transparent internet via radio

[A Gilmore <agilmore@shaw.ca>]

Having always had high-speed internet available, I have never looked
into radio technology before.  However, I have been asked recently if
providing internet to a number of locations (varying between 10-50km
away from central computer lab) is possible.  Neither dial-up or
broadband is accessible in these locations.

So I started looking into radio.  I will have one LAN with broadband
internet, and remote LANs without any internet access.  The idea is to
put a TNC equipped linux gateway at each remote location, to tunnel
TCP/IP over AX.25 to the central LAN with broadband, and route the
TCP/IP from there.

Is this feasible?  Can speed be in the 28kbps or better range? 
Generally how much would the radio equipment cost?  Is providing
transparent internet by these means difficult, regarding routing and
interfacing the protocols?

Sorry if these questions are vague or overly simple, Id just like to
know if this is possible before I spend the next several days
researching it.  Most of the information I have found so far, has been
out-dated, and mostly focused on using TCP/IP to carry AX.25, rather
then the vice-versa.
Adrien