Re: Wireless Communication
Getting small beams is easier with optical communication where you can get beam angles of 3° and below. (Think e.g. of laser diodes with a bit of additional optics.)
You will hardly achieve this with directional antennas even of moderate size and cost - even for GHz frequencies.
PEBKAC / EBKAC / POBCAK / PICNIC (eventually see en.wikipedia.org)