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."

Better Reviews

[eldavojohn (898314)]

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.

Senator Ted Stevens: "This here larptop isn't an intersection for trucks to just ... 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."

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 ... 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."

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 ... 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.

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 ... 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."

Re:Better Reviews

[Linker3000 (626634)]

Bill Gates "The Microsoft MOLPC device embraces, enhances and extends the basic principles and standards already developed to afford the user a greater, more secure and trusted computing environment. When connected to the grid network, the MOLPC device interfaces with the local Exchange server (one per community) in order to provide a local communications hub. A local proxy server (one per community) affords secure, cached Internet access, further enhanced by the use of our specially modified MOLPC browser, user certificate and licensing programme. A community Licence Server (CLS) will ensure that all connected users are protected from non-genuine software and our hi-performance HotMesh2 network includes additional, proprietary protocol layers to ensure that unauthorised users operating with standard TCP/IP-based technologies cannot access the bandwidth. The required MOLPC hardware and software licences will be available from mobile vendors who will tour towns and communities on a scheduled basis in a Microsoft Jeep. Due to the additional security benefits and other enhancements we have added to the original OLPC framework for our MOLPC, some third party equipment may not have the processing power or software technology to operate over the MOLPC grid, but we feel that our approach offers superior returns..er..to the users. There is no truth in the rumour that MOLPC stands for Multiple Operating Licences Per Child."

Re:

[Usquebaugh (230216)]

All anarchy means is the lack of a government.

Sounds like freedom to me.

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[fm6 (162816)]

Basically, you're saying that the only way to hold an audience is to be an idiot. Sad, but true.

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[Goffee71 (628501)]

Well, I've heard of Bob Dylan, so I 'got' about 0.2% of the post. Can you do a universal translation please?

Skynet?

[Serenissima (1210562)]

James Cameron is working on computer networking technology? I think we see where this is going...

Re:

[GJSchaller (198865)]

I don't know if I'd call 1.5 m off the gound "sky"...

1.5 metres

[pipatron (966506)]

Why not chose 0.5-1 metres, as that would be more in line with where the machines will normally operate in hands of kids and on tables.

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[somersault (912633)]

Yeah, why do we even have all this internet stuff in the first place? Why don't we all just sit round a really big table and talk to each other?

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[lexarius (560925)]

1.5m (or higher) seems like a good height for the solar-powered mesh node, though...

What's the deal?

[$RANDOMLUSER (804576)]

Everybody says "Pi R squared", but pi are round. Cake are square.

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[numbski (515011)]

Didn't you get the memo?

*THE CAKE IS A LIE*

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[Stanistani (808333)]

No, no, no. Pie ain't square, cornbreads is square.

Yew ain't from aroun' here, are ya? *cocks shotgun*

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[Stanistani (808333)]

Ellie Mae ftw.

What kind of QA is this?

[Malevolent Tester (1201209)]

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.'

Test data should be extrapolated from to assist in promoting fear and despondency among project managers, not validating requirements. Please hand in your testing card at the next available opportunity and go and work in marketing where you belong.

Why not release schematics and other info?

[Lumpy (12016)]

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?

and in the real world?

[westlake (615356)]

This would be a boon to those of us that are maintaining a community wifi setup.

To test in the Australian outback sounds like a test under ideal conditions. No RFI. No natural or man-made obstructions. No problems with climate or weather.

Maintaining "hundreds repeaters" through a Buffalo winter presents a somewhat greater challenge.

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[mgblst (80109)]

Sure ideal, until you come between a Koala and a gumtree, then we will see how ideal it is to have your guts spread out over the outback.

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[westlake (615356)]

Virtually everyone could have one. So if each person managed their own would it really be that bad? ts cheaper to spend $35 one time and take some ownership in this new interweb thingy then pay $40 a month for high speed access that is throttled to death by our communications overlords.

"I don't do ladders and I don't dig trenches." In this town the odds are two in three that you are an upper income professional or a retiree who can afford the condo on the river and winters in Florida.

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[legutierr (1199887)]

The OLPC wiki [laptop.org] is very extensive and growing, and is a great starting-point for making contact with the core OLPC team (including senior management at OLPC, who are surprisingly accessible). If there isn't an article specifically addressing a person's questions, the wiki at least provides a place where questions can be posted with a reasonable expectation of getting an answer. In addition, there are instructions on how to join OLPC mailing lists and IRC, where you can communicate directly with the team.

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[emilper (826945)]

The OLPC wiki is very extensive and growing, ...

... please, if you know them, could you talk some sense into the folks making the OLPC and persuade them to start distributing it commercially? Unless it will arrive in the hands of the 2000000 people that are not third world children but would benefit a lot from a good rugged ebook reader, the fact that the OLPC wiki is very extensive and growing is absolutely useless.

Please, start selling the damn' thing, please ? I'm upping the amount I am willing to

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[mrogers (85392)]

You can find out more about the repeaters here [laptop.org]. Problem is, mesh networking protocols aren't well suited for covering an entire city. The protocol used by OLPC [laptop.org] is based on AODV [ietf.org], which uses flooding for route discovery. That's efficient if the mesh is sparse and there are a few long-lived connections, but inefficient if the mesh is dense or there's a lot of traffic. You could almost say that if mesh networking is a solution in search of a problem, the problem it's been searching for is two kids under a tree

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[jc42 (318812)]

linux and OSX drivers would be great too, ...

Um, I sorta think that there already is a linux driver for the OLPC. ;-)

The ugly truth about mesh networks

[by Anonymous Coward]

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.

Re:

[by Anonymous Coward]

You speak the truth. I was at a recent community wifi meeting (air-stream.org) and there were 3 or 4 running OLPC's in the room. They absolutely and completely stomped on the wifi. Nobody could use the wifi again until everyone looking at the toys shut them and closed them down.

It reminds me a lot of the early Gnutella days when it used broadcast routing.

Bottom line - OLPC network mesh software is pre-alpha.

Re:The ugly truth about mesh networks

[Chandon Seldon (43083)]

Bottom line - OLPC network mesh software is pre-alpha.

Just because the OLPC is designed to use the entire WiFi band for its mesh network *does not* imply that it's not a mature design, just that it wasn't designed to co-exist with other WiFi networks on the same band.

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[A-Slug (890855)]

2 points:

-- the OLPC's were idle for God's sake! They were open and on. Why in that circumstance should they be DoSing the network with neighbour detection code. Sure, when they first open you want to find your neighbours, but once you know about them - shut up! They should only transmit after initialisation when they have something to communicate!

-- there were 4 of them. I will lose my membership for not knowing this, but aren't there 11 channels (not sure how many non-overlapping channels though). How can

Re:The ugly truth about mesh networks

[Agripa (139780)]

I will lose my membership for not knowing this, but aren't there 11 channels (not sure how many non-overlapping channels though). How can 4 machines DoS every wifi channel when they aren't even doing anything!

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 [wikipedia.org]

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[HangingChad (677530)]

Dense meshes just don't work very well, they implode upon themselves.

I heard the same argument in the early days of the internet. If we let just anyone on the network, requests will slow to a crawl.

Mesh is a fairly new technology, I'm confident the density issues can be mitigated. So, yeah, a dense mesh doesn't work well today. But to me that's not a hugely difficult problem to solve. Latency may be more of a challenge, as you also pointed out. Still, it's Gen I, give them a chance. Reminds me of

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[jc42 (318812)]

Mesh is a fairly new technology, ...

Not really. The OLPC's mesh sounds suspiciously like the "chaosnet" that has been in use on the MIT campus since some time in the 1970s. That, too, was decentralized, with each node forwarding packets for its neighbors. I've wondered whether it was sheer coincidence that the OLPC's mesh was developed at MIT. But so far, I haven't run across any comments on the topic.

It isn't especially surprising that this sort of technology hasn't been available commercially. It doe

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[fm6 (162816)]

You're not down on mesh networks, your down on urban mesh networks. Courtesy requires that you title your post accordingly. I mean, is there any place less urban than the Outback?

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[Hucko (998827)]

Antarctica?

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[fm6 (162816)]

I stand corrected!

The beauty of mesh networks

[SgtChaireBourne (457691)]

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.

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[seanadams.com (463190)]

for each additional hop away you halve the bandwidth and double the latency.

I don't follow you - why couldn't remote nodes continue to pass along a chunk of information at a continuous speed? (i.e. bucket brigade).

You're supposing a half-duplex medium, but even in that case, the medium does not have to remain locked up in the local vicinity just because packets which originated there are still being propagated further down the chain. Indeed for a mesh of any appreciable size you would need to implement loca

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[jeffstar (134407)]

In fact the rate at which latency increases and bandwidth decreases in a mesh network has been shown to be 1.68^N where N is the number of hops (Piyush Gupta, Robert Gray, P.R. Kumar An Experimental Law for Ad Hoc Networks, May 2001). I have measured this myself in an 8 hop half duplex wireless network.

That is only for data being sent straight through the mesh. When clients connect directly to the mesh nodes on the same radio that is used for sending and receiving mesh traffic then there is even less rad

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[soldack (48581)]

The halfing effect will certainly occur if you only use single radio systems. If you use multiple radio systems that run on different frequency ranges, you can do much better. A good meshing algorithm will avoid the halfing effect by properly using the alternate radios available. If the OLPC had multiple radios, it would do much better as a meshing node.

There are some differences between a many hop city mesh and what I would call a dense mesh. City meshes usually are trying to cover as much space with a

open mesh

[qw0ntum (831414)]

For those who want to build their own mesh, check out the open-source ROBIN [blogin.it] project. They are building a complete plug-and-play mesh networking package. they are even configured to automatically connect to the Open Mesh Dashboard [open-mesh.com] so you can manage your network. Open Mesh will start selling pre-flashed nodes this week at their site.

We Need Good Mesh Networking

[bhima (46039)]

I'm been slightly interested in mesh add hock wireless networking for a while now. I'd like to see some combination of wireless access point in Wifi & WiMax with some sort of Bittorrent management / bridging function. If you could put this in a box like what OpenWRT runs on and sell it for less that 100 it would be great. Living in a college town I'm convinced those kids are sharing petabytes of Porn, Pop & House music, and cheesy serial television shows from Hollywood. Having all that sharing pushed off the wired net I pay my ISP for on to a wireless grey market mesh network would free the wired network up... for my *legitimate* traffic of Blues & Classical music, and David Attenborough documentaries... then perhaps I could finish seeding my fair share of "Life in Cold Blood".

But....

[San-LC (1104027)]

But....Pie R Round, not square, so the equation should be:

Area = Pie(Crust + Filling) * Hungry Children + Sticky Keyboards

Area = OLPCs covered with Pie Filling

Area = 0

This isn't right...

[Hanners1979 (959741)]

From the article:

"The school might have a generator or a solar panel, or in one school where we've got laptops deployed now we have two cows who walk around pushing a lever which rotates a generator that powers fifteen laptops for charging"

Shouldn't they be using a couple of penguins instead?

consumer owned telecommunication infrastructure

[FromTheAir (938543)]

A no or low cost Autonomous consumer owned telecommunication infrastructure is what will evolve out of this. No more cable, internet, or cell phone bills.

Re:consumer owned telecommunication infrastructure

[module0000 (882745)]

A no or low cost Autonomous consumer owned telecommunication infrastructure is what will evolve out of this. No more cable, internet, or cell phone bills.

No, it won't.

You might have a small village or education campus implement a community-maintained infrastructure of nodes - but you will not replace mainstream ISP's or Cell providers. That would require everyone making a grand unified switch to mesh networking suddenly at once. Also, who is going to pay for the mesh nodes every 1.5km to cross the oceans in your free-telecommunications-utopia?

If this takes off [at all], at best expect the equivalent of "free wifi!" in a few isolated towns/campus's. This

Bwhahahahaha...dream on

[monkeyboythom (796957)]

You are new to life in general, aren't ya? Didn't anyone tell you that humanity, as a collective, is a lazy and sheep-like group? The autonomous consumer telco is the urban fantasy that is right up there with growing your own vegetables, weaving/sewing your own clothes, and "living off the grid."

Sure, there are examples of people doing just that, but how many others are there that simply want to live without the "hassle" of being self sufficient.

A no or low cost Autonomous consumer owned telecommunication

What about temperate environments?

[Baldrson (78598)]

Inaccessibly placed solar panels (such as the one suggested placed atop trees) are basically worthless in temperate environments due to snow. You can even have an excessive number of such mesh nodes distributed in tree-tops and the redundancy will essentially do you no good due to the fact that snow blankets them all -- and right when you most need communications for the rural areas which are, then, snowed-in.

$35 solar mesh? Thanks for FAKE promises

[drwho (4190)]

I've been working with some people trying to come up with a cheap solar mesh router. now this guy comes along and says it can be done for $35, so no one is going to pay more. he obviously has no idea of what is involved in making a solar mesh router that is the least bit reliable. but people aren't going to know that. They're just going to have heard this magic price of $35, and not be willing to pay more.

olpc was supposed to be an open-source laptop for $100. yea, whatever happened to that? closed wifi har

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[grcumb (781340)]

I've been working with some people trying to come up with a cheap solar mesh router. now this guy comes along and says it can be done for $35, so no one is going to pay more. he obviously has no idea of what is involved in making a solar mesh router that is the least bit reliable. but people aren't going to know that.

Erm, I think you're confusing routers with repeaters. TFA talks about cheap repeaters, and though the price sounds optimistic, it's not inconceivable that you could produce them in volume aro

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[jc42 (318812)]

olpc was supposed to be an open-source laptop for $100. yea, whatever happened to that?

Have you been paying attention to what's happened to the US dollar? ;-)

I don't believe you'll ever see a $35 solar mesh router.

Sure we will, but it'll be $35 Australian or Canadian.

Horrible design!

[Radi-0-head (261712)]

The boxes for the mesh radios are BLACK! Totally stupid decision, as they do not reflect sunlight and allow the guts of the box to heat up to levels which will either degrade performance or cause the radios to malfunction completely.

How do I know this? Let's just say I've learned from personal experience.

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[LunarCrisis (966179)]

Your result is suspiciously like 2*pi.