limits on ad-hoc connections

Martin Langhoff martin.langhoff at
Wed Feb 8 07:23:33 EST 2012

On Wed, Feb 8, 2012 at 6:16 AM, Sridhar Dhanapalan
<sridhar at> wrote:
> Ad-hoc connections only scale to a limited number of participants
> before problems begin to occur.

The technically correct answer is "it depends". And it is true, it
depends on a ton of factors.

As a rule of thumb, I've seen it work for groups of 5~6 units,
physically close and without interference sources or reflective
materials. I would not aim higher than that -- 5~6 units in a channel.
You have 3 channels, so 3 groups of 5~6 units.

To clarify: keep any other laptops and cordless phones in the vicinity
_off_, to allow these 18 users to work. In practice, it won't work in
a school, but if you invite a few schoolmates home after school, or in
the park, you're fine.

No warranties expressed or implied. There's a long laundry list of
things that can interfere, and make things not fine.

For example, professional TV cameras from that friendly news crew
transmit in the 2.4GHz band. That battery pack feeds a powerful
antenna to get the signal back to the van that has the uplink, and it
paves over consumer-grade wifi.

So don't count in wifi (of any kind!) to work for a demo or
show-and-tell when you get TV coverage at a school :-)

> Can we impose a hard limit on the number of clients to prevent too
> many XOs connecting to a single ad-hoc session?

As James says... unfortunately no.

 martin.langhoff at
 martin at -- Software Architect - OLPC
 - ask interesting questions
 - don't get distracted with shiny stuff  - working code first

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