MICROWAVE COMMUNICATION

Great for short distances, but very expensive if reliability AND speed are important. Have you considered using the electricity distribution system for datacomms? We have two buildings approximately 500m apart and send and receive data at about 5Mbit/sec by modulating data onto the neutral and earth lines of the buildings power distribution system. As long as your transceivers are on the same mains phase (most buildings are three-phase enabled so you should be able to match up both ends) then you have no problems. Here in the UK, there are trials by electricity companies bringing internet access to homes using data modulated onto the domestic supply. A simple transceiver in the meter cupboard converts the data to a standard 10/100 Mb ethernet connection and hey-presto! Cat 5 cable to the hub and instant always-on internet!

Cost? Less than ?100 per node, or around US$160 each end. You could even knock up a tranceiver yourself - all the parts are available off the shelf. Maplin Electronics even sold a kit a few years back! Encript your data and you have a cheap and secure WAN. Power outages no problem! Unless they physically dig up a cable, the copper is always there, even if the power isn't!

Microwave requires approximate line-of-sight. If you can get exact line-of-sight, you might consider laser communication. There's a company called Dominion that has a cheap plug-and-play solution. They have available now a 500 meter device that provides full-duplex 10 Mbps for $5900. That's for both ends Other options, including cheaper ones, haven't come out yet.

Not affiliated in any way, nor have I used it, but I saw and touched it, and it impresses me.