How to force wifi to 5Ghz?

[Sajan Parikh]

I have two radios broadcasting for the same network, using the same 
SSID.  One at 2.4Ghz and another at 5Ghz.

I did this because it was my understanding that Ubuntu (and other OSs) 
are capable of some voodoo to automatically choose the best one and roam 
to different ones as signals change.

So first question is, is this true?

If so, exactly how does Ubuntu choose?  I ask this because for the 
longest time I was wondering why my connection was practically non 
existent in some areas of my house.  Areas where every other device 
worked beautifully.

I decided to split the SSIDs and connect to each one individually to see 
if the problem was overall signal, or just a particular frequency.

In these dead zones of my house 2.4 does not work...at all.  However 
5GHz does, amazingly.  The problem is when the SSIDs are the same, 
Ubuntu seems to want to connect to the 2.4.

Is there a way for me to prioritize 5Ghz connections always?  Or can I 
submit a bug report for this to change the way Ubuntu chooses?

In these dead zones where Ubuntu connects to the 2.4Ghz, I get over 80% 
packet loss to my router.  Why would it continue on that when 5Ghz is 
perfect in the same spot?

Hopefully that all makes sense.

Thanks.

- Sajan Parikh