@netsnail - maybe you should call in a company that does radio links? If you're speaking of >99% availability you'll want to have regulated spectrum. To get to 2.5 Gbps you'll want probably need 256 MHz channels, dual polarized at a fairly high order of modulation. To design this and take rain fade into account you'll want to have access to Pathloss or similar. The distance a link can do depends on frequency, antenna gain, transmit power, receive threshold (for the specific modulation), rain fade... It's not merely a function of equipment.
The Huawei RTN series can do it, if you have the right outdoor units, antennas, spectrum, modulation etc. So can the Ericsson Traffic Node series, the SIAE ALCplus2 series. Siemens has radios that can do this, as has Alcatel Lucent, Ceragon, Siklu (but 80 GHz at 18 km simply is a terrible idea, they have radios in lower bands).
There are a few companies who might be willing to take on such a project. You can try Comsol - I think they have operations in Swaziland. You can try Telsaf Data as well.
Very true. However, if a radio planner who knows what he's doing plans a link for 1 Gbps he's pretty likely to get 1 Gpbs.
