Re: what is wifi?
Sorry, maybe I should have been clearer.
I think what your referring to is a standard enterprise class AP in PtMP (point-to-multi-point) mode (a single AP with multiple STA’s (stations) associated to this AP) with standard 5dBi Omni’s, what a non-802.11 professional calls wifi.
802.11 bridging
Take a Cisco 1242 config it for bridge mode, (PtP/point-to-point) put a 30 dBi Yagi (think an antenna that has a beamwidth like a laserbeam, at least as far as 2.4/5GHz is concerned) on it and even without an amplifier it will connect to another 1242 with the same antenna over 20 miles as long as the antennas are mounted high enough to ensure adequate Fresnel zone clearance.
FCC limits PtMP to 4W EIRP
FCC limits PtP (network bridge) to 158W, and with this you can bridge miles/kilometers!
Cisco even makes 802.11a/g bridges 1300/1400 series AP’s with internal Yagi antennas