Slashdot Mirror
OLPC Mesh Networking Tester Explains How It Works
An anonymous reader writes "James Cameron is an engineer working on the OLPC project, specifically testing the wireless network capabilities of the OLPC XO laptop. Cameron lives in a small town called Tooraweenah in a remote region of the Australian outback. There is little noise in the spectrum in the area, so it's perfect for testing the wireless networking capabilities of the XO as it mirrors the kind of rural, spacious environment the XO is intended to be deployed in. Cameron breaks down exactly how the OLPC XO's mesh networking works, including the cheap US$35 solar powered mesh nodes that can be mounted on top of a tree to further the network's reach. Testing in the Australian outback, Cameron discovered that the range of the XO could go up to 1.6km 'quite easily' at 1.5m above ground. 'Assuming a range of 1.6km holds true, (the mathematical formula for area of a circle) Pi R squared tells us one well placed mesh node will cover up to eight square kilometers.' The article also includes numerous pictures of the mesh nodes and testing of the XO."
I found this review to be logical and informative and therefore boring. So I decided to let a few key individuals weigh in on this and tell us exactly how this mesh network works.
... DRIVE over, no, it's a junction for that internet and also your own personal internets. See, just the other day, I got on this here thing and it sent out what I call a "searcher tube" looking for other laptops ... up to 1.5 km away. That's right, once a searcher tube finds another larptop or 'junction tube' then it connects to that and the series of tubes continues to grow. Unfortunately, this series of searcher tubes and junction tubes makes it highly probable that my messages get backed up in those tubes. Therefore, this will provide an own personal internet for poor children in countries we either need to invade or ignore but it will not, however, suffice for bridging islands in Alaska."
... and it was good! Upon God's recognition of my authentication of that which you call "the login screen" a hand descended from the heavens. This hand stretched 3 km end to end and it was then clear to me then that this hand was intended not for me ... not for the rich ... not for the privileged but for the poor and pathetic chillun' of the world that need God's help. Now I have a method by which to contact them and teach them about God and ask them for weekly tithes! And when I realized that a TCP/IP connection had been made, I fell down on my knees and prayed to the Lord God for He is Good and Holy and brings life to these innate objects you call the XO laptop, Amen."
... so anyway the laptop like wanted to be alive so I hit the power switch, man, and then it was like *wham* *whiz* *whazzle* and suddenly like the thing could 'talk' to other things like 1.5 km away and I wasn't sure if it was the uppers I had just taken or if I really was connectin' to another machine or network that far away.
... no steal music at their leisure from a vast expanse of 1.5 km. They may already be using these laptops to steal your diamonds and moneys. Putting an XO laptop into your child's hands is only a gateway to crime and an early death. It's cheap price makes it easy to manufacture and distribute, we are here to warn you about the looming threat of a solid network of these devices stretching out across our free country. Thousands of children in other countries have received them already and their quality of life has plummeted. These laptops are sturdy and brightly colored, they are easily identifiable. Find people that have them and report them to the RIAA."
Senator Ted Stevens: "This here larptop isn't an intersection for trucks to just
The Reverend Billy Graham: "And lo, I did with God's good graces ask for power to be restored and replenished throughout the XO's motherboard thereby bringing the only free BIOS to life
Bob Dylan: "Yeah, ok so like, I got this laptop and it was pretty groovy but I had to put my Mac down because it was like I couldn't use two laptops at once
Mitch Bainwol: "We have discovered that a new technology exists that is a threat to your safety & the economy and will further destroy our income in the near future. It allows criminals, drugs users and child molesters to contact each other freely and unmonitored up to 1.5 km away. They can trade
My work here is dung.
James Cameron is working on computer networking technology? I think we see where this is going...
Give a man a fire and he'll be warm for a day. But light a man on fire and he'll be warm for the rest of his life.
This would be a boon to those of us that are maintaining a community wifi setup. Instead of having to spend a LOT on each node we could easily set up hundreds of these cheap $35.00 repeaters to give users the ability to have wireless throughout the town or city. right now I have dish antennas linking sites and having to buy other gear to get things working for the community Wifi. if I could spend as little as $120.00 per site for a repeater+solar panel+battery and simply get them installed all over the place within range of each other it would be dramatically easier for me. I can put up an unobtrusive box+panel easier than getting permission to put up this box and dish, oh the dish needs to be high up in the air and visible... etc...
They really need to release the whole shebang to the world so that windows drivers can be written to use that mode, linux and OSX drivers would be great too, plus get people making the repeaters better stronger and cheaper.
did I miss the links? do they release all the details of this so It can be implemented commercially?
Do not look at laser with remaining good eye.
In a wireless mesh network, 99.9% of which are implemented using half-duplex transceivers, once past your immediately adjacent nodes, for each additional hop away you halve the bandwidth and double the latency. No way around that, and in a large area mesh (think muni wifi here) you must re-insert an additional backbone feed about every 4 to 8 hops into the mesh either by landline or by point-to-point wireless bridges, else performance across the mesh gets abysmally poor, very quickly.
Dense meshes just don't work very well, they implode upon themselves. Very sparse meshes, such as used in the battlefield by our military, of perhaps in remote areas like the Aussie Outback as mentioned in the FA, are ideal applications of a wireless mesh network, but all the folks who think they can make a successful commercial venture with a wireless mesh in a dense urban or suburban environment are in for a rude awakening if they drink too much of the Koolaid hype that many of the consumer-grade hardware vendors are trying to push.
For those who want to build their own mesh, check out the open-source ROBIN project. They are building a complete plug-and-play mesh networking package. they are even configured to automatically connect to the Open Mesh Dashboard so you can manage your network. Open Mesh will start selling pre-flashed nodes this week at their site.
'Every story, if continued long enough, ends in death.' --Ernest Hemingway
Dude. Mesh is not for synchronous communication. Centralized, synchronous services like WWW just aren't going to happen on mesh.
What can happen is something a synchronous like Usenet or E-mail. You could even supplement the existing network with vehicle-mounted hot points. Postal trucks, mobile health clinics, bookmobiles, and other services make the rounds regularly. No reason why they can't spool or relay messages at each stop.
Besides, centralized services like WWW are too easy to censor. Mesh can help drive a new round of freedom of communication, if it can steer clear of proprietary codecs and formats entirely.
Beta is broken and the link to classic doesn't work. Stop wasting our time or there won't be anybody left here.
In the US, the 2.4 GHz ISM band has 11 channels spaced 5 MHz apart. 802.11b and 802.11g require 25 MHz of separation to prevent interferance which limits the non overlapping channels to 1, 6, and 11. 802.11n and many 802.11g systems support double channel widths of 40 MHz which limits the 2.4 GHz ISM band to just one non overlapping channel.
The 5.0 GHz band used for 802.11a and for some 802.11n radios has 19 20 MHz channels alleviating much of the congestion problem at the expense of cost and using a higher frequency.
http://en.wikipedia.org/wiki/List_of_WLAN_channels