[Bloat] Re: Vol 185, Issue 5

[David Lang <david@lang.hm>]

Michael Richardson wrote:

> David Lang <david@lang.hm> wrote:
>    > It interprets loss as "this is a weak signal, let me do things that will help
>    > in the weak signal case", slowing the transmission speed, which helps in the
>    > face of general noise, but when the problem is interference from other wifi
>    > transmitters, it instead expands the window where the interference will
>    > clobber the retransmission.
>
> That's a very nice, consise explanation. Thank you.   We need a word for this
> https://en.wikipedia.org/wiki/Scaredy_Squirrel_(TV_series) like behaviour :-)
>
>    > This is why at the Scale conference, we use a LOT of APs, all turned down to
>    > very low power and with default or worse antennas on them to shrink the
>    > transmission range of the APs.
>
> I wonder if this is written down somewhere?

I tried to cover it in this llogin article 
https://www.usenix.org/publications/login/april-2013-volume-38-number-2/wireless-means-radio 
and LISA talk 
https://www.usenix.org/conference/lisa12/technical-sessions/presentation/lang_david_wireless

> I think that the IETF NOC tried to write this up at some point, but I'm not
> sure if it went anywhere.
>
> I was told that the enterprise-scale systems (where half of the AP function
> reside in a switch) will use an AP high in the air when the room has few
> people/stations, but then switch to APs on chairs as the room fills.
> The mobile bags of water in the chairs are part of the sheilding :-)

I haven't seen an Enterprise system do that, but that is what I do, (using that 
terminology) so word may be filtering out

Enterprise APs tend to be expensive and so people don't install that many of 
them. they also tend to put multiple sets of radios in a single ap. Which is 
great is you want to use all the channels in once place, but a problem if you 
want to re-use any of those channels. Even the ones with directional antennas 
(tend to be 4 sets of antennas) have a problem. in theory they can re-use 
channels this way in different directions, in practice the stations they are 
talking to hear the other mobile stations that are in another quadrent.

again, all things that work really well when the building is empty and they are 
installing and testing the system, but don't work that well when a lot of people 
are there using it (let alone when you try to do a classroom)

David Lang

> --
> ]               Never tell me the odds!                 | ipv6 mesh networks [
> ]   Michael Richardson, Sandelman Software Works        |    IoT architect   [
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