Hi Darknesis. Your project sound really cool. I personally have not done anything like that (I don't need to, where I live), but I worked for a company that sells WiFi equipment for those exact purposes. I'm not trying to push anything on you, but what you're proposing has been done before.

You will need high-power outdoor Access Points, or, if you have the expertise, you could buy router boards and program them yourselves. Brands like Ubiquiti, MikroTik and EnGenius (Senao) offer such devices. Also, since they will be outdoors, the casing they are enclosed in will also be important. They have to be weather-resistant. In this case, IP65 and above-certified casings will be important, depending on the weather conditions in your area.

You will also need high-gain directional antennas, to focus the beam energy. Otherwise, the RF energy will simply dissapate into the atmosphere, or you will not have a stable connection. Obviously, you will need to make sure the antennas are facing each other.

It would be best to have a repeater. It may even end up being necessary. I have seen set-ups in New Zealand where the repeater stations are solar-powered. On another note, will it be legal for you to set it up where you intend?

On the issue of speed, I think you must understand that when it comes to WiFi, (and RF), if you want distance, then you will need to sacrifice bandwidth, and consequently speed. Depending also on what obstacles are in the path of your signals, your throughput will be affected. Even audiable noise will affect RF signals, not just electronic noise. Most outdoor AP's will be able to operate in the 2.4GHz band (802.11b/g standard), but you might like to look for AP's that can also operate in the 5GHz band (802.11a standard). You may have less interference in this band. Many WISP's use the 5GHz band for their backhaul traffic.

If and when you do proceed with this project, could you keep it updated in this forum? I would personally be very interested to know how it goes.

Thanks!