[Server-devel] [UKids] "XO-1 classrooms" don't reliably connect to many/most Wifi AP's

Bernie Innocenti bernie at codewiz.org
Sat Feb 8 02:25:36 EST 2014

I've seen XO-1s randomly drop off the AP in Paraguay.

I *think* we solved it by disabling 802.11s (the mesh network). This can
be done at boot time by setting a parameter of the libertas kernel module.

Sorry for being vague, it's been a long time ago.

On 02/07/2014 10:10 AM, Adam Holt wrote:
> /[Terry Gillett summarizes his weeks of testing, ///with this very
> revealing report below/.  That's tgillett at gmail.com
> <mailto:tgillett at gmail.com> of the Village Telco project: can
> we/Nepal/Lesotho/others help him add the key takeaways to
> http://wiki.laptop.org/go/Wifi_Connectivity so the "almost 2 million
> XO-1s worldwide" can benefit?  Spoiler Alert: XO-1 deployments must
> carefully buy the correct Wifi Access Point, EG "Linksys WRT54GL" or
> "Billion 7404VGP" appear to solve most all problems.  Likewise we've had
> a lot of success in Haiti with the TP-Link TL-MR3020.]/
> The core problem is that XO-1 laptops will not reliably connect to a
> range of wifi Access Points (AP).  By comparison, XO-1.5 and later
> laptops will successfully connect to the same APs.
> The behaviour of a group of XO-1s is different from that when they are
> tested individually.  A single XO-1 may connect quite reliably, but when
> used in a group of ten or more, many individual XO-1s will fail to
> connect to the AP.
> Note that this issue is just about connecting to the AP, it is not about
> whether the AP can sustain a large number of connections or handle the
> associated data throughput requirements.
> A number of routers configured as APs have been tested to establish a
> baseline.
> The test process used requires 10 XO-1 laptops and is as follows:
> 1. Set up the AP on an unoccupied wifi channel, at least two and
> preferably three channels away from unoccupied channels.
> 2. Connect each XO-1 individually to the AP and check that it is
> operating correctly and has adequate signal strength.
> 3. Power off all the XOs
> 4. Start up one XO and allow it to connect successfully.
> 5. Start up the other none XOs
> 6. When the last XO has completed its boot up sequence, check the
> connection status of each XO.
> The result of a connection test for each XO is one of the following:
> 1. Successful automatic connection
> 2. No connection, but AP icon shows in Network Neighbourhood (NN) window
> 3. The AP icon does not appear.
> Typically there will be a mix of XOs in each of the three states. 
> A Pass requires that all ten XO-1s are successfully connected at the end
> of the test without manual intervention.
> The proportion of XOs in each state will typically vary from 20 to 80%
> in a Failed test.
> The proportion of successful connections seems to vary by router type,
> but changes in repeated tests.
> Individual XOs will typically be in different states in repeated tests.
> A range of routers has been tested with this procedure and the results
> appear in the table below.
> The only two routers that passed the test were the Billion and the Linksys.
> Interestingly both these routers date from the same vintage as the XO-1.
> Note that testing with less than five XO-1s results in a much greater
> likelihood of a Pass result, and if the same AP is tested with ten XO-1s
> it will likely fail. 
> A Pass result with ten XO-1s is considered (at this point) to be a
> reasonable indication of likely success in a real world deployment with
> greater numbers of XOs.
> The working hypothesis is that modern APs have implemented the wifi
> specs and/or default configurations in a way that has resulted in an
> interoperability problem with the wifi implementation in the XO-1.
> Billion 7404VGP        (old, Star Int, proprietary OS)          Pass
> Linksys WRT54GL     (old, Broadcom, DD-WRT)             Pass
> Netgear FWG114P     (old, proprietary OS)                       Fail
> TP Link WR710n          (new, proprietary OS)                     Fail
> TP Link WR703            (Atheros AR9331, OpenWrt)         Fail
> TP Link WR842             (Atheros AR9287, OpenWrt)         Fail
> TP Link MR3020           (Atheros AR9330, OpenWrt)         Fail
> TP Link WDR4300        (Atheros AR9341, OpenWrt)         Fail
> VT  MP01                       (Atheros AR23xx, OpenWrt)          Fail  
> VT  MP02                       (Atheros AR9331, OpenWrt)         Fail
> --
> Unsung Heroes of OLPC, interviewed live @ http://unleashkids.org !
> -- 
> Unsung Heroes of OLPC, interviewed live @ http://unleashkids.org !
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 _ // Bernie Innocenti
 \X/  http://codewiz.org

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