[OLPC-AU] Adhoc wireless sharing help

[Tabitha Roder]

If it helps, here is what we found
You need to create the network, have the others join it, then share the
activity with the neighbourhood after they have already joined.
If the activity was shared before the other XOs had joined the ad hoc
network they couldnt see the activity and could not see invitations to join.

Kind regards
Tabitha Roder
eLearning specialist and olpc volunteer
tabitha at tabitha.net.nz
Cell +64 21 482229
http://tabitharoder.wordpress.com/



On 24 October 2010 22:07, James Cameron <quozl at laptop.org> wrote:

> G'day Jonathan,
>
> You did not mention the software version you are using, so I'm presuming
> you are using the current release 10.1.2 also known as build os852.
>
> 1.
>
> The most likely cause of the symptom you describe is laptops going into
> idle suspend.  There is a known problem where this will prevent the
> neighbourhood view from being updated as activities are shared (#10363).
>
> You can workaround this by turning off Automatic Power Management in My
> Settings -> Power.  A future release (10.1.3 due in December) may
> suppress idle suspend when an activity is shared from a laptop, but not
> prevent it on the other laptops in a group.
>
> 2.
>
> The second most likely cause is noisy radio environment (#10397).
>
> Each ad-hoc group has within it one laptop that is the timing master for
> the group.  The role moves from laptop to laptop dynamically, under
> control of the firmware in the wireless card.  The purpose of the timing
> master is to ensure that the other laptops in the group only transmit
> when no other laptop in the group is transmitting.
>
> When there is another ad-hoc group nearby, with it's own timing master,
> there is very little coordination, and so the transmissions can occur at
> the same time, resulting in several laptops not receiving them.
>
> Further, the transmission of "new shared activity" is done as a
> "multicast" packet using the slowest data rate, and is done only every
> three minutes after the first transmission!  Three minutes is an
> eternity in class time.  So if the first packet is lost, it can take a
> long time before the second packet is heard.
>
> You can workaround this by (a) restricting the number of nearby ad-hoc
> networks, by increasing the distance between groups, (b) ensuring all
> laptops in the same room join the same ad-hoc network, (c) using an
> access point for the timing master, or (d) stopping the shared activity,
> starting a new activity, and sharing it once more.
>
> 3.
>
> The third most likely cause is that not all laptops "saw" each other in
> the neighbourhood view before the activity was shared.
>
> You can workaround this by checking that all laptops can see each other
> in that view before sharing an activity.  The cause of not seeing one
> another relates to #2 above.
>
> References:
>
> http://dev.laptop.org/ticket/10363
> http://dev.laptop.org/ticket/10397
>
> --
> James Cameron
> http://quozl.linux.org.au/
> _______________________________________________
> OLPC-AU mailing list
> OLPC-AU at lists.laptop.org
> http://lists.laptop.org/listinfo/olpc-au
>
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