I agree you need to look at a directional antenna solution versus an omni directional antenna (HGA7S). The directional antenna solution is more of a line of site pattern versus a circle pattern, thus giving you a better chance to reach the building on the other side of the parking lot. I looked into the reflector solution as well, but my logic is I need more of a fixed solution that requires little maintenance and I felt the reflector solution would work but it opens up the possibility of the reflector getting bumped or moved around thus causing issues over time. There are after market directional antenna options you can purchase and then connect directly via coax by replacing the existing omni directional antenna's that comes with the WAP200. My concern are the walls on both ends and penetrating them at the 220 ft distance. You may try the WAP200e which is met to be mounted externally, but you may try to use them internally. I suggest this because the WAP200e comes with a directional antenna built in, thus no need to purchase directional antenna's. You of course pay more for the WAP200e versus the WAP200.