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OLPC Mesh Networking Tester Explains How It Works

Zonk posted more than 6 years ago | from the who-doesn't-love-a-good-mesh dept.

Wireless Networking 92

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."

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92 comments

Better Reviews (4, Funny)

eldavojohn (898314) | more than 6 years ago | (#22635124)

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 (-1, Offtopic)

Anonymous Coward | more than 6 years ago | (#22635206)

That's one of the few posts that requires a '+1 WTF?' moderation

Re:Better Reviews (1)

Goffee71 (628501) | more than 6 years ago | (#22635338)

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

Re:Better Reviews (5, Funny)

Linker3000 (626634) | more than 6 years ago | (#22635724)

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:Better Reviews (1)

Corwn of Amber (802933) | more than 6 years ago | (#22641760)

Humm, the OLPC is the one device to save the world, the direct contrary to everything MS is or does.

Picture this. One Laptop Per Child. Accessing the Open Internet. For Free.

Every child in the world, equipped with a device that connects him to the whole of human knowledge and to everyone they can meet on- or off-line.

Borders and frontiers will disappear. The Market will be Free. Governments will become extinct, replaced by transparent, user-run communities.

Things wil happen to be sold for their real worth : their marginal production value. Intellectual property will disappear, too.

We're heading towards interesting times.

Re:Better Reviews (1)

Hal_Porter (817932) | more than 6 years ago | (#22642550)

Governments will become extinct, replaced by transparent, user-run communities.
If democratic governments disappeared ambitious and ruthless people would fill the power vacuum with something much nastier. Bummer if you live in a rich country, because it's going to turn into something out of a Mad Max movie. Lots of mini states, each run by a warlord.

Intellectual property will disappear, too
Then capital will abandon the rich world and move where the labour is cheap. Face it, IP is what keeps money in the rich world. People are just as smart in say China and a lot more willing to work incredibly hard.

Borders and frontiers will disappear.
Been to many really poor countries? How well do you think your local police would be able to cope with criminals from there arriving en masse. Oh right, no government means no police. Don't worry though the local warlord would probably form a militia to keep outsiders out. Mind you, the resulting gang war would be pretty nasty with no government of police to keep it under control and where the gang leaders have absolute power in their fiefdoms. And there's a danger of other predatory countries taking advantage of the chaos and colonising you.

You think I'm being facetious but this sort of Hobbesian nightmare is quite a good description of a failed state like Somalia or Afghanistan.

Anarchy isn't freedom, it's actually pretty much the opposite.

None of what you said will happen because of the OLPC of course.

Re:Better Reviews (1)

Usquebaugh (230216) | more than 6 years ago | (#22642738)

All anarchy means is the lack of a government.

Sounds like freedom to me.

Re:Better Reviews (1)

Hal_Porter (817932) | more than 6 years ago | (#22642916)

You're free until some ambitious bastard spots a vacancy and declares himself leader and starts killing anyone that stands up to him. If you imagine a graph of freedom vs time, a revolution is sharp spike upwards in the direction of more freedom followed by a sharp spike down as the new regime starts terrorising people into submission. The point is that the system may settle in a stable state with lower freedom level at the end of it. In fact apart from the American revolution I can't think of any examples where this didn't happen.

And you don't need a revolution either, if a society collapses into smoothly into anarchy it's likely someone will take advantage of this to seize total power. Anarchy is a surefire gateway to tyranny.

Re:Better Reviews (0)

Anonymous Coward | more than 6 years ago | (#22644022)

This sounds like the "Digital Sublime." A lot of it was promised with the advent of the Internet during the early 90s. (Yes, I know it really originates during the late 60s.)

The particular claim I remember was that you could talk to anyone, anywhere. The catch is that most of us don't like to talk to our neighbours, let alone people on the other side of the planet.

As for accessing the sum of human knowledge, have you noticed that sum tends to lead to porn, creationism, bad science in general, or content-free blogs?

Yeah, me too.

Re:Better Reviews (1)

Corwn of Amber (802933) | more than 6 years ago | (#22655448)

And the other half of the sum is Project Gutenberg, Googles idea to scan every book and make them searchable, mazn and the Long Tail, "blogs" and sites with articles such as this [kuro5hin.org] (go read it, it will change your mind forever), torrent sitrs where users post cinematic rarities that people loved and lost, or yearn to discover. And that's just off the top of my stoned and drunk head.

If everyone... Everyone has Free access to that, and Free publishing, then the world is heading towards interesting times.

DIE IN A FIRE OLPC (0)

Anonymous Coward | more than 6 years ago | (#22645102)

Wait, already happened!

Re:Better Reviews (1)

fm6 (162816) | more than 6 years ago | (#22637050)

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

Skynet? (4, Funny)

Serenissima (1210562) | more than 6 years ago | (#22635152)

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

Re:Skynet? (1)

GJSchaller (198865) | more than 6 years ago | (#22641376)

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

1.5 metres (0)

pipatron (966506) | more than 6 years ago | (#22635162)

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.

Re:1.5 metres (1)

somersault (912633) | more than 6 years ago | (#22635492)

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?

Re:1.5 metres (1)

lexarius (560925) | more than 6 years ago | (#22636672)

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

Re:1.5 metres (0)

Anonymous Coward | more than 6 years ago | (#22636752)

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.

The higher the better. It's just the way radio waves work. Anyway, kids climb trees. Ok, not in the US any more, but I'm pretty sure kids in countries the XO targets climb plenty of trees.

What's the deal? (3, Funny)

$RANDOMLUSER (804576) | more than 6 years ago | (#22635214)

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

Re:What's the deal? (-1, Offtopic)

Anonymous Coward | more than 6 years ago | (#22635346)

That is a lie.

Re:What's the deal? (-1, Offtopic)

Anonymous Coward | more than 6 years ago | (#22635386)

A porky-pie?

Re:What's the deal? (1)

numbski (515011) | more than 6 years ago | (#22635524)

Didn't you get the memo?

*THE CAKE IS A LIE*

Re:What's the deal? (2, Funny)

Stanistani (808333) | more than 6 years ago | (#22635596)

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

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

Re:What's the deal? (0)

Anonymous Coward | more than 6 years ago | (#22636538)

Yes, I also remember that episode of the Beverly Hillbillies. Jethro is my double-naught hero.

Re:What's the deal? (1)

Stanistani (808333) | more than 6 years ago | (#22636608)

Ellie Mae ftw.

NIMBT. (0)

Anonymous Coward | more than 6 years ago | (#22635270)

So are these solar mesh nodes going to suffer the same problems as cell phone towers. Littering the landscape?

What kind of QA is this? (3, Funny)

Malevolent Tester (1201209) | more than 6 years ago | (#22635288)

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.

Re:What kind of QA is this? (0)

Anonymous Coward | more than 6 years ago | (#22646866)

Your post was in itself funny, but then I read your sig and noticed your handle, and it became a little bit awesome.

Although as a developer, I also feel compelled to add that I hate you, and if we ever meet, I'll probably have to kick you in the balls or something.. ;-)

Why not release schematics and other info? (4, Interesting)

Lumpy (12016) | more than 6 years ago | (#22635336)

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? (3, Interesting)

westlake (615356) | more than 6 years ago | (#22636060)

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.

But at $35... (1)

bryce4president (1247134) | more than 6 years ago | (#22642560)

Virtually everyone could have one. So if each person managed their own would it really be that bad? How hard would it be to write some software that would connect to your specific repeater to test that its working? If you can run this off a solar panel at this point then its not using very much juice. Its 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.

Re:But at $35... (1)

westlake (615356) | more than 6 years ago | (#22643534)

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.

Re:But at $35... (1)

bryce4president (1247134) | more than 6 years ago | (#22648954)

Thus would open up another market opportunity. Just like those people don't want to "own" a property, but rent so that they don't have to do maintenance I'm sure there would be people that would set up and maintain these spots for a nominal fee...

Re:and in the real world? (0)

Anonymous Coward | more than 6 years ago | (#22643698)

If you think that there are "no problems with climate or weather" in the central Australian semi-arid climate, then you are mistaken. The dryness poses its own set of problems (mainly grit) and the warm to cold transition is not always a good environment for outdoor enclosures. And to 'maintain hundreds of repeaters' in an environment where there are no roads or bridges, it might be just as challenging as Buffalo in winter.

Granted, there are no obvious obstructions (which is why it is used as the test environment), but around populated areas there is EM activity. Not as much in a metropolitan area, but there are some RF signals.

Re:and in the real world? (1)

mgblst (80109) | more than 6 years ago | (#22647558)

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.

Re:Why not release schematics and other info? (2, Informative)

legutierr (1199887) | more than 6 years ago | (#22636550)

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.

Nevertheless, I will say that much of what is on the wiki is oriented to software or organization building, and that info on OLPC hardware seems to get the short-shrift. There is a *short* article discussing the wireless repeater here [laptop.org] , which links to the manufacturer's page here [marvell.com] . I'm sure that contributions to the wiki in this area would be appreciated.

Re:Why not release schematics and other info? (1)

emilper (826945) | more than 6 years ago | (#22638290)

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 pay: last time it was 300Euro ... I am ready to shell 350 Euro if I can buy it in a shop nearby and have 12 month guarantee on it.

Re:Why not release schematics and other info? (1)

adriccom (44869) | more than 6 years ago | (#22641106)

Hi,

OLPC (the org) is not working on or interested much in commercial distribution ("It's an education project, not a laptop project."). However lots of other people are, and they are working on it. I'm sure when someone gets something going it'll make the news (and /.)

Cheers,
adric

Re:Why not release schematics and other info? (1)

legutierr (1199887) | more than 6 years ago | (#22641806)

I don't actually know them personally; I'm familiar with the wiki because I used it extensively when I was setting-up/figuring out my give-one-get-one (G1G1) XO. The reason that I say that the management at OLPC is accessible is that one of the people that helped me via the wiki was Walter Bender, the president of OLPC.

I absolutely agree with you, however, that the biggest problem that OLPC has right now (in light of "competition" from Asus and other quarters) is its apparent unwillingness to make the XO generally available to the US and European public. Nicolas Negroponte has made a number of statements to the effect that selling the laptop to consumers would create a market for the laptops and would provide an incentive for individuals receiving laptops gratis (from government or charity) to sell the laptops, or an incentive for criminals to steal laptops from children. It is my view, however, that *in general* even very poor people will see the value of the laptop as an educational tool and will not choose to sell it, and that controls, procedures, and compensating incentives could be created to limit the impact of the exceptions (including criminality). Furthermore, if OLPC meets its very aggressive goals and distributes millions of laptops around the world, a market will inevitably [ebay.com] come to exist; OLPC would do better to anticipate it and take advantage of it, rather than fight it. Aren't you more likely to buy an XO from a Peruvian fourth-grader through ebay if you can't buy it from Walmart than if you can? I think so.

By not selling the XO laptop directly to consumers, OLPC is hurting itself in a number of ways. First, it is failing to take advantage of the economies of scale provided by consumer markets (economies of scale that it needs [popsci.com] ). In some ways, it is also creating a perverse incentive for laptops to be transferred from third-world children to first-world consumers (as I describe above). Most significantly, however, it is giving the impression to government buyers in its target markets that there is something wrong with their product. As someone with experience doing business in Latin America, I can tell you for certain that a product that has not gained wide acceptance by US consumers is treated sceptically. That's not to say that there is a bias against locally-produced products; rather, there has been a history of many poor countries being a "dumping ground" of inferior or obsolete products that cannot be sold in Europe or the US. From the perspective of an over-worked bureaucrat, one clear sign that dumping is not taking place is that the product being sold is also being sold in the US or Europe. A common sign that dumping *is* taking place is that the product is *not* being sold in the US or Europe.

Re:Why not release schematics and other info? (1)

emilper (826945) | more than 6 years ago | (#22642162)

there has been a history of many poor countries being a "dumping ground" of inferior or obsolete products that cannot be sold in Europe or the US

The sad thing is that the XO seems to be the better product, compared with the Intel "educational something" and Eee . I could buy the Eee right now, but ... I still have hope for the XO. Probably misguided hope, since the marketing division of AMD seems to be brain dead. They have a couple of other products that would make good application platforms for SMBs (kind of like extremely cheap low power consumption blades) but they choose to market them as "educational crap" too.

Re:Why not release schematics and other info? (0)

Anonymous Coward | more than 6 years ago | (#22637654)

it may not be quite what you're after, but i found this to be an excellent reference for those of us in the developed bits of the planet without the fat wallets - http://wndw.net/ [wndw.net]

the free ebook is a worth the visit alone, the links and other tidbits are cream, for my money anyhoo....

Re:Why not release schematics and other info? (1)

mrogers (85392) | more than 6 years ago | (#22638208)

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 in the middle of the desert. ;-)

Re:Why not release schematics and other info? (1)

jc42 (318812) | more than 6 years ago | (#22644168)

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 (5, Informative)

Anonymous Coward | more than 6 years ago | (#22635340)

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.

Mod up please. (-1, Offtopic)

Anonymous Coward | more than 6 years ago | (#22635392)

WTF is going on here. All AC posts are suddenly starting at -1 instead of 0. Is Slashdot trying to eliminate anonymous posting by making it completely invisible?

AC posts have tremendous value. I don't like this blanket censorship. It's mean-spirited.

Re:Mod up please. (0)

Anonymous Coward | more than 6 years ago | (#22635638)

No. Its just you. The internet decided to pick on you today.

Re:Mod up please. (0)

Anonymous Coward | more than 6 years ago | (#22636950)

It's not the internet, it's teh t00bs.

Re:Mod up please. (0)

Anonymous Coward | more than 6 years ago | (#22637582)

I've seen the same. I wonder if they're doing something with cookies or ip tracking to karamize the anonymous?

Re:The ugly truth about mesh networks (1, Interesting)

Anonymous Coward | more than 6 years ago | (#22635848)

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 (3, Insightful)

Chandon Seldon (43083) | more than 6 years ago | (#22636790)

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.

Re:The ugly truth about mesh networks (1)

A-Slug (890855) | more than 6 years ago | (#22637276)

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 4 machines DoS every wifi channel when they aren't even doing anything!

I stand by my point: the network code is pre-alpha and all the smart geeks at the meeting agree. (air-stream.org is a geek-only community wifi project).

ps. the last few days slashdot.org has developed an almost infinite loop every couple of refreshes. The status bar seems to blame it on continually downloading from ad.doubleclick.net. I usually hit refresh to try again, but that doesn't work when you want to post comments :(

Re:The ugly truth about mesh networks (4, Informative)

Agripa (139780) | more than 6 years ago | (#22638638)

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]

Re:The ugly truth about mesh networks (1)

Thelasko (1196535) | more than 6 years ago | (#22638990)

the last few days slashdot.org has developed an almost infinite loop every couple of refreshes. The status bar seems to blame it on continually downloading from ad.doubleclick.net. I usually hit refresh to try again, but that doesn't work when you want to post comments :(
Adblock Plus [mozilla.org] works wonders.

hosts file (1)

A-Slug (890855) | more than 6 years ago | (#22640084)

I just now put an entry in my hosts file:
127.0.0.1 ad.doubleclick.net

Hopefully that will do the trick.

Re:The ugly truth about mesh networks (1)

Darinbob (1142669) | more than 6 years ago | (#22642926)

WiFi is really a bad medium for meshed networks, and isn't very good for sharing bandwidth (like ethernet it's CSMA). WiFi mobility is also difficult. But it's the best choice for inexpensive solutions that need off-the-shelf parts and not a lot of development under the hood. Our meshed broadband solution had used a custom TDMA MAC, but our industrial world target user who wants to play Warcraft or use Skype is very different from the OLPC's target user.

Mod Parent Offtopic (0)

Anonymous Coward | more than 6 years ago | (#22636258)

What does that have to do with the stated purpose and use of the OLPC mesh networks? It doesn't. Yes, they are a bad idea for urban areas, but people in urban areas are most likely not going to be buying OLPC's.

Mod Parent Offtopic.

Re:The ugly truth about mesh networks (1)

HangingChad (677530) | more than 6 years ago | (#22636680)

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 people harping on Linux two or three years ago.

Telcos and other providers should tremble at the thought of mesh networks. Network technology that doesn't need them to spring up and function, almost anywhere. Self-discovering local phone networks...that'll keep AT&T up nights.

Re:The ugly truth about mesh networks (1)

jc42 (318812) | more than 6 years ago | (#22644246)

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 does sorta shoot down the central control that the commercial guys like to have. It's a lot easier to keep your customers in line (and cooperate with the feds' demands) if all traffic has to go through a single chokepoint, and you have control of that chokepoint.

It'll be interesting to see if the US government and comm companies permit this sort of network to be deployed widely within the US.

Re:The ugly truth about mesh networks (1)

LarsG (31008) | more than 6 years ago | (#22644338)

Trouble is, you need sufficient production volumes to get cheap mesh networking. Current consumer-level wireless chips (i.e., 802.11a/b/g/n) are less than well suited for mesh.

Re:The ugly truth about mesh networks (1)

fm6 (162816) | more than 6 years ago | (#22637154)

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?

Re:The ugly truth about mesh networks (1)

Hucko (998827) | more than 6 years ago | (#22644856)

Antarctica?

Re:The ugly truth about mesh networks (1)

fm6 (162816) | more than 6 years ago | (#22651566)

I stand corrected!

Re:The ugly truth about mesh networks (0)

Anonymous Coward | more than 6 years ago | (#22637880)

Why would every additional hop halve the bandwidth? I could see that being true if every packet were flood routed, but there is no need to do that.

The beauty of mesh networks (4, Insightful)

SgtChaireBourne (457691) | more than 6 years ago | (#22638132)

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.

Re:The ugly truth about mesh networks (1)

seanadams.com (463190) | more than 6 years ago | (#22638870)

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 local CSMACD and collision recovery in some shape or form anyway, to deal with the case where two transmitters on the mesh, out of range of each other, send overlapping transmissions which eventually collide at some intermediary node.

And doubling the latency is only true _for and half duplex medium_. If you had transceivers which could transmit on one channel while receiving on another, then you could pass through the data with negligible added delay - assuming you don't store the whole packet before forwarding.

All the assumptions you've made here seem to be of a rather specific and primitive mesh technology. They are certainly not true of meshes in general. From a theoretical standpoint it is not hard to see how those limitations could be overcome with slightly more sophisticated technology.

Re:The ugly truth about mesh networks (2, Informative)

jeffstar (134407) | more than 6 years ago | (#22639614)

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 radio time to go around and things slow down even more.

There is a company called Mesh Dynamics [meshdynamics.com] which sells mesh nodes with three radios [meshdynamics.com] : one for send, one for receive and another for clients to connect to.

I recall they have modified or extended in some way the linux kernel to have one radio dedicated for sending and another for receiving. This is something I am interested in doing as well but haven't seen any kernel modules or extensions to allow it thus far.

Re:The ugly truth about mesh networks (1)

soldack (48581) | more than 6 years ago | (#22640750)

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 as little equipment in order to obtain good enough performance. In my idea of a dense mesh each node can see many if not nearly all of the other nodes. The biggest problem becomes route selection when you have lots of very close and similar routes. This can be solved with static configurations but that fails when the mesh nodes themselves are mobile. For that you need a good dynamic route selection algorithm. This kind of dense meshes can occur with mesh nodes in vehicles that are moving around each other.

I wish the OLPC was truely open so that we could understand the route selection and 802.11 rate selection algorithms used. These two algorithms can be a significant effect on mesh performance.

open mesh (4, Informative)

qw0ntum (831414) | more than 6 years ago | (#22635434)

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 (2, Interesting)

bhima (46039) | more than 6 years ago | (#22635460)

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".

fake 'weather' more dangerous than previously (-1, Offtopic)

Anonymous Coward | more than 6 years ago | (#22635484)

believed. let yOUR conscience be yOUR guide. you can be more helpful than you might have imagined. there are still some choices. if they do not suit you, consider the likely results of continuing to follow the corepirate nazi hypenosys story LIEn, whereas anything of relevance is replaced almost instantly with pr ?firm? scriptdead mindphuking propaganda or 'celebrity' trivia 'foam'. meanwhile; don't forget to get a little more oxygen on yOUR brain, & look up in the sky from time to time, starting early in the day. there's lots going on up there.

http://news.yahoo.com/s/ap/20071229/ap_on_sc/ye_climate_records;_ylt=A0WTcVgednZHP2gB9wms0NUE [yahoo.com]
http://news.yahoo.com/s/afp/20080108/ts_alt_afp/ushealthfrancemortality;_ylt=A9G_RngbRIVHsYAAfCas0NUE [yahoo.com]
http://www.nytimes.com/2007/12/31/opinion/31mon1.html?em&ex=1199336400&en=c4b5414371631707&ei=5087%0A [nytimes.com]

is it time to get real yet? A LOT of energy is being squandered in attempts to keep US in the dark. in the end (give or take a few 1000 years), the creators will prevail (world without end, etc...), as it has always been. the process of gaining yOUR release from the current hostage situation may not be what you might think it is. butt of course, most of US don't know, or care what a precarious/fatal situation we're in. for example; the insidious attempts by the felonious corepirate nazi execrable to block the suns' light, interfering with a requirement (sunlight) for us to stay healthy/alive. it's likely not good for yOUR health/memories 'else they'd be bragging about it? we're intending for the whoreabully deceptive (they'll do ANYTHING for a bit more monIE/power) felons to give up/fail even further, in attempting to control the 'weather', as well as a # of other things/events.

http://video.google.com/videosearch?hl=en&q=video+cloud+spraying [google.com]

dictator style micro management has never worked (for very long). it's an illness. tie that with life0cidal aggression & softwar gangster style bullying, & what do we have? a greed/fear/ego based recipe for disaster. meanwhile, you can help to stop the bleeding (loss of life & limb);

http://www.cnn.com/2007/POLITICS/12/28/vermont.banning.bush.ap/index.html [cnn.com]

the bleeding must be stopped before any healing can begin. jailing a couple of corepirate nazi hired goons would send a clear message to the rest of the world from US. any truthful look at the 'scorecard' would reveal that we are a society in decline/deep doo-doo, despite all of the scriptdead pr ?firm? generated drum beating & flag waving propaganda that we are constantly bombarded with. is it time to get real yet? please consider carefully ALL of yOUR other 'options'. the creators will prevail. as it has always been.

corepirate nazi execrable costs outweigh benefits
(Score:-)mynuts won, the king is a fink)
by ourselves on everyday 24/7

as there are no benefits, just more&more death/debt & disruption. fortunately there's an 'army' of light bringers, coming yOUR way. the little ones/innocents must/will be protected. after the big flash, ALL of yOUR imaginary 'borders' may blur a bit? for each of the creators' innocents harmed in any way, there is a debt that must/will be repaid by you/us, as the perpetrators/minions of unprecedented evile, will not be available. 'vote' with (what's left in) yOUR wallet, & by your behaviors. help bring an end to unprecedented evile's manifestation through yOUR owned felonious corepirate nazi glowbull warmongering execrable. some of US should consider ourselves somewhat fortunate to be among those scheduled to survive after the big flash/implementation of the creators' wwwildly popular planet/population rescue initiative/mandate. it's right in the manual, 'world without end', etc.... as we all ?know?, change is inevitable, & denying/ignoring gravity, logic, morality, etc..., is only possible, on a temporary basis. concern about the course of events that will occur should the life0cidal execrable fail to be intervened upon is in order. 'do not be dismayed' (also from the manual). however, it's ok/recommended, to not attempt to live under/accept, fauxking nazi felon greed/fear/ego based pr ?firm? scriptdead mindphuking hypenosys.

consult with/trust in yOUR creators. providing more than enough of everything for everyone (without any distracting/spiritdead personal gain motives), whilst badtolling unprecedented evile, using an unlimited supply of newclear power, since/until forever. see you there?

"If my people, which are called by my name, shall humble themselves, and pray, and seek my face, and turn from their wicked ways; then will I hear from heaven, and will forgive their sin, and will heal their land."

meanwhile, the life0cidal philistines continue on their path of death, debt, & disruption for most of US. gov. bush denies health care for the little ones;

http://www.cnn.com/2007/POLITICS/10/03/bush.veto/index.html [cnn.com]

whilst demanding/extorting billions to paint more targets on the bigger kids;

http://www.cnn.com/2007/POLITICS/12/12/bush.war.funding/index.html [cnn.com]

& pretending that it isn't happening here;

http://www.timesonline.co.uk/tol/news/world/us_and_americas/article3086937.ece [timesonline.co.uk]
all is not lost/forgotten/forgiven

(yOUR elected) president al gore (deciding not to wait for the much anticipated 'lonesome al answers yOUR questions' interview here on /.) continues to attempt to shed some light on yOUR foibles. talk about reverse polarity;

http://www.timesonline.co.uk/tol/news/environment/article3046116.ece [timesonline.co.uk]

But.... (1)

San-LC (1104027) | more than 6 years ago | (#22635496)

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... (1)

Hanners1979 (959741) | more than 6 years ago | (#22635850)

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 (1)

FromTheAir (938543) | more than 6 years ago | (#22636406)

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 (1)

module0000 (882745) | more than 6 years ago | (#22636982)

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 is simply the next evolution of existing 802.X tech.

Bwhahahahaha...dream on (2, Insightful)

monkeyboythom (796957) | more than 6 years ago | (#22637218)

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 infrastructure is what will evolve out of this. No more cable, internet, or cell phone bills.

Re:Bwhahahahaha...dream on (0)

Anonymous Coward | more than 6 years ago | (#22644058)

actually, I know a few people who would be quite keen on the growing your own veges etc. if they could do so with a decent internet connection.

Might be a trend sometime in the future, who knows.

Arithmetic check (0)

Anonymous Coward | more than 6 years ago | (#22636622)

I don't really care whether pi are square or round, but when he says that the radius of 1.6 results in a coverage of 8 square kilometers, I wonder how that was computed.

1.6**2 * pi is about 6.28, isn't it?

Re:Arithmetic check (0)

Anonymous Coward | more than 6 years ago | (#22636924)

Not on my calculator!

Area = Pi*r^2
Pi = 3.14

2*Pi = 6.28
(1.6)*(1.6) = 2.56

So area = 3.14 * 2.56 = 8.0384

So your calculator doesn't work!

Re:Arithmetic check (1)

LunarCrisis (966179) | more than 6 years ago | (#22638874)

Your result is suspiciously like 2*pi.

Re:Arithmetic check (1)

retiredtwice (1128097) | more than 6 years ago | (#22643706)

hmmm, comes out 8.04+ in the math I use....

But, YMMV, LOL

What about temperate environments? (1)

Baldrson (78598) | more than 6 years ago | (#22641462)

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 (1)

drwho (4190) | more than 6 years ago | (#22642150)

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 hardware, microsoft involved, screwed around by intel, the price still high, the computer not available.

you're just salting the earth so nothing else can grow. We had been hoping to create a mesh router that could be sold for $100, but we can't even get the components for that cost. I don't believe you'll ever see a $35 solar mesh router. Now, since you've damaged our already struggling project, you'll likely never see a $100 one, either.

Re:$35 solar mesh? Thanks for FAKE promises (1)

grcumb (781340) | more than 6 years ago | (#22642796)

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 around AUD 35.

Re:$35 solar mesh? Thanks for FAKE promises (1)

jc42 (318812) | more than 6 years ago | (#22644334)

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.

Pi R Square (1)

electricbern (1222632) | more than 6 years ago | (#22642336)

So, like... do I type that in my Playstation joystick? I kinda can't seem to locate the Pi button, it must be the circle one.
Oh, and while we are at it the Playstation 3 is SO much better then the Wii!

Mesh (1)

Darinbob (1142669) | more than 6 years ago | (#22642510)

I worked on an early product line that did mesh radio networking as a broadband alternative to cable and DSL. It was a good solution for where cable and DSL didn't reach, and was better than line-of-sight wireless. We needed one big name ISP to get behind it to keep us viable, but all we had were lots of really tiny ISPs so we were eventually shut down. There was some attempt to get the mesh technology into other realms before that was cancelled too.

Then a year or so later I started seeing reports about all the competitors coming out with meshed solutions, including some of the same research ideas that we had proposed (though usually with WiFi). It's interesting to see if the OLPC goes with this, and I'd like to see how it works out. We had used mesh to get around line of sight problems like hills and tall buildings that the Australian outback won't have to deal with, but the concept is extremely similar and adaptable to other locales that aren't pre-wired.

Horrible design! (2, Interesting)

Radi-0-head (261712) | more than 6 years ago | (#22644728)

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.

Thermodynamic Irony (1)

joebob2000 (840395) | more than 6 years ago | (#22653940)

While black is the best color to radiate heat, it's also the best color to absorb it. When trying to perform passive heat dissipation, there are no easy answers. Your tools are conduction, convection, radiation. Heat flows from hot to cold. The sun is hot and usually whenever you care, the outside is hot too. Have fun!

Re:Horrible design! (0)

Anonymous Coward | more than 6 years ago | (#22678952)

Black exterior does not mean hotter interior, contrary to [what may be] common sense. Search for "black desert robe" or similar and you will find that it's not that simple. Why are roofs black?

See for instance, this article
http://www.nature.com/nature/journal/v283/n5745/abs/283373a0.html [nature.com]

7th grade math error (-1)

z4pp4 (923705) | more than 6 years ago | (#22646598)

The math is not correct.
Antenna effects nonwithstanding, electromagnetic waves propagate according to R^3, not R^2 - since we live in a 3D / sphere world and not a 2D / disc world. Big difference.
Of course, in reality the propagation depends on the kind of antenna you use, which is a more complex function depending on elevation, direction and distance.
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