneously. This means that the same network can connect a soldier to the squad/platoon, to the battalion, and to a fully mobile division. This is critical to meeting the functionality requirements of the FCS program. It is the equivalent of Bluetooth, 802.11, and 3G converging, but in a single network, with a single device."
They also point out (before you ask!) that "The next-generation soldier's communication device has not yet been chosen. There are several DARPA/DoD projects operating simultaneously, all of which have a communications device component. These include the "Warfighter Information Network - Tactical" (WIN-T), "Future Combat Systems" (FCS - formerly known as Future Ground Combat Systems), "Small Unit Operations/Situational Awareness System" (SUO/SAS), and the "Joint Tactical Radio System - Programmable, Modular Communications System" (JTRS-PMCS)."
you would find it very difficult to have a big network as all of the network chatter takes up an increasing amount of spectrum
This is not so, although the articles doesn't really make that clear --- the aggregate bandwidth of these networks grows as the number of nodes increases in density and in geographical extent.
The reason why this is so is that in a wireless mesh network, RF coverage is purposely restricted by turning down the power automatically and/or by dynamic channelization using frequency, time, or code (spread spectrum) multiplexing. This in effect gives you a dynamic cellular type of architecture, with channel reuse in non-adjacent cells.
And that of course is why it's called a mesh network --- it's not a fully connected network of nodes (which would be non-scalable and bandwidth-limited), but a mesh in which locality is strong so that nodes only hear and connect to their nearest neighbours, so each new locale contributes bandwidth to the overall aggregate capacity instead of eating up yet another slice of a dwindling pie.
"The question of whether machines can think is no more interesting than [] whether submarines can swim" - Dijkstra
Mesh wireless networks sound good in theory, kinda like microkernel OS's ;p, but in practice they have been unworkable to this point. Nokia bought a company, whose name I can't remember, for this type of product, Nokia called it Rooftop. The previous company had spent more than 4 years in development, and Nokia pumped in enough cash to add another year or so, but the product was a technical failure. Our company was already experienced deploying wireless systems (Alvarion/Breezecom and Orninoco) so we liked what Nokia had to say about the product and we gave it a try. The system proved to be totally unusable, the customer prem equipment often couldn't figure out which way to send traffic if the node it was previously using went away. I don't think that a mesh system is totally unworkable, but I do think its more complicated than most people think. Nokia has already removed the info from their site, but
google cache here
Tessco was Nokia's reseller on the line and they still have info and pics on it here
We are deploying a city-wide 802.11b network as we speak, and although it 'eliminates the need for expensive cell towers', we are able to get on top of two well-placed high rises and cover a good portion of the area. Less equipment expense for us is ALWAYS a good thing.
:(
We would not be able to afford getting rights in all the places needed to make this feasible. Heck, the hassle of GETTING the rights needed would be make this prohibitive.
Karma: Chameleon (mostly due to the fact that you come and go).
... has been running for several months in Kingsbridge, Devon (UK), based on 'off the shelf' hardware, and free software downloadable from LocustWorld.com. There is also a bootable ISO that turns any PC into a Mesh node without overwriting any of the local data! You can download it here - Build 22 is recommended
Having watched him operate for several years, it seems that Rob Poor thinks that simply by 1) talking about mesh networks for several years, 2) building a half-assed mesh simulator for his M.S. thesis that didn't even work, 3) blustering his way through a Ph.D. on the strength of that old simulator, 4) raising VC for an ill-posed attack on a very difficult problem, and 5) sitting on topic committees that have many fine lunches and dinners at consortium expense, he will somehow gain insight into a problem that he still doesn't even understand.
But if you really want to believe the hype, then perhaps you'll be impressed by the advanced level of technical sophistication evidenced by this presentation on his website. Don't forget your free sample of PIC code that shows us all how gosh-dang simple it is to be a radio engineer! Want to build a mesh? Just sprinkle a few thousand PICs in the environment and they'll self-organize into a network through the emergent properties of entrainment!
It seems so obvious; why didn't we think of that?
The main issue at stake here is that each node in the ad-hoc network is both a router and a network node in itself. Consider an ad-hoc network I am participating in when I am riding a bus. Let us say I am watching a thriller on DVD on my device locally. All of a sudden, my two neighboring co-passengers start streaming video from each other's devices and suck up so much bandwidth (and therefore processing power) from my device that my DVD starts to jump right at the climax of the movie. Clearly, this is quite unacceptable.
In general, if Device A relays some packets on Device B's behalf, then Device B should give it some number of credits that Device A can use in the future to have Device B repay the favor. In choosing an ad-hoc route, the protocol which routes packets through ad-hoc networks must take into account not only how much each device is contributing to the network, but also how equipped they are in terms of processing power, current battery level and the like.