[PATCH] wpa_supplicant: Prefer 5 GHz networks over 2.4 GHz networks.

[Sam Leffler]

On Mon, Aug 15, 2011 at 3:41 PM, Dan Williams <dcbw at redhat.com> wrote:
> On Fri, 2011-08-05 at 16:23 -0700, Gary Morain wrote:
>> In scan.c, merge a channel's noise value into the scan results. ?When comparing
>> scan results, compute the signal-to-noise ratio and use it when available.
>> Prefer a 5 GHz network if its SNR is really big (> 30) or if its SNR is
>> relatively close to the other network's.
>
> Honestly I'd rather have something like a "bands" option on a
> per-netblock basis, so you could do this:
>
> bands=5
> bands=5,2
> bands=2,5
> bands=2
>
> ie, the connection manager can set whichever band it prefers, or leave
> it out entirely to let the supplicant do whatever it's already doing.
> The problem with micro-optimizations like this are that they often
> break, and they aren't necessarily clear. ?I'd advocate for simpler,
> clearer rules here, with behavior set by the connection manager, rather
> than continually more complicated matching rules in the supplicant
> itself...

I'm trying to understand how this would be used.  The point of Gary's
change is to prefer the 5GHz band only when two AP's have equivalent
signal quality. (5GHz is considered better because it has
non-overlapping channels, less likely to have interference, etc.)
This is meant to improve the algorithm by which a BSS is selected.

Also, specifying a preference on a per-netblock basis seems odd; when
would you want to control band preferences only for a specific SSID?
You can lock down a netblock using bssid= and assign priority though
it might be painful to list all the AP's in an ESS.  If we really want
to add this complexity it seems like it belongs per-interface or
global (or at compile-time).

-Sam