A question was posted on the element 14 website.

Amalngg posted the question:    …I want to know  how i connect two or more office located at different places with radio or wireless communication.

Chris Pinter responded:

Wifi was specifically designed for this application.   You want to look at 802.11A devices between buildings.  This protocol operates at 5.8GHz and is very line of sight…so you will not get a lot of interference as long as you use a directional antenna.

For access to the wireless network within your building you want to use 802.11G or N devices to get the maximum bandwidth and user access.

I hope this helps.