OLPC XO BTest-1 Units Span a Kilometer in WiFi Connectivity


How far does your laptop WiFi reach? Do you get 10, maybe 20 meters from your base station before the signal degrades? Wouldn't it be nice to get 500 meters? Or what about a whole kilometer, and that's with a stock laptop, not one modified with a directional antenna like the joe-cool BottleNet?

An OLPC mesh network

You soon shall with One Laptop Per Child. With their claim to be the first implementation of the emerging 802.11s standard, they are making Superman-sized leaps in connectivity using Marvell wireless firmware with full mesh functionality on the Children's Machine XO.

As Walter Bender reports in this week's OLPC Community News, James Cameron's continued wireless distance testing in rural Outback Australia with OLPC XO-1's is producing impressive WiFi connectivity results:

I've just completed a rural range test in ad-hoc mode, using two laptops, at a height above ground of 1.5 metres, over 1.26 kilometers line of sight.

These results are much better than the previous managed mode results, against my test access point. I suspect my access point lowered the previous results.

Both BTest-1 units were running OS build 225 with Q2B16 and Q2B19 firmware. One unit was placed at one end of a straight dirt road, 1.5m above ground, in open position with ears up. The second unit was walked down the test range.

At distance intervals, performance was analysed using iwconfig, ping -i 0.1, and arecord piped to aplay over ssh to listen to the wind on the microphone of the base unit at 8000 Hz. The results from on the second unit are:

  • 200m, signal -72 dBm, noise -85 dBm, rate 11 Mb/s, all okay,
  • 400m, signal -77 dBm, noise -89 dBm, rate 5.5 Mb/s, all okay,
  • 600m, signal -84 dBm, noise -89 dBm, rate 1 Mb/s, all okay,
  • 950m, signal -84 dBm, noise -85 dBm, rate 1 Mb/s, some ping loss,
  • 1260m, signal -87 dBm, noise -89 dBm, rate 1 Mb/s, more ping loss.

OLPC video chat @ 1 Km!
For all you metric-challenged folks, 1,000 meters is a kilometer or just over 1/2 a mile (3,281 feet to be exact). And for anyone annoyed when a WiFi signal fades in and out while just in the next room or the next building, the OLPC XO distances are finger-stopping amazing!

Or as James Cameron succinctly concludes:

I'm sure these units would perform very well if stuck on a tower ... but I agree that isn't their purpose.
Not their main purpose, but at a kilometer of connectivity per laptop, they will facilitate all kinds of purposes!

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Does anyone know whether the 802.11s protocol can be replicated in software? - thus making a normal 802.11b/g device able to make use of (or extend) a OLPC based mesh.


I agree that WIFI over 1Km is impressive, but on a dead flat desert road in outback Aus is not.

What about some testing in typical village environments with lots of huts, washing on the line, trees and shrubs with lots of lush foliage, hills, mounds, slopes and mountains.
This is more typical of where they wil be deployed.

Typically these environments have very poor infrastructure and being able to build a broadband network at the same time as deploying vaulable learning tools like OLPC is a real winner, especially if it "just works"

This is one of the many key advantages that the OLPC initiative has over the other $100 laptop proposals and makes it a no brainer IMHO

I do not think there will be much electromagnetic interference in the typical village environment. I was a Peace Corps Volunteer in Paraguay and there were only a few radios and one TV in our town. Not enough static or physical barriers to stop me from getting a solid cell phone connection from a tower several miles away.

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