[mesh-dev] 802.11 feature questions

[Marc Juul]

On Wed, May 27, 2015 at 8:48 AM, Adrian Chadd <adrian at freebsd.org> wrote:

> Hi,
>
> So there's no way to disable 11b entirely - you just disable using the
> 11b, and you set the beacon/management traffic rate to be an OFDM rate. I
> forget how, but it's configurable. The device still receives 11b, and it
> can transmit 11b - you just don't let it. (You can disable receiving 11b
> CCK on the 11n parts, but the driver always configures it in 2GHz mode.)
>
> Short/long guard interval is an 11n thing. It's to do with how much time
> between OFDM symbols. The reason for it is that the symbol rate is quite
> high and you dont want OFDM symbols bleeding over into the next symbol in a
> large environment with reflections. Since you want to do outdoor work,
> leave short-guard off.
>
> 40MHz in 2GHz is pretty risky - 2GHz is pretty congested, and with 40MHz
> on it'll wait until both halves of the 40MHz channel is free before it
> transmits. (Note: that's mostly configurable, but doing so will break
> regulatory requirements.) The 11ac parts are smarter - you can configure
> separate rate tables for 20, 40 and 80MHz availability and if only 20MHz is
> available at that point, it'll just use 20MHz.
>
> Always enable RX-STBC. It gives you a little more SNR. TX-STBC won't do
> anything on a single antenna as it requires two antennas (space time block
> coding) to work.
>
> DSSS-CCK-40? I think that's "transmit CCK frames duplicated on 40MHz
> channels for legacy interoperability." That's mostly for legacy interop -
> eg if you want to transmit beacons, RTS/CTS, etc, then it allows it to
> appear on both the primary and extension channel so legacy clients can hear
> the 20MHz side management frames. It should be on by default when you're
> doing 40MHz 11n.
>
>
Thank you!

I will keep our 2.4 ghz radio at 20 MHz and disable short_gi (though I've
yet to discover how this is done in uci)

-- 
marc/juul
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://sudoroom.org/lists/private/mesh-dev/attachments/20150528/c9b7605d/attachment.html>